Stimulus representations in body-selective regions of the macaque and human cortex assessed with event-related fMRI

Abstract

Functional imaging studies in humans and monkeys have shown category-selective regions in the temporal cortex, in particular for faces and bodies. However, we still know little about the functional properties of such regions and their correspondence across the two species. To address this question, we investigated the selectivity and spatial distribution of body and face patches testing an identical set of 200 stimuli in both species. We showed achromatic images of headless Monkey and Human Bodies, two sets of man-made Objects, Monkey and Human Faces, four-legged Mammals, Birds, Fruits, and Moore Sculptures to 7 human subjects and 4 macaque monkeys in an event related design. Two regions in the middle and anterior Superior Temporal Sulcus (STS) of the monkey were more strongly activated by monkey bodies compared to objects. These two regions partially overlapped with regions that were more activated by faces than objects. Multivoxel-pattern analyses showed that both body-selective regions primarily distinguished faces from other inanimate and animate objects, including bodies. A secondary distinction was present between inanimate objects and bodies in the middle STS body region. In humans, the extrastriate body area (EBA) primarily distinguished between animate and inanimate stimuli with a secondary distinction between bodies and faces. The fusiform body area (FBA) primarily distinguished faces, animals and birds from the other categories with a secondary distinction between bodies/sculptures and the other inanimate stimuli. At the individual stimulus level, both EBA and FBA showed three main cluster, almost perfectly separating the 80 body stimuli, the 40 face stimuli and the 80 inanimate stimuli. Overall, these data indicate strong spatial clustering of animate categories in the macaque STS and human occipito-temporal cortex. Even though the clustering results were slightly different between humans and monkeys, the overall dissimilarity matrices of EBA and the mid STS body patch were highly congruent.

Meeting abstract presented at VSS 2013