Role of the right inferior frontal gyrus in turn-based cooperation and competition: A near-infrared spectroscopy study

Exploring the neural mechanisms underlying cooperation and competition behavior: Insights from stereo-electroencephalography hyperscanning

Cooperation and competition are essential social behaviors in human society. This study utilized hyperscanning and stereo-electroencephalography (SEEG) to investigate intra- and inter-brain neural dynamics underlying these behaviors within the insula and inferior frontal gyrus (IFG), regions critical for executive function and mentalizing. We found distinct high-gamma responses and connectivity patterns, with a stronger influence from IFG to insula during competition and more balanced interactions during cooperation. Inter-brain synchronization shows significantly higher insula gamma synchronization during competition and higher IFG gamma synchronization during cooperation. Cross-frequency coupling suggests that these gamma synchronizations result from intra- and inter-brain interactions. Competition stems from intra-brain alpha-gamma coupling from IFG to insula and inter-brain IFG alpha synchronization, while cooperation is driven by intra-brain beta-gamma coupling from insula to IFG and inter-brain insula beta synchronization. Our findings provide insights into the neural basis of cooperation and competition, highlighting the roles of both insula and IFG.

Emotions in multi-brain dynamics: A promising research frontier

Emotions drive and influence social interactions. Actions and reactions driven by emotions are dynamically modulated by continuous feedback loops between all interacting subjects. In this framework, interacting brains operate as an integrated system, with neural dynamics coevolving over time. Neuronal synchronization across brains has been observed in a range of species, including humans, monkeys, bats, and mice. This inter-neural synchrony (INS) has been proposed as a potential mechanism facilitating social interaction by enabling the functional integration of multiple brains. However, the role of emotions in modulating these processes remains underexplored and warrants further investigation. Here we provide a brief overview of studies on inter-neural synchrony in humans and other species, emphasizing the critical role that emotions might play in shaping multibrain dynamics.

An EEG hyperscanning study during persuasion toward groupness. The frontal brain area activation as a function of role

This hyperscanning study explored the electrophysiological (EEG) patterns of dyads during a naturalistic persuasive interaction, in which the persuader had to convince the receiver that choosing a group solution was the most effective way to solve a group hypothetical everyday situation. Fifteen dyads composed of a persuader and a receiver were involved in a persuasive interaction while EEG data were recorded. EEG frequency bands (delta, theta, alpha, beta and gamma bands) were analyzed, first, considering the distinct role of the participants and, second, dividing the dyads according to the perceived effectiveness of persuasion. The intra-brain results showed greater activation of the delta, theta and alpha bands in the frontal area of the persuader compared to the receiver. The inter-brain analyses reported a significantly increased dissimilarity activation for delta and theta band in the frontal area compared to more temporo-central and parieto-occipital regions, regardless of the perceived effectiveness of persuasion. To summarize, the process of enhancing groupness during a persuasive interaction generates in the persuader a specific EEG pattern involving mainly low frequency bands activation in the frontal brain regions, suggesting a significant attentional effort and emotional involvement.

When "more for others, less for self" leads to co-benefits: A tri-MRI dyad-hyperscanning study

Unselfishness is admired, especially when collaborations between groups of various scales are urgently needed. However, its neural mechanisms remain elusive. In a tri-MRI dyad-hyperscanning experiment involving 26 groups, each containing 4 participants as two rotating pairs in a coordination game, we sought to achieve reciprocity, or "winning in turn by the two interacting players," as the precursor to unselfishness. Due to its critical role in social processing, the right temporal-parietal junction (rTPJ) was the seed for both time domain (connectivity) and frequency domain (i.e., coherence) analyses. For the former, negative connectivity between the rTPJ and the mentalizing network areas (e.g., the right inferior parietal lobule, rIPL) was identified, and such connectivity was further negatively correlated with the individual's final gain, supporting our task design that "rewarded" the reciprocal participants. For the latter, cerebral coherences of the rTPJs emerged between the interacting pairs (i.e., within-group interacting pairs), and the coupling between the rTPJ and the right superior temporal gyrus (rSTG) between the players who were not interacting with each other (i.e., within-group noninteracting pairs). These coherences reinforce the hypotheses that the rTPJ-rTPJ coupling tracks the collaboration processes and the rTPJ-rSTG coupling for the emergence of decontextualized shared meaning. Our results underpin two social roles (inferring others' behavior and interpreting social outcomes) subserved by the rTPJ-related network and highlight its interaction with other-self/other-concerning brain areas in reaching co-benefits among unselfish players.

Parental involvement affects parent-adolescents brain-to-brain synchrony when experiencing different emotions together: An EEG-based hyperscanning study

Parental involvement (PI) is a broad and multifaceted construct, which refers to the parental demonstration of interest in their child, caring, and warmth (Davis et al., 2021). Parental involvement affects parent-adolescent's relationship and communication. However, there was little research to examine the underlying neural mechanism. The present study aimed to explore how parental involvement is associated with the brain-to-brain synchronous activation between parent-adolescent dyads when sharing emotional experience together by using the electroencephalograph (EEG) hyperscanning. EEG was recorded simultaneously in a sample of 26 parent-adolescent dyads (Mparents'age=43.312, SD=5.468; Madolescents' age=12.077, SD=1.412) when completing the picture processing task. Phase locking values (PLVs) in beta band and gamma band were used to compare the differences in the parent-adolescent dyads' induced brain-to-brain synchrony between the high parental involvement group (HPI) and the low parental involvement group (LPI). Results showed that greater beta brain-to-brain synchrony was observed in the HPIs than in the LPIs when experiencing positive emotions together in the central region. However, there was no significant difference between the HPIs and the LPIs in the negative and neutral condition. Moreover, greater gamma brain-to-brain synchrony was observed when viewing negative emotional stimuli together than viewing positive emotional stimuli together in the LPIs in the central region. However, there was no significant difference between different emotional conditions in the HPIs. Findings of the present study provide neuroscientific evidence that parental involvement may strengthen parent-adolescent's emotional interaction and communication.

Exploring Inter-Brain Electroencephalogram Patterns for Social Cognitive Assessment During Jigsaw Puzzle Solving

Social interaction enables the smooth progression of our daily lives. Mounting evidence from recent hyperscanning neuroimaging studies indicates that key components of social behavior can be evaluated using inter-brain oscillations and connectivity. However, mapping out inter-brain networks and developing neurocognitive theories that explain how humans co-create and share information during social interaction remains challenging. In this study, we developed a jigsaw puzzle-solving game with hyperscanning electroencephalography (EEG) signals recorded to investigate inter-brain activities during social interactions involving cooperation and competition. Participants were recruited and paired into dyads to participate in the multiplayer jigsaw puzzle game with 32-channel EEG signals recorded. The corresponding event-related potentials (ERPs), brain oscillations, and inter-brain functional connectivity were analyzed. The results showed different ERP morphologies of P3 patterns in competitive and cooperative contexts, and brain oscillations in the low-frequency band may be an indicator of social cognitive activities. Furthermore, increased inter-brain functional connectivity in the delta, theta, alpha, and beta frequency bands was observed in the competition mode compared to the cooperation mode. By presenting comparable and valid hyperscanning EEG results alongside those of previous studies using traditional paradigms, this study demonstrates the potential of utilizing hyperscanning techniques in real-life game-playing scenarios to quantitatively assess social cognitive interactions involving cooperation and competition. Our approach offers a promising platform with potential applications in the flexible assessment of psychiatric disorders related to social functioning.

Exploring the role of mutual prediction in inter-brain synchronization during competitive interactions: an fNIRS hyperscanning investigation

Mutual prediction is crucial for understanding the mediation of bodily actions in social interactions. Despite this importance, limited studies have investigated neurobehavioral patterns under the mutual prediction hypothesis in natural competitive scenarios. To address this gap, our study employed functional near-infrared spectroscopy hyperscanning to examine the dynamics of real-time rock-paper-scissors games using a computerized paradigm with 54 participants. Firstly, our results revealed activations in the right inferior frontal gyrus, bilateral dorsolateral prefrontal cortex, and bilateral frontopolar cortex, each displaying distinct temporal profiles indicative of diverse cognitive processes during the task. Subsequently, a task-related increase in inter-brain synchrony was explicitly identified in the right dorsolateral prefrontal cortex, which supported the mutual prediction hypothesis across the two brains. Moreover, our investigation uncovered a close association between the coherence value in the right dorsolateral prefrontal cortex and the dynamic predictive performances of dyads using inter-subject representational similarity analysis. Finally, heightened inter-brain synchrony values were observed in the right dorsolateral prefrontal cortex before a draw compared to a no-draw scenario in the second block, suggesting that cross-brain signal patterns could be reflected in behavioral responses during competition. In summary, these findings provided initial support for expanding the understanding of cognitive processes underpinning natural competitive engagements.

Influence of interpersonal distance on collaborative performance in the joint Simon task-An fNIRS-based hyperscanning study

Collaboration is a critical skill in everyday life. It has been suggested that collaborative performance may be influenced by social factors such as interpersonal distance, which is defined as the perceived psychological distance between individuals. Previous literature has reported that close interpersonal distance may promote the level of self-other integration between interacting members, and in turn, enhance collaborative performance. These studies mainly focused on interdependent collaboration, which requires high levels of shared representations and self-other integration. However, little is known about the effect of interpersonal distance on independent collaboration (e.g., the joint Simon task), in which individuals perform the task independently while the final outcome is determined by the parties. To address this issue, we simultaneously measured the frontal activations of ninety-four pairs of participants using a functional near-infrared spectroscopy (fNIRS)-based hyperscanning technique while they performed a joint Simon task. Behavioral results showed that the Joint Simon Effect (JSE), defined as the RT difference between incongruent and congruent conditions indicating the level of self-other integration between collaborators, was larger in the friend group than in the stranger group. Consistently, the inter-brain neural synchronization (INS) across the dorsolateral and medial parts of the prefrontal cortex was also stronger in the friend group. In addition, INS in the left dorsolateral prefrontal cortex negatively predicted JSE only in the friend group. These results suggest that close interpersonal distance may enhance the shared mental representation among collaborators, which in turn influences their collaborative performance.

Increased interbrain synchronization and neural efficiency of the frontal cortex to enhance human coordinative behavior: A combined hyper-tES and fNIRS study

Coordination is crucial for individuals to achieve common goals; however, the causal relationship between coordination behavior and neural activity has not yet been explored. Interbrain synchronization (IBS) and neural efficiency in cortical areas associated with the mirror neuron system (MNS) are considered two potential brain mechanisms. In the present study, we attempted to clarify how the two mechanisms facilitate coordination using hypertranscranial electrical stimulation (hyper-tES). A total of 124 healthy young adults were randomly divided into three groups (the hyper-tACS, hyper-tDCS and sham groups) and underwent modulation of the right inferior frontal gyrus (IFG) during functional near-infrared spectroscopy (fNIRS). Increased IBS of the PFC or neural efficiency of the right IFG (related to the MNS) was accompanied by greater coordination behavior; IBS had longer-lasting effects on behavior. Our findings highlight the importance of IBS and neural efficiency of the frontal cortex for coordination and suggest potential interventions to improve coordination in different temporal windows.

Epigenetic modification of the oxytocin receptor gene is associated with child-parent neural synchrony during competition

Interpersonal neural synchrony (INS) occurs when neural electrical activity temporally aligns between individuals during social interactions. It has been used as a metric for interpersonal closeness, often during naturalistic child-parent interactions. This study evaluated whether other biological correlates of social processing predicted the prevalence of INS during child-parent interactions, and whether their observed cooperativity modulated this association. Child-parent dyads (n = 27) performed a visuospatial tower-building task in cooperative and competitive conditions. Neural activity was recorded using mobile electroencephalogram (EEG) headsets, and experimenters coded video-recordings post-hoc for behavioral attunement. DNA methylation of the oxytocin receptor gene (OXTRm) was measured, an epigenetic modification associated with reduced oxytocin activity and socioemotional functioning. Greater INS during competition was associated with lower child OXTRm, while greater behavioral attunement during competition and cooperation was associated with higher parent OXTRm. These differential relationships suggest that interpersonal dynamics as measured by INS may be similarly reflected by other biological markers of social functioning, irrespective of observed behavior. Children's self-perceived communication skill also showed opposite associations with parent and child OXTRm, suggesting complex relationships between children's and their parents' social functioning. Our findings have implications for ongoing developmental research, supporting the utility of biological metrics in characterizing interpersonal relationships.

Brain-to-brain synchrony during dyadic action co-representation under acute stress: evidence from fNIRS-based hyperscanning

Unexpected acute stressors may affect our co-representation with other co-actors when completing the joint tasks. The present study adopted the emergent functional near-infrared spectroscopy (fNIRS)-based hyperscanning method to explore the brain-to-brain synchrony when implementing the Joint Simon Task under acute stress induced in the laboratory. The behavioral results reported that the joint Simon effect (JSE) was found in both the stress group and the control group, but the joint Simon effect in the stress group was significantly lessened than the joint Simon effect in the control group, demonstrating that when completing the joint action task in the state of acute stress, women's ability to distinguishing self- from other-related mental representations was improved, and the strength of women's action co-representation was diminished. The fNIRS results showed that when completing the joint Simon task in the state of the acute stress, the brain-to-brain synchrony at the r-TPJ in the stress group was significantly higher than that in the control group, demonstrating that the increased brain-to-brain synchrony at the TPJ may be served as the critical brain-to-brain neural mechanism underlying the joint action task under acute stress.

Inter-Brain Synchrony Pattern Investigation on Triadic Board Game Play-Based Social Interaction: An fNIRS Study

Recent advances in functional neuroimaging techniques, including methodologies such as fNIRS, have enabled the evaluation of inter-brain synchrony (IBS) induced by interpersonal interactions. However, the social interactions assumed in existing dyadic hyperscanning studies do not sufficiently emulate polyadic social interactions in the real world. Therefore, we devised an experimental paradigm that incorporates the Korean folk board game "Yut-nori" to reproduce social interactions that emulate social activities in the real world. We recruited 72 participants aged 25.2 ± 3.9 years (mean ± standard deviation) and divided them into 24 triads to play Yut-nori, following the standard or modified rules. The participants either competed against an opponent (standard rule) or cooperated with an opponent (modified rule) to achieve a goal efficiently. Three different fNIRS devices were employed to record cortical hemodynamic activations in the prefrontal cortex both individually and simultaneously. Wavelet transform coherence (WTC) analyses were performed to assess prefrontal IBS within a frequency range of 0.05-0.2 Hz. Consequently, we observed that cooperative interactions increased prefrontal IBS across overall frequency bands of interest. In addition, we also found that different purposes for cooperation generated different spectral characteristics of IBS depending on the frequency bands. Moreover, IBS in the frontopolar cortex (FPC) reflected the influence of verbal interactions. The findings of our study suggest that future hyperscanning studies should consider polyadic social interactions to reveal the properties of IBS in real-world interactions.

Bidirectional understanding and cooperation: interbrain neural synchronization during social navigation

The complexity of the environment requires humans to solve problems collaboratively. The aim of this study was to investigate the neural mechanism of social navigation in group problem-solving situations. A novel cooperative task was designed in which dyadic participants assumed the role of an operator or a navigator with different skills and knowledge and worked together to complete the task. Using functional near-infrared spectroscopy-based hyperscanning, we found stronger interbrain neural synchronization of the right temporoparietal junction (rTPJ) between dyads when the operator received instructions from the navigator rather than from a computer. The functional connections between the rTPJ and the other brain areas indicated the involvement of the mirror neural system during the task. Further directional analysis using Granger causality analysis revealed a flow of information from the temporal to the parietal and then to the pre-motor cortex in the operator's brain. These findings provide empirical evidence for the neural mechanism of social navigation and highlight the importance of the rTPJ for communication and joint attention in uncertain group problem-solving situations.

Distinct inter-brain synchronization patterns underlying group decision-making under uncertainty with partners in different interpersonal relationships

Humans may behave in different manners when making decisions with friends and strangers. Whether the interpersonal relationship and the characteristics of the individuals in the group affected the group decision-making under uncertainty in the real-time interaction remains unknown. Using the turn-based Balloon Analogue Risk Task (BART), the present study examined the group decision-making propensity under uncertainty with partners in different interpersonal relationships and interpersonal orientations. Corresponding inter-brain synchronization (IBS) patterns at the prefrontal cortex (PFC) were also uncovered with the fNIRS-based hyperscanning approach. Behavioral results identified that dyads in the friend group exhibited the uncertainty-averse propensity when comparing with the stranger group. The fNIRS results reported that feedback-related IBS at the left inferior frontal gyrus (l-IFG) and medial frontopolar cortex (mFPC) during different feedbacks was modulated by interpersonal relationships. The IBS at all channels in the PFC during the positive and negative feedbacks, respectively, predicted the decision-making propensity under uncertainty in the stranger and friend groups based on the support vector machine (SVM) algorithm. The moderating role of the social value orientation (SVO) was also verified in the mediation effect of the dyad closeness on the decision-making propensity under uncertainty via the IBS at the right lateral frontopolar cortex (r-FPC). These findings demonstrated disparate behavioral responses and inter-brain synchronization patterns underlying group decision-making under uncertainty with partners in different interpersonal relationships.

Interpersonal Competition in Elderly Couples: A Functional Near-Infrared Spectroscopy Hyperscanning Study

Elderly people tend not to compete with others, and if they do, the mechanism behind the competition is not clear. In this study, groups of elderly couples and matched cross-sex controls were recruited to perform a competitive button-pressing task, while their brain signals were simultaneously collected using functional near-infrared spectroscopy (fNIRS) hyperscanning. Several fundamental observations were made. First, controls showed attenuated interpersonal competition across task processes, but couples held the competition with each other. Second, couples demonstrated increased inter-brain synchronization (IBS) between the middle temporal cortex and the temporoparietal junction across task processes. Third, Granger causality analysis in couples revealed significant differences between the directions (i.e., from men to women, and from women to men) in the first half of the competitive task, whereas there was no significant difference in the second half. Finally, the groups of couples and controls could be successfully discriminated against based on IBS by using a machine-learning approach. In sum, these findings indicate that elderly couples can maintain interpersonal competition, and such maintenance might be associated with changes in the IBS of the mentalizing system. It suggests the possible positive impact of long-term spouse relationships on interpersonal interactions, both behaviorally and neurally, in terms of competition.

A Functional and Neuroanatomical Model of Dehumanization

The dehumanization of others is a major scourge of mankind; however, despite its significance, physicians have little understanding of the neurobiological mechanisms for this behavior. We can learn much about dehumanization from its brain-behavior localization and its manifestations in people with brain disorders. Dehumanization as an act of denying to others human qualities includes two major forms. Animalistic dehumanization (also called infrahumanization) results from increased inhibition of prepotent tendencies for emotional feelings and empathy for others. The mechanism may be increased activity in the inferior frontal gyrus. In contrast, mechanistic dehumanization results from a loss of perception of basic human nature and decreased mind-attribution. The mechanism may be hypofunction of a mentalization network centered in the ventromedial prefrontal cortex and adjacent subgenual anterior cingulate cortex. Whereas developmental factors may promote animalistic dehumanization, brain disorders, such as frontotemporal dementia, primarily promote mechanistic dehumanization. The consideration of these two processes as distinct, with different neurobiological origins, could help guide efforts to mitigate expression of this behavior.

Greater prefrontal activation during sitting toe tapping predicts severer freezing of gait in Parkinson's disease: an fNIRS study

OBJECTIVE

Previous studies have revealed that, compared with Parkinson's disease (PD) patients without freezing of gait (FoG), the ones with FoG showed greater prefrontal activation while doing lower-limb movements involving standing, walking and turning, which require both locomotor and balance control. However, the relation between FoG and pure locomotor control as well as its underlying mechanism remain unclear.

METHODS

A total of 56 PD subjects were recruited and allocated to PD-FoG and PD-noFoG subgroups, and 34 age-matched heathy adults were included as heathy control (HC). Functional near-infrared spectroscopy was used to measure their prefrontal activation in a sitting lower-limb movement task, wherein subjects were asked to sit and tap their right toes as big and as fast as possible.

RESULTS

Result of one-way ANOVA (Group: PD-FoG vs. PD-noFoG vs. HC) revealed greater activation in the right prefrontal cortex in the PD-FoG group than in the other 2 groups. Linear mixed-effects model showed consistent result. Furthermore, the right prefrontal activation positively correlated with the severity of FoG symptoms in PD-FoG patients.

CONCLUSION

These findings suggested that PD patients with FoG require additional cognitive resources to compensate their damaged automaticity in locomotor control, which is more pronounced in severe FoG patients than milder ones.

Distinct neural couplings to shared goal and action coordination in joint action: evidence based on fNIRS hyperscanning

Joint action is central to human nature, enabling individuals to coordinate in time and space to achieve a joint outcome. Such interaction typically involves two key elements: shared goal and action coordination. Yet, the substrates entrained to these two components in joint action remained unclear. In the current study, dyads performed two tasks involving both sharing goal and action coordination, i.e. complementary joint action and imitative joint action, a task only involving shared goal and a task only involving action coordination, while their brain activities were recorded by the functional near-infrared spectroscopy hyperscanning technique. The results showed that both complementary and imitative joint action (i.e. involving shared goal and action coordination) elicited better behavioral performance than the task only involving shared goal/action coordination. We observed that the interbrain synchronization (IBS) at the right inferior frontal cortex (IFC) entrained more to shared goal, while left-IFC IBS entrained more to action coordination. We also observed that the right-IFC IBS was greater during completing a complementary action than an imitative action. Our results suggest that IFC plays an important role in joint action, with distinct lateralization for the sub-components of joint action.

Systemic physiology augmented functional near-infrared spectroscopy hyperscanning: a first evaluation investigating entrainment of spontaneous activity of brain and body physiology between subjects

Significance: Functional near-infrared spectroscopy (fNIRS) enables measuring the brain activity of two subjects while they interact, i.e., the hyperscanning approach. Aim: In our exploratory study, we extended classical fNIRS hyperscanning by adding systemic physiological measures to obtain systemic physiology augmented fNIRS (SPA-fNIRS) hyperscanning while blocking and not blocking the visual communication between the subjects. This approach enables access brain-to-brain, brain-to-body, and body-to-body coupling between the subjects simultaneously. Approach: Twenty-four pairs of subjects participated in the experiment. The paradigm consisted of two subjects that sat in front of each other and had their eyes closed for 10 min, followed by a phase of 10 min where they made eye contact. Brain and body activity was measured continuously by SPA-fNIRS. Results: Our study shows that making eye contact for a prolonged time causes significant changes in brain-to-brain, brain-to-body, and body-to-body coupling, indicating that eye contact is followed by entrainment of the physiology between subjects. Subjects that knew each other generally showed a larger trend to change between the two conditions. Conclusions: The main point of this study is to introduce a new framework to investigate brain-to-brain, body-to-body, and brain-to-body coupling through a simple social experimental paradigm. The study revealed that eye contact leads to significant synchronization of spontaneous activity of the brain and body physiology. Our study is the first that employed the SPA-fNIRS approach and showed its usefulness to investigate complex interpersonal physiological changes.

Cortical activation during cooperative joint actions and competition in children with and without an autism spectrum condition (ASC): an fNIRS study

Children with an Autism Spectrum Condition (ASC) have social communication and perceptuomotor difficulties that affect their ability to engage in dyadic play. In this study, we compared spatio-temporal errors and fNIRS-related cortical activation between children with and without an ASC during a Lincoln Log dyadic game requiring them to play leader or follower roles, move in synchrony or while taking turns, and move cooperatively or competitively with an adult partner. Children with an ASC had greater motor, planning, and spatial errors and took longer to complete the building tasks compared to typically developing (TD) children. Children with an ASC had lower superior temporal sulcus (STS) activation during Turn-take and Compete, and greater Inferior Parietal Lobe (IPL) activation during Lead and Turn-take compared to TD children. As dyadic play demands increased, TD children showed greater STS activation during Turn-take (vs. Synchrony) and Compete (vs. Cooperate) whereas children with an ASC showed greater IPL activation during Lead and Compete (vs. Cooperate). Our findings suggest that children with an ASC rely on self-generated action plans (i.e., increased IPL activation) more than relying on their partner’s action cues (i.e., reduced STS activation) when engaging in dyadic play including joint actions and competition.

Inter-Brain Neural Mechanism Underlying Turn-Based Interaction Under Acute Stress in Women: A Hyperscanning Study Using Functional Near-Infrared Spectroscopy

With the ever-changing social environment, stress has exerted a substantial influence on social interaction. The present study examined the underlying cognitive and neural mechanism on how acute stress affected the real-time cooperative and competitive interaction with four hypothesized path models. We used the hyperscanning technique based on functional near-infrared spectroscopy (fNIRS) device to examine brain-to-brain coherence within the dyads engaging Pattern Game under acute stress manipulated through Trier Social Stress Test for Groups. Behavioral results showed stressed dyads exhibited better cooperative performance and higher self-other overlap level during the cooperative session than dyads in the control group. The fNIRS results identified higher interpersonal brain synchronization in the right temporal-parietal junction (r-TPJ) stronger Granger causality from partner-to-builder during the cooperative session in the stress group when compared with the control group. Our results corroborated better performance in the cooperative context and further identified that brain-to-brain coherence in r-TPJ and self-other overlap serially mediated the effect of acute stress on cooperative performance.

Inter-group conflict affects inter-brain synchrony during synchronized movements

Interpersonal synchrony refers to alignment in time of interacting individuals. Recent neuroimaging findings indicate that the inferior frontal gyrus (IFG) - a core region of the observation-execution system - is not only activated during tasks that involve synchrony, but also coupled between interaction partners, suggesting a key role for the IFG in mediating interpersonal synchrony. In this study we investigated whether inter-brain synchrony (IBS) is modulated by inter-group relationships. We examined this question in the context of the Israeli-Palestinian conflict - one of the world's most prolonged and intractable conflicts. Using functional Near Infra-Red Spectroscopy (fNIRS) hyperscanning, we measured IBS among ingroup vs. inter-group dyads (same-nationality dyads and Jewish-Palestinian dyads, respectively) while they performed a task entailing 2D movement synchrony. The results point to an increase in behavioral synchrony and greater enjoyment in the ingroup dyads, compared to the inter-group dyads. Critically, IBS in the left IFG significantly increased throughout task and it was higher among ingroup compared to inter-group dyads. Our findings highlight the effect of group membership on IBS plasticity.

Integration of social status and trust through interpersonal brain synchronization

Trust can be a dynamic social process, during which the social identity of the interacting agents (e.g., an investor and a trustee) can bias trust outcomes. Here, we investigated how social status modulates trust and the neural mechanisms underlying this process. An investor and a trustee performed a 10-round repeated trust game while their brain activity was being simultaneously recorded using functional near-infrared spectroscopy. The social status (either high or low) of both investors and trustees was manipulated via a math competition task. The behavioral results showed that in the initial round, individuals invested more in low-status partners. However, the investment ratio increased faster as the number of rounds increased during trust interaction when individuals were paired with a high-status partner. This increasing trend was particularly prominent in the low (investor)-high (trustee) status group. Moreover, the low-high group showed increased investor-trustee brain synchronization in the right temporoparietal junction as the number of rounds increased, while brain activation in the right dorsolateral prefrontal cortex of the investor decreased as the number of rounds increased. Both interpersonal brain synchronization and brain activation predicted investment performance at the early stage; furthermore, two-brain data provided earlier predictions than did single-brain data. These effects were detectable in the investment phase in the low-high group only; no comparable effects were observed in the repayment phase or other groups. Overall, this study demonstrated a multi-brain mechanism for the integration of social status and trust.

Neural Circuits for Social Interactions: From Microcircuits to Input-Output Circuits

Social behaviors entail responses to social information and requires the perception and integration of social cues through a complex cognition process that involves attention, memory, motivation, and emotion. Neurobiological and molecular mechanisms underlying social behavior are highly conserved across species, and inter- and intra-specific variability observed in social behavior can be explained to large extent by differential activity of a conserved neural network. However, neural microcircuits and precise networks involved in social behavior remain mysterious. In this review, we summarize the microcircuits and input-output circuits on the molecular, cellular, and network levels of different social interactions, such as social exploration, social hierarchy, social memory, and social preference. This review provides a broad view of how multiple microcircuits and input-output circuits converge on the medial prefrontal cortex, hippocampus, and amygdala to regulate complex social behaviors, as well as a potential novel view for better control over pathological development.

Experiencing Happiness Together Facilitates Dyadic Coordination through the Enhanced Interpersonal Neural Synchronization

Experiencing positive emotions together facilitates interpersonal understanding and promotes subsequent social interaction among individuals. However, the neural underpinnings of such emotional-social effect remain to be discovered. Current study employed the fNIRS-based hyperscanning to investigate the above mentioned relationship. After participants in dyad watching movie clips with happily or neutral emotion, they were asked to perform the interpersonal cooperative task, with their neural activation of prefrontal cortex (PFC) being recorded simultaneously via functional near infrared spectroscopy. Results suggested that compared with the neutral movie watching together, a higher interpersonal neural synchronization (INS) in left inferior frontal gyrus during participant dyads watching happiness movie together. Subsequently, dyads in happiness showed more effective coordination interaction during performed the interpersonal cooperation task compared to those in the neutral condition, and such facilitated effect was associated with increased cooperation-related INS at left middle frontal cortex. A mediation analysis showed that the coordination interaction fully mediated the relationship between the emotion-induced INS during the happiness movie-viewing and the cooperation-related INS in interpersonal cooperation. Taken together, our findings suggest that the faciliatory effect experiencing happiness together has on interpersonal cooperation can be reliably reflected by the INS magnitude at the brain level.

Reexamining the neural network involved in perception of facial expression: A meta-analysis

Perception of facial expression is essential for social interactions. Although a few competing models have enjoyed some success to map brain regions, they are also facing difficult challenges. The current study used an updated activation likelihood estimation (ALE) method of meta-analysis to explore the involvement of brain regions in facial expression processing. The sample contained 96 functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) studies of healthy adults with the results of whole-brain analyses. The key findings revealed that the ventral pathway, especially the left fusiform face area (FFA) region, was more responsive to facial expression. The left posterior FFA showed strong involvement when participants passively viewing emotional faces without being asked to judge the type of expression or other attributes of the stimuli. Through meta-analytic connectivity modeling (MACM) of the main brain regions in the ventral pathway, we constructed a co-activating neural network as a revised model of facial expression processing that assigns prominent roles to the amygdala, FFA, the occipital gyrus, and the inferior frontal gyrus.

The Underlying neural mechanisms of interpersonal situations on collaborative ability: A hyperscanning study using functional near-infrared spectroscopy

The collaborative ability to coordinate an individual with others is critical to performance of joint actions. Prior studies found that different types of interpersonal situations have more or less impact on the collaborative ability of joint actions, but the results are controversial. To clarify the influence of interpersonal situations on collaborative ability, we adopted the joint Simon task, a choice-reaction task that two people perform together. Functional near-infrared spectroscopy (fNIRS) was used to study the neural mechanisms of interpersonal situations on collaborative ability and task performance under payoffs that fostered competition or cooperation. The fNIRS results showed that significant inter-brain neural synchronization (INS) occurred in the bilateral inferior parietal lobule (IPL) for both situations. Moreover, for the competition situation, the pairs also shown a significant INS in the right IPL. These results imply that the bilateral IPL is involved in cooperation and competition due to involvement of common concern and understanding of intention. The right IPL may be more crucial for competition because of the psychological resources involved in distinguishing self and others. Eventually, the INS in competition was better than in the other situations, correlating with higher performance of the joint task as well.

Inter-brain amplitude correlation differentiates cooperation from competition in a motion-sensing sports game

Cooperation and competition are two basic modes of human interaction. Their underlying neural mechanisms, especially from an interpersonal perspective, have not been fully explored. Using the electroencephalograph-based hyperscanning technique, the present study investigated the neural correlates of both cooperation and competition within the same ecological paradigm using a classic motion-sensing tennis game. Both the inter-brain coupling (the inter-brain amplitude correlation and inter-brain phase-locking) and the intra-brain spectral power were analyzed. Only the inter-brain amplitude correlation showed a significant difference between cooperation and competition, with different spatial patterns at theta, alpha and beta frequency bands. Further inspection revealed distinct inter-brain coupling patterns for cooperation and competition; cooperation elicited positive inter-brain amplitude correlation at the delta and theta bands in extensive brain regions, while competition was associated with negative occipital inter-brain amplitude correlation at the alpha and beta bands. These findings add to our knowledge of the neural mechanisms of cooperation and competition and suggest the significance of adopting an inter-brain perspective in exploring the neural underpinnings of social interaction in ecological contexts.

Team-work, Team-brain: Exploring synchrony and team interdependence in a nine-person drumming task via multiparticipant hyperscanning and inter-brain network topology with fNIRS

Teamwork is indispensable in human societies. However, due to the complexity of studying ecologically valid synchronous team actions, requiring multiple members and a range of subjective and objective measures, the mechanism underlying the impact of synchrony on team performance is still unclear. In this paper, we simultaneously measured groups of nine-participants' (total N = 180) fronto-temporal activations during a drum beating task using functional near infrared spectroscopy (fNIRS)-based hyperscanning and multi-brain network modeling, which can assess patterns of shared neural synchrony and attention/information sharing across entire teams. Participants (1) beat randomly without considering others' drumming (random condition), (2) actively coordinated their beats with the entire group without other external cue (team-focus condition), and (3) beat together based on a metronome (shared-focus condition). Behavioral data revealed higher subjective and objective measures of drum-beat synchronization in the team-focus condition, as well as higher felt interdependence. The fNIRS data revealed that participants in the team-focus condition also showed higher interpersonal neural synchronization (INS) and higher Global Network Efficiency in their left TPJ and mPFC. Higher left TPJ Global Network Efficiency also predicted higher actual synchrony in the team-focus condition, with an effect size roughly 1.5 times that of subjective measures, but not in the metronome-enabled shared-focus condition. This result suggests that shared mental representations with high efficiency of information exchange across the entire team may be a key component of synchrony, adding to the understanding of the actual relation to team work.

Effects of acute psychosocial stress on interpersonal cooperation and competition in young women

Although tend-and-befriend is believed to be the dominant stress response in women, little is known regarding the effects of acute psychosocial stress on different dynamic social interactions. To measure these effects, 80 female participants were recruited, paired into the dyads, and instructed to complete cooperative and competitive key-pressing tasks after experiencing acute stress or a control condition. Each dyad of participants should press the key synchronously when the signal was presented in the cooperative task and as fast as possible in the competitive task. During the tasks, brain activities of prefrontal and right temporo-parietal areas were recorded from each dyad using functional near-infrared spectroscopy (fNIRS). The results showed that acute psychosocial stress evidently promoted competitive behavior, accompanied by increased interpersonal neural synchronization (INS) in the right dorsolateral prefrontal cortex. Despite the lack of a significant difference in the overall cooperation rate, the response time difference between two stressed participants markedly declined over time with more widespread INS in the prefrontal cortex, suggesting that there ensued cooperative improvement among stressed women. These findings behaviorally and neurologically revealed context-dependent response patterns to psychosocial stress in women during dynamic social interactions.

Brain hemodynamic response in Examiner-Examinee dyads during spatial short-term memory task: an fNIRS study

The Corsi Block-Tapping test (CBT) is a measure of spatial working memory (WM) in clinical practice, requiring an examinee to reproduce sequences of cubes tapped by an examiner. CBT implies complementary behaviors in the examiners and the examinees, as they have to attend a precise turn taking. Previous studies demonstrated that the Prefrontal Cortex (PFC) is activated during CBT, but scarce evidence is available on the neural correlates of CBT in the real setting. We assessed PFC activity in dyads of examiner–examinee participants while completing the real version of CBT, during conditions of increasing and exceeding workload. This procedure allowed to investigate whether brain activity in the dyads is coordinated. Results in the examinees showed that PFC activity was higher when the workload approached or reached participants’ spatial WM span, and lower during workload conditions that were largely below or above their span. Interestingly, findings in the examiners paralleled the ones in the examinees, as examiners’ brain activity increased and decreased in a similar way as the examinees’ one. In the examiners, higher left-hemisphere activity was observed suggesting the likely activation of non-spatial WM processes. Data support a bell-shaped relationship between cognitive load and brain activity, and provide original insights on the cognitive processes activated in the examiner during CBT.

Inter-brain synchrony in teams predicts collective performance

Despite decades of research in economics and psychology attempting to identify ingredients that make up successful teams, neuroscientists have only just begun to study how multiple brains interact. Recent research has shown that people's brain activity becomes synchronized with others' (inter-brain synchrony) during social engagement. However, little is known as to whether inter-brain synchrony relates to collective behavior within teams. Here, we merge the nascent field of group neuroscience with the extant literature of team dynamics and collective performance. We recruited 174 participants in groups of 4 and randomly assigned them to complete a series of problem-solving tasks either independently or as a team, while simultaneously recording each person's brain activity using an electroencephalography hyperscanning setup. This design allowed us to examine the relationship between group identification and inter-brain synchrony in explaining collective performance. As expected, teammates identified more strongly with one another, cooperated more on an economic game, and outperformed the average individual on most problem-solving tasks. Crucially, inter-brain synchrony, but not self-reported group identification, predicted collective performance among teams. These results suggest that inter-brain synchrony can be informative in understanding collective performance among teams where self-report measures may fail to capture behavior.

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.

Brain-to-Brain Neural Synchrony During Social Interactions: A Systematic Review on Hyperscanning Studies

The aim of this study was to conduct a comprehensive review on hyperscanning research (measuring brain activity simultaneously from more than two people interacting) using an explicit systematic method, the preferred reporting items for systematic reviews and meta-analyses (PRISMA). Data were searched from IEEE Xplore, PubMed, Engineering Village, Web of Science and Scopus databases. Inclusion criteria were journal articles written in English from 2000 to 19 June 2019. A total of 126 empirical studies were screened out to address three specific questions regarding the neuroimaging method, the application domain, and the experiment paradigm. Results showed that the most used neuroimaging method with hyperscanning was magnetoencephalography/electroencephalography (MEG/EEG; 47%), and the least used neuroimaging method was hyper-transcranial Alternating Current Stimulation (tACS) (1%). Applications in cognition accounted for almost half the studies (48%), while educational applications accounted for less than 5% of the studies. Applications in decision-making tasks were the second most common (26%), shortly followed by applications in motor synchronization (23%). The findings from this systematic review that were based on documented, transparent and reproducible searches should help build cumulative knowledge and guide future research regarding inter-brain neural synchrony during social interactions, that is, hyperscanning research.

Cooperation Makes a Group be More Creative

This study investigated how cooperative and competitive interaction modes affect the group creative performance. The participants were recruited as dyads to solve 2 problems either demanding divergent thinking (alternative uses task, AUT) or not (object characteristic task, OCT). The dyads solved 1 of the 2 problems in the cooperative mode and the other in the competitive mode. Functional near-infrared spectroscopy (fNIRS)-based hyperscanning was used to record their neural activities in the prefrontal and right temporal-parietal junction (r-TPJ) regions. Results revealed the dyads showed higher AUT fluency, AUT originality, OCT fluency, and cooperation level in the cooperative mode than in the competitive mode. The fNIRS data revealed increased (task-baseline) interpersonal brain synchronization (IBS) in the right dorsolateral prefrontal cortex (r-DLPFC) and r-TPJ, only for dyads in the AUT/cooperation condition. In both r-DLPFC and r-TPJ, the IBS of dyads in the AUT/cooperation condition was stronger than in the AUT/competition and OCT/cooperation. Moreover, a stronger IBS was evoked between the regions in prefrontal and posterior temporal regions in the AUT/cooperation condition, as compared with the competition mode. These findings suggest that enhanced IBS may underlie the positive effects of cooperation as compared with the competition in terms of group creativity.

The effect of interbrain synchronization in gesture observation: A fNIRS study

INTRODUCTION

Gestures characterize individuals' nonverbal communicative exchanges, taking on different functions. Several types of research in the neuroscientific field have been interested in the investigation of the neural correlates underlying the observation and implementation of different gestures categories. In particular, different studies have focused on the neural correlates underlying gestures observation, emphasizing the presence of mirroring mechanisms in specific brain areas, which appear to be involved in gesture observation and planning mechanisms.

MATERIALS AND METHODS

Specifically, the present study aimed to investigate the neural mechanisms, through the use of functional Near-Infrared Spectroscopy (fNIRS), underlying the observation of affective, social, and informative gestures with positive and negative valence in individuals' dyads composed by encoder and decoder. The variations of oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin concentrations of both individuals were collected simultaneously through the use of hyperscanning paradigm, allowing the recording of brain responsiveness and interbrain connectivity.

RESULTS

The results showed a different brain activation and an increase of interbrain connectivity according to the type of gestures observed, with a significant increase of O2Hb brain responsiveness and interbrain connectivity and a decrease of HHb brain responsiveness for affective gestures in the dorsolateral prefrontal cortex (DLPFC) and for social gestures in the superior frontal gyrus (SFG). Furthermore, concerning the valence of the observed gestures, an increase of O2Hb brain activity and interbrain connectivity was observed in the left DLPFC for positive affective gestures compared to negative ones.

CONCLUSION

In conclusion, the present study showed different brain responses underlying the observation of different types of positive and negative gestures. Moreover, interbrain connectivity calculation allowed us to underline the presence of mirroring mechanisms involved in gesture-specific frontal regions during gestures observation and action planning.

Affective, Social, and Informative Gestures Reproduction in Human Interaction: Hyperscanning and Brain Connectivity

Gestural communication characterizes daily individuals' interactions in order to share information and to modify others' behavior. Social neuroscience has investigated the neural bases which support recognizing of different gestures. The present research, through the use of the hyperscanning approach, that allows the simultaneously recording of the activity of two or more individuals involved in a joint action, aims to investigate the neural bases of gestural communication. Moreover, by using hyperscanning paradigm we explore the inter-brain connectivity between two inter-agents, the one who performed the gesture (encoder) and the one who received it (decoder), with functional Near-infrared Spectroscopy (fNIRS) during the reproduction of affective, social and informative gestures with positive and negative valence. Result showed an increase in oxygenated hemoglobin concentration (O2Hb) and inter-brain connectivity in the dorsolateral prefrontal cortex (DLPFC) for affective gestures, in the superior frontal gyrus (SFG) for social gestures and the frontal eye fields (FEF) for informative gestures, for both encoder and decoder. Furthermore, it emerged that positive gestures activate more the left DLPFC, with an increase in inter-brain connectivity in DLPFC and SFG. The present study revealed the relevant function of the type and valence of gestures in affecting intra- and inter-brain connectivity.

A gift for gratitude and cooperative behavior: brain and cognitive effects

Recently, different psychological studies have been interested in identifying the factors that regulate the development and maintenance of long-lasting interpersonal and social relationships. Specifically, the present research explored the link between gift exchange, gratitude and cognitive effects. The behavioral performance and neural activity of 32 participants were recorded during a cooperative game to be played before and after gift exchange. Specifically, participants had to perform the task coupled with a dear friend. Half of the couples were asked to exchange a gift before the task performance; the other half was asked to exchange a gift halfway through the task performance. For hemodynamic brain responses, functional near-infrared spectroscopy was used. Results showed that an increase in cognitive performance occurred after the exchange of gifts, with improved accuracy and lower response times in task performance. Regarding hemodynamic responses, an increase in oxygenated hemoglobin was detected, especially in the dorsolateral prefrontal cortex following the gift exchange. Furthermore, it was observed that gift exchange before the beginning of the task increased the performance level. The present study provides a significant contribution to the identification of those factors that enable the increased cognitive performance based on cooperative relationships.

The "gift effect" on functional brain connectivity. Inter-brain synchronization when prosocial behavior is in action

The gift exchange represents a moment that characterizes interpersonal interactions. In particular, research in psychological and neuroscientific fields aimed to observe the social function of gift exchange. Specifically, the present study aimed to investigate the effects of prosocial behavior, experienced during gift exchange, on individuals’ cognitive performance and brain activity. To this aim, behavioral performance and neural activity of 15 dyads of participants, with a consolidated friendship, were collected during the execution of an attentional cooperative task before or after a gift exchange. Individuals’ brain activity was recorded through the use of Functional Near Infrared Spectroscopy (fNIRS) in hyperscanning. Results showed an increase of perceived cooperation and cognitive performance, in terms of accuracy (ACC), after gift exchange. The increase of interpersonal tuning and cooperation was also shown by neural activity with an increase of oxygenated hemoglobin (O2Hb) intra-brain and inter-brain connectivity in the dorsolateral prefrontal cortex (DLPFC) following the gift exchange. Moreover, from ConIndex analysis emerged an increase of inter-brain connectivity compared to intra-brain in DLPFC area. The present study, therefore, highlights how prosocial behavior can have positive effects on cognitive performance improvement and interpersonal relationships and neural coordination strengthen, increasing intra and inter-brain connectivity mechanisms.

Developmental Differences in Cortical Activation During Action Observation, Action Execution and Interpersonal Synchrony: An fNIRS Study

Interpersonal synchrony (IPS) is an important everyday behavior influencing social cognitive development; however, few studies have investigated the developmental differences and underlying neural mechanisms of IPS. functional near-infrared spectroscopy (fNIRS) is a novel neuroimaging tool that allows the study of cortical activation in the presence of natural movements. Using fNIRS, we compared cortical activation patterns between children and adults during action observation, execution, and IPS. Seventeen school-age children and 15 adults completed a reach to cleanup task while we obtained cortical activation data from bilateral inferior frontal gyrus (IFG), superior temporal sulcus (STS), and inferior parietal lobes (IPL). Children showed lower spatial and temporal accuracy during IPS compared to adults (i.e., spatial synchrony scores (Mean ± SE) in children: 2.67 ± 0.08 and adults: 2.85 ± 0.06; temporal synchrony scores (Mean ± SE) in children: 2.74 ± 0.06 and adults: 2.88 ± 0.05). For both groups, the STS regions were more activated during action observation, while the IFG and STS were more activated during action execution and IPS. The IPS condition involved more right-sided activation compared to action execution suggesting that IPS is a higher-order process involving more bilateral cortical activation. In addition, adults showed more left lateralization compared to the children during movement conditions (execution and IPS); which indicated greater inhibition of ipsilateral cortices in the adults compared to children. These findings provide a neuroimaging framework to study imitation and IPS impairments in special populations such as children with Autism Spectrum Disorder.

Hyperscanning: A Valid Method to Study Neural Inter-brain Underpinnings of Social Interaction

Social interactions are a crucial part of human life. Understanding the neural underpinnings of social interactions is a challenging task that the hyperscanning method has been trying to tackle over the last two decades. Here, we review the existing literature and evaluate the current state of the hyperscanning method. We review the type of methods (fMRI, M/EEG, and fNIRS) that are used to measure brain activity from more than one participant simultaneously and weigh their pros and cons for hyperscanning. Further, we discuss different types of analyses that are used to estimate brain networks and synchronization. Lastly, we present results of hyperscanning studies in the context of different cognitive functions and their relations to social interactions. All in all, we aim to comprehensively present methods, analyses, and results from the last 20 years of hyperscanning research.

Dissecting social interaction: dual-fMRI reveals patterns of interpersonal brain-behavior relationships that dissociate among dimensions of social exchange

During social interactions, each individual’s actions are simultaneously a consequence of and an antecedent to their interaction partner’s behavior. Capturing online the brain processes underlying such mutual dependency requires simultaneous measurements of all interactants’ brains during real-world exchange (‘hyperscanning’). This demands a precise characterization of the type of interaction under investigation, however, and analytical techniques capable of capturing interpersonal dependencies. We adapted an interactive task capable of dissociating between two dimensions of interdependent social exchange: goal structure (cooperation vs competition) and interaction structure [concurrent (CN) vs turn-based]. Performing dual-functional magnetic resonance imaging hyperscanning on pairs of individuals interacting on this task, and modeling brain responses in both interactants as systematic reactions to their partner’s behavior, we investigated interpersonal brain-behavior dependencies (iBBDs) during each dimension. This revealed patterns of iBBDs that differentiated among exchanges; in players supporting the actions of another, greater brain responses to the co-player’s actions were expressed in regions implicated in social cognition, such as the medial prefrontal cortex, precuneus and temporal cortices. Stronger iBBD during CN competitive exchanges was observed in brain systems involved in movement planning and updating, however, such as the supplementary motor area. This demonstrates the potential for hyperscanning to elucidate neural processes underlying different forms of social exchange.

The Use of Hyperscanning to Investigate the Role of Social, Affective, and Informative Gestures in Non-Verbal Communication. Electrophysiological (EEG) and Inter-Brain Connectivity Evidence

Communication can be considered as a joint action that involves two or more individuals transmitting different information. In particular, non-verbal communication involves body movements used to communicate different information, characterized by the use of specific gestures. The present study aims to investigate the electrophysiological (EEG) correlates underlying the use of affective, social, and informative gestures during a non-verbal interaction between an encoder and decoder. From the results of the single brain and inter-brain analyses, an increase of frontal alpha, delta, and theta brain responsiveness and inter-brain connectivity emerged for affective and social gestures; while, for informative gestures, an increase of parietal alpha brain responsiveness and alpha, delta, and theta inter-brain connectivity was observed. Regarding the inter-agents' role, an increase of frontal alpha activity was observed in the encoder compared to the decoder for social and affective gestures. Finally, regarding gesture valence, an increase of theta brain responsiveness and theta and beta inter-brain connectivity was observed for positive gestures on the left side compared to the right one. This study, therefore, revealed the function of the gesture type and valence in influencing individuals' brain responsiveness and inter-brain connectivity, showing the presence of resonance mechanisms underlying gesture execution and observation.

Leader-employee emotional "interpersonal tuning".An EEG coherence study

Empirical management research has focused more on the investigation of important interpersonal factors that could be beneficial for a company's well-being, including emotional and empathic engagement between managers and employees. The capacity to understand and mirror others' feelings could result in a mutual adaptation that generates interpersonal tuning (IT). In the present study, we measured IT by applying a hyperscanning approach with simultaneous recording of electroencephalographic (EEG) signals from two participants interacting together. Eleven leaders and 11 employees were recruited and asked to role-play an employee performance review with a rating (R) or no rating (NR) condition. In the NR condition leaders describe by words the employee's proficiency, while in R they provided a quantitative rating. The NR condition emerged as a more engaging situation in terms of empathic responses and mirroring. This difference was detectable from the localization of neurophysiological effects over the frontopolar and frontal brain areas, and the higher synchronization of EEG delta frequency coherence. Behavioral results also revealed an increase of self-perceived emotional tuning, agreement on content, and interpersonal cooperation in the NR condition compared to R condition. These effects were present in both leaders and employees and have several implications for social and company well-being.

Coordination Elicits Synchronous Brain Activity Between Co-actors: Frequency Ratio Matters

People could behave in two different ways when engaging in interpersonal coordination activities: moving at the same frequency (isofrequency pattern, IP; the movement frequency ratio is 1:1) or at different frequencies (multifrequency pattern, MP; the movement frequency ratio is non 1:1). However, how the interpersonal coordination pattern modulates coordination outcome and the related brain-to-brain connectivity is not fully understood. Here, we adopted a continuous joint drawing task in which two participants co-drew parallelogram shapes according to two coordination patterns (i.e., IP vs. MP) while their brain activities were simultaneously recorded by the functional near-infrared spectroscopy (fNIRS) based hyperscanning technique. Dyads showed better coordination performance, as well as relatively greater interpersonal brain synchronization (IBS) at the left frontopolar area, in the MP condition compared to the IP condition. Granger causality analyses further disclosed the bidirectional influences between the brains of the coordinating individuals. Such interpersonal influences were enhanced when individuals coordinated in the MP condition. Finally, the IBS during coordination was related to the dyadic self-control level. Taken together, our study revealed that interpersonal multifrequency coordination pattern facilitates the coordination efficiency, which was associated with the enhanced brain-to-brain connectivity. Our work also suggests the potentially positive role of self-control during the interpersonal coordination process.

Neural signatures of cooperation enforcement and violation: a coordinate-based meta-analysis

The social norms of fairness and reciprocity are fundamental to cooperation and constitute core behavioral principles. Warm glow theory suggests that cooperative behavior is driven by positive emotions, whereas inequity aversion theory proposes that cooperative behavior is necessary to avoid negative feelings. However, the precise characteristics underlying the enforcement (fairness or reciprocity) and violation (unfairness or betrayal) of cooperation remain elusive. Moreover, whether the neural mechanism of cooperation as a partner or a spectator is the same remains unclear. To resolve the above issues, we summarized the findings of human cooperation neuroimaging studies through a meta-analysis. Based on our results, cooperation enforcement activates reward-related brain areas, such as the striatum and orbitofrontal cortex, only during other-cooperation. In contrast, cooperation violation is associated with the negative emotion-related insula in both self- and other-noncooperation. Thus, people expect others to cooperate rather than themselves; however, people are disgusted when cooperation is violated by themselves or others. Taken together, cooperative behavior might be mainly driven by a process designed to avoid negative emotion, which supports the inequity aversion theory but not the warm glow theory, thereby improving our understanding of cooperation theory.