Cortical tracking of hierarchical rhythms orchestrates the multisensory processing of biological motion

When observing others’ behaviors, we continuously integrate their movements with the corresponding sounds to enhance perception and develop adaptive responses. However, how the human brain integrates these complex audiovisual cues based on their natural temporal correspondence remains unknown. Using electroencephalogram, we demonstrated that rhythmic cortical activity tracked the hierarchical rhythmic structures in audiovisually congruent human walking movements and footstep sounds. Remarkably, the cortical tracking effects at different time scales exhibit distinct modes of multisensory integration: an additive mode in a basic-level, narrower temporal integration window (step-cycle) and a super-additive enhancement in a higher-order, broader temporal window (gait-cycle). Moreover, only the cortical tracking of higher-order rhythmic structures is specialized for the multisensory integration of human motion signals and correlates with individuals’ autistic traits, suggesting its functional relevance to biological motion perception and social cognition. These findings unveil the multifaceted roles of entrained cortical activity in the multisensory perception of human motion, shedding light on how neural coding of hierarchical temporal structures orchestrates the processing of complex, rhythmic stimuli in natural contexts.