Activation of lateral geniculate neurons by electrical stimulation of superior colliculus in cats.

Abstract

Electrical responses of the lateral geniculate body (LGB) to stimulation of the superior colliculus (SC) and the optic chiasm (OC) were examined together with the properties of the optic tract (OT) fibers passing to SC, in unanesthetized cats with immobilization.The OT fibers passing to SC were grouped into two types, corresponding to t1 and t2 of P. O. BISHOP, respectively. The OT antidromic action potential produced by LGB-stimulation was found to interact with that produced by SC-stimulation. This supports the histological finding that the OT fibers passing to LGB send collaterals to Sc.The mass response of the LGB neurons to SC-stimulation was much the same in configuration and peak time as that to OC-stimulation. With a few exceptions it was found in many LGB neurons that in each unit the response latency to SC-stimulation was about the same as that to OC-stimulation. Since the two stimulating sites are approximately equidistant from LGB, these findings suggest that activation of the LGB neurons by Sc-and OC-stimulation is made through bifurcating OT fibers. It was suggested that there is a projection from SC to LGB. This was evidenced by studying the LGB response to SC-stimulation in cats with eyes chronically enucleated.