Preparatory modulation of the gain of visuo-motor transmission for smooth pursuit in monkeys.

Brief movement of a foveated target is known to elicit higher velocity ocular (tracking) responses if the target is in motion rather than stationary. We determined whether similar perturbations of a stationary target would have greater ocular effects if we merely increased the probability that the target might undergo sustained motion. For this, we examined the effect of interleaving trials in which the target was always stationary with trials in which the target underwent sustained motion that required the animal to track. We found that perturbation of the stationary target had a greater effect when there were interleaved trials in which the target moved, as though the gain of the visuo-motor transmission had been increased in anticipation of future tracking.