Abstract
Similar to faces, discrimination of human bodies is much worse for inverted than upright bodies. Interestingly, this body inversion effect disappears for headless bodies, which implies a critical role for the head in the generation of this effect. Previous studies have shown that the face inversion effect is mediated by the fusiform face-selective area. Given the central role the head plays in the behavioral body inversion effect, here we asked whether the body inversion effect is mediated by face-selective or body-selective brain areas. In two event-related fMR-adaptation experiments, we measured the response of category-selective occipito-temporal areas to pairs of upright or inverted bodies that were either same or different in posture. The first experiment presented whole bodies, while the second used headless bodies. For all body stimuli internal facial features were covered with a gray ellipsoid. Body-selective areas showed a higher response to inverted than upright bodies, but a similar adaptation effect (higher response to different than same pairs) for the two orientations, suggesting similar discrimination for upright and inverted bodies. This pattern was found for both whole bodies and headless bodies. In contrast, face-selective areas showed adaptation effect to upright but not inverted bodies. This pattern was found for whole bodies but not for headless bodies, where there was no adaptation for both orientations. Response of object-general areas (LOC) was higher for inverted than upright bodies and showed no adaptation effect for both orientations. Thus, only the response of the face-selective regions was consistent with the behavioral body inversion effect in that it shows discrimination for upright but not inverted bodies, for whole but not for headless bodies. We conclude that the body inversion effect is not mediated by body processing mechanisms but by face or head processing mechanisms.
Israeli Science Foundation Grant to GY 65/08.