Altered Hierarchical Visual Rhythm Tracking in Early Deafness

Rhythm perception enables humans to navigate dynamic environments. The auditory system is particularly adept at processing rhythmic temporal structure, and auditory training exerts a greater influence than visual training on visual rhythm perception, leading to the hypothesis that auditory coding may support visual rhythm representation. This raises a fundamental question: whether and to what extent the deprivation of auditory coding capabilities influences visual rhythm processing. To investigate this issue, we assessed cortical tracking of hierarchical visual rhythms in hearing and early deaf participants using electroencephalography (EEG). Participants viewed 2 types of rhythmic sequences: geometric shapes and point-light walkers. Each stimulus type consists of a lower-order basic rhythm defined by stimulus recurrence and a higher-order chunk rhythm built on perceptual or cognitive organization. Results showed that hearing participants exhibited robust cortical tracking of both basic and chunk rhythms across stimuli. In contrast, deaf participants exhibited preserved tracking of basic rhythms but reduced tracking of chunk rhythms. Moreover, compared with the hearing group, the deaf group showed reduced visual-auditory and visual-frontal functional connectivity, and individual differences in connectivity strength were positively correlated with chunk-rhythm tracking. These findings support a hierarchical auditory scaffolding framework, in which auditory experience is selectively associated with higher-order visual rhythm perception through temporal chunking mechanisms.