Cogprints: No conditions. Results ordered -Date, Title.
2018-01-17T14:26:14Z
EPrints
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2014-08-24T21:07:30Z
2015-04-20T11:40:47Z
http://cogprints.org/id/eprint/9756
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2014-08-24T21:07:30Z
Co-Variations among Cognition, Cerebellar
Disorders and Cortical Areas With
Regional Glucose-Metabolic Activities in a
Homogeneous Sample with Uner Tan Syndrome:
Holistic Functioning of the Human Brain
Patients with Uner Tan syndrome (UTS) exhibit habitual quadrupedal locomotion (QL), intellectual disability, dysarthric speech and truncal ataxia. Examination of cognitive ability in this syndrome has not yet been demonstrated in the scientific literature. Aims: (i) To analyze the cognitive abilities of the siblings with UTS; (ii) to assess the grade of their ataxia in relation to cerebellar disorders; (iii) to measure the metabolic activities of various cerebral regions in comparison with healthy individuals; (iv) to detect the interrelationships among all of the measured variables (IQ test scores, ataxia scores, cerebro-cerebellar areas and their metabolic activity levels) to reveal the holistic activity of the
brain. The Minimental State Examination (MMSE) and Wechsler Adult Intelligence Scale (WAIS-R) were applied to the affected cases and healthy subjects. Cerebellar disorders were assessed by the International Cooperative Ataxia Rating Scale (ICARS). Brain MRI scans were performed and cerebro-cerebellar areas were measured on MRI scans, including their metabolic activities (SUV), measured by positron emission tomography (PET) scanning. MMSE and WAIS-R scores both correlated with cerebro-cerebellar areas. Cerebello-vermial areas and their metabolic activities were significantly smaller in patients than in normal controls; areas of the remaining structures were not significantly different between patients and healthy subjects. Brain areas significantly inter-correlated: ICARS negatively correlated with WAIS-R,MMSE scores, SUV, and cerebro-cerebellar areas, which significantly correlated with each other. The results suggested (i) ICARS may not only be a test for cerebellar disorders, but also may be related to global functioning of all of the
cerebro-cerebellar regions; (ii) ICARS, WAIS-R and MMSE may be measures of emergent properties of the holistic
activity of the brain; (iii) the psychomotor disorders in UTS may be related to decreased brain metabolism.
Prof. Dr. Uner Tan
unertan37@yahoo.com
2013-11-18T21:06:44Z
2013-11-18T21:06:44Z
http://cogprints.org/id/eprint/9085
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2013-11-18T21:06:44Z
Direct recordings of grid-like neuronal activity in human spatial navigation
Grid cells in the entorhinal cortex appear to represent spatial location via a triangular coordinate system. Such cells, which have been identified in rats, bats and monkeys, are believed to support a wide range of spatial behaviors. Recording neuronal activity from neurosurgical patients performing a virtual-navigation task, we identified cells exhibiting grid-like spiking patterns in the human brain, suggesting that humans and simpler animals rely on homologous spatial-coding schemes.
Joshua Jacobs
Christoph T. Weidemann
Jonathan F. Miller
Alec Solway
John F. Burke
Xue-Xin Wei
Nanthia Suthana
Michael R. Sperling
Ashwini D. Sharan
Itzhak Fried
Michael J. Kahana
2013-09-17T14:26:28Z
2013-09-17T14:26:28Z
http://cogprints.org/id/eprint/8982
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2013-09-17T14:26:28Z
Human quadrupedalism is not an epiphenomenon caused
by neurodevelopmental malformation and ataxia
Two cases with quadrupedal locomotion (QL) were presented. In both cases, cognitive and psychiatric functions were normal and, no neurological deficits were observed, except for a sequel paralysis of left leg in Case 2. It was suggested that human QL (1) should not be considered as an epiphenomenon caused by neurodevelopmental malformation and
ataxia, but (2) may be considered as a re-emergence of the ancestral diagonal QL, and (3) it may spontaneously emerge in humans with entirely normal brains, by taking advantage
of neural networks such as central pattern generators that have been preserved for about 400 million years.
Prof. Dr. Uner Tan
unertan37@yahoo.com
2013-05-04T23:25:03Z
2013-05-04T23:25:03Z
http://cogprints.org/id/eprint/8968
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2013-05-04T23:25:03Z
Development of bipedal and quadrupedal locomotion in humans from a dynamical systems perspective
The first phase in the development 0f locomotion, pr,öary variability would occur in normal fetuses and infants, and those with Uner Tan syndrome. The neural networks for quadrupedal locomotion have apparently been transmitted epigenetically through many species since about 400 MYA.
The second phase is the neuronal selection process. During infancy, the most effective motor pattern(s) and their associated neuronal group(s) are selected through experience.
The third phase, secondary or adaptive variability, starts to bloom at two to three years of age and matures in adolescence. This third phase may last much longer in some patients with Uner Tan syndrome, with a considerably delay in selection of the well-balanced quadrupedal locomotion, which may emerge very late in adolescence in these cases.
Prof. Dr. Uner Tan
unertan37@yahoo.com
2013-05-04T23:24:57Z
2013-05-04T23:24:57Z
http://cogprints.org/id/eprint/8967
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2013-05-04T23:24:57Z
Üner Tan Syndrome: Review and Emergence of Human Quadrupedalism in Self-Organization,
Attractors and Evolutionary Perspectives
The first man reported in the world literature exhibiting habitual quadrupedal locomotion was discovered by a British traveler and writer on the famous Baghdat road near Havsa/Samsun on the middle Black-Sea coast of Turkey (Childs, 1917). Interestingly, no single case with human quadrupedalism was reported in the scientific literature after Child's first description in 1917 until the first report on the Uner Tan syndrome (UTS: quadrupedalism, mental retardation, and impaired speech or no speech)in 2005 (Tan, 2005, 2006). Between 2005 and 2010, 10 families exhibiting the syndrome were discovered in Turkey with 33 cases: 14 women (42.4%) and 19 men (57.6%). Including a few cases from other countries, there were 25 men (64.1%)and 14 women (35.9%). The number of men significantly exceeded the number of women (p < .05). Genetics alone did not seem to be informative for the origins of many syndromes, including the Uner Tan syndrome. From the viewpoint of dynamical systems theory, there may not be a single factor including the neural and/or genetic codes that predetermines the emergence of the human quadrupedalism.Rather, it may involve a self-organization process, consisting of many decentralized and local interactions among neuronal, genetic, and environmental subsystems. The most remarkable characteristic of the UTS, the diagonal-sequence quadrupedalism is well developed in primates. The evolutionarily advantage of this gait is not known. However, there seems to be an evolutionarily advantage of this type of locomotion for primate evolution, with regard to the emergence of complex neural circuits with related highly complex structures. Namely, only primates with diagonal-sequence quadrupedal locomotion followed an evolution favoring larger brains, highly developed cognitive abilities with hand skills, and language, with erect posture and bipedal locomotion, creating the unity of human being. It was suggested that UTS may be considered a further example for Darwinian diseases, which may be associated with an evolutionary understanding of the disorders using evolutionary principles, such as the natural selection. On the other hand, the human quadrupedalism was proposed to be a phenotypic example of evolution of reverse, i.e., the reacquisition by derived populations of the same character states as those of ancestor populations. It was also suggested that the emergence of the human quadrupedalism may be related to self-organizing processes occurring in complex systems, which select or attract one preferred behavioral state or locomotor trait out of many possible attractor states. Concerning the locomotor patterns, the dynamical systems in brain and body of the developing child may prefer some kind of locomotion, according to interactions of the internal components and the environmental conditions, without a direct role of any causative factor(s), such as genetic or neural codes, consistent with the concept of self-organization, suggesting no single element may have a causal priority.
Prof. Dr. Uner Tan
unertan37@yahoo.com
Prof. Dr. Yusuf Tamam
Dr. Sibel Karaca
sibelemre2003@yahoo.com
Prof. Dr. Meliha Tan
Meliha_Tan@yahoo.com
2017-02-18T20:23:42Z
2017-02-18T20:23:42Z
http://cogprints.org/id/eprint/9649
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2017-02-18T20:23:42Z
Uner Tan Syndrome: Review and Emergence of Human Quadrupedalism in Self-Organization, Attarctors and evolutionary Perspectives
Uner Tan syndrome, discovered in 2005 by Dr. Tan, in Southern Turkey, mainly consists of habitual quadrupedal locomotioni impaired intelligence, and dysarthric or no speech, with or without (rarely) cerebello-vermial hypoplasia and mildly simplified cortical gyri.
This syndrome may be considered wthin the framework of the nonprogressive autosomal recessive cerebellar ataxias, associated with various genetic mutations (genetic heterogeneity). This is a unique condition among disequilibrium syndrome, Cayman ataxia, and Joubert syndrome.
From the viewpoint of dynamical systems theory, there may be not a single factor including a ganetic code that predetermines the emergence of human quıadrupedalism, seen for instance in Uner Tan syndrome. Rather it may involve self-organization process, consisting of many decentralized and local interactions among neuronal, genetic, and environmental subsystems.
Prof. Dr. Uner Tan
unertan37@yahoo.com
Prof. Dr. Yusuf Tamam
Prof. Dr. Sibel Karaca
Prof. Dr. Meliha Tan
Meliha_Tan@yahoo.com
2012-11-25T12:35:22Z
2013-02-18T15:10:43Z
http://cogprints.org/id/eprint/8737
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2012-11-25T12:35:22Z
Complex Neuro-Cognitive Systems
Cognitive functions such as a perception, thinking and acting are based on the working of the brain, one of the most complex systems we know. The traditional scientific methodology, however, has proved to be not sufficient to understand the relation between brain and cognition. The aim of this paper is to review an alternative methodology – nonlinear dynamical analysis – and to demonstrate its benefit
for cognitive neuroscience in cases when the usual reductionist method fails.
Andreas Schierwagen
schierwa@uni-leipzig.de
2012-11-09T19:51:52Z
2013-02-18T15:15:23Z
http://cogprints.org/id/eprint/8676
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2012-11-09T19:51:52Z
SNARE proteins as molecular masters of interneuronal communication
In the beginning of the 20th century the groundbreaking work
of Ramon y Cajal firmly established the neuron doctrine, according to which neurons are the basic structural and functional units of the nervous system. Von Weldeyer coined the term “neuron” in 1891, but the huge leap forward in
neuroscience was due to Cajal’s meticulous microscopic observations of brain sections stained with an improved version of Golgi’s la reazione nera (black reaction). The latter improvement of Golgi’s technique made it possible to visualize the arborizations of single neurons that were “colored brownish black even to their finest branchlets, standing out with unsurpassable clarity upon a transparent yellow background. All was sharp as a sketch with Chinese ink”. The high quality of both the visualization of individual nerve cells and the work performed on studying the anatomy of the central nervous system lead Ramon y Cajal to the conclusion that axons output the nervous impulses to the dendrites or the soma of other target neurons.
Danko D. Georgiev
James F. Glazebrook
2011-12-16T00:58:12Z
2011-12-16T00:58:12Z
http://cogprints.org/id/eprint/7751
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2011-12-16T00:58:12Z
Łukasiewicz-Moisil Many-Valued Logic Algebra of Highly-Complex Systems
A novel approach to self-organizing, highly-complex systems (HCS), such as living organisms and artificial intelligent systems (AIs), is presented which is relevant to Cognition, Medical Bioinformatics and Computational Neuroscience. Quantum Automata (QAs) were defined in our previous work as generalized, probabilistic automata with quantum state spaces (Baianu, 1971). Their next-state functions operate through transitions between quantum states defined by the quantum equations of motion in the Schroedinger representation, with both initial and boundary conditions in space-time. Such quantum automata operate with a quantum logic, or Q-logic, significantly different from either Boolean or Łukasiewicz many-valued logic. A new theorem is proposed which states that the category of quantum automata and automata--homomorphisms has both limits and colimits. Therefore, both categories of quantum automata and classical automata (sequential machines) are bicomplete. A second new theorem establishes that the standard automata category is a subcategory of the quantum automata category. The quantum automata category has a faithful representation in the category of Generalized (M,R)--Systems which are open, dynamic biosystem networks with defined biological relations that represent physiological functions of primordial organisms, single cells and higher organisms.
Professor I.C. Baianu
ibaianu@illinois.edu
Professor George Georgescu
georgescu@funinf.cs.unibuc.ro
Professor James F. Glazebrook
jfglazebrook@eiu.edu
2010-09-13T03:59:01Z
2011-03-11T08:57:40Z
http://cogprints.org/id/eprint/6939
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2010-09-13T03:59:01Z
Uner Tan Syndrome: History, Clinical Evaluations, Genetics, and the
Dynamics of Human Quadrupedalism
Abstract: This review includes for the first time a dynamical systems analysis of human quadrupedalism in Uner Tan syndrome, which is characterized by habitual quadrupedalism, impaired intelligence, and rudimentary speech. The first family was discovered in a small village near Iskenderun, and families were later found in Adana and two other small villages near Gaziantep and Canakkale. In all the affected individuals dynamic balance was impaired during upright walking,and they habitually preferred walking on all four extremities. MRI scans showed inferior cerebellovermian hypoplasia with slightly simplified cerebral gyri in three of the families, but appeared normal in the fourth. PET scans showed a decreased glucose metabolic activity in the cerebellum, vermis and, to a lesser extent the cerebral cortex, except for one patient,
whose MRI scan also appeared to be normal. All four families had consanguineous marriages in their pedigrees,
suggesting autosomal recessive transmission. The syndrome was genetically heterogeneous. Since the initial discoveries
more cases have been found, and these exhibit facultative quadrupedal locomotion, and in one case, late childhood onset. It has been suggested that the human quadrupedalism may, at least, be a phenotypic example of reverse evolution. From the viewpoint of dynamic systems theory, it was concluded there may not be a single factor that predetermines human quadrupedalism in Uner Tan syndrome, but that it may involve self-organization, brain plasticity, and rewiring, from the many decentralized and local interactions among neuronal, genetic, and environmental subsystems.
Prof. Dr. Uner Tan
unertan37@yahoo.com
2009-11-14T11:34:42Z
2011-03-11T08:57:32Z
http://cogprints.org/id/eprint/6698
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2009-11-14T11:34:42Z
Natural Variation and Neuromechanical Systems
Natural variation plays an important but subtle and often ignored role in neuromechanical systems. This is especially important when designing for living or hybrid systems
which involve a biological or self-assembling component. Accounting for natural variation can be accomplished by taking a population phenomics approach to modeling and analyzing such systems. I will advocate the position that noise in neuromechanical systems is partially represented by natural variation inherent in user physiology. Furthermore, this noise can be augmentative in systems that couple physiological systems with technology. There are several tools and approaches that can be borrowed from computational biology to characterize the populations of users as they interact with the technology. In addition to transplanted approaches, the potential of natural variation can be understood as having a range of effects on both the individual's physiology and function of the living/hybrid system over time. Finally, accounting for natural variation can be put to good use in human-machine system design, as three prescriptions for exploiting variation in design are proposed.
Bradly Alicea
freejumper@yahoo.com
2010-05-04T22:12:29Z
2011-03-11T08:57:37Z
http://cogprints.org/id/eprint/6838
This item is in the repository with the URL: http://cogprints.org/id/eprint/6838
2010-05-04T22:12:29Z
AMPLITUDE OF HEART RATE MODULATION WITH THE PERIOD OF
3 CARDIOCYCLES DEPENDS ON THE PHYSIOLOGICAL AROUSAL OF THE BRAIN
Amplitude of the 3-cardiocycle modulation of heart rate in records of 300 cardiointervals depends of the physiological arousal of brain. As arousal is a physiological component of stress, the amplitude of this heart rate modulation may be used as a diagnostic parameter on the arousal in stress related studies.
Dr Valery Mukhin
Valery.Mukhin@gmail.com
2009-03-28T09:32:58Z
2011-03-11T08:57:19Z
http://cogprints.org/id/eprint/6382
This item is in the repository with the URL: http://cogprints.org/id/eprint/6382
2009-03-28T09:32:58Z
The Locus Ceruleus in PTSD
NO ABSTRACT: This is 750 word encyclopedia entry
Dr. H. Stefan Bracha
h.bracha@va.gov
Caitlin Macy
Stacy M. Lenze
Jessica M. Shelton
Michelle Tsang-Mui-Chung
2009-07-02T01:52:05Z
2011-03-11T08:57:22Z
http://cogprints.org/id/eprint/6550
This item is in the repository with the URL: http://cogprints.org/id/eprint/6550
2009-07-02T01:52:05Z
Crosstalk Between Brain-Derived Neurotrophic Factor And N-Methyl-D-Aspartate Receptor Signaling In Neurons
Glutamate is the major excitatory neurotransmitter in brain exerting prosurvival effect on neurons via N-methyl-D-aspartate receptor (NMDAR) signaling under physiological conditions. However in pathological circumstances such as ischemia, NMDARs might have proapoptotic excitotoxic activity. In contrast brain-derived neurotrophic factor (BDNF) signaling via TrkB receptors has been largely considered to promote neuronal differentiation, plasticity and survival during normal development, and protect neurons in pathophysiological conditions antagonizing the NMDAR-mediated excitotoxic cell death. In this review we summarize recent evidence for the existent crosstalk and positive feedback loops between the BDNF and NMDAR signaling and point out some of the important specific features of each signaling pathway.
Danko Georgiev
Hideo Taniura
Yuki Kambe
Yukio Yoneda
2010-05-04T22:12:43Z
2011-03-11T08:57:37Z
http://cogprints.org/id/eprint/6839
This item is in the repository with the URL: http://cogprints.org/id/eprint/6839
2010-05-04T22:12:43Z
MENTAL STATUS AND HEART RATE VARIABILITY
The results let us suppose that there are at least three periodical phenomena of HRV in frequency range related with mental status. Two of them have not been discovered and physiologically explained yet. The most powerful of these phenomena relates to mental status. It has frequencies from 0.25 to 0.5 1/beat and peak 0.35 1/beat. Despite of difference of the peak frequencies the waves of factor loadings are overlapped. Therefore, regression models would be more fit for useful evaluation of mental status, rather then power of spectral density within any frequency range.
Dr Valery Mukhin
Valery.Mukhin@gmail.com
2009-02-13T01:12:55Z
2011-03-11T08:57:18Z
http://cogprints.org/id/eprint/6345
This item is in the repository with the URL: http://cogprints.org/id/eprint/6345
2009-02-13T01:12:55Z
Anxiety and Posttraumatic Stress Disorder in the Context of Human Brain Evolution:A Role for Theory in DSM-V?
The “hypervigilance, escape, struggle, tonic immobility”
evolutionarily hardwired acute peritraumatic response
sequence is important for clinicians to understand. Our
commentary supplements the useful article on human
tonic immobility (TI) by Marx, Forsyth, Gallup, Fusé and Lexington (2008). A hallmark sign of TI is peritraumatic
tachycardia, which others have documented as a
major risk factor for subsequent posttraumatic stress
disorder (PTSD). TI is evolutionarily highly conserved
(uniform across species) and underscores the need for
DSM-V planners to consider the inclusion of evolution
theory in the reconceptualization of anxiety and PTSD.
We discuss the relevance of evolution theory to the
DSM-V reconceptualization of acute dissociativeconversion
symptoms and of epidemic sociogenic disorder(epidemic “hysteria”). Both are especially in need of attention in light of the increasing threat of terrorism
against civilians. We provide other pertinent examples.
Finally, evolution theory is not ideology driven (and
makes testable predictions regarding etiology in “both
directions”). For instance, it predicted the unexpected
finding that some disorders conceptualized in DSM-IV-TR as innate phobias are conditioned responses and thus better conceptualized as mild forms of PTSD. Evolution
theory may offer a conceptual framework in
DSM-V both for treatment and for research on psychopathology.
Dr. H. Stefan Bracha
h.bracha@va.gov
Dr. Jack D. Maser
jmaser@ucsd.edu
2009-02-13T01:14:04Z
2011-03-11T08:57:18Z
http://cogprints.org/id/eprint/6344
This item is in the repository with the URL: http://cogprints.org/id/eprint/6344
2009-02-13T01:14:04Z
Torture, Culture, War Zone Exposure and Posttraumatic Stress Disorder: Criterion A's Bracket Creep
THIS IS A COMMENTARY/LETTER TO THE EDITOR, THUS THERE IS NO ABSTRACT
Dr. H. Stefan Bracha
h.bracha@va.gov
Dr. Kentaro Hayashi
2008-04-24T16:37:30Z
2011-03-11T08:57:06Z
http://cogprints.org/id/eprint/6025
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2008-04-24T16:37:30Z
Tropen & Neuronen.
Transzendentale, physiologische und sprachliche Korrelate von »Begriffen«
Diese Arbeit ist als wiederholte, interdisziplinäre Begriffsbildung über den "Begriff" als Wort- und Denkeinheit angelegt. Begriffe werden als grundlegende Einheiten von Sprache und "Begreifen" aufgefasst, Neuronen als grundlegende Einheiten biologischer "Informationsverarbeitung". Tropen als Überbegriff einer bestimmten Gruppe rhetorischer Sprachfiguren (Metapher, Allegorie, Metonymie und die Synekdoche) verbinden Bezeichnung und (davon verschiedene) Bedeutung durch Sprung und Verschiebung. Die Schwierigkeit ist, zu beschreiben, wie Sprache, Denken und Erkennen grundlegend zusammenwirken könnten, denn es gilt entweder die Trennung von Erfahrung, Gedachtem und sprachlichen Phänomenen (wie Schrift oder Rede) zu überbrücken oder das Gemeinsame zu orten. Diese Brücke, dieses "Dazwischen", wird hier als "tropisches Verhältnis" postuliert. Als das Gemeinsame von Philosophie und Naturwissenschaft wird die Verwendung von Sprache herausgestellt, um Erfahrung und/oder Denken zu übertragen. Im Durchlaufen von Kants Argumentation der transzendentalen Deduktion in der Kritik der reinen Vernunft sowie von physiologischen Beschreibung von Nervenzellaktivitäten bei Lernen und Gedächtnis wird diese These kohärent nachvollzogen. Tropen, Begriffe und Neuronen werden korreliert, die These lässt sich aber durch das sprachliche Regressproblem nicht beweisen. Die Rolle von Einbildungskraft, Schemabildung, Zeit, subjektiver Sinnesphysiologie, kognitiven Kategorisierungsvorgängen etc. verdichtet die Verweise auf Sprung, Verschiebung und Polysemie im Gegensatz zu einer monosemischen (naiven) Abbildungstheorie. Tropen und Neuronen werden als Perspektiven der brauchbaren Verwendung von sprachlichen Figuren in Naturwissenschaft und Philosophie vorgestellt, um "Begriffe" in Bewegung zu halten oder zu hypostasieren.
Mag. Herwig Kopp
kopp@cog-neuro.net
2007-02-19Z
2011-03-11T08:56:46Z
http://cogprints.org/id/eprint/5383
This item is in the repository with the URL: http://cogprints.org/id/eprint/5383
2007-02-19Z
A WRIST-WALKER EXHIBITING NO "UNER TAN
SYDNROME": A THEORY FOR POSSIBLE
MECHANISMS OF HUMAN DEVOLUTION TOWARD
THE ATAVISTIC WALKING PATTERNS
After discovering two families with handicapped children exhibiting the “Uner Tan
syndrome,” the author discovered a man exhibiting only wrist-walking with no
primitive mental abilities including language. According to his mother, he had an
infectious disease with high fever as a three months old baby; as a result, the left
leg had been paralyzed after a penicilline injection. This paralysis most probably
resulted from a viral disease, possibly poliomyelitis. He is now (2006) 36 years
old; the left leg is flaccid and atrophic, with no tendon reflexes; however, sensation
is normal. The boy never stood up on his feet while maturing. The father forced
him to walk upright using physical devices and making due exercises, but the
child always rejected standing upright and walking in erect posture; he always
preferred wrist-walking; he expresses that wrist-walking is much more comfortable
for him than upright-walking. He is very strong now, making daily body building
exercises, and walking quite fast using a “three legs,” although he cannot stand
upright. Mental status, including the language and conscious experience, is quite
normal. There was no intra-familiar marriage as in the two families mentioned
earlier, and there is no wrist-walking in his family and relatives. There were no
cerebellar signs and symptoms upon neurological examination. The brain-MRI was
normal; there was no atrophy in cerebellum and vermis. It was concluded that there
may be sporadic wrist-walkers exhibiting no “Uner Tan Syndrome.” The results
suggest that the cerebellum has nothing to do with human wrist-walking, which
may rather be an atavistic trait appearing from time to time in normal individuals,
Prof. Dr. Üner TAN
2007-11-13T01:00:11Z
2011-03-11T08:57:00Z
http://cogprints.org/id/eprint/5813
This item is in the repository with the URL: http://cogprints.org/id/eprint/5813
2007-11-13T01:00:11Z
Conformational Dynamics and Thermal Cones of C-terminal Tubulin Tails in Neuronal Microtubules
In this paper we present a model for estimation of the C-terminal tubulin tail (CTT) dynamics in cytoskeletal microtubules of nerve cells. We show that the screened Coulomb interaction between a target CTT and the negatively charged microtubule surface as well as its immediate CTT neighbours results in confinement of the CTT motion
within a restricted volume referred to as a thermal cone. Within the thermal cone the CTT motion is driven by the thermal fluctuations, while outside the thermal cone the CTT interaction energy with its environment is above the thermal energy solely due to repulsion from the negatively charged microtubule surface. Computations were performed for different CTT geometries and we have found that the CTT conformation with lowest energy is perpendicular to the microtubule surface. Since the coupling between a target CTT with its neighbour CTTs is 8 orders of magnitude below the thermal energy and considering the extremely short cytosolic Debye length of 0.79 nm, our results rule out generation
and propagation of CTT conformational waves along the protofilament as a result of local CTT perturbations. The results as presented support a model in which the cytosolic electric fields and ionic currents generated by the neuronal excitations are "projected" onto the CTTs of underlying microtubules thus affecting their regulatory function
upon kinesin motion and MAP attachment/detachment.
Danko Georgiev
dankomed@yahoo.com
James Glazebrook
2007-11-13T00:59:56Z
2011-03-11T08:57:00Z
http://cogprints.org/id/eprint/5814
This item is in the repository with the URL: http://cogprints.org/id/eprint/5814
2007-11-13T00:59:56Z
Solitonic Effects of the Local Electromagnetic Field on Neuronal Microtubules
Current wisdom in classical neuroscience suggests that the only direct action of the electric field in neurons is upon voltage-gated ion channels which open and close their gates during the passage of ions. The intraneuronal biochemical activities are thought to be modulated indirectly either by entering into the cytoplasm ions that act as
second messengers, or via linkage to the ion channels enzymes. In this paper we present a novel possibility for subneuronal processing of information by cytoskeletal microtubule tubulin tails and we show that the local electromagnetic field supports information that could
be converted into specific protein tubulin tail conformational states. Long-range collective coherent behavior of the tubulin tails could be modelled in the form of solitary waves such as sine-Gordon kinks, antikinks or breathers that propagate along the microtubule outer
surface, and the tubulin tail soliton collisions could serve as elementary computational gates that control cytoskeletal processes. The biological importance of the presented model is due to the unique biological enzymatic energase action of the tubulin tails, which is experimentally verified for controlling the sites of microtubule-associated protein
attachment and the kinesin transport of post-Golgi vesicles.
Danko Georgiev
dankomed@yahoo.com
Stelios Papaioanou
James Glazebrook
2006-10-05Z
2011-03-11T08:56:35Z
http://cogprints.org/id/eprint/5125
This item is in the repository with the URL: http://cogprints.org/id/eprint/5125
2006-10-05Z
The primary function of REM sleep
In this paper, the physiological features associated with the different stages of REM sleep and with what information processing researchers have called “effort” and “arousal” are compared. It is suggested that tonic REM sleep and effort involve an increase in the metabolism of cerebral glycogen, and phasic REM sleep and arousal involve the transfer of glucose from the body to the brain. Both stages of REM sleep seem to elevate cerebral glucose levels and likely result in increased ATP generation in some part(s) of the brain. It is noted that the functioning of the hippocampus depends heavily on ATP, and that this part of the brain becomes especially active during REM sleep. From this, although many details remain to be clarified, it seems clear that the primary function of REM sleep is to re-energize the brain.
Mr. Andrew E. Bernhard
2006-07-23Z
2011-03-11T08:56:32Z
http://cogprints.org/id/eprint/5011
This item is in the repository with the URL: http://cogprints.org/id/eprint/5011
2006-07-23Z
EVIDENCE FOR "UNERTAN SYNDROME" AND THE EVOLUTION OF THE HUMAN MIND
A new family exhibiting “Unertan Sydnrome” was discovered. The pedigree analysis showed marriages between relatives. This family was similar to the first one (see Tan, 2006a), providing a firm evidence for the new syndrome. The affected children showed habitual quadrupedal walking gait, that is, they walked on wrists and feet with straight legs and arms. Their heads and bodies were mildly flexed; they exhibited mild cerebellar signs, and severe mental retardation. The pedigree demonstrated a typical autosomal-recessive inheritance. The genetic nature of
this syndrome suggests a backward stage in human evolution (devolution), which would be consistent with theories of punctuated evolution. The results reflected a
new theory on the evolution of human beings. That is, the evolution of humans would in fact be the evolution of the extensor motor system, responsible for upright posture, against the gravitational forces. This would be coupled with the emergence of the human mind, which can be considered a reflexion of the human motor system, in accord with the psychomotor theory (see Tan, 2005a). The
most important characteristic of the newly emerged human mind was the resistance against gravitational forces. This was the resistive mind, the origins of human creativity.
Prof. Dr. Uner Tan
2006-04-29Z
2011-03-11T08:56:24Z
http://cogprints.org/id/eprint/4862
This item is in the repository with the URL: http://cogprints.org/id/eprint/4862
2006-04-29Z
Psychosomatic Plasticity: An "Emergent Property" of Personality Research?
Psychosomatic plasticity, defined as an extreme capacity to turn suggestions into bodily realities, is as phenomenon well worth investigating, as it challenges mainstream conceptions about the relationship between mind and body in health as well as illness. The field of psychoneuroimmunology (PNI) offers a framework within which to understand this phenomenon, as PNI makes a compelling case for the biological unity of self. Hartmann’s Boundaries concept is particularly applicable, as it suggests that the minds of ‘thin-boundary’ persons are relatively fluid and able to make numerous connections. Wilson and Barber’s identification of the fantasy prone person, and Thalbourne’s transliminality concept, are similarly relevant. Taking these explorations a step further, the author proposes that the flow of feeling within individuals represents the key to psychosomatic plasticity. Blushing, psoriasis, and immune reactions are offered as examples, as are more anomalous reports such as those provided by heart transplant recipients and cases said to be indicative of reincarnation. In each instance, persons who are highly sensitive (i.e., have a speedier and more direct flow of feeling) are more likely to evidence physical reactions. Psychosomatic plasticity represents an emerging area of interest in personality research, one that clearly merits further investigation.
Michael Jawer
2005-02-26Z
2011-03-11T08:55:43Z
http://cogprints.org/id/eprint/3908
This item is in the repository with the URL: http://cogprints.org/id/eprint/3908
2005-02-26Z
Consciousness And Adaptive Behavior
Consciousness has resisted scientific explanation for centuries. The main problem in explaining consciousness is its subjectivity. Subjective systems may be adaptive. Humans can produce voluntary new or novel intentional (adaptive) action and such action is always accompanied by consciousness. Action normally arises from perception. Perception must be rerepresented in order to produce new or novel adaptive action. The internal explicit states produced by a widespread nonlinear emergent mechanism from perception have all the same properties as consciousness. Hence they may be identical to consciousness. Consciousness is natural, material, and functional; utilized in the production of adaptive action.
Richard/A. Sieb
2006-10-09Z
2011-03-11T08:56:39Z
http://cogprints.org/id/eprint/5216
This item is in the repository with the URL: http://cogprints.org/id/eprint/5216
2006-10-09Z
A situated cognition perspective on presence
During interaction with computer-based 3-D simulations like virtual reality, users may experience a sense of involvement called presence. Presence is commonly defined as the subjective feeling of "being there". We discuss the state of the art in this inno vative research area and introduce a situated cognition perspective on presence. We argue that presence depends on the proper integration of aspects relevant to an agent's movement and perception, to her actions, and to her conception of the overall situ a tion in which she finds herself, as well as on how these aspects mesh with the possibilities for action afforded in the interaction with the artifact. We also aim at showing that studies of presence offer a test-bed for different theories of situated co gnition.›
Antonella Carassa
Francesca Morganti
Maurizio Tirassa
2004-10-22Z
2011-03-11T08:55:42Z
http://cogprints.org/id/eprint/3894
This item is in the repository with the URL: http://cogprints.org/id/eprint/3894
2004-10-22Z
Solitonic effects of the local electromagnetic field on neuronal microtubules – tubulin tail sine-Gordon solitons could control MAP attachment sites and microtubule motor protein function
The current wisdom in the classical neural net theory holds that the only direct action of the electric field in neurons is upon voltage-gated ion channels, which open and close their gates for ions. The intraneuronal biochemical activities are thought to be modulated indirectly either by the entering in the cytoplasm ions that act as second messengers or via linked to the ion channels enzymes. In this paper we present a novel possibility for subneuronal processing of information by cytoskeletal microtubule tubulin tails and we show that the local electromagnetic field brings information that could be converted into specific protein tubulin tail conformational states. Long-range collective coherent behavior of the tubulin tails could transmit solitary waves in the form of sine-Gordon kinks, antikinks or breathers along the microtubule outer surface and the tubulin tail soliton collisions could serve as elementary computational gates that control cytoskeletal processes. The biological importance of the presented model is due to the unique biological enzymatic energase action of the tubulin tails, which is experimentally shown to control the sites of microtubule-associated protein attachment and the kinesin transport of post-Golgi vesicles.
Danko Georgiev
2004-11-13Z
2011-03-11T08:55:43Z
http://cogprints.org/id/eprint/3938
This item is in the repository with the URL: http://cogprints.org/id/eprint/3938
2004-11-13Z
The nervous principle: active versus passive electric processes in neurons
This essay presents in the first section a comprehensive introduction to classical electrodynamics. The reader is acquainted with some basic concepts like right-handed coordinate system, vector calculus, particle and field fluxes, and learns how to calculate electric and magnetic field strengths in different neuronal compartments. Then the exposition comes to explain the basic difference between a passive and an active neural electric process; a brief historical perspective on the nervous principle is also provided. A thorough description is supplied of the nonlinear mechanism generating action potentials in different compartments, with focus on dendritic electroneurobiology. Concurrently, the electric field intensity and magnetic flux density are estimated for each neuronal compartment. Observations are then discussed, succinctly as the calculated results and experimental data square. Local neuronal magnetic flux density is less than 1/300 of the Earth’s magnetic field, explaining why any neuronal magnetic signal would be suffocated by the surrounding noise. In contrast the electric field carries biologically important information and thus, as it is well known, acts upon voltage-gated transmembrane ion channels that generate neuronal action potentials. Though the transmembrane difference in electric field intensity climbs to ten million volts per meter, the intensity of the electric field is estimated to be only ten volts per meter inside the neuronal cytoplasm.
Danko Georgiev
2005-05-27Z
2011-03-11T08:56:04Z
http://cogprints.org/id/eprint/4364
This item is in the repository with the URL: http://cogprints.org/id/eprint/4364
2005-05-27Z
NEURONIC SYSTEM INSIDE NEURONS: MOLECULAR BIOLOGY AND BIOPHYSICS OF NEURONAL MICROTUBULES
Neurons are highly specialized cells that input, process, store and output information. Interneuronal communication is achieved in four basic ways: (i) Ca2+ evoked exocytosis with chemical neurotransmission, (ii) gap junction electrotonic coupling, (iii) secretion of neurosteroids, nitric oxide and derivatives of the arachidonic acid acting in paracrine manner, and (iv) cellular adhesive protein interactions with scaffold protein reorganization. Central structure integrating these anisomorphic signals is the neuronal cytoskeleton that is considered to be both sensitive to the local electromagnetic field and prone to intense biochemical modification. With the use of biophysical modeling we have shown that the local electromagnetic field interaction with neuronal microtubules could result in formation of dissipationless waves (solitons) of tubulin tail conformational states that propagate along the microtubule outer surface. Soliton collisions may subserve the function of elementary computational gates and the output of the computation performed by the microtubules may be achieved by the energase action of the tubulin tails that control microtubule-associated protein and motor protein attachment/detachment on the microtubule outer surface.
Danko Georgiev
Stelios Papaioanou
James Glazebrook
2009-03-04T03:22:32Z
2011-03-11T08:57:19Z
http://cogprints.org/id/eprint/6365
This item is in the repository with the URL: http://cogprints.org/id/eprint/6365
2009-03-04T03:22:32Z
The STRS (shortness of breath, tremulousness, racing heart, and sweating): A brief checklist for acute distress with panic-like autonomic indicators; development and factor structure
Background: Peritraumatic response, as currently assessed by Posttraumatic Stress Disorder (PTSD) diagnostic criterion A2, has weak positive predictive value (PPV) with respect to PTSD diagnosis. Research suggests that indicators of peritraumatic autonomic activation may supplement the PPV of PTSD criterion A2. We describe the development and factor structure of the STRS (Shortness of Breath, Tremulousness, Racing Heart, and Sweating), a one page, two-minute checklist with a five-point Likert-type response format based on a previously unpublished scale. It is the first validated self-report measure of peritraumatic activation of the autonomic nervous system.
Methods: We selected items from the Potential Stressful Events Interview (PSEI) to represent two latent variables: 1) PTSD diagnostic criterion A, and 2) acute autonomic activation. Participants (a convenience sample of 162 non-treatment seeking young adults) rated the most distressing incident of their lives on these items. We examined the factor structure of the STRS in this sample using factor and cluster analysis.
Results: Results confirmed a two-factor model. The factors together accounted for 68% of the variance. The variance in each item accounted for by the two factors together ranged from 41% to 74%. The item loadings on the two factors mapped precisely onto the two proposed latent variables.
Conclusion: The factor structure of the STRS is robust and interpretable. Autonomic activation signs tapped by the STRS constitute a dimension of the acute autonomic activation in response to stress that is distinct from the current PTSD criterion A2. Since the PTSD diagnostic criteria are likely to change in the DSM-V, further research is warranted to determine whether signs of peritraumatic autonomic activation such as those measured by this two-minute scale add to the positive predictive power of the current PTSD criterion A2. Additionally, future research is warranted to explore whether the four automatic activation items of the STRS can be useful as the basis for a possible PTSD criterion A3 in the DSM-V.
H. Stefan Bracha
h.bracha@va.gov
Andrew E. Williams
Stephen N. Haynes
Edward S Kubany
Tyler C. Ralston
Jennifer M. Yamashita
2004-03-23Z
2011-03-11T08:55:30Z
http://cogprints.org/id/eprint/3513
This item is in the repository with the URL: http://cogprints.org/id/eprint/3513
2004-03-23Z
The perception of melodic consonance: an acoustical and neurophysiological explanation based on the overtone series
The melodic consonance of a sequence of tones is explained using the overtone series: the overtones form "flow lines" that link the tones melodically; the strength of these flow lines determines the melodic consonance. This hypothesis admits of psychoacoustical and neurophysiological interpretations that fit well with the place theory of pitch perception. The hypothesis is used to create a model for how the auditory system judges melodic consonance, which is used to algorithmically construct melodic sequences of tones.
Jared E. Anderson
2006-08-01Z
2011-03-11T08:56:32Z
http://cogprints.org/id/eprint/5027
This item is in the repository with the URL: http://cogprints.org/id/eprint/5027
2006-08-01Z
Experimental Combat-Stress Model in Rats: Histological Examination of Effects of Amelogenesis-A Possible Measure of Diminished Vagal Tone Episodes
Developmental defects of enamel-stress histomarker rings (accentuated striae) may be a potential measure of diminished vagal tone in research on extreme stress such as exposure to combat. To develop an animal model of this measure, we examined the enamel of rat incisors which erupt continuously. We examined incisors from 15 stressed-colony rats and 7 control-rats for these histomarkers using the Visible Burrow System (VBS). VBS was developed to study combat stress in rats. No stress rings were found in any of the rat incisors examined. In contrast to humans, rats have likely evolved to prioritize incisor strength during combat stress. Studies of amelogenesis during combat stress in other rodents with continuously growing incisors are warranted. Laboratory animals such as rabbits or marmosets may be especially suitable, since they less frequently use their incisors for self defense.
Dr. Stefan Bracha
Dr. D. Caroline Blanchard
Dr. Jeffrey L. Llyod-Jones
Dr. Andrew Williams
Dr. Robert J. Blanchard
2004-11-06Z
2011-03-11T08:55:43Z
http://cogprints.org/id/eprint/3928
This item is in the repository with the URL: http://cogprints.org/id/eprint/3928
2004-11-06Z
Objective measurement of simulator sickness and the role of visual-vestibular conflict situations: a study with vestibular-loss (a-reflexive) subjects
Simulators, in particular driving simulators, are gaining importance not only for research and development purposes, but also for education, training and even recreation. Progress in computer graphics and performance allow for highly realistic simulator visuals. High-end models are becoming somewhat better at generating acceptable inertial self-motion information, sometimes even providing real (but limited) linear translation in addition to angular movements. Simpler versions do not generate inertial information at all (fixed-base simulators). Here, we present a study on a problem that often occurs with driving simulators, i.e., simulator sickness. This phenomenon closely resembles the classically experienced motion sickness and can make a user abort a simulator run within minutes. We investigated the hypothesis that simulator sickness is caused by a visual-vestibular conflict, comparing susceptibility in normals and in vestibular-loss patients. We studied the psychophysical reactions of subjects, and quantitatively recorded their neurovegetative activity, to improve understanding of the underlying causes of simulator sickness, and to develop an objective measure for monitoring purposes. We used a fixed-base simulator, with an urban circuit with many sharp turns and traffic lights. No vestibular input was received during driving simulation, thus creating numerous visual-vestibular conflict situations. Subjects were asked to indicate continuously their discomfort on a visual-analog scale. We studied 33 normals (19 became sick) and 6 bilateral vestibular-loss subjects (one became truly sick, 2 others somewhat). Sickness correlated strongly with an increase in anxiety (Spielberger STAI). The subjective discomfort readings correlated well with simultaneous neurovegetative data and with a symptom scoring test administered immediately afterwards. There was no clear indication of an age or gender dependence in the normals. The fact that a complete vestibular-loss patient became sick indicates that more parameters may be responsible for simulator sickness than just a visuo-vestibular conflict situation (anxiety, nauseating odours, etc.). - Supported by the European Union (QLK6-CT-2002-00151: EUROKINESIS).
Dr R.J.V. Bertin
Dr A. Guillot
Dr C. Collet
F. Vienne
Dr S. Espié
Dr W. Graf
2004-07-13Z
2011-03-11T08:55:38Z
http://cogprints.org/id/eprint/3719
This item is in the repository with the URL: http://cogprints.org/id/eprint/3719
2004-07-13Z
Siren call of Metaphor: subverting the proper task of System Neuroscience
Under the assumption that nervous systems form a distinct category among the objects in Nature, applying metaphors of psychological and behavioral science disciplines is flawed and invites confusion. Moreover, such practices obscure and detract from the primary task of Neurophysiology: to investigate the intrinsic properties of nervous systems, uncontaminated with concepts borrowed from other disciplines. A comprehensive fundamental theory of nervous systems is expected to have the character of high dimensional nonlinear systems in which state space transitions, set in motion by external influences, self-organize to dynamic state space configuration with consequences for behavior
M.D. Gerhard Werner
2003-12-18Z
2011-03-11T08:55:24Z
http://cogprints.org/id/eprint/3318
This item is in the repository with the URL: http://cogprints.org/id/eprint/3318
2003-12-18Z
Consciousness operates beyond the timescale for discerning time intervals: implications for Q-mind theories and analysis of quantum decoherence in brain
This paper presents in details how the subjective time is constructed by the brain cortex via reading packets of information called "time labels", produced by the right basal ganglia that act as brain timekeeper. Psychophysiological experiments have measured the subjective "time quanta" to be 40 ms and show that consciousness operates beyond that scale - an important result having profound implications for the Q-mind theory. Although in most current mainstream biophysics research on cognitive processes, the brain is modelled as a neural network obeying classical physics, Penrose (1989, 1997) and others have argued that quantum mechanics may play an essential role, and that successful brain simulations can only be performed with a quantum computer. Tegmark (2000) showed that make-or-break issue for the quantum models of mind is whether the relevant degrees of freedom of the brain can be sufficiently isolated to retain their quantum coherence and tried to settle the issue with detailed calculations of the relevant decoherence rates. He concluded that the mind is classical rather than quantum system, however his reasoning is based on biological inconsistency. Here we present detailed exposition of molecular neurobiology and define the dynamical timescale of cognitive processes linked to consciousness to be 10-15 ps showing that macroscopic quantum coherent phenomena in brain are not ruled out, and even may provide insight in understanding life, information and consciousness.
Danko Georgiev
2003-07-16Z
2011-03-11T08:55:19Z
http://cogprints.org/id/eprint/3067
This item is in the repository with the URL: http://cogprints.org/id/eprint/3067
2003-07-16Z
Preponderance of Late-spiking Neurons in Rat Lateral Amygdala
Whole-cell recordings from rat lateral amygdala (LA) revealed two populations of principal neurons, that have similar pyramid-like morphologies but differing in firing pattern: late-spiking (LS, 66%) and regular-spiking (RS, 34%). The presence of large numbers of LS neurons arguably supports recent suggestions that the LA should be considered to be a functional extension of perirhinal cortex.
Dr Ewan C. McNay
Dr Thomas H. Brown
2003-03-03Z
2011-03-11T08:55:13Z
http://cogprints.org/id/eprint/2809
This item is in the repository with the URL: http://cogprints.org/id/eprint/2809
2003-03-03Z
The causal consciousness: beta-neurexin promotes neuromediator release via vibrational multidimensional tunneling
Epiphenomenalism is shown to be absurd because the development of consciousness must be explainable through natural selection. A detailed neuromolecular basis of the neuromediator release is given and it is stressed on the possible key point where the quantum mind could act, namely presynaptic scaffold protein dynamics and detachment of the calcium sensor v-SNARE synaptotagmin-1. The beta-neurexin molecules are tuned via fast propagating solitons by the quantum coherent microtubule network so that the beta-neurexin molecule thermal vibrations could promote or suppress conformational changes via vibrational multidimensional tunneling, which drives synaptotagmin-1 detachment from the SNARE complex under calcium ion binding. Following the synaptotagmin-1 detachment membrane fusion takes place in SNARE dependent fashion and the presynaptic vesicle spills neuromediator in the synaptic cleft. Thus the quantum transfer of information causally affects the neuromediator release.
Dr. Danko Georgiev
2005-07-13Z
2011-03-11T08:56:08Z
http://cogprints.org/id/eprint/4463
This item is in the repository with the URL: http://cogprints.org/id/eprint/4463
2005-07-13Z
On The Dynamic Timescale Of Mind-Brain Interaction
In neurophysiology it is widely assumed that our mind operates in millisecond timescale. This view might be wrong, because if consciousness is quantum coherent phenomenon at the level of protein assemblies, then its dynamic timescale can be picosecond one.
Danko Georgiev
2003-05-25Z
2011-03-11T08:55:17Z
http://cogprints.org/id/eprint/2972
This item is in the repository with the URL: http://cogprints.org/id/eprint/2972
2003-05-25Z
Processing of analogy in the thalamocortical circuit
The corticothalamic feedback and the thalamic reticular nucleus have gained
much attention lately because of their integrative and modulatory functions.
A previous study by the author suggested that
this circuitry can process analogies (i.e., the {\em analogy hypothesis}).
In this paper, the proposed model was implemented as a network of leaky
integrate-and-fire neurons to test the {\em analogy hypothesis}.
The previous proposal required specific delay and
temporal dynamics, and the implemented network tuned
accordingly functioned as predicted. Furthermore, these specific
conditions turn out to be consistent with experimental data, suggesting
that a further investigation of the thalamocortical circuit within the {\em
analogical framework} may be worthwhile.
Yoonsuck Choe
choe
2003-06-03Z
2011-03-11T08:55:17Z
http://cogprints.org/id/eprint/2997
This item is in the repository with the URL: http://cogprints.org/id/eprint/2997
2003-06-03Z
Processing of analogy in the thalamocortical circuit
The corticothalamic feedback and the thalamic reticular nucleus have gained
much attention lately because of their integrative and modulatory functions.
A previous study by the author suggested that
this circuitry can process analogies (i.e., the {\em analogy hypothesis}).
In this paper, the proposed model was implemented as a network of leaky
integrate-and-fire neurons to test the {\em analogy hypothesis}.
The previous proposal required specific delay and
temporal dynamics, and the implemented network tuned
accordingly functioned as predicted. Furthermore, these specific
conditions turn out to be consistent with experimental data, suggesting
that a further investigation of the thalamocortical circuit within the {\em
analogical framework} may be worthwhile.
Yoonsuck Choe
choe
2002-05-04Z
2011-03-11T08:54:55Z
http://cogprints.org/id/eprint/2197
This item is in the repository with the URL: http://cogprints.org/id/eprint/2197
2002-05-04Z
Validity ty of spectral analysis of evoked potentials in brain research
The averaged electronencephologram (EEG) response of the brain to an external stimulus (evoked potential, EP) is usually subjected to spectral analysis using the fast Fourier transform (FFT), especially to discover the relation of cognitive ability to so-called brain dynamics. There is indeed a discrepancy between these two systems, because the brain is a highly complex nonlinear system, analyzed by a linear system (FFT). We present in this work some inaccuracies that occurred when EPs are subjected to spectral analysis, using a model signal. First of all, the EP power spectra depended upon the number of samples used for averaging; the input EP (model signal) and the output EP (from the system) seemed to be similar in forms, but they exhibited completely different spectral power curves. It was concluded that the spectral analysis of evoked responses by using FFT (linear system analysis) in relation to brain (highly complex nonlinear system) may mislead neuroscientists.
Alexander Kramarenko
UNER TAN
2009-03-04T03:29:14Z
2011-03-11T08:57:19Z
http://cogprints.org/id/eprint/6360
This item is in the repository with the URL: http://cogprints.org/id/eprint/6360
2009-03-04T03:29:14Z
A Multi-disciplinary Approach to the Investigation of Aspects of Serial Order in Cognition
Serial order processing or Sequence processing underlies many human activities such as speech, language, skill learning, planning, problem solving, etc. Investigating the
neural bases of sequence processing enables us to understand serial order in cognition and helps us building intelligent devices. In the current paper, various
cognitive issues related to sequence processing will be discussed with examples. Some of the issues are: distributed versus local representation, pre-wired versus
adaptive origins of representation, implicit versus explicit learning, fixed/flat versus hierarchical organization, timing aspects, order information embedded in sequences, primacy versus recency in list learning and aspects of sequence perception such as recognition, recall and generation. Experimental results that give evidence for the involvement of various brain areas will be described. Finally, theoretical frameworks based on Markov models and Reinforcement Learning paradigm will be presented. These theoretical ideas are useful for studying sequential phenomena in a principled way.
Raju S. Bapi
K. P. Miyapuram
V. S. Chandrasekhar Pammi
2002-11-04Z
2011-03-11T08:55:05Z
http://cogprints.org/id/eprint/2572
This item is in the repository with the URL: http://cogprints.org/id/eprint/2572
2002-11-04Z
Biology of Brain waves: natural history and evolution of an information-rich sign of activity.
Using "brain waves" and "EEG" broadly for ongoing electrical activity and stimulus- or event-related activity of organized masses of neural tissue as seen by wideband amplifiers and macro-, micro- or semi-microelectrodes within or in electrical contact with the central nervous system, I consider the character of these signs in animals of many phyla, by various descriptors, emphasizing local field potentials, pregnant questions and research opportunities.
We still have inadequate or hardly tested ideas of why most invertebrates, large and small, have inconspicuous slow waves (<50 Hz) and conspicuous spikes. They can, however, show slow waves under certain conditions, somewhat reminiscent of spinal cord, cerebellum or retina.
We have even less tested explanations of the strong similarity of all vertebrates: fish, amphibians, reptiles, birds and mammals, large and small - with respect to the power spectrum of conspicuous slow and inconspicuous spikes (until hunted by microelectrodes). Amplitude is the only obvious difference among vertebrate classes, mammals being highest. This may come from an evolution of the prevalence of synchrony, attrubutable, if true, to a generally higher coherence between pairs of sites in reptiles, birds and especially mammals.
The strong similarity in the power spectrum, among taxa with and without a cortex, is only one of several reasons to believe that we have not found the most relevant measures to reveal the real structure of the time series, in space and time. Fine structure in the millimeter and fractional second domains, in the seemingly stochastic, wideband component of activity is probably widespread and greater in mammals than in fish.
It has properties that are not obvious, such as nonlinear quadratic phase couplings and pseudo-periodicities, locally and episodically. Wavelet analysis, independent component analysis and other tools that might reveal nonrhythmic fine structure have not yet been applied to evolutionary studies.
A new tool, the Period-Specific-Average (PSA) can show real rhythms even when the power spectrum does not and shows absence of rhythms at some frequencies where the power spectrum peaks showing Fourier components of irregular transients. The PSA shows that most of the spectrum most of the time in most human cortex is without rhythms. Special conditions bring out episodes of delta, theta, alpha, beta and gamma waves and their subtypes, usually only one or two at once, while most of the energy is wideband and seemingly stochastic. Between episodes of one or two rhythms there are major periods of time in normal human life without any significant rhythm in cortical surface (subdural) and depth electrodes. In spite of many kinds of sophisticated analyses, gross mappings, and models, with our present understanding, we cannot yet anticipate the character of scalp or subdural surface or macroelectrode depth recordings from microelectrode data or vice versa. Also lacking, so far, is any general understanding of the relation of slower, local field potentials and spike firing. Examples are known of strong positive correlations and others show no correlation. Communication among neurons by subthreshold, nonsynaptic routes is probably important in some evolving places and times.
The relative neglect of the basic biology, natural history, evolution, and system identification of local field potentials at different scales in different places is undeserved and a prime opportunity for new tools .
Professor of Neuroscience Theodore Holmes Bullock
2002-11-08Z
2011-03-11T08:55:05Z
http://cogprints.org/id/eprint/2581
This item is in the repository with the URL: http://cogprints.org/id/eprint/2581
2002-11-08Z
Grades in neural complexity: how large is the span?
The span of complexity in brains, between the simplest flatworms and the most advanced mammals is exceedingly great, measured by the number of different anatomical parts, physiological processes, sensory discriminations, and behavioral alternatives in the repertoire. Most evolution of brains has been adaptive radiation within the same grade of complexity. Distinct grades of complexity have appeared a dozen or more times and quite often in the retrograde direction. Advancement has not been inevitable or obviously advantageous in survival value but has happened - long before primates or mammals or vertebrates. Compare cuttlefish and the most advanced gastropods, bees and the best brine shrimp, primates and the most advanced reptiles known - all twigs with common branches. This repeated achievement of evolution has had all too little study in respect of the detailed listing of differences between major taxa of distinct grades of complexity. Connectivity at the level now known for the mammalian cortex is much needed in other classes, with estimates of reciprocity, intrinsic differentiation, dendritic parcellation and afferent and efferent connections, both locally and projecting to other centers, each done quantitatively to permit comparison. Physiological system organization, personality properties of neurons and circuits, proclivities and emergent phenomena at several integrative levels are sketchily known only for parts of a few systems. Examples are given of opportunities for new research that can more adequately characterize grades of brains.
TH Bullock
2002-12-18Z
2011-03-11T08:55:07Z
http://cogprints.org/id/eprint/2665
This item is in the repository with the URL: http://cogprints.org/id/eprint/2665
2002-12-18Z
Have brain dynamics evolved?
Should we look for unique dynamics in the sapient species?
Ongoing "spontaneous" electrical field potentials of assemblies of neurons in the brains of diverse animal groups differ widely in character and amplitude without obvious explanation. There may be correlates with other measures of brain complexity, such as histological differentiation but there are so far no known differences between the EEG s of humans and other mammals or between mammals and reptiles, amphibians or fish, apart from amplitude. The proposition is defended that further search for descriptors or statistical, probably non-linear features of the time series will reveal consistent differences - meaning that we have so far missed major features of the natural history of EEGs, just as we have, thus far, relatively neglected the identification of features of the physiology of the brain relevant to its evolution of complexity through major grades of phyla, classes and orders.
T.H. Bullock
2003-02-17Z
2011-03-11T08:55:10Z
http://cogprints.org/id/eprint/2777
This item is in the repository with the URL: http://cogprints.org/id/eprint/2777
2003-02-17Z
Have brain dynamics evolved?
Should we look for unique dynamics in the sapient species?
Ongoing “spontaneous” electrical field potentials of assemblies of neurons in the brains of diverse animal groups differ widely in character and amplitude without obvious explanation. There may be correlates with other measures of brain complexity, such as histological differentiation but there are so far no known differences between the EEG s of humans and other mammals or between mammals and reptiles, amphibians or fish, apart from amplitude. The proposition is defended that further search for descriptors or statistical, probably non-linear features of the time series will reveal consistent differences - meaning that we have so far missed major features of the natural history of EEGs, just as we have, thus far, relatively neglected the identification of features of the physiology of the brain relevant to its evolution of complexity through major grades of phyla, classes and orders.
T.H. Bullock
2002-10-01Z
2011-03-11T08:55:01Z
http://cogprints.org/id/eprint/2489
This item is in the repository with the URL: http://cogprints.org/id/eprint/2489
2002-10-01Z
Microgenesis, immediate experience and visual processes in reading
The concept of microgenesis refers to the development on a brief present-time scale of a percept, a thought, an object of imagination, or an expression. It defines the occurrence of immediate experience as dynamic unfolding and differentiation in which the ‘germ’ of the final experience is already embodied in the early stages of its development. Immediate experience typically concerns the focal experience of an object that is thematized as a ‘figure’ in the global field of consciousness; this can involve a percept, thought, object of imagination, or expression (verbal and/or gestural). Yet, whatever its modality or content, focal experience is postulated to develop and stabilize through dynamic differentiation and unfolding. Such a microgenetic description of immediate experience substantiates a phenomenological and genetic theory of cognition where any process of perception, thought, expression or imagination is primarily a process of genetic differentiation and development, rather than one of detection (of a stimulus array or information), transformation, and integration (of multiple primitive components) as theories of cognitivist kind have contended.
My purpose in this essay is to provide an overview of the main constructs of microgenetic theory, to outline its potential avenues of future development in the field of cognitive science, and to illustrate an application of the theory to research, using visual processes in reading as an example.
Victor Rosenthal
2003-03-03Z
2011-03-11T08:55:13Z
http://cogprints.org/id/eprint/2805
This item is in the repository with the URL: http://cogprints.org/id/eprint/2805
2003-03-03Z
Periodicity in wide-band time series
Summary: To test the hypotheses that (i) electroencephalograms (EEGs) are largely made up of oscillations at many frequencies and (ii) that the peaks in the power spectra represent oscillations, we applied a new method, called the Period Specific Average (PSA) to a wide sample of EEGs. Both hypotheses can be rejected.
T.H. Bullock
M.C. McClune
J.T. Enright
2002-04-05Z
2011-03-11T08:54:55Z
http://cogprints.org/id/eprint/2164
This item is in the repository with the URL: http://cogprints.org/id/eprint/2164
2002-04-05Z
Human Pheromones: Integrating Neuroendocrinology and Ethology
The effect of sensory input on hormones is essential to any explanation of mammalian behavior, including aspects of physical attraction. The chemical signals we send have direct and developmental effects on hormone levels in other people. Since we don't know either if, or how, visual cues might have direct and developmental effects on hormone levels in other people, the biological basis for the development of visually perceived human physical attraction is currently somewhat questionable. In contrast, the biological basis for the development of physical attraction based on chemical signals is well detailed.
James V. Kohl
Michaela Atzmueller
Bernhard Fink
Karl Grammer
2001-08-15Z
2011-03-11T08:54:44Z
http://cogprints.org/id/eprint/1676
This item is in the repository with the URL: http://cogprints.org/id/eprint/1676
2001-08-15Z
Response Dynamics of Entorhinal Cortex in Awake, Anesthetized, and Bulbotomized Rats. <i>Brain Research</i> <b>911</b>(2)
The generation of oscillatory activity may be crucial to brain function. The coordination of individual neurons into rhythmic and coherently active populations is thought to result from interactions between excitatory and inhibitory cells mediated by local feedback connections. By using extracellular recording wires and silicon microprobes to measure electrically evoked damped oscillatory responses at the level of neural populations in the entorhinal cortex, and by using current-source density analysis to determine the spatial pattern of evoked responses, we show that the propagation of activity through the cortical circuit and consequent oscillations in the local field potential are dependent upon background neural activity. Pharmacological manipulations as well as surgical disconnection of the olfactory bulb serve to quell the background excitatory input incident to entorhinal cortex, resulting in evoked responses without characteristic oscillations and showing no signs of polysynaptic feedback. Electrical stimulation at 200 Hz applied to the lateral olfactory tract provides a substitute for the normal background activity emanating from the bulb and enables the generation of oscillatory responses once again. We conclude that a nonzero background level of activity is necessary and sufficient to sustain normal oscillatory responses and polysynaptic transmission through the entorhinal cortex.
Kurt F. Ahrens
Walter J. Freeman
2001-06-20Z
2011-03-11T08:54:43Z
http://cogprints.org/id/eprint/1634
This item is in the repository with the URL: http://cogprints.org/id/eprint/1634
2001-06-20Z
Functional Neuroanatomy of Dynamic Visuo-Spatial Imagery
The aim of this thesis was the examination of the neural bases of dynamic visuo-spatial imagery. In addition to the assessment of brain activity during dy-namic visuo-spatial imagery using single-trial functional magnetic resonance im-aging (fMRI) and slow cortical potentials (SCPs), several methodological issues have been investigated.
The theoretical part of this thesis consists of a selective overview of fMRI and SCPs, and of the advantages of their combination for functional neuroimaging (chapter 2). The methodological and empirical chapters include:
Ø the presentation of a new, highly accurate and practicable method for the co-registration of MRI- and EEG-data (chapter 3),
Ø the description of the increase in the accuracy of SCP mapping resulting from the use of individual electrode coordinates and realistic head models (chapter 4),
Ø the description of regional differences in the consistency of brain activity across several executions of the same task type, as assessed by a new analysis con-cept based on single-trial fMRI data (chapter 5),
Ø the demonstration of the involvement of premotor regions in dynamic visuo-spatial imagery, as assessed via a combination of single-trial fMRI and SCPs (chapter 6),
Ø the description of a combined fMRI-SCP investigation in which earlier findings concerning individual differences in neural efficiency during dynamic imagery could not be replicated (chapter 7).
Claus Lamm
2001-06-20Z
2011-03-11T08:54:43Z
http://cogprints.org/id/eprint/1633
This item is in the repository with the URL: http://cogprints.org/id/eprint/1633
2001-06-20Z
Direct Current Auditory Evoked Potentials During Wakefulness, Anesthesia, and Emergence from Anesthesia
Direct current auditory evoked potentials (DC-AEPs)
are a sensitive indicator of depth of anesthesia in ani-mals. However, they have never been investigated in
humans. To assess the potential usefulness of DC-AEPs
as an indicator of anesthesia in humans, we performed
an explorative study in which DC-AEPs were recorded
during propofol and methohexital anesthesia in hu-mans.
DC-AEPs were recorded via 22 scalp electrodes
in 19 volunteers randomly assigned to receive either
propofol or methohexital. DC-AEPs were evoked by
binaurally presented 2-s, 60-dB, 800-Hz tones; meas-urements
were taken during awake baseline, anesthesia,
and emergence. Statistical analysis included analy-sis
of variance and discriminant analysis of data
acquired during these three conditions. About 500 ms
after stimulus presentation, DC-AEPs could be ob-served.
These potentials were present only during base-line
and emergencenot during anesthesia. Statistically
significant differences were found between
baseline and anesthesia and between anesthesia and
emergence. In conclusion, similar effects, as reported in
animal studies of anesthetics on the DC-AEPs, could be
observed in anesthetized humans. These results dem-onstrate
that DC-AEPs are potentially useful in the assessment
of cortical function during anesthesia and
might qualify the method for monitoring anesthesia in
humans.
Robert Fitzgerald
Claus Lamm
Wolfgang Oczenski
Thomas Stimpfl
Walter Vycudilik
Herbert Bauer
2001-06-02Z
2011-03-11T08:54:39Z
http://cogprints.org/id/eprint/1536
This item is in the repository with the URL: http://cogprints.org/id/eprint/1536
2001-06-02Z
Losing the error related negativity (ERN): an indicator for willed action
When people make errors in a discrimination task, a negative-going waveform can be observed in scalp-recorded EEG that has been coined the error-related negativity (ERN). We hypothesized that the ERN only occurs with slips, that is unwilled action errors, but not if an error is committed willingly and intentionally. We investigated the occurrence of the ERN in a choice reaction time task that has been shown to produce an ERN and in an error simulation task where subjects had to fake errors while the EEG was recorded. We observed a loss of the ERN when errors were committed in willed actions but not in unwilled actions thus supporting the idea that the production of the ERN is tied to slips in unwilled actions but not mistakes in willed actions.
Brigitte Stemmer
Wolfgang Witzke
Paul Walter Schoenle
2002-01-29Z
2011-03-11T08:54:53Z
http://cogprints.org/id/eprint/2050
This item is in the repository with the URL: http://cogprints.org/id/eprint/2050
2002-01-29Z
Novelty-elicited mismatch negativity in patients with schizophrenia on admission and discharge
Introduction:
MMN, an electrophysiological measure of auditory working memory, is usually recorded as the difference in the event-related potential (ERP) elicited by a rare deviant and a common standard sound. The amplitude is usually reduced in patients with schizophrenia (refs below). Here we looked at the response in the extreme and most simple case of the deviant being always a novel, different tone on every presentation. We compared the novelty-MMN with clinical symptoms expressed - both measures being made soon after admission and again 2-3 months later just before discharge.
Methods:
We compared 20 patients (mean age 26y) with a first, second or third episode of schizophrenia on admission with 21 healthy controls (mean age 26y) and were able to repeat the measures with 12 patients at discharge and with 15 controls. An early MMN component (80-140 ms), a later component (140-300 ms) and the P3a were recorded and topography examined after min-max norming from 19 sites. Symptoms were assessed with the positive and negative syndrome scale (PANSS).
Results:
a) Novelty-elicited MMN was not significantly reduced on admission.
b) The early component remained unaltered, but the amplitude of the later component decreased significantly during inpatient treatment. While the decrease appeared significant over the left hemisphere in the raw data, the lateral difference was lost after normalizing the data.
c) Improved positive symptom ratings were associated with increases of the early component latency, but decreases of the late component latency.
d) P3a at Fz showed an increased latency between sessions in the patients but there were no group differences in amplitude.
Conclusions:
Our results are partially consistent with two other studies using a conventional MMN that showed a lack of MMN normalization where symptoms improved (Schall et al., 1998; Umbricht et al., 1998) - in the present study MMN deteriorated. While trait features have been attributed to conventional MMN reductions in schizophrenia, our results suggest that if novelty responses are impaired in patients with schizophrenia then the differences may be sensitive to state.
Grzella
Müller
Oades
Bender
Schall
Zerbin
Wolstein
Sartory
2000-05-09Z
2011-03-11T08:53:42Z
http://cogprints.org/id/eprint/143
This item is in the repository with the URL: http://cogprints.org/id/eprint/143
2000-05-09Z
Error detection and the Error-related ERP in patients with lesions involving the anterior cingulate and adjacent regions
Evidence indicates that the anterior cingulate region generates what appears to be a specific electrophysiological marker for the monitoring of error responses. When an auditory or visual stimulus is presented in such a way that the subject is likely to make an error, averaged encephalography (EEG) trials to erroneous responses consistently show a negative-going waveform which has been coined the error-related negativity (ERN). We examined ERNs in patients with a ruptured aneurysm of the anterior communicating artery (AACA), who are particularly prone to showing damage in the anterior cingulate and adjacent regions, and frequently display a variety of behavioral and cognitive disturbances such as disorientation, confabulation, apathy, unawareness of deficit, and problems of attention, control and monitoring. We found that these patients generally did not produce an ERN in comparison to healthy control participants suggesting that the anterior cingulate is essential for the ERN response. However, the patients' error rates were comparable to that of the controls and they showed a dissociation between overt error awareness and ERN production, suggesting that the ERN does not simply represent an error detection signal.
Brigitte Stemmer
Sidney J. Segalowitz
Wolfgang Witzke
Sieglinde Lacher
Paul Walter Schönle
2000-06-14Z
2011-03-11T08:53:42Z
http://cogprints.org/id/eprint/149
This item is in the repository with the URL: http://cogprints.org/id/eprint/149
2000-06-14Z
THE MIND AND BRAIN SCHOLAR AS A HITCH-HIKER IN POST-GUTENBERG GALAXY: PUBLISHING AT 2000 AND BEYOND
Electronic journal (e-journal) publishing has started to change the ways we think about publish-ing. However, many scholars and scientists in the mind and brain sciences are still ignorant of the new possibilities and on-going debates. This paper will provide a summary of the issues in-volved, give an update of the current discussion, and supply practical information on issues re-lated to e- journal publishing and self-archiving relevant for the mind and brain sciences. Issues such as differences between traditional and e-journal publishing, open archive initiatives, world-wide conventions, quality control, costs involved in e-journal publishing, and copyright questions will be addressed. Practical hints on how to self-archive, how to submit to the e-journal Psycolo-quy, how to create an open research archive, and where to find information relevant to e-publishing will be supplied.
Brigitte Stemmer
Marianne Corre
Yves Joanette
2000-05-13Z
2011-03-11T08:53:42Z
http://cogprints.org/id/eprint/147
This item is in the repository with the URL: http://cogprints.org/id/eprint/147
2000-05-13Z
The study of the regenesis of mind in the 21st century
The enigma of consciousness and the brain-mind relationship will - most likely - be unveiled in the 21st century through the new technologies developed at the end of the 20th century and new technologies yet to come. The new technologies will be used to tackle the problem from evolu-tionary, developmental, normal and pathological brain functioning. A major contribution, how-ever, will surface when investigating a particular perspective of pathological brain functioning - a perspective that has not received any attention in the past: the investigation of the re-emergence of mind out of prolonged coma and coma like states.
Paul Walter Schönle
Brigitte Stemmer
2000-02-04Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/138
This item is in the repository with the URL: http://cogprints.org/id/eprint/138
2000-02-04Z
Direct evidence for local oscillatory current sources and intracortical phase gradients in turtle visual cortex
Visual stimuli induce oscillations in the membrane potential of neurons in cortices of several species. In turtle, these oscillations take the form of linear and circular traveling waves. Such waves may be a consequence of a pacemaker that emits periodic pulses of excitation that propagate across a network of excitable neuro-nal tissue or may result from continuous and possibly reconfigu-rable phase shifts along a network with multiple weakly coupled neuronal oscillators. As a means to resolve the origin of wave propagation in turtle visual cortex, we performed simultaneous measurements of the local field potential at a series of depths throughout this cortex. Measurements along a single radial pen-etration revealed the presence of broadband current sources, with a center frequency near 20 Hz ( g band), that were activated by visual stimulation. The spectral coherence between sources at two well-separated loci along a rostral caudal axis revealed the pres-ence of systematic timing differences between localized cortical oscillators. These multiple oscillating current sources and their timing differences in a tangential plane are interpreted as the neuronal activity that underlies the wave motion revealed in previous imaging studies. The present data provide direct evidence for the inference from imaging of bidirectional wave motion that the stimulus-induced electrical waves in turtle visual cortex corre-spond to phase shifts in a network of coupled neuronal oscillators.
James C. Prechtl
T.H. Bullock
David. Kleinfeld
2000-05-12Z
2011-03-11T08:53:42Z
http://cogprints.org/id/eprint/144
This item is in the repository with the URL: http://cogprints.org/id/eprint/144
2000-05-12Z
The relation between movement parameters and motor learning.
In a recent paper, Flament et al (1999) studied the learning to flex the elbow fast. They concluded from their data that time-related parameters (e.g. movement time) changed faster during learning than magnitude-related parameters (e.g. peak velocity), and discussed this finding in terms of neural substrates responsible for the apparently different learning mechanisms. In this note, I will argue that finding different time constants does not imply different learning mechanisms. I will give a theoretical example of the development of parameters during learning to move faster. Despite the fact that I model only one learning process, various kinematic parameters show different time courses of learning. The differences the model predicts are comparable with the experimental results.
Jeroen B.J. Smeets
2000-12-01Z
2011-03-11T08:54:26Z
http://cogprints.org/id/eprint/1089
This item is in the repository with the URL: http://cogprints.org/id/eprint/1089
2000-12-01Z
Revisiting the Concept of Identifiable Neurons
Although eutely in nematodes was known, giant neurons in several taxa and unique motor neurons to leg muscles in decapod crustaceans, the idea that many animals have many identifiable neurons with relatively consistent dynamical properties and connections was only slowly established in the late 1960s and early 1970s. This has to be one of the important quiet revolutions in neurobiology. It stimulated a vast acquisition of specific information and led to some euphoria in the degree and pace of understanding activity of nervous systems and consequent behavior in terms of neuronal connections and properties. Some implications, problems and opportunities for new discovery are developed. The distribution of identifiable neurons among taxa and parts of the nervous system is not yet satisfactorily known. Their evolution may have been a case of several independent inventions. The degree of consistency has been quantified only in a few examples and the plasticity is little known. Identified neurons imply identifiable circuits but whether this extends to discrete systems, functionally definable, seems likely to have several answers in different animals or sites. Very limited attempts have been made to extend the concept to cases of two or ten or a hundred fully equivalent neurons, on all kinds of criteria. These attempts suggest a much smaller redundancy and vaster number of types of neurons than hitherto believed. Theory as well as empirical information has not yet interpreted the range of systems from those with small sets of relatively reliable neurons to those with large numbers of parallel, partially redundant units. The now classical notion of local circuits has to be extended to take account and find roles for the plethora of integrative variables, of evidence for neural processing independent of spikes and classical synapses, of spatial configurations of terminal arbors and dendritic geometry, of modulators and transmitters, degrees of rhythmicity (regularity varying several orders of magnitude), and of synchrony. Adequate language and models need to go beyond "circuits" in any engineering sense. Identifiable neurons can contribute to a broad spectrum of issues in neurobiology.
Theodore Bullock
2000-02-02Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/135
This item is in the repository with the URL: http://cogprints.org/id/eprint/135
2000-02-02Z
Incidences of asymmetries for the palmar grasp reflex in neonates and hand preference in adults
It was hypothesized that adult handedness might be predicted from the neonatal grasp reflex. Grasp reflex was measured from right and left hand (10 trials for each hand) in neonates. According to significance for the difference between the mean grasp reflex strength from the right and left hands, the subjects were designated as right-, left-, and mixed-handers. Adult hand preference was assessed by Edinburgh Handedness Inventory. The percentage of left-handedness (8.3%) in neonates coincided with adult left-handedness (6.3-9.2%). The percentage of consistent right-hand preference in adults coincided with percentage of right-handedness in neonates (25.7%). The high percentage of neonatal mixed-handedness was similar to that to be expected from the right shift model of hand preference. It was concluded that left-handedness and consistent right- handedness may be determined prenatally, under genetic and/or hormonal control, and that a large majority of neonatal handedness, mixed-handers, might change their hand preference in favor of right-handedness under socio-cultural and developmental influences of speech centres.
Uner Tan
Meliha Tan
1999-08-31Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/117
This item is in the repository with the URL: http://cogprints.org/id/eprint/117
1999-08-31Z
Differences in the ability to process a visuo-spatial task are reflected in event-related slow cortical potentials of human subjects.
Recent Positron Emission (PET) and EEG studies suggest that higher ability in a cognitive task is associated with a more efficient neuronal processing of this task. However, the validity and generalizability of these studies is limited for several reasons. We investigated 20 male and 18 female human subjects with good vs. poor spatial ability performing a visuo-spatial task (cube test). Processing-related slow event-related potentials were recorded via 22 electrodes, evenly distributed over the scalp. Significant differences between good and poor performers were found in both sexes: Poor subjects showed higher activity in the parietal region, and their topography was more extended into fronto-central regions. Since the amount and topography of brain activity may vary considerably depending on subjects' ability, we conclude that careful (experimental) control of task-specific ability of subjects is mandatory for cognitive neuroscience studies.
Claus Lamm
Herbert Bauer
Oliver Vitouch
Reinhard Gstättner
1999-04-28Z
2011-03-11T08:53:39Z
http://cogprints.org/id/eprint/83
This item is in the repository with the URL: http://cogprints.org/id/eprint/83
1999-04-28Z
The number of synaptic inputs and the synchrony of large sparse neuronal networks
The prevalence of coherent oscillations in various frequency ranges in the central nervous system raises the question of the mechanisms that synchronize large populations of neurons. We study synchronization in models of large networks of spiking neurons with random sparse connectivity. Synchrony occurs only when the average number of synapses, M that a cell receives is larger than a critical value, $M_c$. Below $M_c$, the system is in an asynchronous state. In the limit of weak coupling, assuming identical neurons, we reduce the model to a system of phase oscillators which are coupled via an effective interaction, $\Gamma$. In this framework, we develop an approximate theory for sparse networks of identical neurons to estimate $M_c$ analytically from the Fourier coefficients of $\Gamma$. Our approach relies on the assumption that the dynamics of a neuron depend mainly on the number of cells that are presynaptic to it. We apply this theory to compute $M_c$ for the integrate-and-fire (\IF) model as a function of the intrinsic neuronal properties (\eg the refractory period $T_r$), the synaptic time constants and the strength of the external stimulus, $\Iapp$. When the neurons are inhibitory, $M_c$ is found to be non-monotonous with the strength of $\Iapp$. For $T_r=0$, we estimate the minimum value of $M_c$ over all the parameters of the model to be $363.8$. Above $M_c$, the neurons tend to fire in: 1) smeared one cluster states at high firing rates and 2) smeared two or more cluster states at low firing rates. For excitatory interactions synchrony can be achieved only if the firing rate is not too high. However, our estimates of $M_c$ are, in general, much smaller than for inhibitory networks for similar level of activity. Above $M_c$ excitatory networks settle into smeared 1-cluster states.Refractoriness decreases $M_c$ at intermediate and high firing rates. These results are compared against numerical simulations. We show numerically that systems with different sizes, $N$, behave in the same way provided the connectivity, $M$, is such a way that $1/ \Meff = 1 / M - 1 / N$ remains constant when $N$ varies. This allows one to extrapolate the large $N$ behavior of a network from numerical simulations of networks of relatively small sizes ($N=800$ in our case). We find that our theory predicts with remarkable accuracy the value of $M_c$ and the patterns of synchrony above $M_c$, provided the synaptic coupling is not too large. We also study the strong coupling regime of inhibitory sparse networks. All of our simulations demonstrate that increasing the coupling strength reduces the level of synchrony of the neuronal activity. Above a critical coupling strength, the network activity is asynchronous. We point out that there is a fundamental limitation for the mechanisms of synchrony relying on inhibition alone, if heterogeneities in the intrinsic properties of the neurons and spatial fluctuations in the external input are also taken into account.
David Golomb
David Hansel
2000-07-10Z
2011-03-11T08:53:42Z
http://cogprints.org/id/eprint/152
This item is in the repository with the URL: http://cogprints.org/id/eprint/152
2000-07-10Z
Quantitative morphology of human hippocampus early neuron development
Background: Previous findings in adults revealed significant hemispheric asymmetry in size of neuronal somata in hippocampal subfield CA2 (the resistant sector) with no age-related changes. Paucity of quantitative data on the developmental status of these protected neurons has led to the investigation of their morphology in comparison to neurons in adjacent subfield CA3, bilaterally. Methods: Bilateral coronal sections from postmortem hippocampus, 24 and 76 weeks postmenstrual age (gestational age plus postnatal age) were studied. The neurons were digitized and measured on a computer. Results: Soma size correlated positively and significantly with age in CA2 and CA3, bilaterally. CA2 somata were significantly larger (left 34%, right 32%) than adjacent CA3 somata. Variability in soma form or size increased appreciably with age, in both subfields, bilaterally, while variability in soma orientation was weakly correlated with brain growth. Conclusions: The results suggest that in early development there are similarities in hemispheric growth patterns in CA2 and CA3. Large CA2 soma size implies axonal connectivity to distantly located targets very early in development. The results have functional implications, including memory, to brain development
Dahlia W. Zaidel
1999-08-23Z
2011-03-11T08:53:40Z
http://cogprints.org/id/eprint/115
This item is in the repository with the URL: http://cogprints.org/id/eprint/115
1999-08-23Z
Correlations and the encoding of information in the nervous system
Is the information transmitted by an ensemble of neurons determined solely by the number of spikes fired by each cell, or do correlations in the emission of action potentials also play a significant role? We derive a simple formula which enables this question to be answered rigorously for short timescales. The formula quantifies the corrections to the instantaneous information rate which result from correlations in spike emission between pairs of neurons. The mutual information that the ensemble of neurons conveys about external stimuli can thus be broken down into firing rate and correlation components. This analysis provides fundamental constraints upon the nature of information coding - showing that over short timescales, correlations cannot dominate information representation, that stimulus-independent correlations may lead to synergy (where the neurons together convey more information than they would considered independently), but that only certain combinations of the different sources of correlation result in significant synergy rather than in redundancy or in negligible effects. This analysis leads to a new quantification procedure which is directly applicable to simultaneous multiple neuron recordings.
S. Panzeri
S. R. Schultz
A. Treves
E. T. Rolls
1999-07-14Z
2011-03-11T08:53:40Z
http://cogprints.org/id/eprint/106
This item is in the repository with the URL: http://cogprints.org/id/eprint/106
1999-07-14Z
The Future of Research on Electroreception and Electrocommunication.
Besides the rounding out of presently active areas, six are selected for predictions of marked advance. (1) Most discoveries will be in cellular componentry and molecular mechanisms for one or another class of receptors or central pathways. (2) More major taxa will be found with electroreceptive species, possibly birds, reptiles or invertebrates, representing independent evolutionary "inventions". (3) Electric organs with weak and episodic electric discharges will be found in new taxa; first, among siluriforms. (4) New examples are expected, like lampreys, where synchronized muscle action potentials add up to voltages in the range of weakly electric fish. Some of these will look like intermediates in the evolution of electric organs. (5) Ethological significance will be found for a variety of known physiological features. Exs.: uranoscopids, skates and weakly electric catfish with episodic electric discharges of unknown role; electroreceptive ability of some of the diverse group having Lorenzinian-type ampullae (besides elasmobranchs) including lampreys, chimaeras, lungfish, sturgeons, paddlefish, and salamanders; gymnotiform and mormyrid detection of capacitive component of impedance. (6) The organization of some higher functions in the cerebellum and forebrain will gradually come to light.
Theodore H. Bullock
2000-01-21Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/128
This item is in the repository with the URL: http://cogprints.org/id/eprint/128
2000-01-21Z
Neuroethology has pregnant agendas
Two of the many agendas of neuroethology are illustrated with examples. (1) What cells or assemblies of cells and what patterns of activity are sufficient to accomplish recognition of ethologically important stimulus configurations and initiation of behavioral action? The theme is the opportunities available in relatively neglected approaches to these objectives. As an example, the approach is developed of gentle microstimulation of loci in the brain where cells have been found responsive to complex, natural stimuli, under conditions conducive to the performance of tell-tale behavior. Other approaches include (a) microinjection of modulatory substances into regions with such complex recognition cells and (b) recording in efficient and informative ways, by using multiple electrode arrays, recording wideband activity, in behaving animals. (2) What brain and behavior differences has evolution produced between major taxa at distinct grades of complexity? Emphasized are our relative ignorance of basic aspects of connectivity, physiology and cognitive capacities in the major grades and the probability of surprises from new studies that employ comparison.
T.H. Bullock
1998-10-19Z
2011-03-11T08:53:39Z
http://cogprints.org/id/eprint/66
This item is in the repository with the URL: http://cogprints.org/id/eprint/66
1998-10-19Z
A new view on grasping
Reaching out for an object is often described as consisting of two components that are based on different visual information. Information about the objects position and orientation guides the hand to the object, while information about the objects shape and size determines how the fingers move relative to the thumb to grasp it. We propose an alternative description, which consists of determining suitable positions on the object on the basis of its shape, surface roughness, and so on and then moving ones thumb and fingers more or less independently to these positions. We modelled this description using a minimum jerk approach, whereby the finger and thumb approach their respective target positions approximately orthogonally to the surface. Our model predicts how experimental variables such as object size, movement speed, fragility, and required accuracy will influence the timing and size of the maximum aperture of the hand. An extensive review of experimental studies on grasping showed that the predicted influences correspond to human behaviour.
Jeroen B.J. Smeets
Eli Brenner
2000-02-02Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/136
This item is in the repository with the URL: http://cogprints.org/id/eprint/136
2000-02-02Z
Power spectra of ongoing activity of the snail brain can discriminate odorants
To test the hypothesis that different odorants are likely to cause distinctive changes in the ongoing electrical activity of populations of olfactory cells, we investigated field potentials (FP) in the Helix brain and their alterations by odorants as seen by semimicroelectrodes in an isolated preparation of the rostrum with ist olfactory organ and whole central nervous system. Five pure chemicals and two natural odorants were applied as stimulants. Signals recorded both from the procerebrum (PC) and the visceral ganglion (VG) were analyzed. In the PC the five pure chemical odorants induce stimulus-specific characteristic responses, mainly in the low frequency range (<15 Hz). Regardless of odor intensity, the frequency of the peak power of sustained induced activity is constant for each chemical: ammonia at 0.2 ( <0.02 Hz; formic acid at 0.36 ( 0.03 Hz; 2-pentanol at 0.48 ( 0.04 Hz; 2-butanol at 0.67 ( 0.03 Hz; ethanol at 1.31 ( 0.09 Hz (means ( 95% confidence limits). These peak power frequencies, which we define as (odor-specific frequencies(, are confined to the low frequency range of < 2.5 Hz. Those of natural odorants are: onion (0.36 ( 0.14 Hz) and apple (1.1 ( 0.25 Hz). The activities evoked in the PC propagate to VG. The order of behavioral aversion determined by withdrawal reactions of the tentacles, 1% ammonia > formic acid > 2-pentanol > 2-butanol > ethanol, coincides with (the order of molecular affinity( as well as with the sequence of peak power frequencies. There seems to be a strong correlation among behavioral valence, chemical nature of an odorant, and odor-specific frequency. The finding that, in the Helix olfactory center, odor input is processed as odorant specific low frequency FP activity may represent some general phenomena of olfactory information processing.
A. Schutt
E. Basar
T.H. Bullock
2000-02-02Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/137
This item is in the repository with the URL: http://cogprints.org/id/eprint/137
2000-02-02Z
Slow potentials in the brain: still little understood but gradually getting analytical attention
Two classes of electrical activity in the central nervous system have been known for a long time: spikes with synaptic potentials and "slow" fluctuations (components mainly below ca. 100 Hz). Their relations to each other are still little known and an unfortunate schism persists in mutual disparagement by investigators who chiefly study one class or the other. The news I wish to highlight is that this schism is waning and this essay will be outmoded as more workers study both. I focus here on the class of slow potentials which in certain respects is the more neglected. This class should extend down into the less-known "infraslow" domain (power mainly below 0.1 Hz) - omnipresent, higher in amplitude and clearly significant functionally.
T.H. Bullock
2000-02-09Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/139
This item is in the repository with the URL: http://cogprints.org/id/eprint/139
2000-02-09Z
The theory of the organism-environment system: III. Role of efferent influences on receptors in the formation of knowledge.
The present article is an attempt to give - in the frame of the theory of the organism-environment system (Jarvilehto 1998a) - a new interpretation to the role of efferent influences on receptor activity and to the functions of senses in the formation of knowledge. It is argued, on the basis of experimental evidence and theoretical considerations, that the senses are not transmitters of environmental information, but they create a direct connection between the organism and the environment, which makes the development of a dynamic living system, the organism-environment system, possible. In this connection process the efferent influences on receptor activity are of particular significance, because with their help the receptors may be adjusted in relation to the parts of the environment which are most important in the achievement of behavioral results. Perception is the process of joining of new parts of the environment to the organism-environment system; thus, the formation of knowledge by perception is based on reorganization (widening and differentiation) of the organism-environment system, and not on transmission of information from the environment. With the help of the efferent influences on receptors each organism creates its own peculiar world which is simultaneously subjective and objective. The present considerations have far reaching influences as well on experimental work in neurophysiology and psychology of perception as on philosophical considerations of knowledge formation.
Timo Jarvilehto
1998-10-12Z
2011-03-11T08:53:39Z
http://cogprints.org/id/eprint/64
This item is in the repository with the URL: http://cogprints.org/id/eprint/64
1998-10-12Z
Event-related alpha oscillations are functionally associated with P300 during information processing
Recent findings indicate that the electroencephalographic alpha (7-14 Hz) activity is functionally involved in cognitive brain functioning, but the issue of whether and how event-related alpha oscillations may relate to the processes indexed by the P300 component of the event-related brain potentials (ERPs) has not been addressed. The present study assessed the effect of auditory oddball task processing on slow (7-10 Hz) and fast (10-14 Hz) alpha activity from the P300 latency range. ERPs from mentally counted targets (20%) and not counted nontargets (80 %) were recorded at Fz, Cz, and Pz in nine subjects. Single-sweep phase-locking, power of phase-locked, and power of non-phase-locked alpha responses during P300 activity were quantified. The results demonstrated that larger and more synchronized phase-locked fast alpha components at anterior (frontal-central) locations, with reduced non-phase-locked slow alpha responses at the parietal site were produced by targets relative to nontargets. Because the simultaneously recorded P300 and alpha activity manifested a similar sensitivity to the oddball task, event-related alpha appears to be functionally associated with the cognitive processing demands eliciting P300. Also, evidence is provided for the functional involvement of frontally synchronized and enhanced alpha oscillations in task processing. NeuroReport 9: 3159-3164 © 1998 Lippincott Williams & Wilkins
Juliana Yordanova
Vasil Kolev
1999-07-23Z
2011-03-11T08:53:40Z
http://cogprints.org/id/eprint/112
This item is in the repository with the URL: http://cogprints.org/id/eprint/112
1999-07-23Z
Sensory processing in the pallium of a mormyrid fish
To investigate the functional organization of higher brain levels in fish we test the hypothesis that the dorsal gray mantle of the telencephalon of a mormyrid fish has discrete receptive areas for several sensory modalities. Multiunit and compound field potentials evoked by auditory, visual, electrosensory and water displacement stimuli in this weakly electric fish are recorded with multiple semimicroelectrodes placed in many tracks and depths in or near area dorsalis telencephali, pars medialis (Dm). Most responsive loci are unimodal; some respond to two or more modalities. Each modality dominates a circumscribed area, chiefly separate. Auditory and electrical responses cluster in the dorsal 500 m of rostral and caudolateral Dm, respectively. Two auditory subdivisions underline specialization of this sense. Mechanoreception occupies a caudal area overlapping electroreception but centered 500 m deeper. Visual responses scatter widely through ventral areas. Auditory, electrosensory and mechanosensory responses are dominated by a negative wave within the first 50 ms, followed by 15-55 Hz oscillations and a slow positive wave with multiunit spikes lasting from 200-500 ms. Stimuli can induce shifts in coherence of certain frequency bands between neighboring loci. Every electric organ discharge command is followed within 3 ms by a large, mainly negative but generally biphasic, widespread corollary discharge. At certain loci large, slow ("delta F") waves usually precede transient shifts in electric organ discharge rate. Sensory evoked potentials in this fish pallium may be more segregated than in elasmobranchs and anurans and have some surprising similarities to those in mammals. Key Words: cerebral cortex; corollary discharge; induced rhythms; evoked potential; gamma band; lateral line; mormyrid.
James C. Prechtl
Gerhard von der Emde
Jakob Wolfart
Saçit Karamürsel
George N. Akoev
Yuri N. Andrianov
Theodore H. Bullock
1998-08-06Z
2011-03-11T08:53:38Z
http://cogprints.org/id/eprint/57
This item is in the repository with the URL: http://cogprints.org/id/eprint/57
1998-08-06Z
From Neurons to Brain: Adaptive Self-Wiring of Neurons
During embryonic morpho-genesis, a collection of individual neurons turns into a functioning network with unique capabilities. Only recently has this most staggering example of emergent process in the natural world, began to be studied. Here we propose a navigational strategy for neurites growth cones, based on sophisticated chemical signaling. We further propose that the embryonic environment (the neurons and the glia cells) acts as an excitable media in which concentric and spiral chemical waves are formed. Together with the navigation strategy, the chemical waves provide a mechanism for communication, regulation, and control required for the adaptive self-wiring of neurons.
Ronen Segev
Eshel Ben-Jacob
1999-07-06Z
2011-03-11T08:53:40Z
http://cogprints.org/id/eprint/105
This item is in the repository with the URL: http://cogprints.org/id/eprint/105
1999-07-06Z
Submicrosecond pacemaker precision is behaviorally modulated: The gymnotiform electromotor pathway
What are the limits and modulators of neural precision? We address this question in the most regular biological oscillator known, the electric organ command in the brainstem of wave-type electric fish. The oscillating electric organ discharge (EOD), used in electrolocation and communication, has high regularity measured by a low coefficient of variation (CV as low as 2 x 10-4) in five species from three families ranging in mean EOD from 70 to 1250 Hz. Intracellular recording in the nucleus (Pn) pacing EODs reveals that individual Pn neurons also display an extremely low CV. While the CV can remain at its minimum for hours, it varies with novel environmental conditions, during communication, and spontaneously. Spontaneous changes occur as abrupt steps (250 msec), oscillations (35 Hz), or slow ramps (1030 sec). Several findings suggest that these changes are under active control and depend on behavioral state. Mean EOD frequency and CV can change independently. CV often decreases in response to stimuli. Lesions of one of the two inputs to the Pn had more influence on CV than lesions of the other input
Katherine T. Moortgat
Clifford H. Keller
Theodore H. Bullock
Terrence J. Sejnowski
1998-10-20Z
2011-03-11T08:53:51Z
http://cogprints.org/id/eprint/365
This item is in the repository with the URL: http://cogprints.org/id/eprint/365
1998-10-20Z
THE THEORY OF THE ORGANISM-ENVIRONMENT SYSTEM: II. SIGNIFICANCE OF NERVOUS ACTIVITY IN THE ORGANISM-ENVIRONMENT SYSTEM
The relation between mental processes and brain activity is studied from the point of view of the theory of the organism-environment system. It is argued that the systemic point of view leads to a new kind of definition of the primary tasks of neurophysiology and to a new understanding of the traditional neurophysiological concepts. Neurophysiology is restored to its place as a part of biology: its task is the study of neurons as living units, not as computer chips. Neurons are living units which are organised as metabolic systems in connection with other neurons; they are not units which would carry out some psychological functions or maintain states which are typical only of the whole organism-environment system. Psychological processes, on the other hand, are processes always comprising the whole organism-environment system.
Timo Jarvilehto
1998-06-18Z
2011-03-11T08:53:38Z
http://cogprints.org/id/eprint/45
This item is in the repository with the URL: http://cogprints.org/id/eprint/45
1998-06-18Z
A single sweep analysis of the theta frequency band during auditory oddball task
The P300 component and the oscillatory 47 Hz electroencephalographic activity of auditory event-related brain potentials (ERPs) were assessed to study differences between passive and oddball task conditions. Theta responses from 15 adults were analyzed for single-sweep amplitude, phase-locking, and enhancement against prestimulus activity. ERPs were characterized by enhanced and strongly phase-locked theta oscillations in the early (0300 ms) post-stimulus epoch, with only the late (300600 ms) theta responses at Fz and Pz affected by the oddball condition. P300 was strongly associated not only with the concurrent theta oscillations but also with the evoked theta activity preceding P300 (0300 ms). It is concluded that single theta response parameters can reveal specific functional differences between passive and oddball conditions, and there is a strong relationship between the theta frequency component and the time-domain P300 ERP component.
Juliana Yordanova
Vasil Kolev
2005-02-16Z
2011-03-11T08:55:51Z
http://cogprints.org/id/eprint/4095
This item is in the repository with the URL: http://cogprints.org/id/eprint/4095
2005-02-16Z
Activation of G protein-coupled receptors entails cysteine modulation of agonist binding
The increase of the affinity of agonists with an increase in pH and experiments using thiol-specific reagents indicate that G protein-coupled receptors contain an ionizable cysteine residue at the ligand binding site. Since treatment of receptors with reducing agents produces functional activation and potentiates agonist stimulation, it is likely that this free sulfhydryl modulates receptor activation. We have derived a two-state acid-base model for cysteine modulation of ligand binding which leads to a description of ligand efficacy. We have shown that pH-dependent binding of agonists is closely correlated with measurements of ligand efficacy at the 5-HT2A receptor. In general, efficacy is determined by the preference of a ligand for the base of the receptor. Efficacy may also be described in thermodynamic terms as the coupling free energy involving a ligand and the acid and base states of the receptor. Molecular modeling of the third transmembrane domain of the 5-HT2A receptor, which contains a conserved cysteine, shows that efficacy is determined by the difference between the electrostatic interaction energies of a ligand with the acid and base forms of the receptor model. The difference in interaction energy between the two forms of cysteine makes the largest contribution to this electrostatic interaction energy difference. Therefore, the cysteine makes the largest contribution to ligand efficacy. Using this approach, we can distinquish between the efficacies of agonists with varying molecular structures and account for the differences between the properties of agonists and antagonists.
Lester A. Rubenstein
Richard G. Lanzara
1998-03-16Z
2011-03-11T08:53:36Z
http://cogprints.org/id/eprint/5
This item is in the repository with the URL: http://cogprints.org/id/eprint/5
1998-03-16Z
Discovering Structure From Motion In Monkey, Man And Machine
The ability to obtain three-dimensional structure from visual motion is important for survival of human and non-human primates. Using a parallel processing model, the current work explores how the biological visual system might solve this problem and how the neurophysiologist might go about understanding the solution.
Ralph M Siegel
1999-07-14Z
2011-03-11T08:53:40Z
http://cogprints.org/id/eprint/107
This item is in the repository with the URL: http://cogprints.org/id/eprint/107
1999-07-14Z
Forays with the additive periodogram applied to the EEG.
The most information-rich measure of the working brain is the electrical activity, recorded as wideband, extracellular local field potentials from multiple sites, in extent and depth, with millisecond and millimeter resolution. We still lack a common view of the electrical activity in terms of simple description - which must precede explanation in terms of mechanisms. The situation is much like the diverse views on the nature and characteristics of a jungle. We have elsewhere addressed related questions. (i) How much of the wideband activity is stochastic - concluding that a significant and highly labile amount of coherence and bicoherence bespeak temporal fine structure and cooperativity. (ii) How much fine structure is spatial, concluding that differentiation increases as the volume sampled is smaller (Bullock et al. 1995a,b, 1997).
T.H. Bullock
J.T. Enright
K.M. Chong
2001-03-30Z
2011-03-11T08:54:36Z
http://cogprints.org/id/eprint/1420
This item is in the repository with the URL: http://cogprints.org/id/eprint/1420
2001-03-30Z
Frontal, temporal and lateralized brain function in children with attention-defiocit hyperactivity disorder: a psychophysiological and neuropsychological viewpoint on development
Introduction: This review considers deficits in the selective aspects of perception (i.e. attention) underlying symptoms of impaired attention and impulsivity in children with attention-deficit hyperactivity syndrome (ADHD) in terms of frontal and temporal lobe function and cerebral asymmetry.
Review: Tomographic studies suggest a disturbance of fronto-striatal function, but have neglected limbic contributions under activating conditions and are contradictory or equivocal on the nature of apparent lateralised differences of structure.
Functional neuropsychological (e.g. go/no-go and covert orienting of attention tasks) and psychophysiological studies (e.g. event-related potentials and mismatch negativity [1]) suggest that early and late stages of information processing are affected in both the frontal and temporal lobes.
Performance differences in young ADHD patients imply an impairment in the inter-cortical dialogue. Given the evidence for a normal specialisation in global processing in the right and the processing of details in the left hemisphere, the lateralised impairment may progress from situational ADHD (resulting in impaired selective aspects of perception on the right) to pervasive ADHD (inducing an additional impairment in decision making on the left: compare risk taking).
Conclusions: Accordingly a proportion of ADHD children may experience an early negative neurodevelopmental influence that only appears as the brain region matures (especially around 8-12 years of age) while others show an independent, longer term, delayed development of CNS function.
R.D. Oades
1998-06-18Z
2011-03-11T08:53:38Z
http://cogprints.org/id/eprint/46
This item is in the repository with the URL: http://cogprints.org/id/eprint/46
1998-06-18Z
Measuring the dynamics of neural responses in primary auditory cortex
We review recent developments in the measurement of the dynamics of the response properties of auditory cortical neurons to broadband sounds, which is closely related to the perception of timbre. The emphasis is on a method that characterizes the spectro-temporal properties of single neurons to dynamic, broadband sounds, akin to the drifting gratings used in vision. The method treats the spectral and temporal aspects of the response on an equal footing.
Didier A. Depireux
Jonathan Z. Simon
Shihab A. Shamma
1998-08-25Z
2011-03-11T08:53:38Z
http://cogprints.org/id/eprint/61
This item is in the repository with the URL: http://cogprints.org/id/eprint/61
1998-08-25Z
SIMULATION IN NEUROBIOLOGY -- THEORY OR EXPERIMENT?
Investigation in neurophysiology usually involves measurements of large population average signals or small sample recordings. There is an underlying assumption that the observations express activity of large groups of similarly acting neurons that is the result of a bottom-up scenario in which individual cells, via their synaptic interactions, lead to the large scale phenomena. The connection between the levels must be provided by theory, which must also provide the relevant variables to observe. It is suggested that between the experiment and the full theory there is a creative, mixed role for simulation: both experimental and theoretical. A simulation presents complex dynamics and hence is an empirical board for testing theoretical tools, yet its controlled behavior can make predictions about the biological system.
Daniel J. Amit
2000-05-18Z
2011-03-11T08:53:42Z
http://cogprints.org/id/eprint/148
This item is in the repository with the URL: http://cogprints.org/id/eprint/148
2000-05-18Z
Visuomotor delays when hitting running spiders.
In general, information about the environment (for instance a target) is not instantaneously available for the nervous system. A minimal delay for visual information to affect the movement of the hand is about 110 ms. However, if the movement of a target is predictable, humans can pursue it with zero delay. To make this prediction, information about the speed of the target is necessary. Our results show that this information is used with a delay of about 200 ms. We discuss that oculomotor efference is a likely source of information for this prediction.
Jeroen B.J. Smeets
Eli Brenner
Marc H.E. de Lussanet
2000-05-12Z
2011-03-11T08:54:20Z
http://cogprints.org/id/eprint/852
This item is in the repository with the URL: http://cogprints.org/id/eprint/852
2000-05-12Z
Visuomotor delays when hitting running spiders.
In general, information about the environment (for instance a target) is not instantaneously available for the nervous system. A minimal delay for visual information to affect the movement of the hand is about 110 ms. However, if the movement of a target is predictable, humans can pursue it with zero delay. To make this prediction, information about the speed of the target is necessary. Our results show that this information is used with a delay of about 200 ms. We discuss that oculomotor efference is a likely source of information for this prediction.
Jeroen B.J. Smeets
Eli Brenner
Marc H.E. de Lussanet
1998-06-22Z
2011-03-11T08:53:38Z
http://cogprints.org/id/eprint/49
This item is in the repository with the URL: http://cogprints.org/id/eprint/49
1998-06-22Z
The Phase-Locking of Auditory Gamma Band Responses in Humans is Sensitive to Task Processing
The present study assessed the effects of stimulus task-relevance and certainty on early and late 40 Hz (gamma band) responses (GBRs) in humans. Auditory GBRs of nine young adults were recorded in passive listening, simple reaction task, and choice-reaction task (target probability = 0.5) conditions and evaluated in three consecutive post-stimulus periods (0-120, 120-250, 250-400 ms) corresponding to the serial occurrence of gamma oscillation bursts. Amplitude and phase-locking of GBRs within these bursts were analyzed separately at the level of single sweeps by applying a method that allows the independent quantification of between-sweep synchronization. Major results showed that the effects of stimulus certainty and task-relevance on single-response amplitude were specific and different from the effects on the phase-locking. Also, the functional involvement of the early and late auditory gamma responses was distinct: early auditory gamma band responses appear primarily associated with focused attention, while the late gamma responses vary with motor-task relevance. It is concluded that along with power measures, the stability of phase-locking of gamma band responses should be regarded as a functionally meaningful parameter that varies with processing demands and recording site.
Juliana Yordanova
Vasil Kolev
Demiralp Tamer
1998-08-04Z
2011-03-11T08:53:38Z
http://cogprints.org/id/eprint/55
This item is in the repository with the URL: http://cogprints.org/id/eprint/55
1998-08-04Z
Developmental changes in the event-related EEG theta response and P300
Event-related potentials (ERPs) from 50 children (6 to 11 years) and ten adults were elicited by auditory passive, and by rare target and frequent nontarget stimuli, and analyzed in the time and frequency domains. The latency of the maximal theta response (or the theta frequency component of the ERP) was evaluated with respect to age and scalp topography effects. The major findings were: (1) The latency of the maximal theta response decreased with increasing age in children, although for each stimulus type and location adults had shorter latencies than the children. (2) The developmental time course of latency reduction depended on the electrode location, with the most prominent reduction occurring at 8 years at Cz, and no differences between children groups obtained for the frontal site. (3) Maximal theta response latency was strongly associated with the latency of the late parietal P400-700 (P3b) component in children. The results suggest that the developmental latency decrease in P300 processes originate from a decrease in the preceding theta-related processes and may reflect a speeding of cognitive stimulus evaluation.
Juliana Yordanova
Vasil Kolev
1998-06-22Z
2011-03-11T08:53:38Z
http://cogprints.org/id/eprint/48
This item is in the repository with the URL: http://cogprints.org/id/eprint/48
1998-06-22Z
Time-Frequency Analysis Reveals Multiple Functional Components During Oddball P300
A time-frequency decomposition was applied to rare target and frequent non-target event-related potentials (ERPs) elicited in an oddball condition to assess whether multiple functional components occur in the P300 latency range. The wavelet transform (WT) was used because it allows capture of simultaneous or partly overlapping components in ERPs without loosing their temporal relationships. The application of a four-octave quadratic B-spline wavelet transform at the level of single-sweep data allowed us to obtain new information and revealed the presence of separate events during P300 development. Several delta, theta, and alpha frequency components in the P300 latency range differed between target and non-target processing. These findings indicate that P300 is composed of multiple functional components and that the WT method is of use for the study of P300 functional correlates more precisely.
Vasil Kolev
Tamer Demiralp
Juliana Yordanova
Ahmet Ademoglu
Ümmühan Isoglu-Alkaç
1999-10-27Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/122
This item is in the repository with the URL: http://cogprints.org/id/eprint/122
1999-10-27Z
Bicoherence of intracranial EEG in sleep, wakefulness and seizures
The hypothesis that the intracranial EEG has local structure and short-term non-stationarity is tested with a little-studied measure of nonlinear phase coupling, the bicoherence in human subdural and deep temporal lobe probe data from 11 subjects during sleeping, waking and seizure states. This measure of cooperativity estimates the proportion of energy in every possible pair of frequency components, F1, F2 (from 1-50 Hz in this study), that satisfies the definition of quadratic phase coupling (phase of component at F3 , which is F1+F2, equals phase of F1 + phase of F2). Derived from the bispectrum, which segregates the nonGaussian energy, auto-bicoherence uses the frequency components in one channel; cross-bicoherence uses one channel for F1 and F2 and another for F3. These higher order spectra are used in physical systems for detection of episodes of nonlinearity and transients, for pattern recognition and robust classification, relatively immune to Gaussian components and low signal to noise ratios. Bicoherence is found not to be a fixed character of the EEG but quite local and unstable, in agreement with the hypothesis. Bicoherence can be quite different in adjacent segments as brief as 1.6 s as well as adjacent intracranial electrodes as close as 6.5 mm, even when the EEG looks similar. It can rise or fall steeply within millimeters. It is virtually absent in many analysis epochs of 17s duration. Other epochs show significant bicoherence with diverse form and distribution over the bifrequency plane. Isolated peaks, periodic peaks or rounded mountain ranges are either widely scattered or confined to one or a few parts of the plane. Bicoherence is generally an invisible feature: one cannot usually recognize the responsible form of nonlinearity or any obvious correlate in the raw EEG. During stage II/III sleep overall mean bicoherence is generally higher than in the waking state. During seizures the diverse EEG patterns average a significant elevation in bicoherence but have a wide variance. Maximum bispectrum, maximum power spectrum, maximum and mean bicoherence, skewness and asymmetry all vary independently of each other. Cross-bicoherence is often intermediate between the two auto-bicoherence spectra but commonly resembles one of the two. Of the known factors that contribute to bicoherence, transient as distinct from ongoing wave forms can be more important in our data sets. This measure of nonlinear higher moments is very sensitive to weak quadratic phase coupling,; this can come from several kinds of waveforms. New methods are needed to evaluate their respective contributions. Utility of this descriptor cannot be claimed before more carefully defined and repeatable brain states are studied.
T.H. Bullock
J.Z. Achimowicz
R.B. Duckrow
S.S. Spencer
V.J. Iragui-Madoz
1999-07-15Z
2011-03-11T08:53:40Z
http://cogprints.org/id/eprint/108
This item is in the repository with the URL: http://cogprints.org/id/eprint/108
1999-07-15Z
Comparative Physiology of Acoustic and Allied Central Analyzers
To exploit comparisons among classes of vertebrates and invertebrates, and between higher and lower levels of the brain, and between modalities, some important needs and opportunities for new research into the way central processing of acoustic input takes place are pointed out. Most of these are suggested by unfamiliar results on fish and reptiles that call for new controls in mammalian experiments as well as more systematic study of nonmammalian taxa. Three frameworks or basic agendas are outlined: (i) systematic comparison of dynamical properties to acoustic variables, including especially repetition at different rates and the related states of expectation; (ii) comparison of response measures, including especially sequences such as oscillations and measures of assembly cooperativity such as synchrony, coherence and bicoherence; and (iii) comparison of auditory subsystems, including especially modal categories such as complex feature selective regions and small sets.
Theodore H. Bullock
2000-12-08Z
2011-03-11T08:54:27Z
http://cogprints.org/id/eprint/1144
This item is in the repository with the URL: http://cogprints.org/id/eprint/1144
2000-12-08Z
Development and topography of auditory event-related potentials (ERPs): Mismatch and processing negativity in individuals 8-22 years of age
Introduction: How do ERPs reflecting auditory information processing develop across adolescence? This development is described for the amplitude and latency of five ERP components and four difference-waves in four groups of 11 healthy subjects with mean ages of 10, 14, 17 & 21 years.
Methods: Vector normalised data were recorded from 19 sites during diffuse and focused attention in a three-tone oddball. (i.e. in passive, diffuse-attention and active, focussed-attention, discrimination conditions) to see how ERP loci varied with age for tone-type, attention-condition and for four types of difference-wave reflecting nontarget and target comparisons: (mismatch negativity, MMN, an auditory working memory trace; Negative difference, Nd, an attentional trace, but also Processing Negativity, PN and the Goodin-waveform).
Results: Age interacted with site for most components. P1 loci sensitive to rare tones moved posteriorly and N1 loci lost their right bias at early puberty. But P2 loci did not move anterior to Cz until adulthood. N2 amplitude, sensitive to attention condition, developed a mature frontal focus by 17 years. Right-biased P3 loci move to the midline with focused attention in young and old alike.
Difference-waves reflected three developmental stages (figure 2): In 10 year-olds early deflections (<150 ms) were diffusely distributed; in mid-adolescence the main frontal negative component (150-300 ms) became well-formed and lost an earlier right bias; over 17 years the late positive complex developed a right bias in target-derived waves. Latency decreases for early frontal components were marked in 10-14y olds and for later posterior components in 14-17y olds. MMN topography matured (from a right lateral to bilateral distribution) between 10 and 14 y, while Nd topography matured and became bilateral between 14 and 17y.
Conclusions: Major developments of brain function appear at the onset of adolescence (<14y) in early stimulus-selection processes and during adolescence in the differential use of this information (N2- and P3-like latencies.
Robert D. OADES
Alexandra DITTMANN-BALCAR
Dieter ZERBIN
1998-08-03Z
2011-03-11T08:53:38Z
http://cogprints.org/id/eprint/54
This item is in the repository with the URL: http://cogprints.org/id/eprint/54
1998-08-03Z
Developmental changes in the theta response system: a single-sweep analysis
Recently, increased interest was focused on the EEG frequency responses in the theta (4-7 Hz) range because of their association with stimulus information processing. However, it is not known whether the event-related theta response depends on the development of the spontaneous theta activity and how it varies with age in children. In the present study, a single-sweep analysis was applied to assess the developmental changes in the event-related EEG theta activity. Auditory passive, oddball target, and standard event-related potentials (ERPs) were recorded at Fz, Cz, and Pz from 50 children aged 6-11 years and 10 young adults. Theta responses were analyzed in two time windows of the post-stimulus epochs for three single-sweep parameters: amplitude, phase-locking with stimulus, and enhancement relative to prestimulus activity. For all three types of stimuli adults had theta responses with lower amplitude, higher enhancement, and stronger phase-locking than those of children. Unlike adults, no reliable differences between the early and late theta response were found for children. Significant developmental changes were observed for theta response amplitude that decreased and phase-locking of early theta responses that increased with advancing age. These findings indicate that the theta component of the auditory ERP differs remarkably between children and adults and undergoes developmental alterations, possibly reflecting specific differences in stimulus information processing.
Juliana Yordanova
Vasil Kolev
1999-04-22Z
2011-03-11T08:54:17Z
http://cogprints.org/id/eprint/803
This item is in the repository with the URL: http://cogprints.org/id/eprint/803
1999-04-22Z
The influence of affective factors on time perception
Several studies have suggested that both affective valence and arousal affect the perception of time. How-ever, in previous experiments these two affective dimensions were not systematically controlled. In the present study, a set of emotional slides rated for valence and arousal (International Affective Picture System) were projected to two groups of subjects for 2, 4 and 6 sec. One group estimated the duration on an analog scale and a second group reproduced the interval by pushing a button. Heart rate and skin conductance responses were also recorded. A highly significant valence by arousal interaction affected duration judg-ments. For low arousal stimuli, the duration of negative slides was judged relatively shorter than the duration of positive slides. For high arousal stimuli, the duration of negative slides was judged longer than the dura-tion of positive slides. These results are interpreted within a model of action tendency, in which the level of arousal controls two different motivational mechanisms, one emotional and the other attentional.
Alessandro Angrilli
Paolo Cherubini
Antonella Pavese
Sara Manfredini
1998-04-01Z
2011-03-11T08:53:37Z
http://cogprints.org/id/eprint/12
This item is in the repository with the URL: http://cogprints.org/id/eprint/12
1998-04-01Z
Neural mechanisms of timing
A crucial step in timing research is to isolate clock components from other sources of temporal variability. Significant progress has been made both behaviorally and neurologically. More elaborate experimental designs have helped researchers separate timing mechanisms from motoric, sensory, and mnemonic processes. Marked similarities in the temporal characteristics of the clock in perception and production tasks implicate a common timing system. Similar conclusions can be reached from studies of patient populations: Individuals with neocerebellar damage are impaired at discriminating and reproducing short intervals. However, other patient populations, especially those with disorders affecting the basal ganglia, also exhibit deficits in timing tasks. Temporal computation may be distributed throughout the brain, but recent evidence suggests specific roles for different neural structures.
Eliot Hazeltine
Laura L Helmuth
Richard B Ivry
2000-01-21Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/127
This item is in the repository with the URL: http://cogprints.org/id/eprint/127
2000-01-21Z
Neuroethology of Zooplankton
Whereas the neural analysis of behavior of planktonic species and stages has been relatively neglected, we have many clues that it is going to be rich, diverse and interesting. The aims of this contribution are to defend that statement, with selected examples, and to suggest that neural analysis, particularly sensory physiology, has great explanatory power of ecologically significant behavior. I have to begin with a personal note about plankton, recalling the lasting impression made long ago by a film on invertebrates in the Arctic where scyphomedusan jellyfish were pulsing at a rate well within the range familiar in summer temperate waters, warmer by 20º C. I must have been influenced by this observation and my own experiences in a study of the neural basis of fluctuations in the rate of pulsation of medusae (Bullock 1943), some of which was made in December 1941 in Pensacola, where my wife and I collected Rhopilema cruising at random in the Sound, stopped now and then by Army bridge guards concerned about saboteurs in that first fortnight after Pearl Harbor. At any rate, by the early fifties about half of my laboratory group was devoted to the physiological ecology of temperature acclimation in marine invertebrates. That field, which I left in the early sixties, still offers a challenge in the ecologically fundamental question of why some species are able to acclimate much more than others. The proposal I made in 1955, that different rates in the same organism acclimate to different degrees, resulting in greater disharmony in some species than others, may still be viable and most likely applies to rate processes in sensory and central nervous functions, among others. Medusae are large animals, relatively, although generally treated as planktonic. The first reaction from most workers when neurophysiology of plankton is mentioned concerns their small size or gelatinous nature. The first message I bring is not new but also not widely appreciated.
T.H. Bullock
1998-08-27Z
2011-03-11T08:53:39Z
http://cogprints.org/id/eprint/63
This item is in the repository with the URL: http://cogprints.org/id/eprint/63
1998-08-27Z
A paradigmatic working memory (attractor) cell in it cortex
We discuss paradigmatic properties of activity of single cells comprising an attractor -- a developed stable delay activity distribution. To demonstrate these properties and a methodology for measuring their values, we present a detailed account of the spike activity recorded from one single cell in infero-temporal (IT) cortex of a monkey performing a delayed match-to-sample (DMS) task of visual images. In particular, we discuss and exemplify: 1. the relation between spontaneous activity and activity immediately preceding the first stimulus in each trial during a series of DMS trials; 2. the effect on the visual response (i.e. activity {\bf during} stimulation) of stimulus degradation (moving in the space of IT afferents); 3. the behaviour of the delay activity (i.e. activity {\bf following} visual stimulation) under stimulus degradation (attractor dynamics, and the basin of attraction); and, 4. the propagation of information between trials -- the vehicle for the formation of (contextual) correlations by learning a fixed stimulus sequence, as found in Miyashita 1988. In the process of the discussion and demonstration, we expose effective tools for the identification and characterisation of attractor dynamics.
Daniel J. Amit
Stefano Fusi
Volodya Yakovlev
1998-07-18Z
2011-03-11T08:53:38Z
http://cogprints.org/id/eprint/53
This item is in the repository with the URL: http://cogprints.org/id/eprint/53
1998-07-18Z
Developmental changes in the alpha response system
Evoked and event-related brain potentials (ERPs) may be regarded as originating from the reorganization of the spontaneous EEG rhythms. The main objective of the present research was to study the alpha responses in 6-11 year-old children to determine whether the ability to reorganize alpha activity after external stimulation demonstrates developmental changes that could reflect variations in information processing with increased age. A total of 50 children aged 6-11 years, divided into 5 age groups, and 10 young adults were assessed in a passive and an oddball condition. Alpha responses in the passive and non-target ERPs at Fz, Cz and Pz were analyzed to assess quantitatively the repeatability (phase-locking) of the evoked alpha oscillations. The alpha responses in 6-11 year-old children were different from those in adults: (1) Adults had significantly lower amplitude and stronger phase-locking than children; (2) Adults had maximal alpha amplitudes and phase-locking over the vertex, whereas children displayed maximal responses over the parietal site; (3) The phase-locking of eldest (10-11 year-old) children was as strong as in adults. These findings indicate that the alpha response system is functionally involved in 6-11 year-old children, though its development is not complete at the age of 11, and the magnitude and the phase-locking parameters may relate to different functional aspects of the alpha response system. Thus, younger children do produce alpha responses during information processing, but are not able to engage this system as strongly as older children and adults.
Juliana Yordanova
Vasil Kolev
1998-07-05Z
2011-03-11T08:54:13Z
http://cogprints.org/id/eprint/715
This item is in the repository with the URL: http://cogprints.org/id/eprint/715
1998-07-05Z
The Neurons In The Brain Cannot Implement Symbolic Systems
It is widely accepted that symbolic systems are useful in understanding the working of the brain, and there are many symbolic models of functions of the brain. This is based on the assumption, commonly implicit, that in the brain itself there is a symbolic system. In this article I challenge this belief, by showing that symbolic systems cannot be implemented by neurons in the brain. I based the argument on textbook knowledge from neurobiology, and the basic requirements for implementing symbolic systems. In particular, I show that there is no way to implement symbol tokens in neuronal substrate, where the individual connections of individual neurons (as opposed to cell populations) are not well defined.
Yehouda Harpaz
2000-12-28Z
2011-03-11T08:54:28Z
http://cogprints.org/id/eprint/1167
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2000-12-28Z
Auditory event-related potential (ERP) and difference-wave topography in schizophrenic patients with/without active hallucinations and deluisions: a comparison with young obsessive-compulsive disorder (OCD) and healthy subjects
Introduction:
Event-related potentials (ERPs) in schizophrenics have been reported to show a reduced P3 on the left and less frontal mismatch negativity. But the specificity of such findings to component, its locus, the type of eliciting event and patient group remains uncertain. Hence, we examined ERP topography for P3, N2 and 3 precursor peaks according to stimulus (3-tone oddball), attention condition (diffuse/focused) and four types of difference-waves (Mismatch negativity, Processing negativity, Negative difference (Nd) and the 'Goodin-Waveform').
Method:
We contrasted ERPs in a 3-tone oddball task-form in 24 healthy (mean 18.5y of age) and 13 OCD (mean age 16.3 y) subjects with schizophrenic patients with high versus low ratings of active delusions and hallucinations (12 paranoid-hallucinatory, PH [mean age 18.5y]; 12 nonparanoid, NP [mean age 18.9y])
Results:
1. P3 peaks were delayed and reduced in NP and PH groups. Peaks in the midline were usual in the focused attention condition, but a right bias in diffuse attention (passive presentation).
2. P3 responses to irrelevant non-targets remained lateralised in NP, and small in OCD patients. All showed a small left and anterior bias in the P3-like peak recorded after subtraction in the difference waves.
3. Mismatch negativity (MMN) peaks shifted to the right in OCD, laterally to both sides in PH and more posteriorly in NP patients.
4. Frontal processing negativity was biased to the left (early) in NP and to the right (late) in PH groups.
5. Early peak topography in the difference waveforms reflected some of these later changes (e.g., for PH and NP groups the normal right bias in the P1-like peak was absent; the N1-like peak was reduced and widely distributed: for the NP group, the P2-like peak appeared smaller on the left).
6. In OCD patients, the peak latencies were topographically undifferentiated for P1 and P2, or delayed in the case of the N2 component.
Conclusions:
A) The OCD group showed an unusual regional allocation of processing effort.
B) Before 200 ms, fronto-central activity was more widespread in both the PH and NP groups.
C) NP patients, in particular, treated irrelevant stimuli anomalously.
D) Lateralisation of negativity in target- and nontarget-derived difference waves may reflect differential disruption of the frontal-temporal dialogue in registering important vs. unimportant features. Indeed, the apparent left/right differences of negative difference (Nd) or processing negativity amplitude may not so much reflect amplitude differences as a delayed latency over left frontal areas in PH and over the right frontal areas in NP patients with schizophrenia.
Robert D. OADES
D. ZERBIN
A. DITTMANN-BALCAR
C. EGGERS
2000-12-28Z
2011-03-11T08:54:28Z
http://cogprints.org/id/eprint/1168
This item is in the repository with the URL: http://cogprints.org/id/eprint/1168
2000-12-28Z
Auditory event-related potentials (ERPs) and mismatch negativity (MMN) in healthy children and those with attention-deficit or Tourette/tic symptoms
Introduction: This study compared 5 auditory, event-related potential (ERP) components (from P1 to P3, 50 to 500 ms post stimulus) after 3 tones differing in pitch and in rarity presented to three groups of children. The mismatch negativity (MMN), the ERP trace of auditory working memory for deviant stimuli was also studied.
Methods: Topographic recordings were derived from 19 electrodes over the scalp of 12 children with attention-deficit/hyperactivity disorder (ADHD): mean 10.2 years-of age), 12 healthy controls matched for age, and 10 with chronic complex Tic- or Tourette syndrome (TS), who also showed symptoms of attention-deficit.
Results:
Four major effects are reported:
a) Shorter ERP latencies were evident in ADHD children as early as 100 ms after the stimulus;
b) Both ADHD and TS children showed larger P2 component amplitudes than the controls with their maxima shifted more anteriorly;
c) Frontal MMN was not significantly different between ADHD and healthy controls, but the normalised data showed a left-sided distribution in the ADHD group and a right-sided distribution in the normal children. Maxima for TS children was unusually more posterior. (In adults the distribution is normally frontal and bilateral.)
d) ADHD patients did not show the usual right-biased P3 asymmetric distribution (nor a frontal vs. parietal latency difference).
Conclusions: These results suggest that ADHD children process information faster from the early N1 (c. 100 ms) stage. Both groups of children with attention-deficit symptoms showed a marked enhancement of the inhibitory phase of processing in the auditory cortex marked by P2. That this is shown even after a standard stimulus indicates an increased likelihood of unimportant stimuli being further processed and coming to control behaviour, while stimuli competing for attention are suppressed. Later indices of processing (N2-P3) showed a frontal impairment (TS), especially in the right hemisphere (ADHD) that are suggested to be indicative of anomalous timing in the development of frontal function.
Robert D. OADES
Alexandra DITTMANN-BALCAR
Renate SCHEPKER
Christian EGGERS
Dieter ZERBIN
2001-01-05Z
2011-03-11T08:54:28Z
http://cogprints.org/id/eprint/1181
This item is in the repository with the URL: http://cogprints.org/id/eprint/1181
2001-01-05Z
Event-related potentials during an auditory discrimination with prepulse inhibition in patients with schizophrenia, obsessive-compulsive disorder and healthy subjects
Introduction: Prepulse inhibition (PPI) is a measure of the influence of a stimulus (S1) on the response elicited by a second stimulus (S2) occurring shortly afterwards. Most S1/S2 measures of gating have used behavioral startle and the P50 event-related potential (ERP) amplitudes to detect PPI in a simple paired stimulus paradigm.
Aims: Here we report on two behavioral (EOG and reaction time, RT) and 5 ERP measures of PPI where S2 was the target or standard in an oddball discrimination. Subjects were 21 healthy controls (CON), 11 obsessive-compulsive (OCD) and 9 schizophrenic patients (SCH).
Results: The prepulse 100ms before S2 induced fewer omission errors and longer RTs compared to a 500ms S1-S2 interval in all subjects. PPI was also evident in EOG, P50, N1, P3 but not P2 or N2 amplitudes of CON subjects. SCH patients showed attenuation of PPI on the same measures. OCD patients were characterized only by their slow RT and a marginal attenuation of EOG-PPI.
Discussion: A correlational analysis implied separate relationships of ERP indices of PPI to the cognitive and psychomotor consequences of the prepulse on behavioral and discrimination responses. However SCH patients showed a general rather than a specific impairment of these indices.
Ulrich Schall
Anja Schoen
Dieter Zerbin
Christian Eggers
Robert D. Oades
2000-05-12Z
2011-03-11T08:54:20Z
http://cogprints.org/id/eprint/853
This item is in the repository with the URL: http://cogprints.org/id/eprint/853
2000-05-12Z
Multiple specification of an object's size for picking it up.
Subjects were asked to pick up disks. The apparent size of the disks was manipulated by a visual illusion. Of the two aspects of the action which depend on the objects size, only one was affected by the illusion. We conclude that different aspects of an action are controlled independently, instead of being co-ordinated on the basis of one perceptual variable.
Jeroen B.J Smeets
Eli Brenner
2000-05-30Z
2011-03-11T08:54:21Z
http://cogprints.org/id/eprint/854
This item is in the repository with the URL: http://cogprints.org/id/eprint/854
2000-05-30Z
Multiple Specification of an Objects Size for Picking it up.
Subjects were asked to pick up disks. The apparent size of the disks was manipulated by a visual illusion. Of the two aspects of the action which depend on the objects size, only one was affected by the illusion. We conclude that different aspects of an action are controlled independently, instead of being co-ordinated on the basis of one perceptual variable.
Smeets Jeroen.B.J.
Eli Brenner
1998-03-16Z
2011-03-11T08:53:36Z
http://cogprints.org/id/eprint/8
This item is in the repository with the URL: http://cogprints.org/id/eprint/8
1998-03-16Z
On the origins of aperiodicities in sensory neuron entrainment
Aperiodic entrainment to rhythmic sensory input was obtained with either a single neuron or an excitatory network model, without addition of a stochastic or "noisy" element. The entrainment properties of primary sensory neurons were well captured by the dynamics of the Hodgkin-Huxley ordinary differential equations with a quiescent resting state or threshold for spike output. The frequency-amplitude parameter space was compressed and aperiodic regimes were small in comparison to those of periodically activated pacemaker like neurons. Transitions between phase-locked and aperiodic entrainment patterns were predictable and determined by the equation dynamics; supporting the contention that some aperiodicities observed ${in}$ ${situ}$ arise from the inherent membrane properties of neurons. When the rhythmically activated neuron was embedded in an excitatory network of Hodgkin-Huxley neurons with heterogeneous synaptic delays, aperiodic entrainment patterns were more frequently encountered and these were associated with asynchronous output from the network. Embedding the rhythmically activated neuron in a network with synaptic delays, greatly reduced the range of entrained spike frequencies. Other biological mechanisms of modifying the entrainment properties and promoting aperiodic entrainment are discussed.
Heather L Read
Ralph M Siegel
2009-01-05T23:58:11Z
2011-03-11T08:57:17Z
http://cogprints.org/id/eprint/6311
This item is in the repository with the URL: http://cogprints.org/id/eprint/6311
2009-01-05T23:58:11Z
Opioid stimulation in the ventral tegmental area facilitates the onset of maternal behavior in rats
This research investigated the effect of an increase or decrease in opioid activity in the ventral tegmental area (VTA) on the onset of maternal behavior in rats. In Experiment 1, the latency to show maternal behavior toward foster rat pups (sensitization latency) was determined in maternally naive female rats given either nothing or a unilateral intra-VTA injection of morphine sulfate (MS) (0.0, 0.01, 0.03, 0.1 or 0.3 µg), on the first three days of a 10-day period of constant exposure to pups. Rats treated with 0.03 µg MS had significantly shorter sensitization latencies than did rats treated with 0.0 µg MS, 0.01 µg MS, or receiving no treatment (higher doses of morphine produced intermediate results). The facilitating effect of intra-VTA MS on the onset of maternal behavior was blocked by pretreatment with naltrexone hydrochloride and was found to have a specific site of action in the VTA (MS injections dorsal to the VTA were ineffective). In Experiment 2, sensitization latencies were determined in periparturitional rats given a bilateral intra-VTA injection of either the opioid antagonist naltrexone methobromide (quaternary naltrexone), its vehicle, a sham injection, or left untreated 40 min after delivery of the last pup. The mothers' own pups were removed at delivery; mothers were nonmaternal at the time of testing. Quaternary naltrexone treatment produced significantly slower sensitization to foster pups than did control conditions. Total activity and pup-directed activity did not differ significantly with treatment. The results demonstrate that increased opioid activity in the VTA facilitates the onset of maternal behavior in inexperienced nonpregnant female rats, and decreased opioid activity in the VTA disrupts the rapid onset of maternal behavior at parturition.
Alexis C. Thompson
Mark B. Kristal
2000-01-24Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/130
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2000-01-24Z
Theodore Holmes Bullock
They tell me I was born on a sunny Sunday in May in Nanking, China, in 1915. I was the second of four children of Presbyterian missionary parents, Amasa Archibald Bullock and Ruth Beckwith, who had come to China in 1909, honeymooning on the way for six months in Europe and India. Several years before, father had answered a call for western teachers, published by the Empress; he spent a contract year in Chengtu, in western Szechuan, teaching chemistry, his major subject at U.C. Berkeley. He fell in love with the people, their eagerness to listen, and their respect for learning. Seeing a niche that called him, in the scattered experiments with western style education, especially teacher training, he returned to the states to take a master's degree in education at Chicago and then advanced work in psychology with Thorndike at Columbia. His college roommate's sister was preparing to be a missionary in Hartford Theological Seminary and they had corresponded but not met before he came to visit and in four days secured her assent to return with him and spend a life in China. He joined the faculty of the University of Nanking to start its normal school and, among other activities, its program in agriculture. The still extant guest book of our home shows the signatures of Sun Yat Sun, then President of China, and several members of his cabinet.
T.H. Bullock
2000-08-14Z
2011-03-11T08:54:22Z
http://cogprints.org/id/eprint/935
This item is in the repository with the URL: http://cogprints.org/id/eprint/935
2000-08-14Z
Physiological responses to verbally inaccessible pictorial information in the left and right hemispheres. Neuropsychology
We investigated the effects of very brief pictorial information on transfer between the cerebral hemispheres through recordings of skin conductance responses. The pictorial stimuli had been judged previously as "neutral", "positive", or "negative" by an independent group of subjects. The verbally-available stimuli (VA) were neutral whereas the very brief, verbally-unavailable stimuli (VU) were positive or negative. The VA and VU stimuli were presented simultaneously, either in the same visual half-field (intra-hemispheric interference) or in the opposite visual half-field (inter-hemispheric interference). In a third condition, there were only VA stimuli in either visual field (no interference). We found that the right hemisphere was especially sensitive to negative VU presentations, both in the inter-and intra-hemispheric interference groups. The left hemisphere showed a corresponding sensitivity to positive interference, but only in the inter-hemispheric interference group. These findings confirm the hemispheric roles in mediating positive versus negative emotions and they show that in the interplay between hemispheric specialization and commissural transfer, left to right transfer can take place without linguistic cognition.
Dahlia W. Zaidel
Kenneth Hugdahl
Bjoern Helge Johnsen
2001-01-10Z
2011-03-11T08:54:28Z
http://cogprints.org/id/eprint/1198
This item is in the repository with the URL: http://cogprints.org/id/eprint/1198
2001-01-10Z
Connections between studies of the neurobiology of attention, psychotic processes and event-related potentials
Attention: the selective aspect of perception, requires wakefulness (organism), activation (behavior) and inhibition (neuronal systems). It may be observed momentarily (concentration), over time (vigilance) and in the selection between channels (e.g. the rejection of irrelevance in focussed and divided conditions).
Anatomical Organisation: Information ascending through the thalamus not only alerts the sensory cortices, but thalamic projections to association areas receive direct feedback allowing gating and preparation of sensory areas for further analysis. A frontal organizational role is subserved by descending pathways allowing for valuation (orbitofrontal cortex, amygdala), association (hippocampal complex) and response possibilities (basal forebrain). Interactions between the latter allow for automatic processes, but with the former limbic connections bring the possibility of conscious control.
Neurotransmitters: Additional involvement of brainstem mechanisms allows for volume-control (serotonin, 5HT), tuning (noradrenaline, NA) and switching (dopamine, DA) mechanisms in determining priority in selective mechanisms. Failures of brainstem mechanisms can impair the modulation of several systems ranging from affect (e.g. 5HT, hostility) to the assessment of information relevance (DA, perseveration, switching). Such non-specific features of psychotic processes can be incurred by unusual amino-acid transmission (e.g. Glu, Asp, GABA) from the neo- and archicortices.
Psychopathology: The locus of supra- or sub-liminal damage may provide specificity to the symptom and speculatively the schizophrenic syndromes of poverty, disorganization and reality distortion. Useful "attentional" paradigms for the study of the nature and distribution of these processes include sustained attention, the influence of irrelevant stimuli (learned inattention -"blocking"), the covert orienting of attention (cost/benefits of cueing), dichotic and multidiscrimination (allocation), prepulse inhibition and masking (sensory gating) and concept formation.
Psychophysiology: Our own work shows, for example, that mismatch negativity is severely reduced in young patients with schizophrenia with or without reality distortion (by 50% and again by 50%, respectively). But only the non-paranoid patients show an abnormal loosening of selection processes, reflected in reduced conditioned blocking (that in turn reflects switching between relevant and irrelevant stimuli and learning about both). This latter result proved to be related to changes of daily DA utilization (measured in 24h-urine samples) consistent with a DA role in switching.
Robert D. Oades
2000-01-31Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/133
This item is in the repository with the URL: http://cogprints.org/id/eprint/133
2000-01-31Z
EEG coherence has structure in the millimeter domain
Subdural recordings from 8 patients via rows of eight electrodes with either 5 or 10 mm spacing plus depth recordings from 3 patients with rows of 8-12 electrodes either 6.5 or 9 mm center-to-center were searched for signs of significant local differentiation of coherence calculated between all possible pairs of loci. EEG samples of 2-4 min were taken during four states: alertness, stage 2-3 sleep, light surgical anesthesia permitting the patient to respond to questions or commands, and electrical seizures. Coherence was computed for all frequencies from 1-50 Hz or 0.3-100 Hz and then compared for 6 or 7 narrower bands between 2 and 70 Hz. In both the subdural surface samples and those from temporal lobe depth electrode arrays coherence declines with distance between electrodes of the pair, on the average. This is nearly the same for all frequency bands. Whether computed for 5, 20 or 60 s epochs, coherence pooled across all pairs of a given separation, in a given subject, differs only slightly, in the direction of lower coherence for longer samples, indicating good stationarity of the samples chosen. For middle bands like 8-13 and 13-20 Hz, mean coherence typically declines most steeply in the first 10 mm, from values indistinguishable from 1.0 at <0.5 mm distance to 0.5 at 5-10 mm and to 0.25 in another 10-20 mm in the subdural surface data. Temporal lobe depth estimates decline ca. half as fast; coherence 0.5 extends for 9-20 mm and 0.25 for another 20-35 mm. Low frequency bands (1-5, 5-8 Hz) usually fall slightly more slowly than high frequency bands (20-35, 35-50 Hz) but the difference is small and variance large. The steepness of decline with distance in humans is significantly but only slightly smaller than that we reported earlier for the rabbit and rat, averaging < one half. Local coherence, for individual pairs of loci, shows differentiation in the millimeter range, i.e. nearest neighbor pairs may be locally well above or below average and this is sustained over minutes. Local highs and lows tend to be similar for widely different frequency bands. Coherence varies quite independently of power, although they are sometimes correlated. Regional differentiation is statistically significant in average coherence among pairs of loci on temporal vs frontal cortex or lateral frontal vs subfrontal strips in the same patient, but such differences are usually small. We could not test how consistent they are over hours or between patients. Differences between left and right hemispheres, whether symmetrical pairs or pooled from two or more lobes on each side, can be quite large; in our patients the right side is usually higher, especially in the waking state. Brain state has a large influence. Slow wave sleep usually shows slightly more coherence at each distance, in all bands, compared to the waking EEG, but not consistently. Coherence at a given distance or its rate of decline with distance is a more direct measure of synchrony than naked-eye "synchronization," which is dominated by the power spectrum. Among the range of EEG states classified as seizures, coherence varies widely but averages higher by 0.05-0.2 than in pre-ictal states, usually in all frequencies when computed over the whole seizure but much more in the higher bands during the height of the electrical paroxysm. The findings point to still finer structure and more variance with closer spacing of electrodes. They could not predict the known large scale coherence between scalp electrodes, but are not in conflict with them. Scalp recording blurs the finer spatial structure, but reveals macrostructure missed by subdural and depth recording with limited numbers of channels. The strong tendency for correlated fluctuations across frequency bands is contrary to expectation from the common model of independent oscillators.
T.H. Bullock
M. McClune
J. Achimowicz
Iragui-Madoz V.J.
Duckrow R.B.
Spencer S.S.
1998-03-13Z
2011-03-11T08:53:36Z
http://cogprints.org/id/eprint/2
This item is in the repository with the URL: http://cogprints.org/id/eprint/2
1998-03-13Z
The Limits of Neuropsychological Models of Consciousness
This commentary elaborates on Gray's conclusion that his neurophysiological model of consciousness might explain how consciousness arises from the brain, but does not address how consciousness evolved, affects behaviour or confers survival value. The commentary argues that such limitations apply to all neurophysiological or other third-person perspective models. To approach such questions the first-person nature of consciousness needs to be taken seriously in combination with third-person models of the brain.
Max Velmans
2001-01-05Z
2011-03-11T08:54:28Z
http://cogprints.org/id/eprint/1182
This item is in the repository with the URL: http://cogprints.org/id/eprint/1182
2001-01-05Z
Mismatch negativity (MMN) is altered by directing attention
Introduction: MMN is a negative component resulting from the difference in event-related potential (ERP) waveforms elicited by a standard and a deviant stimulus. It is usually studied in the absence of attentional requirements.
Method: Here we compare this measure of perceptual comparison in a nontask situation (3 tones presented) with that obtained in a task requiring focussed attention and response to the third tone. Subjects were 9 male and 16 female healthy volunteers aged 18-25 years
Results: MMN amplitude (comparison of standard and deviant irrelevant tones) increased with focussed attention to the third (target) tone and frontal maxima shifted slightly posteriorly.
The succeding P3 in the difference waveform increased more posteriorly than frontally confirming continued differential processing of irrelevant stimuli under active conditions.
Conclusion: This demonstrates that not only attending to stimuli, but the active processing of irrelevant stimuli (vs passive perception) involves small changes of the amount and distribution of neural activity. i.e. active controlled processing in focussed attention can affect the capacity or distribution of resources even for automatic processing of information (the MMN).
Robert D. OADES
Alexandra DITTMANN-BALCAR
1999-07-16Z
2011-03-11T08:53:40Z
http://cogprints.org/id/eprint/109
This item is in the repository with the URL: http://cogprints.org/id/eprint/109
1999-07-16Z
On Thermal Sensation and Entropy
A neurophysiological thesis is proposed for thermal sensitivity that accounts for the disorder in physical processes that is fundamental to temperature. There is likely some form of thermal equilibrium rapidly established between thermoreceptors and the external environment local to those thermoreceptors that accounts for gauging the temperature accurately within a certain range.
Douglas M. Snyder
2001-01-15Z
2011-03-11T08:54:29Z
http://cogprints.org/id/eprint/1225
This item is in the repository with the URL: http://cogprints.org/id/eprint/1225
2001-01-15Z
The topography of 4 subtraction ERP-waveforms derived from a 3-tone auditory oddball task in healthy young adults
Introduction: Five components were studied in 4 subtraction waveforms derived from ERPs obtained in passive and active conditions of a 3-tone oddball task (common=70%, C, 0.8 KHz; deviant=15%, D, 2 KHz; 1.4 KHz=15%, t, also used as a target (T)). These waveforms reflect different stimulus-mismatch processes and thus their topography could be revealing of different brain regions mediating them.
Methods: The following mismatches were studied: stimulus-mismatch (deviant - common, D/C, rarity and pitch confounded, known as the mismatch negativity, MMN), pitch-mismatch (T - deviant, T/D, rarity not target features controlled, known as processing negativity PN), attention - mismatch (T - t), T/t, controlled for pitch and rarity to show the influence of target features, known as the Negative difference Nd). These are compared with Goodin's procedure (G-wv, (T-common (active) - (t-common (passive)- the "Goodin-waveform").
Results: There were main site effects in normalized data in all cases (not P2 and N2 latency). There were separate frontal and posterior contributions to P1, with the former emphasized where target comparisons were involved.
Frontal N1 peaks, largest in D/C (MMN), spread posterior and to the right where target matching was involved. P2 posterior maxima were also less localized where target features were involved in the comparison. N2 topography was similar between waveforms but spread slightly more to each side in the T/t comparison (i.e. Nd).
Onset was earlier in the D/C comparison (i.e MMN). Parietal P3 peaks in waves based on target-ERPs showed a left temporal shift (vs D/C), though in T/D P3 was in fact maximal on the right (i.e. PN waveform).
Conclusions: Thus an attentional effect(controlled processing) is evident as early as 60 ms. Target features modify the anteroposterior distribution of positivity and negativity for the early components and in the lateralization of P3-like positivity. A comparison of waveforms by latency of potential shift (running t-test) vs. peak identification (MANOVA) is illustrated and discussed. D/C (MMN) and T/t (Nd) waveforms, rather than T/D or G-wv (PN & Goodin waveforms) waveforms are recommended for distinguishing comparator mechanisms for stimulus- and task-relevant features.
Robert D. Oades
Dittmann-Balcar
Zerbin
2001-01-15Z
2011-03-11T08:54:29Z
http://cogprints.org/id/eprint/1224
This item is in the repository with the URL: http://cogprints.org/id/eprint/1224
2001-01-15Z
The topography of event-related potentials in passive and active conditions of a 3-tone auditory oddball test
Introduction: Normalized event-related potential (ERP) data were analysed for topographical differences of ERP amplitude or latency in two conditions of a 3-tone oddball paradigm. The aim was to compare perception-related features relating to tone-type (passive non-task condition) with focussed attention-related features (active discrimination of target from non-target) in 5 ERP components from 23 young healthy subjects.
Methods: The tones used were a common standard (70%, 0.8 KHz), a deviant standard (15%, 2 KHz) and a 1.4 KHz tone (15%, t) also used as the target (T).
Results:
a)A site x tone interaction was obtained for P1/P50 amplitude (augmenting with pitch anterior to posterior). The opposite tendency was seen for P2 to the right of midline maxima.
b) No interaction was obtained for N1 amplitude.
c) Condition became relevant for the N2-P3 complex. Frontal N2 amplitude increased after rare tones in the active condition. Posterior P3 peak size distinguished between tone (more widespread response to the common tone) and condition (more right-sided in the passive condition).
d) The common tone elicited more widespread shift to the right than the rare tones. Latency was affected by condition from the P2 onwards and confirmed many of the amplitude interaction.
Conclusion: This report extends and qualifies well-known main effects of tone and condition through main site effects to lateral sites. It supports claims of multiple sources of ERP components, except for N1 and P2. The contributions of these sources are influenced by tone-features (from P1) and the presence or absence of focussed attention (from the N2-P3 complex).
Robert D. Oades
D. Zerbin
A. Dittmann-Balcar
1999-11-10Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/123
This item is in the repository with the URL: http://cogprints.org/id/eprint/123
1999-11-10Z
A Comparative Survey Of Oscillatory Brain Activity, especially gamma-band rhythms.
Nature loves to oscillate. Ongoing oscillations of a wide range of periods are familiar in animals, for example circannual, circalunar and circadian, the so-called minute rhythms of Galambos and Makeig (1988), respiratory, cardiac, and EEG rhythms of delta, theta and alpha frequencies, ca. 40 Hz cerebral, 200 Hz cerebellar, and pacemakers of electric organ discharges in certain electric fish which run at 1000-2000 Hz, night and day. In addition many living systems - or parts of them - love to show event-related oscillation. The gamma band of frequencies is popular from invertebrates to mammals, especially for transient oscillations, such as event-related rhythms, which have recently come to prominence and have been called induced rhythms in a recent book of that title (Baar and Bullock 1992). The purpose of this paper is to shed some perspective on the topic of the symposium by surveying the literature for examples of event-related oscillations, particularly those in the gamma band. I ask, for each example, four kinds of questions. (i) Are the events with which they are related similar? (ii) Are they suggestive of a common meaning, or (iii) of a common mechanism. (iv) Are the dynamics of the oscillation basically common or diverse?
Theodore H. Bullock
Jerzy Z. Achimowicz
1999-08-30Z
2011-03-11T08:53:40Z
http://cogprints.org/id/eprint/116
This item is in the repository with the URL: http://cogprints.org/id/eprint/116
1999-08-30Z
Dynamic properties of human visual evoked and omitted stimulus potentials
Visual evoked potentials (VEP) and omitted stimulus potentials (OSPs) are reexamined in scalp recordings from 19 healthy subjects. The principal finding is a distinction in form, latency and properties between OSPs in the conditioning stimulus range <2 Hz, used in previous human studies, and those in the range >5 Hz, used in previous studies of selected elasmobranchs, teleost fish and reptiles. We cannot find OSPs between 2 and 5 Hz. The high frequency ("fast,"ca. 6 to >40 Hz) and the low frequency ("slow," ca. 0.3-1.6 Hz) OSPs have different forms and latencies but both tend to a constant latency after the omission, over their frequency ranges, suggesting a temporally specific expectation. Fast OSPs (typically N120, P170-230 and later components including induced rhythms at 10-13 Hz) resemble an OFF effect, and require fixation but not attention to the ISI. Slow OSPs (usually P500-1100) require attention but not fixation; they are multimodal, unlike the fast OSPs. Based on cited data from fish and reptiles, fast OSPs probably arise in the retina, to be modified at each subsequent level. We have no evidence on the origin of slow OSPs. In both ranges not only large, diffuse flashes; but weak, virtual point sources (colored LEDs) meters away suffice. They are difficult to habituate. Both require very short conditioning periods. The transition from the single, rested VEP to the steady state response (SSR) at different frequencies is described. Around 8-15 Hz in most subjects larger SSRs suggest a resonance. Alternation between large and small SSR amplitude occurs around 4 Hz in some subjects and conditions of attention, and correlates with an illusion that the flash frequency is two Hz or is irregular. Jitter of the conditioning intervals greatly reduces the slow OSP but only slightly affects the fast OSP. Differences between scalp loci are described.
T.H. Bullock
Sacit Karamürsel
Jerzy Z. Achimowicz
McClune Michael C.
Baar-Eroglu Canan
1999-11-16Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/124
This item is in the repository with the URL: http://cogprints.org/id/eprint/124
1999-11-16Z
Dynamics of event-related potentials to trains of light and dark flashes: responses to missing and extra stimuli in elasmobranch fish.
To characterize the dependencies of ERPs in lower vertebrates and brain levels upon recent history and sequences of stimuli, trains of flashes were delivered at various frequencies to unanesthetized rays while recording in optic tectum and telencephalon. ERPs to repetitive stimuli cannot be understood in terms of simple refractoriness and recovery. Processes must be invoked such as simultaneous excitation and suppression, facilitation and its opposite, rebound and induced rhythms, each with development and decay times and nonlinearities. Some of these processes are uncovered by omitting a stimulus from a train. Omitted stimulus potentials (OSPs) act as though the brain expects a stimulus within 5-7 ms of the interstimulus interval (ISI) of the train. Very few ISIs suffice. The effect upon VEP form and duration of the number of stimuli in short trains, before the steady state response (SSR) is established, is complex. Alternation of the amplitude of successive VEPs (1 large every 2 VEPs, 1 in 3, 1 in 4) is one indication of complexities in the SSR. OSPs also alternate. A single extra stimulus interpolated into a regular train causes distinct effects according to its position. Sharp discontinuities in these effects appear with <5 ms shifts. Total power of the SSR decreases with stimulation frequency but there is a large peak of increased power at 7 Hz and another at 12 Hz. Induced rhythms are a labile, late phase of OSPs as well as of rested VEPs and of the OFF response to a long light pulse. Jittered ISI experiments show that the apparent expectation of the OSP is little affected and that the intervals in the last few hundred milliseconds are most influential. The OSP studied here (ISI <0.5 s)is quite different from that so far studied in human subjects (ISI >1s). We predict further similarities when each taxon is tested in the other ISI range. A major category of response characteristics, besides sensitivity, receptive fields and recovery times, is dependence upon recent history of iterative events, including intervals, delays, omissions and perhaps multiple facilitating and forgetting time constants. The variables examined parametrically in this study are only some of those available. Such dynamical characteristics are important neglected properties of afferent systems at each level.
Sacit Karamürsel
T.H. Bullock
1999-09-23Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/118
This item is in the repository with the URL: http://cogprints.org/id/eprint/118
1999-09-23Z
Event-related potentials to omitted visual stimuli in a reptile
Visual omitted stimulus potentials (OSPs) were recorded from awake pond turtles with arrays of 3-20 electrodes in the dorsal cortex (DC), dorsal ventricular ridge (DVR) and optic tectum. Since they are generally longer in duration than the interstimulus interval (ISI), the standard experiment is a short conditioning train of regular light or dark flashes (1-20 Hz) whose termination elicits the OSP. Tectal surface OSPs after trains >7 Hz have two major positive peaks, P120-140 and P220-250 after the due-time of the first omission; after <7 Hz down to the minimum of 1.5 Hz only the slower peak appears. Some deep tectal loci also have one to three 100 ms wide negative waves peaking at variable times from 200-1300 ms. Forebrain OSPs in DC and DVR are approximately 30 ms later and often include induced 17-25 Hz oscillations, not phase-locked and attenuated in averages. Both tectal and forebrain OSP main waves tend toward a constant latency after the due-time, over a wide range of ISIs, as though the system expects a stimulus on schedule. Jitter of ISI around the mean does not greatly reduce the OSP. At all loci higher conditioning rates cause the amplitudes of the steady state response (SSR) VEPs to decline and of the OSPs to increase. Some similarities and correlations of regional amplitude fluctuations between OSPs and VEPs are noted. The OSP dynamics are consistent with the hypothesis of a postinhibitory rebound of temporally specific VEP components increasingly inhibited with higher stimulation rates; much of this response is retinal but each higher brain level further modulates. OSPs in this reptile are similar to those known in fish and to the "high frequency" type in humans, quite distinct in properties from the "low frequency" OSPs. It will be important to look at the high frequency type in laboratory mammals to determine whether they are present in the midbrain and retina, as in fish and reptiles.
James C. Prechtl
Theodore H. Bullock
1999-08-05Z
2011-03-11T08:54:18Z
http://cogprints.org/id/eprint/819
This item is in the repository with the URL: http://cogprints.org/id/eprint/819
1999-08-05Z
On the Nature of Intelligence: The Relevance of Statistical Mechanics
A conundrum that results from the normal distribution of intelligence is explored. The conundrum concerns the chief characteristic of intelligence, the ability to find order in the world (or to know the world) on the one hand, and the random processes that are the foundation of the normal distribution on the other. Statistical mechanics is explored to help in understanding the relation between order and randomness in intelligence. In statistical mechanics, ordered phenomena, like temperature or chemical potential, can be derived from random processes, and empirical data indicate that such a relationship between ordered phenomena and random processes must exist as regards intellect. The apparent incongruity in having both order and randomness characterize intelligence is found to be a feature that allows for intelligence to be known without recourse to underpinnings that are independent of the knowing individual. The contrast of ordered processes and random processes indicates that probabilistic knowledge of the world, stemming from the latter processes, is a basis for knowing the world in a fundamental manner, whether the concern is the physical world or mind. It is likely that physiological concomitants involved in the development, and perhaps current operation, of intellect also demonstrate the same relationship between ordered and random phenomena found on a psychological level. On a microscopic level, it is expected that random neurophysiological processes would give rise to ordered patterns of neurophysiological activity on a macroscopic level.
Douglas M. Snyder
1999-10-21Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/121
This item is in the repository with the URL: http://cogprints.org/id/eprint/121
1999-10-21Z
Interval-specific event related potentials to omitted stimuli in the electrosensory pathway in elasmobranchs: an elementary form of expectation
Multiunit activity and slow local field potentials show Omitted Stimulus Potentials (OSP) in the electrosensory system in rays after a missing stimulus in a 3 to >20 Hz train of microvolt pulses in the bath, at levels from the primary medullary nucleus to the telencephalon. A precursor can be seen in the afferent nerve. The OSP follows the due-time of the first omitted stimulus with a, usually, constant main peak latency, 30-50 ms in medullary dorsal nucleus, 60-100 ms in midbrain, 120-190 ms in telencephalon - as though the brain has an expectation specific to the interstimulus interval (ISI). The latency, form and components vary between nerve, medulla, midbrain and forebrain. They include early fast waves, later slow waves and labile induced rhythms. Responsive loci are quite local. Besides ISI, which exerts a strong influence, many factors affect the OSP slightly, including train parameters and intensity, duration and polarity of the single stimulus pulses. Jitter of ISI does not reduce the OSP substantially, if the last interval equals the mean; the mean and the last interval have the main effect on both amplitude and latency. Taken together with our recent findings on visually evoked OSPs, we conclude that OSPs do not require higher brain levels or even the complexities of the retina. They appear in primary sensory nuclei and are then modified at midbrain and telencephalic levels. We propose that the initial processes are partly in the receptors and partly in the first central relay including a rapid increase of some depressing influence contributed by each stimulus. This influence comes to an ISI-specific equilibrium with the excitatory influence; withholding a stimulus and hence its depressing influence causes a rebound excitation with a specific latency.
T.H. Bullock
Sacit Karamürsel
Michael H. Hofmann
1998-11-15Z
2011-03-11T08:53:43Z
http://cogprints.org/id/eprint/180
This item is in the repository with the URL: http://cogprints.org/id/eprint/180
1998-11-15Z
Enhancement of Opioid-Mediated Analgesia: A Solution to the Enigma of Placentophagia
Two major consequences of placentophagia, the ingestion of afterbirth materials that occurs usually during mammalian parturition, have been uncovered in the past several years. The first is that increased contact, associated with ingesting placenta and amniotic fluid from the surface of the young, causes an accelerated onset of maternal behavior toward those young. The second, which probably has importance for a broader range of mammalian taxa than the first, is that ingestion of afterbirth materials produces enhancement of ongoing opioid-mediated analgesia. The active substance in placenta and amniotic fluid has been named POEF, for Placental Opioid-Enhancing Factor. Recent research on both consequences is summarized, with particular attention to POEF, the generalizability of the enhancement phenomenon, its locus and mode of action, and its significance for new approaches to the management of pain and addiction.
Mark B. Kristal
1998-04-25Z
2011-03-11T08:53:37Z
http://cogprints.org/id/eprint/23
This item is in the repository with the URL: http://cogprints.org/id/eprint/23
1998-04-25Z
Islands in the Mind: Dynamic Subdivisions of Association Cortex and the Emergence of a Darwin Machine
To model cognitive processing, language construction, and "intelligence" at a neurophysiological level using darwinian evolutionary mechanisms requires more than a survival-of-the-fittest principle. Darwinism is all about the copying success of patterns (typically DNA strings); here I outline a seconds-to-minutes competition between different spatiotemporal firing patterns in a multifunctional cortical workspace. The proposed mechanism for recall from a passive distributed memory into an active working memory is analogous to genotypes and phenotypes. The ephemeral working patterns copy themselves in the manner of wallpaper pattern repeats; they occupy flexible islands in the workspace (useful for multi-tasking and analogical reasoning) that compete with one another for the limited workspace, with a widespread pattern signaling object identification or readiness to act. Pattern evolution is accelerated by cortical equivalents of the roles played by climate change and lowered sea level in island biogeography. Chimeric islands containing a pastiche of patterns are judged against episodic memories in a way that bears some correspondence to the known organization of human language cortex.
William H. Calvin
1999-10-08Z
2011-03-11T08:53:41Z
http://cogprints.org/id/eprint/120
This item is in the repository with the URL: http://cogprints.org/id/eprint/120
1999-10-08Z
On the Time of Peripheral Sensations and Voluntary Motor Actions
Libet's notions of backwards referral for peripheral sensations and unconscious cerebral initiative accompanying voluntary motor action are explored. It is proposed that the unexpected discrepancy between the time at which a peripheral sensation is experienced and the time at which cerebral neuronal adequacy underlying the sensation is attained is due to fundamentally different forms of temporality which are applicable to experiential and neurophysiological reference frames. A similar proposal is made for the unexpected discrepancy in the time of a neurophysiological readiness potential accompanying a voluntary motor action and the time of onset of the intention accompanying the action. Correspondences between experiential and neurophysiological levels of peripheral sensations and voluntary motor actions indicated by Libet's empirical evidence are shown to be adaptive if an individual's experience is important in his interaction with the environment.
Douglas M. Snyder
1999-08-01Z
2011-03-11T08:53:40Z
http://cogprints.org/id/eprint/114
This item is in the repository with the URL: http://cogprints.org/id/eprint/114
1999-08-01Z
Complementarity and the Relation Between Psychological and Neurophysiological Phenomena
In their recent article, Kirsch and Hyland questioned the relation between psychological and associated neurophysiological phenomena in the introduction of complementarity into psychology. Mishkin's work on the neurophysiological basis of memory and perception provides an example of the extension of complementarity that I have proposed and that can serve as the basis for empirical testing of this extension. Mishkin's thesis that memory storage occurs at sensory stations in the cortex allows for the resolution of a fundamental problem in cognitive psychology, namely the reciprocal dependence of perception and memory. Also, Mishkin's thesis allows that psychological phenomena do not depend on an objective world for their existence.
Douglas M. Snyder
2001-01-24Z
2011-03-11T08:54:29Z
http://cogprints.org/id/eprint/1256
This item is in the repository with the URL: http://cogprints.org/id/eprint/1256
2001-01-24Z
Event-related potentials and monoamines in autistic children on a clinical trial of fenfluramine
Introduction: As autistic persons have problems with selecting and encoding meaningful stimuli and multi-centre studies (Ritvo et al., 1983, 1986) had reported mild behavioural improvements following treatment with fenfluramine, event-related potential (ERP) stages of information processing were studied in childhood autism as part of a double blind crossover study of the efficacy of dl fenfluramine. .
Methods: Acceptable recordings were derived from midline and 4 lateral sites on the scalp of 7 from 14 young persons with autism who understood the task (6 male, 1 female 5.8-17.7 years-of-age). A three-tone oddball paradigm was presented in a passive and active-task form (72% at 1 kHz, 14% at 0.5 kHz and 14% at 2.0 kHz) under placebo and drug conditions (where each condition lasted 5 months). Eleven patients provided blood and urine samples for monoamine analyses in both conditions.
Results:
a) With fenfluramine treatment blood serotonin decreased and urinary catecholamine levels fell (25-45%, but dopamine utilization (HVA/DA) increased 2-4-fold.
b) Under fenfluramine autistic subjects responded non-significantly faster, with fewer errors of omission and improved /decreased beta criterion (signal detection). [IQ measures increased 7.5 points.]
c) N1 amplitudes (Fz) decreased and latencies increased in the fenfluramine condition.
Early negativity (especially on the right) correlated inversely with HVA/DA actvivity.
Subtraction of the ERPs in nontarget from target conditions showed that the Negative difference (Nd) increased during fenfluramine treatment.
d) P3 amplitudes (especially after the deviants) increased with fenfluramine treatment. But in the difference waveform (active-minus-passive condition) the P3 amplitude was halved. The distribution of the P3 component moved rostrally with treatment.
Conclusions: N1 and P3 components of the ERP were responsive to fenfluramine treament. Treatment appears to have mildly improved early stimulus processing at stages represented by the early negative components, but to have mildly impaired processing at the P3-stage. The N1 / Nd - related improvement seems to be related to increased dopamine activity (cf. neuroleptic-like properties of racemate fenfluramine).
R.D. Oades
L.M. Stern
M.K. Walker
C.R. Clark
V. Kapoor
2001-04-05Z
2011-03-11T08:54:37Z
http://cogprints.org/id/eprint/1436
This item is in the repository with the URL: http://cogprints.org/id/eprint/1436
2001-04-05Z
The role of noradrenaline in tuning and dopamine in switching between signals in the CNS
Introduction- Thesis:
Neuronal catecholaminergic activity modulates central nervous (CNS) function. - Specifically -
Noradrenaline (NA) can exert a tuning or biassing function, whereby the signal-to-noise ratio is altered.
Dopamine (DA) activity may promote switching between inputs and outputs of information to specific brain regions.
Background:
It has been ten years since evidence for a tuning function was advanced for NA (Segal & Bloom, 1976 a, b), and in the last five years the switching hypothesis for DA has been tentatively put forward (Cools, 1980).
Review:
Recent studies are reviewed to show that while catecholamine activity contributes to neural interactions in separate brain regions, that give rise to the organization of different functions, their working principles may be common between species and independent of the nucleus of origin. Behavioral examples are discussed and an attempt is made to integrate this with evidence from intracellular recording studies. It is suggested that the tuning principle in NA systems is particularly important for the formation of associations and neural plasticity (interference control), and that the switching principle of DA systems modulates the timing, time-sharing and initiation of responses (program-control).
R.D. Oades
1998-04-25Z
2011-03-11T08:53:37Z
http://cogprints.org/id/eprint/20
This item is in the repository with the URL: http://cogprints.org/id/eprint/20
1998-04-25Z
Normal Repetitive Firing and Its Pathophysiology
A neuron communicates over long distances (more than a few millimeters) by generating a train of impulses which propagates down the axon to release a series of prepackaged quanta of neurotransmitter molecules. The rate, or perhaps the patterning, of the impulse train carries the information. One of the hallmarks of an interictal epileptogenic focus is that many of its neurons are observed to cluster their impulses into bursts, with the intervals between impulses being unusually short (several milliseconds). Is the bursting neuron some sort of pacemaker, driving other normal neurons into synchronous activity and thus spreading the trouble? Or is the bursting one observes just one of those recruited neurons, having nothing more wrong with it than an oversized synaptic input? Or perhaps there are no pacemaker neurons; the trouble could be subtly distributed over many neurons, changing the balance of excitation and inhibition so that the whole circuit tends to go into a bursting-type oscillation.
William H Calvin
2001-06-26Z
2011-03-11T08:54:43Z
http://cogprints.org/id/eprint/1638
This item is in the repository with the URL: http://cogprints.org/id/eprint/1638
2001-06-26Z
Escape, hiding and freezing behaviour elicited by electrical stimulation of the chick diencephalon
Introduction:
An escape, hide and freeze (EHF) system has been plotted in the chick diencephalon and compared with that described in mammals, with particular reference to the defensive threat and fleeing system described for the cat. It is largely medially distributed and supra-threshold stimulation at different sites in the core of this system can elicit a mix of these behaviours. (These EHF behaviours can also be elicited peripherally. These results emerged from a broadly based study of CNS sites that were investigated for their potential to support electrical self-stimulation.)
Results:
1/ The EHF system starts in the rostral anterior hypothalamus and runs backward through the medial dorsal hypothalamus.
2/ A lateral extension occurs at the entry of the hypothalamic component of the Tractus occipito-mesencephalicus (TOM).
3/ Posterior to this TOM junction the system shows a ventral extension, but this does not include the N. ventromedialis: it coincides instead with medial and periventricular fibres.
4/ The preoptic area, lateral hypothalamic and mamillary areas were all free of EHF sites.
Conclusions:
a - The EHF system thus corresponds well with the distribution of the defensive escape-threat system in mammals.
b - In both mammals and birds similar behaviour can be elicited from both the diencephalic escape system and the central mesencephalic gray. The two are probably connected in the bird by periventricular routes, part of which can be identified by EHF sites.
c - The discussion also refers to other properties of the EHF system such as its role in vocalisation and activation by non-reinforcement.
Andrew
Oades
1998-03-19Z
2011-03-11T08:53:36Z
http://cogprints.org/id/eprint/6
This item is in the repository with the URL: http://cogprints.org/id/eprint/6
1998-03-19Z
Synaptic noise as a source of variability in the interval between action potentials.
The source of variability in the interval between action potentials has been identified in a class of cat spinal motoneurons. The observed random fluctuations in membrane potential (synaptic noise) together with an empirical description of spike generation accurately predict the statistical structure of variability observed to occur in the neuron's discharge.
W H Calvin
C F Stevens