Eye movement-related inhibition of primate visual neurons

The influence of saccadic eye movements (EM) upon spontaneous neuronal activity was studied in the lateral geniculate nucleus (LGN) and striate visual cortex (VC) of encéphale isolé monkeys. EM were spontaneous and occurred in total darkness to eliminate the effects of retinal image displacement. The activity of LGN cells was not altered in association with EM. In contrast, 76% of cells studied in VC displayed a period of inhibition related to spontaneous EM in total darkness. EM-related inhibition of VC neurons was directionally specific; for each cell there was one quadrant of EM direction for which inhibition was most prominent. The majority of VC neurons showed inhibition in relation to EM directed into only one quadrant of the visual field. Reliable detection of EM-related inhibition required the formation of average histograms of neuronal firing time-locked to EM. For individual EM (even of optimum direction), a consistent degree of inhibition was not seen. The time course of EM-related inhibition of VC neurons is consistent with that reported for saccadic suppression. These results support the concept of a central mechanism (corollary discharge) acting at the cortical level being of significance in saccadic suppression.