Extraretinal inputs to neurons in the rostral superior colliculus of the monkey during smooth-pursuit eye movements.

The intermediate and deep layers of the monkey superior colliculus (SC) are known to be important for the generation of saccadic eye movements. Recent studies have also provided evidence that the rostral SC might be involved in the control of pursuit eye movements. However, because rostral SC neurons respond to visual stimuli used to guide pursuit, it is also possible that the pursuit-related activity is simply a visual response. To test this possibility, we recorded the activity of neurons in the rostral SC as monkeys smoothly pursued a target that was briefly extinguished. We found that almost all rostral SC neurons in our sample maintained their pursuit-related activity during a brief visual blink, which was similar to the maintained activity they also exhibited during blinks imposed during fixation. These results indicate that discharge of rostral SC neurons during pursuit is not simply a visual response, but includes extraretinal signals.