Adaptive modifications of human postsaccadic pursuit eye movements induced by a step-ramp-ramp paradigm.

The main purpose of the present study was to investigate adaptive properties in human smooth-pursuit eye movements generated by a peripheral moving target. In adaptation trials, a target appeared in the peripheral visual field and immediately moved away at a constant speed, and a subject made a saccade and postsaccadic pursuit responses to track it. The target speed was, however, changed to a higher or lower constant speed (step-ramp-ramp target motion) at the termination of the saccade. This adaptation paradigm induced adaptive modifications in postsaccadic pursuit responses and our results revealed the following properties of the pursuit adaptation system. TOPOGRAPHIC MODIFICATION: Modification of the initial pursuit velocity depends on the position of a moving target. PURSUIT GAIN CHANGE: Pursuit velocity is modified not by the addition of a constant bias to the pre-adaptation pursuit velocity, but by a change in the pursuit gain (pursuit velocity/target velocity). LACK OF INFLUENCE ON SACCADE PROPERTIES: Pursuit adaptation does not change the amplitude and latency of saccades either to a moving target or to a stationary target.