A Synaptic Corollary Discharge Signal Suppresses Midbrain Visual Processing During Saccade-Like Locomotion

ABSTRACT In motor control, the brain not only sends motor commands to the periphery, but it also generates concurrent internal signals known as corollary discharge that influence the processing of sensory information around the time of movement. Corollary discharge signals are important for the brain to identify sensory input arising from self-motion and to compensate for it, but the underlying mechanisms remain unclear. Using whole-cell patch clamp recordings from single neurons in the optic tectum of zebrafish, we discovered an inhibitory synaptic signal which was temporally locked to spontaneous and visually driven swim patterns. This motor-related synaptic signal transiently suppressed tectal output and was appropriately timed to counteract visually driven excitatory input arising from the fish’s own motion. High-resolution calcium imaging revealed brief, highly localized post-swim signals in the tectal neuropil, suggesting that corollary discharge enters the tectum in its most superficial layer. Our results demonstrate how spurious visual input is suppressed during self-motion by motor-related phasic inhibition in the tectum. This may help explain perceptual saccadic suppression observed in many species.