Corticofugal influence on evoked activity of lateral geniculate neurons in the rabbit.

Corticofugal influence upon lateral geniculate units was evaluated by inactivating the visual cortex with a topical application of 3M KCL in rabbits. The results revealed a decrease of spontaneous firing in slow P cells following cortical depression suggesting a tonic corticofugal influence. The most consistently observed alteration was an enhancement of the ON response with a decrease of the response to the opposite stimulus (OFF); and vice versa: the short latency excitation being augmented. It is suggested that the visual cortex exerts a powerful influence on intra-geniculate inhibitory processes.