Neural mechanisms for selectively tuning in to the target speaker in a naturalistic noisy situation

Educational diversity and group creativity: Evidence from fNIRS hyperscanning

Educational diversity is defined as the diversity of educational backgrounds measured by multiple subjects. This study aimed to unveil the interpersonal neural correlates that underlie the effect of group educational diversity on group creativity. One hundred and sixteen college students were assigned to high educational diversity (HD; the members respectively majored in science or social science) or low educational diversity (LD; the members both majored in either science or social science) groups based on their academic majors. They were required to solve two problems that either demanded creativity (alternative uses task, AUT) or not (object characteristics task). We used functional near-infrared spectroscopy (fNIRS)-based hyperscanning to simultaneously record the neural responses of pairs of interacting participants in each group. The LD group showed more AUT fluency and perspective-taking behaviours than the HD group, whereas no group difference was observed for AUT uniqueness. Additionally, collective flexibility was higher in the HD group than in the LD group. The fNIRS results showed that the interpersonal brain synchronisation (IBS) increments at the right angular gyrus and right primary somatosensory cortex were greater in the LD group than in the HD group. These findings indicate that although high educational diversity benefits cognitive flexibility, it does not necessarily lead to a better idea quality or greater idea quantity. The greater IBS increments and perspective-taking behaviours that we observed in the LD group may account for this.

Speaker-Listener Neural Coupling Reveals an Adaptive Mechanism for Speech Comprehension in a Noisy Environment

Comprehending speech in noise is an essential cognitive skill for verbal communication. However, it remains unclear how our brain adapts to the noisy environment to achieve comprehension. The present study investigated the neural mechanisms of speech comprehension in noise using an functional near-infrared spectroscopy-based inter-brain approach. A group of speakers was invited to tell real-life stories. The recorded speech audios were added with meaningless white noise at four signal-to-noise levels and then played to listeners. Results showed that speaker-listener neural couplings of listener's left inferior frontal gyri (IFG), that is, sensorimotor system, and right middle temporal gyri (MTG), angular gyri (AG), that is, auditory system, were significantly higher in listening conditions than in the baseline. More importantly, the correlation between neural coupling of listener's left IFG and the comprehension performance gradually became more positive with increasing noise level, indicating an adaptive role of sensorimotor system in noisy speech comprehension; however, the top behavioral correlations for the coupling of listener's right MTG and AG were only obtained in mild noise conditions, indicating a different and less robust mechanism. To sum up, speaker-listener coupling analysis provides added value and new sight to understand the neural mechanism of speech-in-noise comprehension.

Motor Learning Based on Oscillatory Brain Activity Using Transcranial Alternating Current Stimulation: A Review

Developing effective tools and strategies to promote motor learning is a high-priority scientific and clinical goal. In particular, motor-related areas have been investigated as potential targets to facilitate motor learning by noninvasive brain stimulation (NIBS). In addition to shedding light on the relationship between motor function and oscillatory brain activity, transcranial alternating current stimulation (tACS), which can noninvasively entrain oscillatory brain activity and modulate oscillatory brain communication, has attracted attention as a possible technique to promote motor learning. This review focuses on the use of tACS to enhance motor learning through the manipulation of oscillatory brain activity and its potential clinical applications. We discuss a potential tACS-based approach to ameliorate motor deficits by correcting abnormal oscillatory brain activity and promoting appropriate oscillatory communication in patients after stroke or with Parkinson's disease. Interpersonal tACS approaches to manipulate intra- and inter-brain communication may result in pro-social effects and could promote the teaching-learning process during rehabilitation sessions with a therapist. The approach of re-establishing oscillatory brain communication through tACS could be effective for motor recovery and might eventually drive the design of new neurorehabilitation approaches based on motor learning.

How Mother-Child Interactions are Associated with a Child's Compliance

While social interaction between a mother and her child has been found to play an important role in the child's committed compliance, the underlying neurocognitive process remains unclear. To investigate this process, we simultaneously recorded and assessed brain activity in 7-year-old children and in children's mothers or strangers during a free-play task using functional near-infrared spectroscopy-based hyperscanning. The results showed that a child's committed compliance was positively associated with the child's responsiveness but was negatively associated with mutual responsiveness and was not associated with the mother's responsiveness during mother-child interactions. Moreover, interpersonal neural synchronization (INS) at the temporoparietal junction mediated the relationship between the child's responsiveness and the child's committed compliance during mother-child interactions when the child's brain activity lagged behind that of the mother. However, these effects were not found during stranger-child interactions, nor were there significant effects in the mother-child pair when no real interactions occurred. Finally, we found a transfer effect of a child's committed compliance from mother-child interactions to stranger-child interactions via the mediation of mother-child INS, but the opposite did not occur. Together, these findings suggest that a child's responsiveness during mother-child interactions can significantly facilitate her or his committed compliance by increasing mother-child INS.

A hierarchical model for interpersonal verbal communication

The ability to use language makes us human. For decades, researchers have been racking their minds to understand the relation between language and the human brain. Nevertheless, most previous neuroscientific research has investigated this issue from a ‘single-brain’ perspective, thus neglecting the nature of interpersonal communication through language. With the development of modern hyperscanning techniques, researchers have begun probing the neurocognitive processes underlying interpersonal verbal communication and have examined the involvement of interpersonal neural synchronization (INS) in communication. However, in most cases, the neurocognitive processes underlying INS are obscure. To tentatively address this issue, we propose herein a hierarchical model based on the findings from a growing amount of hyperscanning research. We suggest that three levels of neurocognitive processes are primarily involved in interpersonal verbal communication and are closely associated with distinctive patterns of INS. Different levels of these processes modulate each other bidirectionally. Furthermore, we argued that two processes (shared representation and interpersonal predictive coding) might coexist and work together at each level to facilitate successful interpersonal verbal communication. We hope this model will inspire further innovative research in several directions within the fields of social and cognitive neuroscience.

Neural synchrony in mother-child conversation: Exploring the role of conversation patterns

Conversations are an essential form of communication in daily family life. Specific patterns of caregiver–child conversations have been linked to children’s socio-cognitive development and child-relationship quality beyond the immediate family environment. Recently, interpersonal neural synchronization has been proposed as a neural mechanism supporting conversation. Here, we present a functional near-infrared spectroscopy (fNIRS) hyperscanning study looking at the temporal dynamics of neural synchrony during mother–child conversation. Preschoolers (20 boys and 20 girls, M age 5;07 years) and their mothers (M age 36.37 years) were tested simultaneously with fNIRS hyperscanning while engaging in a free verbal conversation lasting for 4 min. Neural synchrony (using wavelet transform coherence analysis) was assessed over time. Furthermore, each conversational turn was coded for conversation patterns comprising turn-taking, relevance, contingency and intrusiveness. Results from linear mixed-effects modeling revealed that turn-taking, but not relevance, contingency or intrusiveness predicted neural synchronization during the conversation over time. Results are discussed to point out possible variables affecting parent–child conversation quality and the potential functional role of interpersonal neural synchronization for parent–child conversation.

Affiliative bonding between teachers and students through interpersonal synchronisation in brain activity

Human beings organise socially. Theories have posited that interpersonal neural synchronisation might underlie the creation of affiliative bonds. Previous studies tested this hypothesis mainly during a social interaction, making it difficult to determine whether the identified synchronisation is associated with affiliative bonding or with social interaction. This study addressed this issue by focusing on the teacher–student relationship in the resting state both before and after a teaching period. Brain activity was simultaneously measured in both individuals using functional near-infrared spectroscopy. The results showed a significant increase in brain synchronisation at the right sensorimotor cortex between the teacher and student in the resting state after, but not before, the teaching period. Moreover, the synchronisation increased only after a turn-taking mode of teaching but not after a lecturing or video mode of teaching. A chain mediation analysis showed that brain synchronisation during teaching partially mediated the relationship between the brain synchronisation increase in the resting state and strength of the affiliative bond. Finally, both role assignment and social interaction were found to be required for affiliative bonding. Together, these results support the hypothesis that interpersonal synchronisation in brain activity underlies affiliative bonding and that social interaction mechanically mediates the bonding process.

Reduced listener-speaker neural coupling underlies speech understanding difficulty in older adults

An increasing number of studies have highlighted the importance of listener-speaker neural coupling in successful verbal communication. Whether the brain-to-brain coupling changes with healthy aging and the possible role of this change in the speech comprehension of older adults remain unexplored. In this study, we scanned with fMRI a young and an older speaker telling real-life stories and then played the audio recordings to a group of young (N = 28, aged 19-27 year) and a group of older adults during scanning (N = 27, aged 53-75 year), respectively. The older listeners understood the speech less well than did the young listeners, and the age of the older listeners was negatively correlated with their level of speech understanding. Compared to the young listener-speaker dyads, the older dyads exhibited reduced neural couplings in both linguistic and extra-linguistic areas. Moreover, within the older group, the listener's age was negatively correlated with the overall strength of interbrain coupling, which in turn was associated with reduced speech understanding. These results reveal the deficits of older adults in achieving neural alignment with other brains, which may underlie the age-related decline in speech understanding.

Association of CXCR6 with COVID-19 severity: Delineating the host genetic factors in transcriptomic regulation

Background:

The coronavirus disease 2019 (COVID-19) is an infectious disease that mainly affects the host respiratory system with ~80% asymptomatic or mild cases and ~5% severe cases. Recent genome-wide association studies (GWAS) have identified several genetic loci associated with the severe COVID-19 symptoms. Delineating the genetic variants and genes is important for better understanding its biological mechanisms.

Methods:

We implemented integrative approaches, including transcriptome-wide association studies (TWAS), colocalization analysis and functional element prediction analysis, to interpret the genetic risks using two independent GWAS datasets in lung and immune cells. To understand the context-specific molecular alteration, we further performed deep learning-based single cell transcriptomic analyses on a bronchoalveolar lavage fluid (BALF) dataset from moderate and severe COVID-19 patients.

Results:

We discovered and replicated the genetically regulated expression of CXCR6 and CCR9 genes. These two genes have a protective effect on the lung and a risk effect on whole blood, respectively. The colocalization analysis of GWAS and cis-expression quantitative trait loci highlighted the regulatory effect on CXCR6 expression in lung and immune cells. In the lung resident memory CD8⁺ T (T_RM) cells, we found a 3.32-fold decrease of cell proportion and lower expression of CXCR6 in the severe than moderate patients using the BALF transcriptomic dataset. Pro-inflammatory transcriptional programs were highlighted in T_RM cells trajectory from moderate to severe patients.

Conclusions:

CXCR6 from the 3p21.31 locus is associated with severe COVID-19. CXCR6 tends to have a lower expression in lung T_RM cells of severe patients, which aligns with the protective effect of CXCR6 from TWAS analysis. We illustrate one potential mechanism of host genetic factor impacting the severity of COVID-19 through regulating the expression of CXCR6 and T_RM cell proportion and stability. Our results shed light on potential therapeutic targets for severe COVID-19.

Interpersonal Neural Synchronization during Interpersonal Touch Underlies Affiliative Pair Bonding between Romantic Couples

Interpersonal touch plays a key role in creating and maintaining affiliative pair bonds in romantic love. However, the neurocognitive mechanism of interpersonal touch in affiliative pair bonding remains unclear. Here, we hypothesized that interpersonal neural synchronization (INS) during interpersonal touch underlies affiliative pair bonding between romantic couples. To test this hypothesis, INS between heterosexual romantic couples and between opposite-sex friends was measured using functional near-infrared spectroscopy-based hyperscanning, while the pairs of participants touched or vocally communicated with each other. The results showed significantly greater INS between the mentalizing and sensorimotor neural systems of two members of a pair during interpersonal touch than during vocal communication between romantic couples but not between friends. Moreover, touch-induced INS was significantly correlated with the self-reported strength of romantic love. Finally, the results also showed that men's empathy positively modulated the association between touch-induced INS increase and the strength of romantic love. These findings support the idea that INS during interpersonal touch underlies affiliative pair bonding between romantic couples and suggest that empathy plays a modulatory role in the neurocognitive mechanism of interpersonal touch in affiliative pair bonding.

Brain and motor synchrony in children and adolescents with ASD-a fNIRS hyperscanning study

Brain-to-brain synchrony has been proposed as an important mechanism underlying social interaction. While first findings indicate that it may be modulated in children with autism spectrum disorder (ASD), no study to date has investigated the influence of different interaction partners and task characteristics. Using functional near-infrared spectroscopy hyperscanning, we assessed brain-to-brain synchrony in 41 male typically developing (TD) children (8-18 years; control sample), as well as 18 children with ASD and age-matched TD children (matched sample), while performing cooperative and competitive tasks with their parents and an adult stranger. Dyads were instructed either to respond jointly in response to a target (cooperation) or to respond faster than the other player (competition). Wavelet coherence was calculated for oxy- and deoxyhemoglobin brain signals. In the control sample, a widespread enhanced coherence was observed for parent-child competition, and a more localized coherence for parent-child cooperation in the frontopolar cortex. While behaviorally, children with ASD showed a lower motor synchrony than children in the TD group, no significant group differences were observed on the neural level. In order to identify biomarkers for typical and atypical social interactions in the long run, more research is needed to investigate the neurobiological underpinnings of reduced synchrony in ASD.

fNIRS Assessment of Speech Comprehension in Children with Normal Hearing and Children with Hearing Aids in Virtual Acoustic Environments: Pilot Data and Practical Recommendations

The integration of virtual acoustic environments (VAEs) with functional near-infrared spectroscopy (fNIRS) offers novel avenues to investigate behavioral and neural processes of speech-in-noise (SIN) comprehension in complex auditory scenes. Particularly in children with hearing aids (HAs), the combined application might offer new insights into the neural mechanism of SIN perception in simulated real-life acoustic scenarios. Here, we present first pilot data from six children with normal hearing (NH) and three children with bilateral HAs to explore the potential applicability of this novel approach. Children with NH received a speech recognition benefit from low room reverberation and target-distractors' spatial separation, particularly when the pitch of the target and the distractors was similar. On the neural level, the left inferior frontal gyrus appeared to support SIN comprehension during effortful listening. Children with HAs showed decreased SIN perception across conditions. The VAE-fNIRS approach is critically compared to traditional SIN assessments. Although the current study shows that feasibility still needs to be improved, the combined application potentially offers a promising tool to investigate novel research questions in simulated real-life listening. Future modified VAE-fNIRS applications are warranted to replicate the current findings and to validate its application in research and clinical settings.

Capturing Human Interaction in the Virtual Age: A Perspective on the Future of fNIRS Hyperscanning

Advances in video conferencing capabilities combined with dramatic socio-dynamic shifts brought about by COVID-19, have redefined the ways in which humans interact in modern society. From business meetings to medical exams, or from classroom instruction to yoga class, virtual interfacing has permeated nearly every aspect of our daily lives. A seemingly endless stream of technological advances combined with our newfound reliance on virtual interfacing makes it likely that humans will continue to use this modern form of social interaction into the future. However, emergent evidence suggests that virtual interfacing may not be equivalent to face-to-face interactions. Ultimately, too little is currently understood about the mechanisms that underlie human interactions over the virtual divide, including how these mechanisms differ from traditional face-to-face interaction. Here, we propose functional near-infrared spectroscopy (fNIRS) hyperscanning-simultaneous measurement of two or more brains-as an optimal approach to quantify potential neurocognitive differences between virtual and in-person interactions. We argue that increased focus on this understudied domain will help elucidate the reasons why virtual conferencing doesn't always stack up to in-person meetings and will also serve to spur new technologies designed to improve the virtual interaction experience. On the basis of existing fNIRS hyperscanning literature, we highlight the current gaps in research regarding virtual interactions. Furthermore, we provide insight into current hurdles regarding fNIRS hyperscanning hardware and methodology that should be addressed in order to shed light on this newly critical element of everyday life.

Experience-Dependent Counselor-Client Brain Synchronization during Psychological Counseling

The role of the counselor’s experience in building an alliance with the clients remains controversial. Recently, the expanding nascent studies on interpersonal brain synchronization (IBS) using functional near-infrared spectroscopy (fNIRS) on human subjects have hinted at the possible neural substrates underlying the relationship qualities between the counselor-client dyads. Our study assessed the clients’ self-report working alliance (WA) as well as simultaneously measured IBS by fNIRS in 14 experienced versus 16 novice counselor-client dyads during the first integrative-orientation psychological counseling session. We observed that synchronous brain activity patterns were elicited from the right temporo-parietal junction (rTPJ) across counselor-client dyads. Furthermore, such IBS, together with alliance quality, was especially evident when counselors had more psychotherapy experience. Time-lagged counselor-client brain synchronization might co-vary with the alliance (goal component) when the client’s brain activity preceded that of the counselor. These findings favor the notion that the IBS between counselor-client associated with the WA is an experience-dependent phenomenon, suggesting that a potential adaptive mechanism is embedded in psychological counseling.

A Multi-Brain Framework for Social Interaction

Social interaction can be seen as a dynamic feedback loop that couples action, reaction, and internal cognitive processes across individual agents. A fuller understanding of the social brain requires a description of how the neural dynamics across coupled brains are linked and how they coevolve over time. We elaborate a multi-brain framework that considers social interaction as an integrated network of neural systems that dynamically shape behavior, shared cognitive states, and social relationships. We describe key findings from multi-brain experiments in humans and animal models that shed new light on the function of social circuits in health and disease. Finally, we discuss recent progress in elucidating the cellular-level mechanisms underlying inter-brain neural dynamics and outline key areas for future research.

Neural alignment during face-to-face spontaneous deception: Does gender make a difference?

This study investigated the gender differences in deception and their neural basis in the perspective of two‐person neuroscience. Both male and female dyads were asked to perform a face‐to‐face spontaneous sender–receiver deception task, while their neural activities in the prefrontal cortex (PFC) and right temporal parietal junction (rTPJ) were recorded simultaneously using functional near‐infrared spectroscopy (fNIRS)‐based hyperscanning. Male and female dyads displayed similar deception rate, successful deception rate, and eye contact in deception trials. Moreover, eye contact in deception trials was positively correlated with the success rate of deception in both genders. The fNIRS data showed that the interpersonal neural synchronization (INS) in PFC was significantly enhanced only in female dyads when performed the deception task, while INS in rTPJ was increased only in male dyads. Such INS was correlated with the success rate of deception in both dyads. Granger causality analysis showed that no significant directionality between time series of PFC (or rTPJ) in each dyad, which could indicate that sender and receiver played equally important role during deception task. Finally, enhanced INS in PFC in female dyads mediated the contribution of eye contact to the success rate of deception. All findings in this study suggest that differential patterns of INS are recruited when male and female dyads perform the face‐to‐face deception task. To our knowledge, this is the first interbrain evidence for gender difference of successful deception, which could make us a deeper understanding of spontaneous face‐to‐face deception.

Interpersonal Neural Synchronization During Cooperative Behavior of Basketball Players: A fNIRS-Based Hyperscanning Study

Accumulating evidence has consistently shown that team-based sports (such as basketball) are beneficial to interpersonal cooperation. However, its neural correlate remains to be discovered, especially in the perspective of two-person neuroscience. In this study, 12 dyads of basketball players and 12 dyads of college students who had no experience of team-based sports training were asked to perform joint-drawing task and control task. During task performance, neural activities were recorded in frontal area by the functional near-infrared spectroscopy (fNIRS)-based hyperscanning approach. The results demonstrated that dyads of basketball players were faster to finish joint-drawing task and showed higher subjective cooperativeness than dyads of college students. Meanwhile, significant interpersonal neural synchronization (INS) was observed in the dorsolateral prefrontal area only when pairs of basketball players performed joint-drawing task, but not control task. Therefore, we provide the first piece of inter-brain evidence for enhanced cooperative behavior in the individuals with team-based sports training, which could make us deeply understand exact neural correlate for experience-dependent changes of cognitions in humans.

Gender of partner affects the interaction pattern during group creative idea generation

This study aimed to determine how gender composition affects the group creative process. Participants were recruited into dyads with different gender compositions (female-male dyad, F-M; female-female, F-F; male-male, and M-M) to solve two problems. One problem demanded creativity alternative use task (AUT) and the other did not object characteristic task. Functional near-infrared spectroscopy (fNIRS)-based hyperscanning was used to record interpersonal neural responses. Results demonstrated no significant difference in creative performance among the three types of dyads. However, the F-F dyad showed higher levels of cooperative behaviour (i.e. the index of convergence) and collective flexibility than the other dyads. Also, in the fNIRS data, the F-F dyad showed higher interpersonal brain synchronization (IBS) increments in the right posterior parietal cortex during the AUT than the other dyads, which covaried with their creative performance. These findings indicate that while solving a creativity problem together, females are more likely than males to consider others' perspectives. This gender difference might be due to the enhanced IBS increment in the right posterior parietal cortex.

What Can Computational Models Learn From Human Selective Attention? A Review From an Audiovisual Unimodal and Crossmodal Perspective

Selective attention plays an essential role in information acquisition and utilization from the environment. In the past 50 years, research on selective attention has been a central topic in cognitive science. Compared with unimodal studies, crossmodal studies are more complex but necessary to solve real-world challenges in both human experiments and computational modeling. Although an increasing number of findings on crossmodal selective attention have shed light on humans' behavioral patterns and neural underpinnings, a much better understanding is still necessary to yield the same benefit for intelligent computational agents. This article reviews studies of selective attention in unimodal visual and auditory and crossmodal audiovisual setups from the multidisciplinary perspectives of psychology and cognitive neuroscience, and evaluates different ways to simulate analogous mechanisms in computational models and robotics. We discuss the gaps between these fields in this interdisciplinary review and provide insights about how to use psychological findings and theories in artificial intelligence from different perspectives.

Enhanced amplitude modulations contribute to the Lombard intelligibility benefit: Evidence from the Nijmegen Corpus of Lombard Speech

Speakers adjust their voice when talking in noise, which is known as Lombard speech. These acoustic adjustments facilitate speech comprehension in noise relative to plain speech (i.e., speech produced in quiet). However, exactly which characteristics of Lombard speech drive this intelligibility benefit in noise remains unclear. This study assessed the contribution of enhanced amplitude modulations to the Lombard speech intelligibility benefit by demonstrating that (1) native speakers of Dutch in the Nijmegen Corpus of Lombard Speech produce more pronounced amplitude modulations in noise vs in quiet; (2) more enhanced amplitude modulations correlate positively with intelligibility in a speech-in-noise perception experiment; (3) transplanting the amplitude modulations from Lombard speech onto plain speech leads to an intelligibility improvement, suggesting that enhanced amplitude modulations in Lombard speech contribute towards intelligibility in noise. Results are discussed in light of recent neurobiological models of speech perception with reference to neural oscillators phase-locking to the amplitude modulations in speech, guiding the processing of speech.

English spoken word segmentation activates the prefrontal cortex and temporo-parietal junction in Chinese ESL learners: A functional near-infrared spectroscopy (fNIRS) study

A direct measure of spoken lexical processing based on neuroimaging technology would provide us useful information to understand the neural mechanisms underlying speech or auditory language processing. The neural mechanisms of spoken word segmentation for English as a second language (ESL) learners remain elusive. The present study, using functional near-infrared spectroscopy (fNIRS), addresses this issue by measuring hemodynamic responses in the temporo-parietal junction (TPJ) and the prefrontal cortex (PFC) in a word-spotting task, designed with two task conditions (easy vs. difficult). Thirty participants, divided into a high listening proficiency group (HLG) and a low listening proficiency group (LLG), were tested. Results revealed significantly less TPJ activation in the HLG than in the LLG. Further analyses supported this result by showing that activation in the TPJ was in a negative correlation with listening proficiency. This association appears to be related to the more efficient use of processing resources in a bottom-up fashion for accurate and efficient sensory representations in high proficient language learners. In contrast, cortical activation in the PFC increased with listening proficiency and was stronger in the difficult task condition than in the easy task condition, implying that recruitment of top-down cognitive control functions might play a role in word segmentation. Our results suggest that the combination of the functions mediated via bottom-up sensory input processing (demonstrated in the TPJ activation) and top-down cognitive processing (demonstrated in the PFC activation) are crucial for ESL listeners' spoken word segmentation.

When do we fall in neural synchrony with others?

This study aimed to investigate the situation in which interpersonal brain synchronization (IBS) occurs during a collaborative task and examined its trajectory over time by developing a novel functional near-infrared spectroscopy (fNIRS)-based hyperscanning paradigm. Participants were asked to perform a collaborative task in three-person groups where two of the members are real participants and one is a confederate. Compared to dyads between real participants and confederates, real-participant pairings showed greater cooperation behavior and IBS between bilateral dorsolateral prefrontal cortex. And, IBS and cooperation increased over time in real-participant pairings, whereas they remained low and constant in dyads with the confederate. These findings indicate that IBS occurs between individuals engaging in interpersonal interaction during a collaborative task, during which both IBS and cooperatively interpersonal interaction tend to increase over time.

Two-Person Approaches to Studying Social Interaction in Psychiatry: Uses and Clinical Relevance

Social interaction is ubiquitous in human society. The two-person approach-a new, powerful tool to study information exchange and social behaviors-aims to characterize the behavioral dynamics and neural mechanisms of real-time social interactions. In this review, we discuss the benefits of two-person approaches compared to those for conventional, single-person approaches. We describe measures and paradigms that model social interaction in three dimensions (3-D), including eye-to-eye, body-to-body, and brain-to-brain relationships. We then discuss how these two-person measures and paradigms are used in psychiatric conditions (e.g., autism, mood disorders, schizophrenia, borderline personality disorder, and psychotherapy). Furthermore, the advantages of a two-person approach (e.g., dual brain stimulation, multi-person neurofeedback) in clinical interventions are described. Finally, we discuss the methodological and translational challenges surrounding the application of two-person approaches in psychiatry, as well as prospects for future two-/multi-person studies. We conclude that two-person approaches serve as useful additions to the range of behavioral and neuroscientific methods available to assess social interaction in psychiatric settings, for both diagnostic techniques and complementary interventions.

Behavioral and brain synchronization differences between expert and novice teachers when collaborating with students

Differences in behavior and neural mechanisms between expert and novice teachers when collaborating with students are poorly understood. This study investigated whether expert teachers do better in collaborating with students than novice teachers and explored the neural basis of such differences. Novice teacher and student (NT-S) dyads and expert teacher and student (ET-S) dyads were recruited to complete an interactive task consisting of a cooperation and an independent condition. During the experiment, neural activity in the prefrontal cortex of the participants was recorded with functional near-infrared spectroscopy. The results show higher accuracy for the ET-S dyads than the NT-S dyads in the cooperation condition; however, no difference was found in the independent condition. Increased interpersonal brain synchronization (IBS) was detected in the left dorsolateral prefrontal cortex of participants in ET-S dyads, but not in NT-S dyads in the cooperation condition. Moreover, an interaction effect of dyad type and conditions on IBS was observed, revealing IBS was stronger in ET-S dyads than in NT-S dyads. In ET-S dyads, IBS was positively correlated with the teachers' perspective-taking ability and accuracy. These findings suggest that expert teachers collaborate better with students than novice teachers, and IBS might be the neural marker for this difference.

Simultaneous EEG Acquisition System for Multiple Users: Development and Related Issues

Social interaction is one of humans' most important activities and many efforts have been made to understand the phenomenon. Recently, some investigators have attempted to apply advanced brain signal acquisition systems that allow dynamic brain activities to be measured simultaneously during social interactions. Most studies to date have investigated dyadic interactions, although multilateral interactions are more common in reality. However, it is believed that most studies have focused on such interactions because of methodological limitations, in that it is very difficult to design a well-controlled experiment for multiple users at a reasonable cost. Accordingly, there are few simultaneous acquisition systems for multiple users. In this study, we propose a design framework for an acquisition system that measures EEG data simultaneously in an environment with 10 or more people. Our proposed framework allowed us to acquire EEG data at up to 1 kHz frequency from up to 20 people simultaneously. Details of our acquisition system are described from hardware and software perspectives. In addition, various related issues that arose in the system's development-such as synchronization techniques, system loads, electrodes, and applications-are discussed. In addition, simultaneous visual ERP experiments were conducted with a group of nine people to validate the EEG acquisition framework proposed. We found that our framework worked reasonably well with respect to less than 4 ms delay and average loss rates of 1%. It is expected that this system can be used in various hyperscanning studies, such as those on crowd psychology, large-scale human interactions, and collaborative brain-computer interface, among others.

Neurobehavioral Interpersonal Synchrony in Early Development: The Role of Interactional Rhythms

Social interactions are essential for understanding others' actions and their mental and affective states. Specifically, interpersonal coordination - also referred to as synchrony - allows actors to adjust their behaviors to one another and thus demonstrate their connectedness to each other. Much behavioral research has demonstrated the primacy of mutually synchronized social exchanges in early development. Additionally, new methodological advances now allow us to examine interpersonal synchrony not only at the behavioral and physiological but also neural level. Nevertheless, it remains unclear how infants and their caregivers actually achieve interpersonal synchrony in their exchanges. Here we discuss recent evidence showing that adults provide rhythmical information during early social interactions with their infants, such as affective touch and singing. We propose that entrainment to these social rhythms underlies the formation of interpersonal synchrony and thus stimulates reciprocal interactions between infants and their caregivers.

What Guides Us to Neurally and Behaviorally Align With Anyone Specific? A Neurobiological Model Based on fNIRS Hyperscanning Studies

An emerging body of hyperscanning functional near-infrared spectroscopy (fNIRS) research shows interbrain neural synchrony (IBS) during different forms of social interaction. Here we review the recent literature and propose several factors that facilitate IBS, leading us to ask the following question: In a world full of people and opportunities to synchronize with them, what directs our neural and behavioral alignment with anyone specific? We suggest that IBS between what we deem the "mutual social attention systems" of interacting partners-that is, the coupling between participants' temporoparietal junctions and/or prefrontal cortices-facilitates and enhances the ability to tune in to the specific interaction, its participants and its goals. We propose that this process is linked to social alignment, reinforcing one another to facilitate successful and lucrative social interactions. We further suggest that neurochemical mechanisms of dopamine and oxytocin underlie the activation of this suggested loop. Finally, we suggest possible directions for future studies, emphasizing the need to develop a brain-to-brain neurofeedback system with IBS between the mutual social attention systems of the participants as the direct regulating target.

Shared neural representations of syntax during online dyadic communication

When people communicate, they come to see the world in a similar way to each other by aligning their mental representations at such levels as syntax. Syntax is an essential feature of human language that distinguishes humans from other non-human animals. However, whether and how communicators share neural representations of syntax is not well understood. Here we addressed this issue by measuring the brain activity of both communicators in a series of dyadic communication contexts, by using functional near-infrared spectroscopy (fNIRS)-based hyperscanning. Two communicators alternatively spoke sentences either with the same or with different syntactic structures. Results showed a significantly higher-level increase of interpersonal neural synchronization (INS) at right posterior superior temporal cortex when communicators produced the same syntactic structures as each other compared to when they produced different syntactic structures. These increases of INS correlated significantly with communication quality. Our findings provide initial evidence for shared neural representations of syntax between communicators.

Interpersonal brain synchronization associated with working alliance during psychological counseling

The mechanisms underlying behavioral synchrony during psychological counseling are not clear. Recent research has provided evidence that pervasive synchrony is associated with interpersonal brain synchronization (IBS) and possibly contributes to the positive working alliance-the degree to which the counseling dyads engage in collaborative and purposive work. Our study explored the IBS between the clients and the counselors using functional near-infrared spectroscopy (fNIRS)-based hyperscanning. Thirty-four participants (as clients) were randomly assigned either to the psychological counseling group or to the chatting group; three female professional counselors provided them with 40 minutes of psychological counseling or chatting. We found better working alliances and increased IBS in the right temporo-parietal junction (rTPJ) between clients and counselors during psychological counseling (versus chatting). Such IBS also correlated with the bond of working alliance. To our knowledge, our work represents the first demonstration of fNIRS-hyperscanning measurements for synchronous brain activity between the clients and counselors. This study refines the neural explanation of behavioral synchrony during psychological counseling.

Differential brain-to-brain entrainment while speaking and listening in native and foreign languages

The study explores interbrain neural coupling when interlocutors engage in a conversation whether it be in their native or nonnative language. To this end, electroencephalographic hyperscanning was used to study brain-to-brain phase synchronization during a two-person turn-taking verbal exchange with no visual contact, in either a native or a foreign language context. Results show that the coupling strength between brain signals is increased in both, the native language context and the foreign language context, specifically, in the alpha frequency band. A difference in brain-to speech entrainment to native and foreign languages is also shown. These results indicate that between brain similarities in the timing of neural activations and their spatial distributions change depending on the language code used. We argue that factors like linguistic alignment, joint attention and brain-entrainment to speech operate with a language-idiosyncratic neural configuration, modulating the alignment of neural activity between speakers and listeners. Other possible factors leading to the differential interbrain synchronization patterns as well as the potential features of brain-to-brain entrainment as a mechanism are briefly discussed. We concluded that linguistic context should be considered when addressing interpersonal communication. The findings here open doors to quantifying linguistic interactions.

Concurrent mapping of brain activation from multiple subjects during social interaction by hyperscanning: a mini-review

Social interaction plays an essential role in acquiring knowledge and developing our own personalities in our daily life. Meanwhile, functional magnetic resonance imaging (fMRI)-, electroencephalograph (EEG)-, and functional near inferred spectroscopy (fNIRS)-hyperscanning, enables us to concurrently map brain activation from two or more participants who are engaged in social interaction simultaneously. In this review, we first highlight the recent technologies advances and the most significant findings towards social interaction by using the hyperscanning method. In addition, we also illustrate several well-designed hyperscanning tasks that have been extensively adopted for the study of social interaction. Basically, hyperscanning contains six categories of experimental paradigms that can track the interactive neural process of interest. Furthermore, it contains two main elucidated neural systems which are involved in social interaction, including the mirror neuron system (MNS) and mentalizing system (MS). Finally, future research directions and clinical implications that are associated with hyperscanning are also highlighted and discussed.