Direction-selective visual responses in macaque superior colliculus induced by behavioral training

Abstract

In a previous report, we described a heretofore undetected population of neurons in the intermediate and deep layers of the monkey superior colliculus (SC) that yielded directionally selective visual responses to stimuli presented within the central 4° of the visual field. We observed these neurons in three monkeys that had been extensively trained to perform a visual direction discrimination task in this region of the visual field. The task required the monkeys to report the perceived direction of motion by making a saccadic eye movement to one of two targets aligned with the two possible directions of motion. We hypothesized that these neurons reflect a learned association between visual motion direction and saccade direction formed through extensive training on the direction discrimination task. We tested this hypothesis by searching for direction-selective visual responses in two monkeys that had been trained to perform a similar motion discrimination task in which the direction of stimulus motion was dissociated from the direction of the operant saccade. Strongly directional visual responses were absent in these monkeys, consistent with the notion that extensive training can induce highly specific visual responses in a subpopulation of SC neurons.