| Abstract: | The distribution of retinal afferents to the dorsal lateral geniculate nucleus of the cat and the fox has been studied using ocular injections of 3(H)-leucine and autoradiographic techniques. Whereas fiber degeneration methods have shown only five distinct layers in the lateral geniculate nucleus, autoradiographs show six well defined layers in both species. Laminae A and C receive afferents from the contralateral eye, while laminae A1 and C1 receive from the ipsilateral eye. A retinal input to the region lying between lamina C1 and the optic tract could not be demonstrated by fiber degeneration methods, but this region can now be divided into two distinct layers. The antero-dorsal of these two layers (lamina C2) receives afferents from the contralateral eye, while the postero-ventral layer, nearest the optic tract, appears to receive no direct afferents from either eye. Since the rapid component of the axoplasmic transport labels axon terminals to a greater extent than fibers of passage, the autoradiographic method demonstrates, more successfully than fiber degeneration methods, that there is no significant binocular overlap between the retinal projections to alternate geniculate layers. |
