Spatial Motion Coordinates that Determine the Perceptual Dominance in Binocular Rivalry

It is known that moving stimuli perceptually dominate over static stimuli during binocular rivalry. Recent evidence shows that visual motions can be processed in spatiotopic, or object-based as well as retinotopic coordinates. Here we examined which spatial coordinate determines the motion dominance in binocular rivalry. Observers viewed a dichoptic pair of stimuli, each consisting of a fixation marker, a gray square background, and a diagonal grating (45 deg in one eye and 135 deg in the other). The observer judged which grating appeared dominant. Drifting gratings were dominant over static gratings when observers maintained stationary fixation. However, when they tracked the fixation marker that moved together with the drifting grating, the physically drifting but retinotopically stationary grating became dominant. When observers tracked fixation marker and stimulus background both moving together, the gratings that were physically stationary but moving in retinotopic and object-based coordinates were perceptually dominant. Subsequent quantitative analyses revealed that spatiotopic and object-based motions contribute equally with or even more than retinotopic motion. These results demonstrate a significant role of nonretinotopic motion signals in triggering the conscious awareness of visual stimuli.