Compensation for smooth pursuit eve movements in expanding, contracting, and rotating optic flow

Abstract

Viewing expanding optic flow while tracking a moving target results in a retinal pattern of expansion with a focus that is displaced in the direction of the pursuit eye movement. This displacement results from the addition of retinal slip (due to the pursuit velocity) to the instantaneous flow field. To an observer, the focus appears somewhere between the physical and the retinal location, suggesting a compensation for the visual effects of pursuit velocity on the flow field. Here, we investigate compensation in other types of flow. In addition to expansion, we used contracting and rotating flow. This revealed a novel component of shift that did not depend on the pursuit velocity per se, but rather on the overall change in gaze direction. Interestingly, compensation appears to be more complete for the novel component of displacement than for the classic (pursuit-velocity-dependent) component. Correcting for the novel component showed that the compensation for the classic component of displacement was of similar magnitude in expanding, contracting, and rotating flow.