Abstract
Stationary and moving textured backgrounds have been shown to reduce initial velocity and steady-state gain of smooth pursuit eye movements [e.g., Kimmig, Schwarz, & Miles, J. Neurophys., 68(6), 2147–2164 (1992)]. We recorded eye movements from human observers to a small bright Gaussian dot that moved horizontally at 12 deg/s. The visual context in the vicinity consisted of two vertical sinusoidal gratings, one above and one below the stimulus trajectory that were either stationary or moved at the same speed as the target, into the same or opposite direction. We observed that during pursuit initiation, eye velocity was increased/decreased by up to 50% when the context gratings moved into the same/opposite direction as the target. The effect was persistent but smaller (25% velocity change) throughout the steady-state tracking phase. In a second experiment, the moving context changed speed to 0, 6, or 18 deg/s during the steady-state phase and remained stationary, slower, or faster until the end of the trial. This perturbation only had an effect on steady-state eye velocity when the gratings moved along with the target. At about 70 ms after perturbation, eye velocity increased/decreased by about 20% for an increase/decrease in contextual velocity. We conclude that a visual context flanking the stimulus trajectory can produce the same effect on pursuit performance than a full-field textured background.