Abstract
The perception of other people is important in daily life. Our typical visual experience of bodies includes seeing our own body (from an egocentric viewpoint) and others' bodies (from an allocentric viewpoint). The superior temporal sulcus (STS), fusiform face area (FFA), and extrastriate body area (EBA) are among the regions selective for biological stimuli (e.g. faces and bodies). In an fMRI study, we asked if these regions are sensitive to the identity of the person being viewed, and if so, whether this depends on an egocentric or allocentric viewpoint. The stimuli were photos of each subject (N=10) holding 20 poses (heads obscured), shot from an egocentric and an allocentric view. Three variables were tested factorially: Hemisphere, Identity (self or other), and Familiarity of view (familiar: self-egocentric and other-allocentric; unfamiliar: self-allocentric and other-egocentric). We measured the effect of these variables in the individually-localised STS, FFA, and EBA. Each region showed a significant three-way interaction. The right EBA preferred allocentric to egocentric views, but the left EBA showed no effects. The right STS preferred others in the familiar (allocentric) view to the self in a familiar (egocentric) view; no difference was found between self and other in the unfamiliar views. The left FFA showed a main effect preference for other vs. self; no effect was found on the right. The right EBA's preference for an allocentric view regardless of identity hints at an “early” role in processing body images. The right STS may play a higher-level role given that its sensitivity to identity depends on view. The left FFA, consistent with its ventral location, is sensitive to identity but not view. These results help identify the relative roles of these three regions in processing biological stimuli, and reveal a surprising sensitivity to manipulations of body stimuli in two regions (STS and FFA) that were identified on the basis of face selectivity.
A.C. is funded by the Economic and Social Research Council, UK.