Curvature-biased cortical areas in human visual cortex

Abstract

A recent study comparing functional MRI activity in rhesus macaques evoked by distinguishing between round and rectilinear shapes strongly suggests that there exists a network of cortical areas selective for curvature processing. Additionally, these curvature-based areas partially overlap with the well-studied face-processing areas. However, further research is required to ascertain: 1) whether there are equivalent human homologues of monkey curvature-biased cortical areas; 2) if so, is there an anatomical relationship between the curvature-processing areas and the face-processing cortical areas in the human brain. FMRI was acquired in a 7T SIEMENS scanner (1.43 mm voxels) in response to visual presentation of different round vs. rectilinear shapes matched to those used in monkey fMRI. Stimuli included: 1) images of round and rectilinear real world objects, 2) computer-generated arrays of 3D shapes (e.g. spheres or pyramids). The independent runs were included to localize the known cortical areas, such as the face-selective, object-selective, scene-selective, and early visual areas. Our preliminary results reveal significant fMRI biases in the ventral visual pathway to round vs. rectilinear shapes; however, the rectilinear-biased areas are solely confined to bilateral parahippocampal gyrus. These results are consistent with those observed in macaques. Areas biased to round shapes include human V4, OFA, FFA1, EBA, and possibly V8. Curvature-biased areas in the human V4 correspond to the posterior curvature-biased patches in monkeys. The OFA, which has been shown to encode round shapes, seems to be the homologue of middle curvature-biased patches in monkeys. However, it remains unclear from the preliminary data where the human homologue of the monkey anterior curvature-biased patches is. The close proximity of curvature-biased areas and face-processing areas in human visual cortex is consistent with results collected from monkey fMRI experiments, suggesting a functional link between face and curvature processing in both human and non-human primates. Meeting abstract presented at VSS 2015