Body-part tuning in the macaque superior temporal sulcus

Neurons in the macaque superior temporal sulcus respond selectively to faces and headless bodies, but their selectivity for individual body parts is not well understood. We recorded from the middle superior temporal sulcus and anterior superior temporal sulcus regions activated by whole monkeys in functional MRI to examine tuning for body parts, including heads. In experiment 1, body parts were shown in color, achromatic, or with scrambled internal features to test contributions of internal structure. In experiment 2, parts were presented at the same location and size as in whole-body images across viewpoints. In both regions, faces were represented distinctly from other body parts, and genitalia, rumps, and torso formed subclusters. A hand cluster appeared variably in anterior superior temporal sulcus. Units preferring body parts other than faces or hands did not form large anatomical clusters. Modeling with convolutional neural networks indicated that part tuning relies on mid- to high-level features. Scrambling internal features showed that these contribute to, but do not fully determine, body part representations. Non-head-preferring units showed stronger response suppression when their preferred part appeared within a body than did head-preferring units. Together, these findings indicate a distinction between face and other body-part representations, with stronger modulation by body context for non-head units.