?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.title=Response+Dynamics+of+Entorhinal+Cortex+in+Awake%2C+Anesthetized%2C+and+Bulbotomized+Rats.+%3Ci%3EBrain+Research%3C%2Fi%3E+%3Cb%3E911%3C%2Fb%3E(2)&rft.creator=Ahrens%2C+Kurt+F.&rft.creator=Freeman%2C+Walter+J.&rft.subject=Neurophysiology&rft.description=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%2C+and+by+using+current-source+density+analysis+to+determine+the+spatial+pattern+of+evoked+responses%2C+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%2C+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.%0A&rft.date=2001-08&rft.type=Preprint&rft.type=PeerReviewed&rft.format=application%2Fpdf&rft.identifier=http%3A%2F%2Fcogprints.org%2F1676%2F3%2FKFAWJF.pdf&rft.identifier=++Ahrens%2C+Kurt+F.+and+Freeman%2C+Walter+J.++(2001)+Response+Dynamics+of+Entorhinal+Cortex+in+Awake%2C+Anesthetized%2C+and+Bulbotomized+Rats.+%3Ci%3EBrain+Research%3C%2Fi%3E+%3Cb%3E911%3C%2Fb%3E(2).++%5BPreprint%5D+++++&rft.relation=http%3A%2F%2Fcogprints.org%2F1676%2F