Differential sensitivity for viewpoint between familiar and unfamiliar faces in human visual cortex.

People are extremely proficient at recognizing faces that are familiar to them, but are poor at identifying unfamiliar faces. We used fMR-adaptation to ask whether this difference in recognition might be reflected in the relative viewpoint-dependence of face-selective regions in the brain. A reduced response (adaptation) to repeated images of unfamiliar or familiar faces was found in the fusiform face area (FFA), but not in the superior temporal sulcus (STS) face-selective region. To establish if the neural representation of faces was invariant to changes in viewpoint, we parametrically varied the viewing angle of successive images using 3-dimensional models of unfamiliar and familiar faces. We found adaptation to familiar faces across all changes in viewpoint in the FFA. In contrast, a release from adaptation was apparent in the FFA when unfamiliar faces were viewed at increasing viewing angles. These results provide a neural basis for differences in the recognition of familiar and unfamiliar faces.