Audiovisual integration elicited by stimuli peripherally in divided attention task: An event-related potential study

To investigate the neural mechanisms of audiovisual integration in divided attention, we recorded event-related potentials (ERPs) during a divided attention task, in which the stimulus was presented in the auditory (A), visual (V), and in the audiovisual (AV) modalities. ERPs were recorded in normal young subjects, and ERPs elicited by the auditory and visual stimuli when presented alone were summed ('sum' ERP) and compared to the ERP elicited when they were presented simultaneously ('simultaneous' ERP). Two tones (20% white noise and 80% frequent 1000 Hz) and two visual stimuli (20% red white block and 80% black white block) were delivered. Behavioral data and ERPs of AV and (A + V) were analyzed according to different location. Reaction times (RTs) to the stimuli when presented simultaneously were significantly faster than when they were presented alone. Audiovisual integration elicited by stimuli peripherally, which was followed by three more phases of effects that were marked by scalp distribution: (1) the right fronto-central area at 200-220ms after the presentation of the stimulus, (2) centro-medial area at 260-320ms after the presentation of the stimulus, and (3) right posterior area at 340-440ms. We found that these interaction effects occurred slightly later than those reported in previously published AV interaction studies in which AV stimuli were presented centrally.