Control of recurrent inhibition of the lateral geniculate nucleus by afferents from the superior colliculus of the rabbit: a possible mechanism of saccadic suppression.

Stimulation of the ipsilateral superior colliculus elicited a short burst of discharges of the recurrent inhibitory interneurones in the geniculocortical pathway of the rabbit. The most effective stimulating sites for this excitation were located in the deep layers rather than the superficial layers of the superior colliculus. The short latency of the response (2.3 +/- 0.6 ms) implied an oligo-synaptic excitatory pathway from the deep layers of the superior colliculus to the recurrent interneurones located in the caudal reticular nucleus of the thalamus. Following the excitation of the interneurone, there was a prolonged inhibition which started 10-30 ms and ended 150 ms after the collicular stimulation. The maximal inhibition occurred 50-70 ms after the stimulation. The effects of collicular stimulation on the recurrent inhibitory interneurones may be concerned with the inhibition of the visual pathway during saccades and with the disinhibition of "facilitation" during fixation of a new visual target.