Different organization of cat lateral geniculate neurons in binocular inhibitory interaction.

The principal cells of the geniculate nucleus are generally classified into two types in terms of their anatomical connection with the optic nerve fibers; the contralateral geniculate cell on which the contralateral optic nerve fibers make excitatory synapses and the homolateral geniculate cell on which homolateral optic nerve fibers synapse. In the present experiments, the organization of binocular inhibition in the two different types of geniculate cells was investigated in the cats anesthetized with a chloralose-urethane mixture. In homolateral geniculate cells, an action spike produced by a volley in the ipsilateral optic nerve was often suppressed by a conditioning volley in the contralateral optic nerve (binocular inhibition). In the contralateral geniculate neurons, a conditioning volley in the homolateral optic nerve only occasionally inhibited the generation of an action spike produced by a contralateral optic nerve volley. Intracellular recording from the geniculate cells confirmed the results obtained by extracellular studies. It was concluded that binocular interaction at the lateral geniculate level was seen more commonly in the homolateral geniculate cells than in the contralateral cells.