Cross-modal processing of auditory–visual stimuli in a no-task paradigm: A topographic event-related potential study

Objective The aim of this study was to investigate in healthy adults the electrophysiological correlates of auditory–visual interactions involved in perception of bimodal events in a no-task paradigm. Methods Event-related potentials were recorded in response to unimodal auditory (A), unimodal visual (V) and bimodal (AV) stimuli. Cross-modal interactions were estimated using the additive [AV − (A + V)] model. Results The spatio-temporal analysis of ERPs and scalp current densities revealed several interaction patterns occurring at both early and late stages of sensory cortical processing: (1) amplitude decrease of the unimodal auditory N1 wave as early as 55 ms, (2) amplitude increase of the unimodal auditory P2 wave from 150 to 195 ms concomitant with new neural activity over the right fronto-temporal region, and (3) amplitude increase of the late unimodal visual response within 245–350 ms post-stimulus. Conclusions Our study provides evidence that several patterns of cross-modal interactions can be generated even if no task is required from subjects. Significance The paradigm used here can thus be utilized for studying the maturation of the cross-modal processes in young children and in children with pathological development.