Emergence of perceptual Gestalts in the human visual cortex: the case of the configural-superiority effect.

Many Gestalt phenomena have been described in terms of perception of a whole being not equal to the sum of its parts. It is unclear how these phenomena emerge in the brain. We used functional MRI to study the neural basis of the behavioral configural-superiority effect (i.e., visual search is more efficient when an odd element is part of a configuration than when it is presented by itself). We found that searching for the odd element in a display of four line segments (parts) was facilitated by adding two additional line segments to each of them (creating whole shapes). Functional MRI-based decoding of neural responses to the position of the odd element revealed a neural configural-superiority effect in shape-selective regions but not in low-level retinotopic areas, where decoding of parts was more pronounced. These results show how at least some Gestalt phenomena in vision emerge only at the higher stages of visual information processing and suggest that feed-forward processing might be sufficient to produce such phenomena.