A bilateral occipitotemporal network mediates face perception

The aim of the present study was to further explore the neuronal mechanisms of face processing in healthy subjects which may help to understand the difficulties experienced by prosopagnosia subjects. A further goal was to compare face specific activation patterns in the right and left occipital face area (OFA) and fusiform face area (FFA) for famous faces, non-famous faces and caricatures of famous faces in four individuals suffering from developmental prosopagnosia (DP) and seven healthy controls, using functional magnetic resonance imaging and psychophysiological interaction analysis (PPI). Control subjects showed higher face related activations in the right compared to the left FFA. Caricatures of faces of famous people and photographs of non-famous faces yielded higher percent signal changes in the OFA and FFA compared to photographs of famous faces. These data support the idea that the OFA and FFA discriminate between familiar and new face representations. The activation patterns of DP subjects were heterogeneous, with none of the patients showing bilateral face related activations in both OFA and FFA. There was no evidence of a left hemispheric activation when the right homologue failed to be activated, supporting the view of a right hemispheric dominance in face perception. PPI analysis indicated a link between activation of the right FFA and the other three tested regions, the left FFA and the right and left OFA. In summary, all four face related brain regions appear to be necessary for successful face processing, and disruption of one component may lead to face recognition deficits.