Localization and motion perception during smooth pursuit eye movements.

We investigated the relationship between compensation for the effects of smooth pursuit eye movements in localization and motion perception. Participants had to indicate the perceived motion direction, the starting point and the end point of a vertically moving stimulus dot presented during horizontal smooth pursuit. The presentation duration of the stimulus was varied. From the indicated starting and end points, the motion direction was predicted and compared with the actual indicated directions. Both the directions predicted from localization and the indicated directions deviated from the physical directions, but the errors in the predicted directions were larger than those in the indicated directions. The results of a control experiment, in which the same tasks were performed during fixation, suggest that this difference reflects different transformations from a retinocentric to a head-centric frame of reference. This difference appears to be mainly due to an asymmetry in the effect of retinal image motion direction on localization during smooth pursuit.