OPTIC NERVE POPULATION RESPONSES TO TRANSRETINAL ELECTRICAL STIMULATION

Responses of the fast conducting (F) ganglion cell population of the rabbit retina were studied in separation from other populations by determining periods of fast fiber refractoriness in the optic nerve. Stimulation was by brief electrical pulses across the retina which were also used to determine inhibitory phases following light stimuli. The F-cell population proved to be remarkably uniform in its responsiveness to electrical pulses. The typical response is a precisely timed period of synchronous activity (bursts of high frequency discharges) followed or preceded by a phase of network inhibition depending on current polarity. Outward (anodal) current elicits first a period of strong inhibition, as does the on" of diffuse light; while inward (cathodal) current and "off" activate an excitatory input to the F-cells. Excitation and inhibition alternate rhythmically so that synchronous bursts of firing are separated by silent periods of 25-40 msec in duration. Results of combining two transretinal stimuli suggest that the rhythmic alteration is due to the interactions of an excitatory and an inhibitory system and that the electrical pulse primarily activitates the one or the other system depending upon current direction. © 1969."