Use of target velocity in saccadic programming

Previous studies indicate that in response to a step-ramp visual target movement, the saccade amplitude approximates target displacement 100 ms before saccade onset. This study examines whether the saccadic system takes target motion into consideration when computing saccadic amplitude, if target movement is seen by the subject before he is requested to make a saccade. In the first experiment, while the subject fixated at the target (laser dot) and maintained fixation, the target jumped to the left and moved to the right at a fixed velocity. At some predetermined site, the target jumped a step to the right and continued to move in that direction. After the target step, the subject had to make a saccade and follow target motion. In the second experiment, while the subject fixated at the target and maintained fixation, the target jumped to the right and up and moved down at a fixed velocity. At some predetermined site, an auditory signal was given, and the subject had to make a saccade and follow target motion. Results in both experiments showed that the eye position was statistically different from the target displacement at 100 ms before saccade onset, indicating that the saccadic system uses target velocity in computing saccade amplitude.