Abstract
Introduction. Our ability to recognize familiar faces depends more on texture (surface pigmentation) than shape (feature positioning) cues (Bruce et al., 1991; Burton et al., 2005). Accordingly, brain areas involved in processing facial identity should be more sensitive to changes in the texture of the face compared to changes in the shape of the face, and this difference should be more evident for familiar faces.
Methods. We used an fMRI adaptation paradigm to test the sensitivity of face selective regions in human visual cortex to variations in the shape or texture of familiar and unfamiliar faces. Twenty participants were scanned (3T GE Signa scanner) while viewing images of faces in a block design. A block consisted of 8 images of faces (either all familiar or all unfamiliar) presented in the following conditions: 1) same face image repeated; 2) 8 faces varying in shape only; 3) 8 faces varying in texture only; 4) 8 faces varying in both shape and texture. FMRI responses were evaluated statistically in regions of interest that were identified independently by a localiser scan for each participant.
Results. The fusiform face area (FFA) and occipital face area (OFA) showed strong adaptation to repeated images of the same face, consistent with previous results. However, both regions showed a similar release from adaptation to either shape or texture changes for both familiar and unfamiliar faces.
Conclusions. We find that the FFA and OFA are sensitive to both the shape and the texture of familiar and unfamiliar faces. These findings suggest that the responses of face selective regions (such as the FFA) are less invariant than current models imply.