Auditory stimuli extend the temporal window of visual integration by modulating alpha-band oscillations

In multisensory environments, how inputs from different sensory modalities interact to shape perception are not fully understood. In this study, we investigated how auditory stimuli influence the temporal dynamics of visual processing using electroencephalography (EEG). Participants were presented with two consecutive visual flashes, either accompanied by an auditory beep or without, and were asked to report their perception of one or two flashes. Behaviorally, we found that the introduction of auditory input induced a longer temporal window for integration. Alpha frequency analysis further revealed that the presence of auditory stimuli led to poststimulus alpha frequency degradation, positively correlating with the prolonged temporal window, supporting the idea that alpha oscillations represent the temporal window of visual integration. Further exploration of prestimulus alpha oscillations revealed that auditory stimuli diminished the predictive role of prestimulus alpha frequency while enhancing the predictive role of prestimulus alpha phase in shaping perceptual outcomes. A follow-up transcranial alternating current stimulation (tACS) experiment confirmed that alpha oscillations have a causal role in modulating visual perception in the absence of auditory stimuli but not when auditory stimuli were present. To probe the underlying mechanisms, we developed a computational model based on the phase-resetting hypothesis and perceptual cycle theory, which successfully replicated the core findings. These results reveal that auditory input extends the temporal window of visual integration by resetting alpha oscillations in the visual cortex, leading to alpha frequency reduction and an altered perception of visual events. This study advances the understanding of cross-modal interactions and highlights the dynamic, adaptive processes underlying sensory integration.