INTRARETINAL RESPONSES OF THE CYNAMOLGUS MONKEY TO ELECTRICAL STIMULATION OF THE OPTIC NERVE AND RETINA

Abstract

In the monkey (Macaca irus) under pentothal anesthesia intraretinal microelectrodes were used to record responses evoked by electrical stimulation of the retina or optic nerve. Five separate responses were distinguished. The compound action potential of the optic fiber layer. Single unit antidromic impulses of ganglion cells. A monophasic positive wave, termed the P-wave, which was delayed with respect to optic fiber activity. This response, previously undescribed, was found to be postsynaptic. Evidence is presented that it is generated in the ganglion cells. The hypothesis is proposed that it is evoked by efferent fibers to amacrine cells, which act as inhibitory interneurons and generate the P-wave as a hyperpolarizing IPSP in the ganglion cell dendrites. An early negative wave, previously undescribed, termed the EN-wave. A late negative wave, termed the LN-wave. Both the EN- and LN-waves were evoked only by direct stimulation of the retina, and both responses were shown to involve cells of the inner nuclear layer. The LN-wave appears to be generated in that layer, but the EN-wave may be generated by the receptors.