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Abstract:
Successful interaction with our environment requires constant sampling of new sensory information by our brain. In vision, sampling is achieved by means of orienting eye movements, which entail both receiving visual input as well as generating movement commands. Indeed, oculomotor structures like the midbrain superior colliculus (SC) contribute to both processes. Conventionally, however, SC visuo-motor integration is believed to occur in a sequential manner: “vision” first takes place, and “action” follows. Thus, if the same saccade is made towards two different image features, the SC motor bursts should be completely the same; it should not matter, from a motor perspective, whether the saccade target is a car or a face. Here, by recording from SC neurons while monkeys generated saccades towards peripheral stimuli of varying visual features, we found intriguing evidence to the contrary. SC movement commands exhibit robust sensory tuning that is not explained by systematic changes in saccade properties; for a given saccade, the SC motor burst could be strong or weak simply as a function of the image features at the saccade target location. This sensory tuning of SC neural movement commands can afford higher brain areas with information about the upcoming foveated visual stimulus, which can aid in establishing perceptual stability in the face of saccade-induced retinal image shifts. To explore this possibility, we measured human peri-saccadic perceptual thresholds when saccades were made to different image features. As expected, participants exhibited elevated thresholds around saccades. Critically, however, the thresholds varied significantly with the saccade targets’ image features. These results provide a novel insight on the functional role of SC motor bursts, and they suggest that corollary discharge of SC neural movement commands can extend beyond simple spatial location updating to relaying information about the visual properties of saccade targets.
