Decoding the Viewpoint and Identity of Faces and Bodies

Abstract

Our visual system allows us to recognize familiar individuals across different viewpoints, despite large differences in low-level visual information. Previous neuroimaging research has shown that there is a hierarchical organisation across face-responsive brain regions, with lower-level regions representing head viewpoint and higher-level regions representing face identity. In this study, we investigated whether a similar hierarchy is present in body-responsive brain regions, as we also see bodies from many different viewpoints and psychological research has shown we also use information from the body for identification. Furthermore, we investigated whether representations of viewpoint and identity are face and body specific, or generalise to a common representation. We trained participants to recognize three individuals from images of their face and body. We then recorded their brain activity using fMRI while they viewed images of the face and body (shown separately) of the individuals from different viewpoints. Participants responded to the identity or viewpoint, revealing differences in neural representation depending on which feature participants attended to. We found that the occipital face area and extrastriate body area contain representations of face and body viewpoint, and that these viewpoint representations generalize across the face and body (e.g. a classifier trained to distinguish viewpoint of faces could decode viewpoint of bodies). Furthermore, we found that the fusiform body area (FBA) represents body identity in a viewpoint-invariant manner. We decoded face identity in the FBA, and also found a trend in the anterior temporal face area, that has previously been shown to represent face identity. In total, our results show that lower-level face- and body-responsive regions represent viewpoint, and these representations are not driven by low-level visual similarity. We show that the FBA represents body identity, indicating that a similar hierarchy is present for body identity representations in occipi-totemporal cortex as has been previously identified for faces.