Oscillatory signatures of crossmodal congruence effects: An EEG investigation employing a visuotactile pattern matching paradigm

Abstract

Coherent percepts emerge from the accurate combination of inputs from the different sensory systems. There is ongoing debate about the neurophysiological implementation of crossmodal interactions in the brain, and it has been proposed that transient synchronization of neurons might be of central importance. Specifically, oscillatory activity in lower frequency ranges (< 30 Hz) has been implicated in mediating long-range communication as typically studied in multisensory research. In the current study, we recorded high-density electroencephalograms (EEG) while human participants were engaged in a visual-tactile pattern matching paradigm. Employing the same physical stimulation, separate tasks of the experiment either required the detection of predefined targets in visual and tactile modalities or the explicit evaluation of crossmodal stimulus congruence. Analysis of the behavioral data showed benefits for congruent visual-tactile stimulus combinations. Differences in oscillatory dynamics within the two tasks related to crossmodal congruence involved effects in the theta-(2-7 Hz), alpha-(813 Hz) and beta-band (13-25 Hz). Contrasting neuronal activity between the two tasks revealed differences in pre-stimulus alpha- and beta-band power, as well as differences in post-stimulus theta-band activity. Source reconstruction for these effects showed prominent involvement of superior temporal, parietal and prefrontal cortices - regions commonly implicated in multisensory integration. These results add to the increasing evidence that low frequency oscillations are well suited for studying integration in distributed brain networks, as demonstrated for crossmodal interactions in visual-tactile pattern matching in the current study. Additionally, neuronal activity at theta-, alpha- and beta-frequencies might subserve distinct processes relevant for multisensory integration, such as multisensory gating and crossmodal perceptual decision making.