Electrophysiological evidence of global structure-from-motion processing of biological motion in 6-month-old infants.

Understanding the actions of others is a fundamental and important skill for navigating our social world. A striking example of how our visual system is sensitive to others' actions is the phenomenon of biological motion (BM), in which the visual system encodes socially relevant information regarding action from as few as a dozen point-lights of motion. Previous studies have demonstrated that infants can discriminate between BM and other types of actions. However, there is a lack of electrophysiological evidence outlining the exact point of time within the first year of life when global structure-from-motion processing of BM emerges. We herein show a clear event-related potential (ERP) response related to the global structure-from-motion processing of a coherent human point-light walker in 6-month-old infants. We introduced a novel experimental paradigm composed of two stimuli phases to extract a single ERP component related to the global structure-from-motion processing of a coherent human point-light walker. Furthermore, we demonstrated that an enhanced single ERP component observed at approximately 482-586 ms following the onset of the stimulus of a coherent human point-light walker was larger than that of a spatially scrambled point-light walker in 6-month-old infants. These findings suggest that 6-month-old infants can process the global structure-from-motion information of a coherent human point-light walker, which may involve the posterior part of the superior temporal sulcus region. The current findings further refine the recently outlined developmental theory of BM processing.