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Communication is one of the most important abilities in human society, which makes clarification of brain functions that underlie communication of great importance to cognitive neuroscience. To investigate the rapidly changing cortical-level brain activity underlying communication, a hyperscanning system with both high temporal and spatial resolution is extremely desirable. The modality of magnetoencephalography (MEG) would be ideal, but MEG hyperscanning systems suitable for communication studies remain rare. Here, we report the establishment of an MEG hyperscanning system that is optimized for natural, real-time, face-to-face communication between two adults in sitting positions. Two MEG systems, which are installed 500m away from each other, were directly connected with fiber optic cables. The number of intermediate devices was minimized, enabling transmission of trigger and auditory signals with almost no delay (1.95–3.90 μs and 3 ms, respectively). Additionally, video signals were transmitted at the lowest latency ever reported (60–100 ms). We furthermore verified the function of an auditory delay line to synchronize the audio with the video signals. This system is thus optimized for natural face-to-face communication, and additionally, music-based communication which requires higher temporal accuracy is also possible via audio-only transmission. Owing to the high temporal and spatial resolution of MEG, our system offers a unique advantage over existing hyperscanning modalities of EEG, fNIRS, or fMRI. It provides novel neuroscientific methodology to investigate communication and other forms of social interaction, and could potentially aid in the development of novel medications or interventions for communication disorders.

Auditory communication is an essential form of human social interaction. However, the intra-brain cortical-oscillatory drivers of auditory communication exchange remain relatively unexplored. We used improvisational music performance to simulate and capture the creativity and turn-taking dynamics of natural auditory communication. Using magnetoencephalography (MEG) hyperscanning in musicians, we targeted brain activity during periods of music communication imagery, and separately analyzed theta (5–7 Hz), alpha (8–13 Hz), and beta (15–29 Hz) source-level activity using a within-subjects, two-factor approach which considered the assigned social role of the subject (leader or follower) and whether communication responses were improvisational (yes or no). Theta activity related to improvisational communication and social role significantly interacted in the left isthmus cingulate cortex. Social role was furthermore differentiated by pronounced occipital alpha and beta amplitude increases suggestive of working memory retention engagement in Followers but not Leaders. The results offer compelling evidence for both musical and social neuroscience that the cognitive strategies, and correspondingly the memory and attention-associated oscillatory brain activities of interlocutors during communication differs according to their social role/hierarchy, thereby indicating that social role/hierarchy needs to be controlled for in social neuroscience research.

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Face to face communication is interactive, and involves continuous feedforward and feedback of information, thoughts, and feelings to the opposite party. To accurately assess the neural processing underlying these interactions, synchronous and simultaneous recording of the brain activity from both parties is needed, a method known as hyperscanning. Here, we investigated the neural processing underlying nonverbal face-to-face communication using a magnetoencephalographic (MEG) hyperscanning system, comprising two fiber optically connected MEGs. Eight pairs of subjects participated. Each individual in each pair viewed a combined 80 randomized 20 s trials of 40 real-time and 40 recorded (hereafter, real and simulated, respectively) videos of the opposite party's face. Non-verbal communication through actions such as gaze, eye blinks, and facial expression was intrinsically only possible during real videos. After each trial, subjects individually subjectively discriminated whether the viewed video was real or simulated. Overall subjective discrimination accuracies were slightly but significantly above chance level. Statistical analysis of brain activity revealed a significant three way interaction between theta-band rhythm amplitude, video type, and subjective discrimination response in the right frontal cortex. Additionally, when subjects responded that videos were simulated, theta activity was significantly lower for real videos compared with simulated videos (p = 0.01). This result not only demonstrates the importance of right frontal theta activity during non-verbal communication, but also indicates the existence of unconscious, semi-automated neural processing during non-verbal communication that underlies one's ability to subjectively discriminate whether or not the opposite party is real. I. INTRODUCTION During communication between two people, each person perceives the other's words, tone, and facial expressions. Each person then cognizes the others' emotion or intention, in accordance with experience, and predicts the next step of communication [1], ultimately producing some action or output. Thereby, there is a continuous mutual-feedback of output and input between both people during communication [2-3]. These mutual feedback processes, in addition to higherorder processes, are thought to involve dynamic, semiautomatic processing such as coordination of movement [4] and blink synchronization [5] that subserve conscious predictions and decision making. Thus, to truly capture the behaviors and neurophysiological correlates of communication between two people requires simultaneous and synchronous recording of the behavioral and/or neurophysiological states of both parties. However, previous research [6-7] has largely focused on simulated communication tasks using static facial stimulation and prerecorded video with single subject, despite the fact that there is no continuous and mutual feedback in these types of tasks. Consequently, the neurocorrelates underlying two-way communication remains unclarified.

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