CENTRIFUGAL AND ANTIDROMIC EFFECTS ON GANGLION CELLS OF RETINA

Abstract

Effect of stimulation within the brain upon spikes recorded by micro-electrodes from the retina was studied in cats. Tetaniza-tion of centripetal optic tract, lateral geniculate or pretectal fibers is succeeded by long-lasting acceleration of both spontaneous discharge or discharge to a test light. This presupposes antidromic driving of large ganglion cells from above. Sometimes, particularly often with optic tract stimulating electrodes, this effect is a long-lasting inhibition. In this connection a full description is given of antidromic effects on single retinal ganglion cells with respect to variations in stimulus variables such as duration, frequency and strength and interference phenomena between ortho- and antidromic excitation of ganglion cells. Delayed conduction within unmyelinated intraretinal course of optic nerve fibers is described. It is also shown that identical long-lasting effects of excitation or inhibition can be obtained by tetanization of tegmental structures from which it is impossible to drive retinal ganglion cells antidromically. These effects, therefore, are true centrifugal ones. It is concluded that, since antidromic post-tetanic potentiation is improbable on the basis of what is known about antidromic stimulation, antidromic effects are identical with the ones obtained by true centrifugal stimulation, both being ascribed to the centrifugal fibers of Cajal, Dogiel and Polyak.