Integration of form and motion for biological motion displays in the monkey

Abstract

fMRI experiments in the human using point-light animations have shown that the extrastriate and the fusiform body area are involved in the integration of form and motion features of biological motion (Jastorff & Orban, 2009). Using the same design as in our previous study, we performed fMRI experiments in awake monkeys to investigate whether monkeys would be sensitive to point-light animations, and if the body areas in the monkey would play a similar role as the ones in the human. 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 2 × 2 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 areas and retinotopic areas in separate localizer runs. The body localizer points to two main body areas, one anterior to FST, the other one located on the lower bank of the anterior STS (Popivanov et al., 2010). Similar to the human results, we obtained a significant superposition of both main effects and thus strongest activation for intact point-light monkeys, when using the independently defined body areas as regions of interest. Moreover, the main effect of kinematics elicited significant activation in the upper bank of the STS, possibly area STPm, and the one of configuration lead to activation in the lower bank and lip of STS up to the level of TEO. Our results indicate that monkey STS processes biological motion (Oram & Perrett, 1996) and that the principle of processing of complex actions seems very similar between humans and monkeys.

FWO-Vlaanderen, EFV/10/008, GOA, IUAP.