CONDUCTION VELOCITY OF OPTIC NERVE FIBERS INNERVATING LATERAL GENICULATE BODY AND SUPERIOR COLLICULUS IN RAT

Conduction velocities of the optic nerve (ON) in the rat were measured by recording evoked unitary discharges of postsynaptic cells to stimulation of the ON at two separate sites. The velocity of ON impulses to activate a given postsynaptic cell was calculated from the distance between the two stimulating sites and the difference in response latency of the same postsynaptic cell. Recordings were made from the lateral geniculate body (LGB) and the superior colliculus (SC), both contralateral to stimulation. ON fibers innervating principal cells of the LGB (P cells of Burke and Sefton) fell into three groups (tg0, tg1 and tg2) having average velocities of 19.2, 11.9, and 5.2 m/sec, respectively. Internuncial cells (I cells) received tg2 fibers only. There were also three groups of ON fibers destined for the SC (tc0, tc1 and tc2). Their average velocities were 15.4, 9.1, and 3.7 m/sec, respectively. © 1969.