Apparent movement and appearance of periodic stripes during eye movements across a stroboscopically illuminated random dot pattern.

When the eyes follow a small target moving across a stationary random dot pattern illuminated stroboscopically at 3--45 flashes . s-1, the structure of the random dot pattern is seen as moving in the direction of the eye pursuit movements (sigma-movement). At flash frequencies above 9.5 flashes . s-1, periodic stripes oriented perpendicularly to the direction of the pursuit eye movements appear and are also seen as moving in the direction of the eye pursuit movement. The period Ps of the apparent stripes depended on the flash frequency fs and the angular speed of the eyes Ve: Formula: see text. Apparent sigma-movement and apparent stripes were also seen when eye pursuit movements were initiated outside of the random dot pattern and they continued autonomously without a moving target across the pattern. The angular velocity of the sigma-pursuit movement across the random dot pattern depended on the flash frequency and the angular velocity of the initiating target. With the eyes stationary but a moving random dot pattern, the apparent stripes also appeared at flash frequencies fs greater than or equal to 9.5 flashes . s-1. Eq. (1) was valid when Ve was replaced by the target angular velocity Vs (k = 1).