Smooth-pursuit initiation in the presence of a textured background in monkey.

Smooth pursuit eye movements in the monkey were studied by measuring the average eye acceleration in the first 100 msec of the ocular response to suddenly moving constant velocity discrete visual targets. The tracking target's motion was initiated on or eccentric to the fovea against a very dimly lit homogeneous background or an illuminated, highly textured, large-field background. The effect of the textured background was always to reduce the initial eye acceleration as compared to that present in the homogeneous background case. Movement of the background in the opposite direction to target spot movement also reduced the initial eye acceleration. In contrast, steady-state tracking measured several hundred msec after the onset of pursuit under the same conditions was only marginally reduced by the presence of the textured background.