Faciotopy a face-feature map with face-like topology in the occipital face area
55.25, Tuesday, May 14, 5:15 - 7:15 pm, Royal Ballroom 4-5
Nikolaus Kriegeskorte1, Marieke Mur1, Linda Henriksson1,2; 1MRC Cognition and Brain Sciences Unit, Cambridge, UK, 2Brain Research Unit, O.V. Lounasmaa Laboratory, Aalto University, Espoo, Finland
Brain imaging studies have suggested several brain regions specialized for face perception. However, the intrinsic functional organization of these regions and their status as cortical areas with clearly defined boundaries is unclear. Here we test for "faciotopy" in human face-selective brain regions, i.e. a face-feature map on the cortical surface, where cortical distances reflect the physical distance between the different face features. We measured responses to visual presentation of isolated face features with functional magnetic resonance imaging (fMRI). The features were extracted from frontal face photographs (12 in total) and included the left and right eyes, nose, mouth, ears, chin, and parts of the neck and hairline. Different exemplars of the different features were presented in an fMRI block design. All stimuli were shown in the center of the visual field. Primary visual cortex (V1), occipital face area (OFA) and fusiform face area (FFA) were localized in each individual (N=12) using independent localizer data. All regions-of-interest responded to the isolated face features, and their response patterns also distinguished between the features. In addition, OFA, but not V1, showed a substantial tolerance to retinal feature size. We compared the distances between the cortical face-feature representations to the physical distances between the features in a face, and found a significant faciotopic organization in both left and right OFA, but not in V1 or FFA. This finding suggests that OFA might be spatially organised as a single map of a face, with local patches detecting individual features with some degree of invariance. Faciotopy would be the first example, to our knowledge, of a cortical map reflecting the topology, not of a part of the organism itself (its retina in retinotopy, its body in somatotopy), but of an external object of particular perceptual significance.