Dynamic reorganization of functional networks underlying audiovisual interactions.

Crossmodal interactions involve crosstalk between different cortical areas and dynamic recruitment of regions, which is crucial for integrating sensory information into a coherent percept. Despite their significance, the dynamic cortical networks underlying the crossmodal influence of auditory information on visual motion processing-particularly in terms of temporally resolved EEG connectivity-have yet to be comprehensively characterized. In the present study, we investigated frequency-specific networks underlying audiovisual interactions during motion and speed estimation. Functional networks were generated using directed transfer function (DTF) and adaptive DTF (ADTF) to estimate connectivity patterns of electroencephalogram (EEG) data. Network-based statistical analyses revealed frequency-specific networks in the theta and alpha bands, which supported long-range communication between occipital/parieto-occipital, parietal, and frontal regions during audiovisual interactions compared to unisensory visual motion processing. Graph theory analyses demonstrated a transition from localized and segregated processing to global integration, emphasizing cortical network reorganization according to the demands of sensory processing. Moreover, these analyses further revealed frequency-specific shifts in connectivity over time, with low-frequency oscillations exhibiting sustained connectivity increases, while high-frequency bands showed transient patterns, reflecting the temporal flexibility of neural networks. These findings illustrate how local and global network modulations reflect the brain's dynamic reorganization, balancing integration and segregation during crossmodal influences.