An fMRI-based study of the effect of audiovisual stimulus temporal pacing on brain responses

Research on the effect of stimulus temporal pacing on brain states is a central topic in neuroscience and psychology. Studies of audiovisual integration (AVI) in the fields of Brain-Computer Interfaces (BCIs) and neuropsychology have often yielded inconsistent findings, potentially due to variations in stimulus temporal pacing. Although a number of psychological experiments have investigated the effects of stimulus temporal pacing on brain activity, the underlying neural mechanisms remain poorly understood. This study aims to investigate how stimulus temporal pacing modulates the dynamic reconfiguration of brain activity and connectivity using functional magnetic resonance imaging (fMRI). A multimodal audiovisual oddball paradigm was employed, presenting stimuli at two temporal pacing conditions (rapid and slow) across three sensory modalities (visual, auditory, and audiovisual) to compare brain activation and functional connectivity across conditions. Results showed that in the unimodal condition, rapid stimuli preferentially engaged primary sensory cortices, indicating efficient perceptual encoding under high temporal pressure. In contrast, slow stimuli shifted processing toward higher-order cognitive regions, suggesting greater engagement in higher-order cognitive regions and enhance global network efficiency. For audiovisual condition, both rapid and slow stimuli elicit comparable functional connectivity patterns, whereas slow stimuli showed stronger connectivity in specific regions (e.g., occipital-motor areas, STG-DMN nodes), suggesting that the core audiovisual network and the extended whole-brain networks act in concert, forming a dual-layer processing mechanism. These findings provide a neural basis for understanding how stimulus temporal pacing acts as a modulator, shaping the dynamic balance between localized sensory analysis and integrated global processing.