Neural adaptation of imaginary visual motion.

Observers made time-to-contact judgements about an imagined moving object that passed through an area of the visual field previously adapted to a single direction of real motion. The direction of imagined motion varied relative to the direction of adapting motion. When imagined motion was in the same direction as that experienced during adaptation, imagined speed was slowed; when imagined motion was in the opposite direction, its speed was increased; when adaptation and imagined motions were orthogonal, imagined speed was unaffected. The particular influence that prior adaptation has on imagined speed suggests that imagined motion and real vision may engage common neural mechanisms without being functionally equivalent. Negative aftereffects observed in imagined motion imply that the imagination represents movement as an inference from position changes of static images.