Electrophysiological Evidence for Visual Suppression prior to the Onset of a Voluntary Saccadic Eye Movement

Abstract

INABILITY to perceive one's own eye movement in a mirror is a common observation. To explain this, Holt¹ was the first to propose a central inhibitory mechanism. On the other hand, Dodge^2,3 and Woodworth⁴ claimed that retinal blurring could account for the apparent suppression and pointed out that a blurred image could be seen if the illumination was increased in intensity. Volkman⁵, using tests for visual acuity and threshold, stated that although vision was not “blanked out” during eye movements, visual recognition and resolution were markedly diminished, as opposed to steady fixation. LaTour⁶ found that the chance of perceiving a flash three log units above threshold was markedly decreased during the 50 ms before the onset of the voluntary eye movement. He also noted that the chance of flash perception did not return to normal until one or two hundred ms after the onset of eye movement. Zuber, Stark and Forbes⁷, also using psychophysical methods, confirmed LaTour's observation. They also noted that pupillary response to light decreased about 60–70 ms before the onset of eye movement. Gross, Vaughan and Valenstein⁸ found that the peak to peak amplitude of the visual evoked response (derived on a signal averaging computer) showed a marked decrease just after the onset of an eye movement and did not return to normal for 100–200 ms. They did not examine the visual evoked responses which occurred before the onset of the voluntary saccade.