EARLY CORTICAL INFLUENCES IN OBJECT SEGREGATION AND THE PERCEPTION OFSURFACE LIGHTNESS

The apparent brightness of a surface is profoundly influenced by the b rightness of an adjacent surface, but these contrast effects are reduc ed when the surfaces are perceived as separate three-dimensional entit ies. Previous work has suggested that high-level perceptual and cognit ive processes involved in scene segmentation may be responsible for mo difying a surface's appearance. We demonstrate large reductions in con trast effects when the cues available for segmentation are restricted to those that isolate separate groups of early cortical neurons in the visual system. Out data contradict standard contrast-signaling models of brightness perception and imply that mechanisms of figure-ground s egmentation are already available at low levels of visual processing.