Loci of the release from fMRI adaptation for changes in facial expression, identity, and viewpoint

Face recognition involves collaboration of a distributed network of neural correlates. However, how different attributes of faces are represented has remained unclear. We used functional magnetic resonance imaging-adaptation (fMRIa) to investigate the representation of viewpoint, expression, and identity of faces in the fusiform face area (FFA) and the occipital face area (OFA). In an event-related experiment, subjects viewed sequences of two faces and judged whether they depicted the same person. The images could vary in viewpoint, expression and/or identity. Critically, the physical similarity between view-changed and between expression-changed faces of the same person were matched by the Gabor-jet metric, a measure that predicts almost perfectly the effects of image similarity on face discrimination performance. In FFA, changes of identity produced the largest release from adaptation followed by changes of expression; but the release caused by changes of viewpoint was smaller and not reliable. OFA was sensitive only to changes in identity, even when image changes produced by identity variations were matched to those of expression and orientation. These results suggest that FFA is involved in the perception of both identity and expression of faces, a result contrary to the hypothesis of independent processing of changeable and invariant attributes of faces in the face-processing network.