The body inversion effect is mediated by face-selective, not body-selective, mechanisms

Evidence suggesting that the brain has specialized mechanisms for processing human bodies include the discovery of body-selective brain areas and the behavioral body inversion effect (BIE). Interestingly, the BIE (worse discrimination of inverted vs upright bodies) disappears for headless bodies, implying a critical role of the head in this effect. Previous studies have shown that the face inversion effect is mediated by the fusiform face-selective area. Given the central role that the head plays in the behavioral BIE, we asked whether it is mediated by face-selective or body-selective areas. In two event-related functional magnetic resonance-adaptation experiments, we examined the representation of upright and inverted bodies in category-selective occipitotemporal areas. In the first experiment we presented whole (faceless) bodies, while in the second we presented headless bodies. Both experiments consisted of pairs of upright and inverted bodies that were either the same or different in posture. Body-selective areas showed similar adaptation effects for upright and inverted whole or headless bodies, suggesting similar discrimination for the two orientations regardless of the head. In contrast, face-selective areas showed an adaptation effect to upright but not inverted bodies, and for whole but not for headless bodies. Thus, the response of the face-selective, but not body-selective areas, is consistent with the behavioral BIE in that it shows better discrimination for upright than inverted bodies, for whole but not for headless bodies. These results suggest a critical role for the head in the processing of human bodies.