Abstract
Recent evidence reveals specialized processing mechanisms for human bodies, including the discovery of body-selective areas in occipito-temporal cortex and a face-size body inversion effect. These findings have led to the suggestion that like faces, bodies are processed by holistic mechanisms. Evidence for holistic body representation includes a behavioral Whole-Part effect, and a step-like increase in response of the fusiform body area to large relative to small body parts. However, no study has directly examined whether body-selective mechanisms indeed prefer a whole body over the sum of its parts. Here we used fMRI to determine whether body-selective areas in occipito-temporal cortex discriminate intact vs. scrambled body configurations. Subjects were presented with blocks of faceless bodies that were intact, headless, armless or legless, in either whole or scrambled (part-based) configuration. For each subject we defined face, body and object-selective areas with a separate functional localizer scan. Body-selective areas showed a higher response to whole than scrambled bodies for all body types. The fusiform face area (FFA) showed higher response to whole than scrambled bodies only for intact bodies. This effect was not significant for headless, armless or legless bodies. The occipital face area (OFA) and the object-general areas showed no preference for whole over scrambled bodies. Finally, both FFA and OFA showed lower responses for headless bodies relative to intact, armless and legless bodies, which included a head. These findings suggest that holistic representation of human bodies uniquely exists in body-selective areas, but not in object-general areas. The response of face-selective areas was influenced by the presence of the head and may reflect mechanisms of face imagery, which are more likely to be generated by whole intact bodies than by headless or scrambled bodies.
Israeli science foundation to GY.