Binocular rivalry: spreading dominance through complex images.

When different images are presented to the two eyes, each can intermittently disappear, leaving the other to dominate perception. This is called binocular rivalry. When using radial gratings, focal contrast increments can trigger a traveling wave of perceptual dominance change, originating at the locus of the contrast increment and circling the stimulus. This has been linked to a sweep of activity through V1 that can be traced via fMRI. The dominance of more complex images, like human faces, has been linked to higher level processing structures characterized by more holistic object centered properties. We therefore decided to assess how dominance would spread through more complex images. Using Kanisza squares and human faces we found that dominance tended to spread gradually away from the locus of the contrast increment, often along real or illusory contours. We also found that perceptual dominance was slow to spread between facial regions encoded by different monocular channels. These data are consistent with low-level monocular mechanisms, like those found in V1, playing a determinant role in the spread of perceptual dominance through complex images during binocular rivalry.