Dynamics of saccades occuring during smooth pursuit eye movement

The dynamics of saccades which occur during smooth pursuit eye movement (SP) were studied. Two stationary targets and a stepping target were applied to elicit internally guided saccades (IGS) and visually triggered saccades (VTS), respectively. The saccades differed in their peak velocities (VTS>IGS). When the above two kinds of stimuli were moved sinusoidally, the peak velocities of the saccades differed similarly to the difference between the stationary and stepping targets. Furthermore, the peak velocities of the saccades, which occurred when tracking a sinusoidally moving target, was almost the same as that when tracking the stepping target and the stepping and sinusoidally moving target. The results suggest that, during SP, both IGSs and VTSs can occur, and suggest that during the SP which occurs when human tracks a smoothly moving target, VTSs predominantly occur