Suppression of visual phosphenes during saccadic eye movements

Abstract

A loss of visual sensitivity is shown to accompany a saccadic eye movement even under conditions of total darkness. Optical factors are eliminated by the use of electrically produced phosphenes, rather than flashes of light, to test the changes in visual threshold. Separate experiments matching the brightness of electrical phosphenes to real lights allow the threshold changes to be expressed in terms of real light. The results point to the conclusion that a substantial portion of saccadic suppression is neural, rather than optical in its origin. The time course of the suppression is consistent with electrophysiological studies in cat and monkey in which inhibition of nerve impulses occurs over a period that includes, but is considerably longer than the duration of the eye movement. No correlation has yet been shown, however, between the occurrence of saccadic suppression and identifiable features of the human visually evoked occipital responses. Saccades of a given amplitude are found to be slower in total darkness.