Vision during saccadic eye movements. II. A corollary discharge to monkey superior colliculus

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Abstract
Many cells in the superficial layers of monkey [Macaca mulatta] superior colliculus have a reduced sensitivity to visual stimulation during rapid or saccadic eye movements. The change in sensitivity is accompanied by a suppression of the background rate of discharge. Whether the suppression of activity results from feedback from the periphery (particularly from proprioception) or from a central signal (a corollary discharge) was studied. Cells with suppression of background rate following saccades were identified in the superficial layers of the superior colliculus. The suppression persisted during a retrobulbar block. The suppression results from a corollary discharge from the oculomotor to the visual system. The suppression is associated with visually guided saccades, with spontaneous saccades made in the light or total darkness, and with the reset saccades of vestibular nystagmus. Attempted head movements are associated with every visually guided saccade, but such head movements are not necessarily associated with spontaneous eye movements. Head movement cannot be a hidden source of proprioception during paralysis of the extraocular muscles in the experiments. The reduced visual sensitivity during saccadic eye movements protects the sensitivity of some superior colliculus cells from adaptation due to stimulation by the monkey''s own eye movements.