Velocity profile of smooth pursuit eye movements in humans: pursuit velocity increase linked with the initial saccade occurrence.

To investigate a possible relationship between the initiation of saccade and pursuit eye movements, we examined the velocity dynamics of pursuit eye movements when human subjects tracked a peripheral moving target after fixating a stationary target. The pursuit velocity dynamics differed markedly depending on the latency of the initial saccade. The presaccadic pursuit velocity remained small even when the initial saccade latency was long, and the postsaccadic pursuit velocity was increased greatly even when the initial saccade latency was short. A large increase in pursuit eye acceleration occurred tightly coupled with the initial saccade. These results suggest synchronization between the processes underlying the generation of saccade and pursuit eye movements.