Brain activity supporting alternating speech for semantic words: simultaneous magnetoencephalographic recording.

Communication, especially conversation, is essential for human social life. Many previous studies have examined the neuroscientific underpinnings of conversation, i.e. language comprehension and speech production. However, conversation inherently involves two or more people, and unless two people actually interact with one another, the nature of the conversation cannot be truly revealed. Therefore, in this study, we used two magnetoencephalographs that were connected together, and simultaneously recorded brain activity while two people took turns speaking in a word association/alphabet completion task. We compared the amplitude modulation of the alpha- and beta-band rhythms within each of the 62 brain regions under semantic (word association; less predictable) and non-semantic (alphabet completion; more predictable) conditions. We found that the amplitudes of the rhythms were significantly different between conditions in a wide range of brain regions. Additionally, significant differences were observed in nearly the same group of brain regions after versus before each utterance, indicating that a wide range of brain areas is involved in predicting a conversation partner's next utterance. This result supports the idea that mentalizing, e.g. predicting another person's speech, plays an important role in conversation, and suggests that the neural network implicated in mentalizing extends over a wide range of brain regions.

Magnetoencephalography Hyperscanning Evidence of Differing Cognitive Strategies Due to Social Role During Auditory Communication.

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.

Construction of a fiber-optically connected MEG hyperscanning system for recording brain activity during real-time communication.

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.

Development of a reading difficulty questionnaire for adolescents in Japanese.

BACKGROUND: Dyslexia is a neurodevelopmental disorder which occurs in childhood but continues to influence academic and occupational function in adulthood. Recently, a Japanese dyslexia questionnaire and diagnostic procedure was established for primary school children. However, there is currently no procedure for the diagnosis or screening of dyslexia in individuals at or above junior high school age; accordingly, we aimed to develop a questionnaire to screen for reading difficulties in those individuals. METHODS: A questionnaire with various candidate items was developed from two English questionnaires, one Japanese questionnaire, and newly devised items focusing on the Japanese writing system and the most appropriate 28 items were selected. In total, 462 adults and 127 junior high to high school students were enrolled. Of those, 191 participants also took part in reading tests. After the exploratory factor analysis, reliability and validity were evaluated using the above control participants and 12 adolescents with dyslexia. RESULTS: The questionnaire included three factors, i.e., silent reading sub-scale (four items), writing sub-scale (four items), and aloud reading sub-scale (three items). Five were newly devised items focusing on the Japanese writing system. Cronbach's alphas of the three factors were 0.706, 0.638, and 0.568, respectively, and the interclass correlation coefficients (2,1) were 0.743, 0.609, and 0.695, respectively. The silent reading and aloud reading sub-scales were positively correlated with word, non-word, and passage reading time. DISCUSSION: The newly developed questionnaire correlated well with actual reading performance and may be used to screen reading difficulty in Japanese individuals at or above junior high school age.

Semi-automated brain responses in communication: A magnetoencephalographic hyperscanning study.

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.

Turning a cylindrical treadmill with feet: An MR-compatible device for assessment of the neural correlates of lower-limb movement.

BACKGROUND: Locomotion, which is one of the most basic motor functions, is critical for performing various daily-life activities. Despite its essential function, assessment of brain activity during lower-limb movement is still limited because of the constraints of existing brain imaging methods. NEW METHOD: Here, we describe an MR-compatible, cylindrical treadmill device that allows participants to perform stepping movements on an MRI scanner table. The device was constructed from wood and all of the parts were handmade by the authors. RESULTS: We confirmed the MR-compatibility of the device by evaluating the temporal signal-to-noise ratio of 64 voxels of a phantom during scanning. Brain activity was measured while twenty participants turned the treadmill with feet in sync with metronome sounds. The rotary speed of the cylinder was encoded by optical fibers. The post/pre-central gyrus and cerebellum showed significant activity during the movements, which was comparable to the activity patterns reported in previous studies. Head movement on the y- and z-axes was influenced more by lower-limb movement than was head movement on the x-axis. Among the 60 runs (3 runs × 20 participants), head movement during two of the runs (3.3%) was excessive due to the lower-limb movement. COMPARISON WITH EXISTING METHODS: Compared to MR-compatible devices proposed in the previous studies, the advantage of this device may be simple structure and replicability to realize stepping movement with a supine position. CONCLUSIONS: Collectively, our results suggest that the treadmill device is useful for evaluating lower-limb-related neural activity.