Event-related potential study of auditory-visual interactions during passive (no-task) perception

Julie Vidal, INSERM U619, Tours, France

Abstract
The aim of this study was to investigate the time-course and scalp topography of auditory-visual interactions in adults using event-related potentials (ERPs) in a no-task paradigm. ERPs were recorded from 31 scalp electrodes while auditory and visual stimuli were presented separately (A and V) or simultaneously (AV) to the subject. Multisensory interactions were assessed by comparing the ERPs in response to bimodal stimulation with the sum of the ERPs in response to the unimodal stimulations. The analysis of [AV-(A+V)] difference displayed different significant spatio-temporal patterns that included: (1) an early effect occurring in the 55-95 ms latency range recorded over fronto-central sites, (2) an interaction pattern in the 150-195 ms latency range spreading over a wide central region - this was the most prominent effect observed - and (3) two late significant effects around 245-300 and 320-360 ms over occipital sites. Scalp current density mapping performed in these latency windows showed that different generators are involved in these auditory-visual interaction effects. These electrophysiological results indicate that crossmodal auditory-visual interactions occur even in passive situation, when no task is requested from the subject.

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