Comparing motion and static feature selectivity between the macaque dorsal and ventral temporal visual cortical body patches

Abstract

Previous studies identified body patches in the macaque inferotemporal cortex that were activated more strongly by static images of bodies compared to faces and objects (Vogels, 2022). Recently we mapped 'dynamic body patches' using twenty 1 s videos of dynamic monkey bodies, 20 dynamic monkey faces, and 20 dynamic objects (Bognar et al., SfN 2022). In this fMRI-guided single-unit study, we investigated the contribution of shape and motion to the neural representations underlying the visual processing of moving bodies. We recorded single neurons, using the same videos and monkey subjects as for the fMRI mapping, in the dorsal (upper bank/ fundus Superior Temporal Sulcus (STS)) and ventral (ventral bank/ ventral to STS) dynamic body patches in the anterior temporal visual cortex. Most neurons responded more to body videos in both ventral and dorsal patches. Many neurons responded equally well to static frames and the original videos, whereas others responded only to videos, requiring motion. Some cells were also selective for the frame order of a video (video reversal). Estimated optical flow and neural inter-video distances were highly correlated across body videos, indicating that neurons captured the dynamics of body movements. Dorsal patches captured more body motion than ventral patches (p < 0.05, bootstrapping). These regions also tended to respond to facial movements, but not to the movements of objects. Deeper layer (5-7) AlexNet feature and neural inter-video distances were correlated across body videos in the ventral patches, indicating selectivity for static features of bodies. Interestingly, no significant correlation was found in the dorsal patches. These findings suggest that both the dorsal and ventral body patches in the anterior temporal visual cortex are sensitive to body motion. Unlike ventral body patches, the selectivity of dorsal patches for moving bodies is not accounted for by Alexnet features.