Submicrosecond pacemaker precision is behaviorally modulated: The gymnotiform electromotor pathway

Abstract

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