Motion aftereffect after monocular adaptation to filled-in motion at the blind spot.

Although the blind spot encodes no visual information, one never perceives an odd blob or blank there, but sees a complete scene of the world even when viewing monocularly. This phenomenon called "filling-in" might be related to mechanisms essential to surface perception, but the neural representation has still been unclear. To determine at what stage the computation for filling-in is established in the visual system, whether prolonged observation of a filled-in motion including the blind spot of one eye could cause motion aftereffect at the corresponding visual field of the other eye was examined. The result was positive--interocular transfer of motion aftereffect was obtained at the tested eye. This finding suggests the possibility that real motion and filled-in motion share a common motion pathway in an early stage in the human visual system.