Integration of shape and motion cues in biological motion processing in the monkey STS

To correctly perceive biological actions, the movement pattern generated in the course of the action has to be linked to the configuration of the actor. Recently, we showed that in humans, motion and configuration cues are processed separately in occipito-temporal cortex, and that both cues are integrated in the extrastriate (EBA) and fusiform (FBA) body areas (Jastorff and Orban, 2009). Using the same factorial design as in our human study, we performed fMRI experiments in awake monkeys to compare biological motion processing in the two species. Point-light displays of monkeys engaged in various actions were presented in a 2×2 factorial design. One factor manipulated the configuration of the stimuli, the other, the kinematics. As in humans, the two factors were anatomically segregated in the superior temporal sulcus (STS) rostral to the MT/V5 complex, with the effect of configuration significant along the lower bank and that of kinematics significant in the fundus and the upper bank of the STS. Moreover, voxels showing a significant interaction between the two factors were mainly confined to body-selective patches within the STS, mimicking our human findings. Importantly, this study reports for the first time differential activation for biological actions presented as point-light displays in the monkey. Moreover, our results suggest that the processing mechanisms of biological actions are remarkably similar in humans and macaque monkeys, and provide the basis for linking existing and future single-cell physiology in the monkey with human functional imaging.