Abstract
An experiment was designed to study the target predictability subserving pursuit eye movements.
Horizontal eye movements were measured by binocular recording of the electronystagmography (ENG) in 18 normal subjects. Targets were projected on a screen and moved horizontally at a constant velocity (12°/sec) and fixed-cycle (0.1 Hz). The maximum displacement of the target was 30° from center. Near the center of the screen, targets were caused to disappear by a mechanical shutter for three short intervals (417, 833, 1250 msec). Horizontal angular deviations of these intervals were 5°, 10°, 15° respectively.
Smooth pursuit eye movements were maintained and no saccadic eye movements were recorded by tracking 5° center off stimuli. Under 10° and 15° center off stimuli, searching saccades occurred after 300 msec from the disappearence of the target and corrective saccades occurred after 200-240 msec from the reappearence of the target. Smooth pursuit eye movements were maintained for about 300 msec without visual stimuli. Our results suggest that target predictability contributes to the pursuit system.
