Coordination of smooth pursuit and saccades

Smooth pursuit and saccades are two components of tracking eye movements. Their coordination has usually been studied by investigating latencies of pursuit onset in response to a moving target appearing simultaneously with the disappearance of the stationary fixation target. The general finding from such studies has been that latencies of saccades and pursuit are different and reflect independent processes. We discuss several limitations of the used targets. In this paper, we study latencies of saccades and smooth pursuit in response to a moving target that overlaps in time with a pursued moving target. We find that saccades and pursuit changes are synchronized. Furthermore, pursuit changes are made fast. Directional changes occur almost entirely within the accompanying saccade. To explain the results we hypothesize a two-stage mechanism for the coordinated generation of saccades and pursuit.