Brain Activity Evoked by the Perception of Human Walking: Controlling for Meaningful Coherent Motion

TLDR

Biological‑motion studies using point‑light displays have shown superior temporal sulcus (STS) activation, but the use of random‑motion controls leaves open whether meaningful nonbiological motion could similarly activate the STS, questioning its specificity. The authors aimed to test a hierarchy of three questions about STS activity. They employed functional magnetic resonance imaging with an anatomical region‑of‑interest approach. The STS responded preferentially to biological motion, showing stronger activation for human and robot walkers than for nonbiological movements, with robust right‑lateralized activity and distinct deactivations, while additional motion‑related activity was observed in MT/V5, fusiform gyri, right premotor cortex, and intraparietal sulci.

Abstract

Many functional neuroimaging studies of biological motion have used as stimuli point-light displays of walking figures and compared the resulting activations with those evoked by the same display elements moving in a random or noncoherent manner. Although these studies have established that biological motion activates the superior temporal sulcus (STS), the use of random motion controls has left open the possibility that coordinated and meaningful nonbiological motion might activate these same brain regions and thus call into question their specificity for processing biological motion. Here we used functional magnetic resonance imaging and an anatomical region-of-interest approach to test a hierarchy of three questions regarding activity within the STS. First, by comparing responses in the STS with animations of human and robot walking figures, we determined (1) that the STS is sensitive to biological motion itself, not merely to the superficial characteristics of the stimulus. Then we determined that the STS responds more strongly to biological motion (as conveyed by the walking robot) than to (2) a nonmeaningful but complex nonbiological motion (a disjointed mechanical figure) and (3) a complex and meaningful nonbiological motion (the movements of a grandfather clock). In subsequent whole-brain voxel-based analyses, we confirmed robust STS activity that was strongly right lateralized. In addition, we observed significant deactivations in the STS that differentiated biological and nonbiological motion. These voxel-based analyses also revealed regions of motion-related positive activity in other brain regions, including MT or V5, fusiform gyri, right premotor cortex, and the intraparietal sulci.