Non-target influences on the initiation of smooth pursuit.

Smooth pursuit is usually regarded as a relatively stereotyped oculomotor response in which the early part of the response reflects primarily the properties of the visual stimulus and cortical motion processing. We have investigated pursuit initiation in human subjects using the gap paradigm to alter fixation conditions, and single stationary distractors to alter visual context. The results suggest that a number of processes, distinct from motion processing, are involved in pursuit initiation. The processes which are modified by gaps and distractors are closely related and interact with each other. They may be shared with the saccade system.