Abstract
Filling-in occurs when a retinally stabilized object undergoes perceptual fading. It is commonly believed that information about the apparently vanished object is lost and replaced solely by information arising from the surrounding background. Here we propose a new theory according to which the mechanism of filling-in is in fact a process of feature mixing, whereby features on either side of a perceptually faded boundary merge additively. Our psychophysical data show that, after prolonged viewing of visual stimuli composed of different colors in the background and the foreground, the filled-in percept is the additive mixture of the two colors. fMRI results using multi-voxel pattern analysis reveal that while subjects were in a perceptual fading/filling-in state (after prolonged viewing of blue disks on a red background), the BOLD activation pattern in V1 behaves as if the subjects were perceiving a perceptually mixed color (purple). Together, these results imply that the mechanism of “filling-in” is in fact a process of featural mixing.