Influence of motion signals on the perceived position of spatial pattern.

After adaptation of the visual system to motion of a pattern in a particular direction, a static pattern appears to move in the opposite direction-the motion aftereffect (MAE). It is thought that the MAE is not accompanied by a shift in perceived spatial position of the pattern being viewed, providing psychophysical evidence for a dissociation of the neural processing of motion and position that complements anatomical and physiological evidence of functional specialization in primate and human visual cortex. However, here we measure the perceived orientation of a static windmill pattern after adaptation to rotary motion and find a gradual shift in orientation in the direction of the illusory rotation, though at a rate much lower than the apparent rotation speed. The orientation shift, which started to decline within a few seconds, could persist longer than the MAE, and disappeared when the MAE was nulled by physical motion of the windmill pattern. Our results indicate that the representation of the position of spatial pattern is dynamically updated by neurons involved in the analysis of motion.