TY - JOUR T1 - Synchronization of sensory gamma oscillations promotes multisensory communication JF - eneuro JO - eNeuro DO - 10.1523/ENEURO.0101-19.2019 SP - ENEURO.0101-19.2019 AU - Jonas Misselhorn AU - Bettina C. Schwab AU - Till R. Schneider AU - Andreas K. Engel Y1 - 2019/10/10 UR - http://www.eneuro.org/content/early/2019/10/10/ENEURO.0101-19.2019.abstract N2 - Rhythmic neuronal activity in the gamma range is a signature of cortical processing and its synchronization across distant sites has been proposed as a fundamental mechanism of network interactions. While this has been shown within sensory streams, we tested whether crosstalk between the senses relies on similar mechanisms. Direct sensory interactions in humans (male and female) were studied with a visual-tactile amplitude matching paradigm. In this task, congruent stimuli are associated with behavioral benefits, proposed to be mediated by increased binding between sensory cortices through coherent gamma oscillations. We tested this hypothesis by applying 4-in-1 multi-electrode transcranial alternating current stimulation (tACS) with 40 Hz over visual and somatosensory cortex. In-phase stimulation (0°) was expected to strengthen binding and thereby enhance the congruence effect, while anti-phase (180°) stimulation was expected to have opposite effects. Gamma tACS was controlled by alpha (10 Hz) and sham stimulation, as well as by applying tACS unilaterally while visual-tactile stimuli were presented lateralized. Contrary to our expectations, gamma tACS over the relevant hemisphere delayed responses to congruent trials. Additionally, re-analysis of EEG data revealed decoupling of sensory gamma oscillations during congruent trials. We propose that gamma tACS prevented sensory decoupling and thereby limited the congruence effect. Taken together, our results favor the perspective that processing multisensory congruence involves corticocortical communication rather than feature binding. Furthermore, we found control stimulation over the irrelevant hemisphere to speed responses under alpha stimulation and delay responses under gamma stimulation, consistent with the idea that contralateral alpha/gamma dynamics regulate cortical excitability.Significance statement Cortical gamma oscillations structure segregated neural activity and were suggested to represent a fundamental mechanism of network communication. While there is ample evidence for the role of long-range gamma synchronization in unisensory processing, its significance in multisensory networks is still unclear. We show that coordinated sensory gamma oscillations play an important role for direct cross-modal interactions and propose that phase synchronization promotes communication between sensory cortices. To that end, we carried out a state-of-the-art multi-electrode transcranial alternating current stimulation (tACS) experiment designed to modulate coherence between sensory cortices and analyzed connectivity in a previously recorded high-density EEG dataset. By complementing an interventional with an observational method, we provide novel evidence for the role of synchronized gamma oscillations in multisensory communication. ER -