Structural Neural Correlates of Biological Motion Detection Ability

Abstract

Detection of biological motion is both commonplace and important. Humans vary considerably in their ability to detect biological motion but the neural correlates of these individual differences remain poorly understood. A network of brain areas (the action perception system or APS) including the posterior superior temporal sulcus (pSTS) is linked to biological motion processing. Here, we investigated neural substrates of individual differences in biological motion perception in a large group (n = 31) of healthy individuals. We measured performance in several different psychophysical experiments hypothesizing that consistent individual differences across tasks would indicate joint mechanisms supporting these tasks. We also examined whether the anatomical structure of action perception regions was associated with biological motion detection ability using voxel-based morphometry (VBM). In a biological motion detection task, point-light animations depicting familiar actions were presented with a variable number of noise points, and detection thresholds were estimated adaptively. We also obtained thresholds for biological motion direction discrimination, non-biological object motion detection and direction discrimination, and motion coherence. Structural MRI scans were used to identify neural correlates of behavioral performance. Behaviorally, weak or absent correlations between individual differences in biological motion detection performance and other tasks suggested that different mechanisms may contribute to these abilities. These results can also explain some inconsistencies in the literature on biological motion processing. VBM analyses revealed that grey matter volume in the left pSTS was significantly associated with the ability to detect biological motion. This structural relationship was specific to biological motion, because no correlation with pSTS gray matter volume was found for the other tasks, including direction discrimination task with biological motion stimuli. Furthermore, the left pSTS was the only region in the APS that predicted individual differences in biological motion detection performance. Our results delineate the structural neural basis of inter-individual variability in biological motion detection.

Wellcome Trust (GR), Marie-Curie (SGD), Danish National Research Foundation (BB), JSPS (RK).