Common mechanisms for processing of perceived, inferred, and imagined visual motion

Does mental imagery of motion recruit populations of direction-selective neurons that also respond to perceptual motion? We show first that imagining a moving pattern while fixating a stationary target yielded a motion aftereffect (MAE), as measured by the response to directionally ambiguous perceptual test stimuli (dynamic dot displays). In a second experiment we replicated the effect and also observed the MAE when subjects' eyes were closed during imagery. In a further set of experiments, we asked whether photographs of objects frozen in motion (animals, people and vehicles) could also lead to motion adaptation. When a series of unrelated photographs was viewed, all with implied motion in the same direction, an MAE in the opposite direction was induced, again measured with dynamic dot test stimuli. The MAE was found both for right / left implied motion and for in / out implied motion, the latter created by using mirror-revered pairs of identical implied motion images either facing towards or away from each other. Similar to the perceptual MAE, the MAE to implied motion significantly declined if a delay (3 s) was introduced between adaptation and test. The MAEs to imagined and implied motion ranged from 20 – 35 % of the size of the MAE from perceived motion. The transfer of adaptation from imagined and implied motion to perception of real motion demonstrates that at least some of the same direction-selective neurons are involved in imagination and actual perception.