The neural correlates of change detection in the face perception network.

A common view is that visual processing within the ventral visual stream is modulated by attention and awareness. We used fMRI adaptation to investigate whether activation in a network of brain regions involved with face recognition--namely the fusiform face area (FFA), occipital face area (OFA) and right superior temporal sulcus (rSTS)--was modulated by physical changes to face stimuli or by observers' awareness of the changes. We sequentially presented two matrices of four faces. In two thirds of the trials one of the faces changed. We compared activations generated in three conditions (i) change detected trials, (ii) change blind trials, and (iii) no change trials. If face areas were sensitive to physical changes then we expected similar levels of activation for face changes regardless of change detection. If face areas were sensitive to levels of awareness of change then we expected greater levels of activation for detected changes compared to no change detection. We found that all three-face regions recovered from adaptation when subjects were aware of changes, but only OFA recovered from adaptation when subjects were not aware of the changes. These results suggest that within the face network OFA is involved in representing information that has not yet entered awareness and that consciousness is not an all-or-none phenomenon throughout the ventral stream.