Author:

Keywords:

MACAQUE, superior temporal sulcus, action processing

Abstract:

In order 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, the posterior middle temporal gyrus (pMTG) and posterior occipito-temporal sulcus (pOTS) separately process motion and configuration cues of biological motion. Furthermore, these cues are integrated in the extrastriate (EBA) and fusiform (FBA) body areas (Jastorff & Orban, 2009). Using the same design as in our human study, we performed fMRI experiments in awake monkeys to investigate the similarities and differences of action processing between the two species, thereby providing a link between existing neurophysiological data and human imaging. The point-light stimuli consisted of sixteen white dots indicating the position of the head, the major joints of the limbs and the tail of macaque monkeys performing different actions like running, jumping and climbing. In a 2x2 factorial design, one factor manipulated the configuration of the stimuli by spatially randomizing the starting position of each dot. The second one modified the kinematics of the stimuli by changing the trajectory of each dot to simple translation. In addition, we identified body selective areas in separate localizer runs (Popivanov et al. SfN 2010). As in the human study, the main effects of the two factors were anatomically segregated, with the effect of configuration significant mainly along the lower bank of the superior temporal sulcus (STS), and that of kinematics significant in the fundus and the upper bank of the STS. We also identified three separate body selective patches in posterior, middle and anterior STS using the localizer. Analysis of the activation within these body patches showed a significant interaction of the two factors in the posterior and anterior body patch as well as in the lower bank of the middle body patch that co-localized with the lower superior temporal area (LST). To the best of our knowledge, this study reports for the first time differential activation for biological actions presented as point-light displays in the monkey. Whereas future studies are needed to investigate whether or not monkeys are able to perceive point-light displays, our results provide strong evidence that the processing mechanisms of biological actions are remarkably similar in humans and macaque monkeys and provide a link between existing single-cell physiology and human imaging.