Effects of ipsilateral and bilateral auditory stimuli on audiovisual integration: a behavioral and event-related potential study.

We used event-related potential measures to compare the effects of ipsilateral and bilateral auditory stimuli on audiovisual (AV) integration. Behavioral results showed that the responses to visual stimuli with either type of auditory stimulus were faster than responses to visual stimuli only and that perceptual sensitivity (d') for visual detection was enhanced for visual stimuli with ipsilateral auditory stimuli. Furthermore, event-related potential components related to AV integrations were identified over the occipital areas at ∼180-200 ms during early-stage sensory processing by the effect of ipsilateral auditory stimuli and over the frontocentral areas at ∼300-320 ms during late-stage cognitive processing by the effect of ipsilateral and bilateral auditory stimuli. Our results confirmed that AV integration was also elicited, despite the effect of bilateral auditory stimuli, and only occurred at later stages of cognitive processing in response to a visual detection task. Furthermore, integration from early-stage sensory processing was observed by the effect of ipsilateral auditory stimuli, suggesting that the integration of AV information in the human brain might be particularly sensitive to ipsilaterally presented AV stimuli.