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Abstract

Neuronal oscillations are considered crucial for information processing in the brain as they can potentially regulate information flow and dynamically bind different cortical regions. This MEG study investigated the interactions between a transient sound and a steady state visual signal. To induce steady state oscillations in the visual cortex, we presented subjects with a continuous visual signal that was luminance-modulated at 10Hz. The transient sounds were presented locked to four different equidistant phases of the periodic visual stimulus (i.e. 0, pi, pi, pi). More specifically, our experimental design factorially manipulated (i) the presence/absence of the auditory input and (ii) the phase of the visual input thus providing four types of phase-dependent AV(a) and V(a) trials, where a denotes the specific phase of the visual stimulus In addition, the design included pure auditory (A) and ’fixation’ trials. This allowed us to dissociate non-specific and specific phase-dependent audiovisual interactions. Non-specific interactions were identified by comparing AV(a) + Fixation vs A + V(a). In the frequency domain, this revealed increased activity and phase locking at 10 Hz during the audiovisual conditions. Specific phase-dependent interactions [AV(a) 4 V(a)] were revealed in the time domain at about 300 ms poststimulus, where activity was enhanced mainly for synchronous audiovisual trials (phase 0). Collectively, our results suggest that auditory transients and visual steady signals interact in a non-specific and in a phase-dependent fashion.