The Effect of Attentional Locus on Multisensory Congruence: An ERP Study.

Extensive research has established the pivotal role of the congruence effect for multisensory integration of audiovisual stimuli. However, little is known about whether the attentional locus on one or other sensory domain has a differential impact on the neurophysiological dynamics of the congruence effect, particularly under conditions of frequent incongruence. Therefore, the aim of this study was to compare the temporal and topographic features of event-related potentials (ERPs) associated with the congruence effect between attended sensory modalities. Thirty healthy young adults underwent a crossmodal (visual/auditory) attention task with simultaneous audiovisual stimuli (75% incongruent trials, 25% congruent trials) during an EEG recording. Behaviorally, a stronger congruence effect for visual attention than for auditory attention was observed. The congruence effect ERP (ERPce) was extracted by subtracting the ERPs of incongruent trials from the ones of congruent trials for each attentional locus modality (visual/auditory). The ERPce mainly consisted of an N1-P2-P3 complex with a left fronto-central distribution and similar amplitudes regardless of the attended sensory modality, which was associated with behavioral performance. Interestingly, the attentional locus significantly influenced the temporality of the congruence effect, as revealed by delayed latencies of the ERPce for auditory versus visual attention. These results suggest that the attentional locus plays a significant role in integrating simultaneous congruent (though irrelevant) signals with relevant ones in a context of broad incongruency.