How the Listener's Attention Dynamically Switches Between Different Speakers During a Natural Conversation.

The neural mechanisms underpinning the dynamic switching of a listener's attention between speakers are not well understood. Here we addressed this issue in a natural conversation involving 21 triadic adult groups. Results showed that when the listener's attention dynamically switched between speakers, neural synchronization with the to-be-attended speaker was significantly enhanced, whereas that with the to-be-ignored speaker was significantly suppressed. Along with attention switching, semantic distances between sentences significantly increased in the to-be-ignored speech. Moreover, neural synchronization negatively correlated with the increase in semantic distance but not with acoustic change of the to-be-ignored speech. However, no difference in neural synchronization was found between the listener and the two speakers during the phase of sustained attention. These findings support the attenuation model of attention, indicating that both speech signals are processed beyond the basic physical level. Additionally, shifting attention imposes a cognitive burden, as demonstrated by the opposite fluctuations of interpersonal neural synchronization.

Neural synchrony underlies the positive effect of shared reading on children's language ability.

Although it is well recognized that parent-child shared reading produces positive effects on children's language ability, the underlying neurocognitive mechanisms are not well understood. Here, we addressed this issue by measuring brain activities from mother-child dyads simultaneously during a shared book reading task using functional near infrared spectroscopy hyperscanning. The behavioral results showed that the long-term experience of shared reading significantly predicted children's language ability. Interestingly, the prediction was moderated by children's age: for older children over 30 months, the more the shared reading experience, the better the language performance; for younger children below 30 months, however, no significant relationship was observed. The brain results showed significant interpersonal neural synchronization between mothers and children at the superior temporal cortex, which was closely associated with older children's language ability through the mediation of long-term experience of shared reading. Finally, the results showed that the instantaneous quality of shared reading contributed to children's language ability through enhancing interpersonal neural synchronization and increasing long-term experience. Based on these findings, we tentatively proposed a theoretical model for the relationship among interpersonal neural synchronization, shared reading and children's language ability. These findings will facilitate our understanding on the role of shared reading in children's language development.

Biasing the neurocognitive processing of videos with the presence of a real cultural other.

In the digital age, while short videos present vital events with powerful information, the presence of cultural cues may bias our processing of videos of foreign cultures. However, the underlying neurocognitive processes remain unclear. In this study, we hypothesized that cultural cues might bias video processing by either enhancing cultural perspective-taking or shifting cultural self-schema. To test these hypotheses, we used a novel paradigm in which the cultural cue was a real cultural other (the priming participants) who watched American/Chinese videos together with the primed participants. The results showed that when the cue was present, the right temporoparietal junction (rTPJ) response to videos with other cultural content was shifted, showing a priming effect. Moreover, the activity pattern in the rTPJ was more congruent with the primed culture than with the original culture, reflecting a neural biasing effect. Finally, intersubject representational similarity analysis indicated that the neural biasing effect in the rTPJ was more closely associated with cultural perspective-taking than with cultural self-schema. In summary, these findings support the perspective-taking hypothesis, suggesting that cultural cues can significantly bias our cultural mindset by altering cultural perspective-taking when we are exposed to culture-relevant naturalistic stimuli.

Processing negative emotion in two languages of bilinguals: Accommodation and assimilation of the neural pathways based on a meta-analysis.

Numerous functional magnetic resonance imaging (fMRI) studies have examined the neural mechanisms of negative emotional words, but scarce evidence is available for the interactions among related brain regions from the functional brain connectivity perspective. Moreover, few studies have addressed the neural networks for negative word processing in bilinguals. To fill this gap, the current study examined the brain networks for processing negative words in the first language (L1) and the second language (L2) with Chinese-English bilinguals. To identify objective indicators associated with negative word processing, we first conducted a coordinate-based meta-analysis on contrasts between negative and neutral words (including 32 contrasts from 1589 participants) using the activation likelihood estimation method. Results showed that the left medial prefrontal cortex (mPFC), the left inferior frontal gyrus (IFG), the left posterior cingulate cortex (PCC), the left amygdala, the left inferior temporal gyrus (ITG), and the left thalamus were involved in processing negative words. Next, these six clusters were used as regions of interest in effective connectivity analyses using extended unified structural equation modeling to pinpoint the brain networks for bilingual negative word processing. Brain network results revealed two pathways for negative word processing in L1: a dorsal pathway consisting of the left IFG, the left mPFC, and the left PCC, and a ventral pathway involving the left amygdala, the left ITG, and the left thalamus. We further investigated the similarity and difference between brain networks for negative word processing in L1 and L2. The findings revealed similarities in the dorsal pathway, as well as differences primarily in the ventral pathway, indicating both neural assimilation and accommodation across processing negative emotion in two languages of bilinguals.

Neurocomputational mechanisms of young children's observational learning of delayed gratification.

The ability to delay gratification is crucial for a successful and healthy life. An effective way for young children to learn this ability is to observe the action of adult models. However, the underlying neurocomputational mechanism remains unknown. Here, we tested the hypotheses that children employed either the simple imitation strategy or the goal-inference strategy when learning from adult models in a high-uncertainty context. Results of computational modeling indicated that children used the goal-inference strategy regardless of whether the adult model was their mother or a stranger. At the neural level, results showed that successful learning of delayed gratification was associated with enhanced interpersonal neural synchronization (INS) between children and the adult models in the dorsal lateral prefrontal cortex but was not associated with children's own single-brain activity. Moreover, the discounting of future reward's value obtained from computational modeling of the goal-inference strategy was positively correlated with the strength of INS. These findings from our exploratory study suggest that, even for 3-year-olds, the goal-inference strategy is used to learn delayed gratification from adult models, and the learning strategy is associated with neural interaction between the brains of children and adult models.

Neurocomputations on dual-brain signals underlie interpersonal prediction during a natural conversation.

Prediction on the partner's speech plays a key role in a smooth conversation. However, previous studies on this issue have been majorly conducted at the single-brain rather than dual-brain level, leaving the interpersonal prediction hypothesis untested. To fill this gap, this study combined a neurocomputational modeling approach with a natural conversation paradigm in which two salespersons persuaded a customer to buy their product with their haemodynamic signals being collected using functional near-infrared spectroscopy hyperscanning. First, the results showed a cognitive hierarchy in a natural conversation, with the lower-level process (i.e., pragmatic representation of the persuasion) in the salesperson interacting with the higher-level process (i.e., value representation of the product) in the customer. Next, we found that the right dorsal lateral prefrontal cortex (rdlPFC) and temporoparietal junction (rTPJ) were associated with the representation of the product's value in the customer, while the right inferior frontal cortex (rIFC) was associated with the representation of the pragmatic processes in the salesperson. Finally, neurocomputational modeling results supported the prediction of the salesperson's lower-level brain activity based on the customer's higher-level brain activity. Moreover, the updating weight of the prediction model based on the neural computation between the rIFC of the salesperson and the rTPJ of the customer was closely associated with the interaction context, whereas that based on the rIFC-rdlPFC was not. In summary, these findings provide initial support for the interpersonal prediction hypothesis at the dual-brain level and reveal a hierarchy for the interpersonal prediction process.

Distinct brain state dynamics of native and second language processing during narrative listening in late bilinguals.

The process of complex cognition, which includes language processing, is dynamic in nature and involves various network modes or cognitive modes. This dynamic process can be manifested by a set of brain states and transitions between them. Previous neuroimaging studies have shed light on how bilingual brains support native language (L1) and second language (L2) through a shared network. However, the mechanism through which this shared brain network enables L1 and L2 processing remains unknown. This study examined this issue by testing the hypothesis that L1 and L2 processing is associated with distinct brain state dynamics in terms of brain state integration and transition flexibility. A group of late Chinese-English bilinguals was scanned using functional magnetic resonance imaging (fMRI) while listening to eight short narratives in Chinese (L1) and English (L2). Brain state dynamics were modeled using the leading eigenvector dynamic analysis framework. The results show that L1 processing involves more integrated states and frequent transitions between integrated and segregated states, while L2 processing involves more segregated states and fewer transitions. Our work provides insight into the dynamic process of narrative listening comprehension in late bilinguals and sheds new light on the neural representation of language processing and related disorders.

The cerebellum and cognition: further evidence for its role in language control.

The cognitive function of the human cerebellum could be characterized as enigmatic. However, researchers have attempted to detail the comprehensive role of the cerebellum in several cognitive processes in recent years. Here, using functional magnetic resonance imaging (fMRI) and transcranial direct current stimulation (tDCS), we revealed different functions of bilateral cerebellar lobules in bilingual language production. Specifically, brain activation showed the bilateral posterolateral cerebellum was associated with bilingual language control, and an effective connectivity analysis built brain networks for the interaction between the cerebellum and the cerebral cortex. Furthermore, anodal tDCS over the right cerebellum significantly optimizes language control performance in bilinguals. Together, these results reveal a precise asymmetrical functional distribution of the cerebellum in bilingual language production, suggesting that the right cerebellum is more involved in language control. In contrast, its left counterpart undertakes a computational role in cognitive control function by connecting with more prefrontal, parietal, subcortical brain areas.

The "two-brain" approach reveals the active role of task-deactivated default mode network in speech comprehension.

Exhibiting deactivation and anticorrelation with task-positive networks, the default mode network (DMN) has been traditionally thought to be suppressed to support externally oriented cognitive processes during spoken language comprehension. In contrast, recent studies examining listener-listener intersubject correlation (ISC) have proposed an active role of DMN in language comprehension. How can we reconcile those seemingly conflicting results? This study adopted a "two-brain" paradigm and combined "within-brain" and "across-brain" analyses to address this issue. We found, despite being deactivated and anticorrelated with the language network (LN) and executive control network (ECN), both the anterior and posterior DMN in the listeners' brains were temporally coupled with the homologous networks in the speaker's brain. Interestingly, the listener-speaker neural couplings persisted even after controlling for listener-listener ISC. Moreover, the coupling strength of posterior DMN positively correlated with the listeners' speech comprehension. Further dynamic causal modeling showed that the LN and ECN, the anterior DMN, and the posterior DMN occupied the bottom, intermediate, and top layers of a hierarchical system, respectively. We suggest the DMN may primarily serve as an internal module that cooperates with the externally oriented modules, potentially supporting the transformation of external acoustic signals into internal mental representations during successful language comprehension.

Interpersonal conflict increases interpersonal neural synchronization in romantic couples.

Previous studies on dual-brain social interaction have shown different patterns of interpersonal neural synchronization (INS) between conflictual and supportive interactions, but the role of emotion in the dual-brain mechanisms of such interactions is not well understood. Furthermore, little is known about how the dual-brain mechanisms are affected by relationship type (e.g., romantic relationship vs. friendship) and interaction mode (e.g., verbal vs. nonverbal). To elaborate on these issues, this study used functional near-infrared spectroscopy to collect hemodynamic signals from romantic couples and cross-sex friends while they were discussing conflictual, neutral, or supportive topics. For the couples but not the friends, INS between the sensorimotor cortex of both participants was greater when discussing the conflictual topic than when discussing the supportive topic. INS was positively correlated with the arousal level but not the valence level of communication contents. INS was also positively correlated with interpersonal physiological synchronization based on galvanic skin response, a physiological measure of arousal. Furthermore, the differences in INS between the conflictual and supportive topics were closely associated with verbal rather than nonverbal behaviors. Together, these findings suggest that it is the arousal level induced by verbal interactions during interpersonal conflicts that increases romantic couples' INS.

Increased or decreased? Interpersonal neural synchronization in group creation.

Group creation is the process by which group members collaborate to produce novel and useful ideas or products, including ideas generation and evaluation. However, the interpersonal neural mechanism of group creation during natural communication remains unclear. In this study, two groups of same-sex dyads with similar individual creativity collaborated to complete the Product Improvement Task (creative condition) and the Item Purchase Plan Task (control condition), respectively. Functional near-infrared spectroscopy (fNIRS) was used to record both members' neural activity in the left prefrontal (lPFC) and right temporal-parietal junction (rTPJ) regions during the task. Considering that the role asymmetry of group members may have an impact on interpersonal neural patterns, we identified leaders and followers in the dyads based on participant performance. The results showed that leaders and followers in the creative condition had significantly lower interpersonal neural synchronization (INS) in the right superior temporal gyrus-left superior frontal gyrus, right supramarginal gyrus-left superior frontal gyrus, and right supramarginal gyrus-left middle frontal gyrus than in the control condition. Partial multivariate Granger causality analyses revealed the influence between dyads was bidirectional but was significantly stronger from the leaders to the followers than the other direction. In addition, in the creative task, the INS was significantly associated with novelty, appropriateness, and conflict of views. All these findings suggest that the ideas generation and ideas evaluation process in group creation have poor interpersonal neural activity coupling due to factors such as the difficulty of understanding novel ideas. However, performances may be improved when groups can better integrate views and reach collective understanding, intentions, and goals. Furthermore, we found that there are differences in the dynamics of INS in different brain regions. The INS related to the novelty of the group creation decreased in the early stages, while the INS related to the appropriateness decreased in the middle stages. Our findings reveal a unique interpersonal neural pattern of group creation processes in the context of natural communication.

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.

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.

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.

Auditory-Articulatory Neural Alignment between Listener and Speaker during Verbal Communication.

Whether auditory processing of speech relies on reference to the articulatory motor information of speaker remains elusive. Here, we addressed this issue under a two-brain framework. Functional magnetic resonance imaging was applied to record the brain activities of speakers when telling real-life stories and later of listeners when listening to the audio recordings of these stories. Based on between-brain seed-to-voxel correlation analyses, we revealed that neural dynamics in listeners' auditory temporal cortex are temporally coupled with the dynamics in the speaker's larynx/phonation area. Moreover, the coupling response in listener's left auditory temporal cortex follows the hierarchical organization for speech processing, with response lags in A1+, STG/STS, and MTG increasing linearly. Further, listeners showing greater coupling responses understand the speech better. When comprehension fails, such interbrain auditory-articulation coupling vanishes substantially. These findings suggest that a listener's auditory system and a speaker's articulatory system are inherently aligned during naturalistic verbal interaction, and such alignment is associated with high-level information transfer from the speaker to the listener. Our study provides reliable evidence supporting that references to the articulatory motor information of speaker facilitate speech comprehension under a naturalistic scene.

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.

Differences between child and adult large-scale functional brain networks for reading tasks.

Reading is an important high-level cognitive function of the human brain, requiring interaction among multiple brain regions. Revealing differences between children's large-scale functional brain networks for reading tasks and those of adults helps us to understand how the functional network changes over reading development. Here we used functional magnetic resonance imaging data of 17 adults (19-28 years old) and 16 children (11-13 years old), and graph theoretical analyses to investigate age-related changes in large-scale functional networks during rhyming and meaning judgment tasks on pairs of visually presented Chinese characters. We found that: (1) adults had stronger inter-regional connectivity and nodal degree in occipital regions, while children had stronger inter-regional connectivity in temporal regions, suggesting that adults rely more on visual orthographic processing whereas children rely more on auditory phonological processing during reading. (2) Only adults showed between-task differences in inter-regional connectivity and nodal degree, whereas children showed no task differences, suggesting the topological organization of adults' reading network is more specialized. (3) Children showed greater inter-regional connectivity and nodal degree than adults in multiple subcortical regions; the hubs in children were more distributed in subcortical regions while the hubs in adults were more distributed in cortical regions. These findings suggest that reading development is manifested by a shift from reliance on subcortical to cortical regions. Taken together, our study suggests that Chinese reading development is supported by developmental changes in brain connectivity properties, and some of these changes may be domain-general while others may be specific to the reading domain.

Enhancement of teaching outcome through neural prediction of the students' knowledge state.

The neural mechanism for the dyadic process of teaching is poorly understood. Although theories about teaching have proposed that before any teaching takes place, the teacher will predict the knowledge state of the student(s) to enhance the teaching outcome, this theoretical Prediction-Transmission hypothesis has not been tested with any neuroimaging studies. Using functional near-infrared spectroscopy-based hyperscanning, this study measured brain activities of the teacher-student pairs simultaneously. Results showed that better teaching outcome was associated with higher time-lagged interpersonal neural synchronization (INS) between right temporal-parietal junction (TPJ) of the teacher and anterior superior temporal cortex (aSTC) of the student, when the teacher's brain activity preceded that of the student. Moreover, time course analyses suggested that such INS could mark the quality of the teaching outcome at an early stage of the teaching process. These results provided key neural evidence for the Prediction-Transmission hypothesis about teaching, and suggested that the INS plays an important role in the successful teaching.

Leader emergence through interpersonal neural synchronization.

The neural mechanism of leader emergence is not well understood. This study investigated (i) whether interpersonal neural synchronization (INS) plays an important role in leader emergence, and (ii) whether INS and leader emergence are associated with the frequency or the quality of communications. Eleven three-member groups were asked to perform a leaderless group discussion (LGD) task, and their brain activities were recorded via functional near infrared spectroscopy (fNIRS)-based hyperscanning. Video recordings of the discussions were coded for leadership and communication. Results showed that the INS for the leader-follower (LF) pairs was higher than that for the follower-follower (FF) pairs in the left temporo-parietal junction (TPJ), an area important for social mentalizing. Although communication frequency was higher for the LF pairs than for the FF pairs, the frequency of leader-initiated and follower-initiated communication did not differ significantly. Moreover, INS for the LF pairs was significantly higher during leader-initiated communication than during follower-initiated communications. In addition, INS for the LF pairs during leader-initiated communication was significantly correlated with the leaders' communication skills and competence, but not their communication frequency. Finally, leadership could be successfully predicted based on INS as well as communication frequency early during the LGD (before half a minute into the task). In sum, this study found that leader emergence was characterized by high-level neural synchronization between the leader and followers and that the quality, rather than the frequency, of communications was associated with synchronization. These results suggest that leaders emerge because they are able to say the right things at the right time.

Short-term language switching training tunes the neural correlates of cognitive control in bilingual language production.

The present study investigated how language switching experience would modulate the neural correlates of cognitive control involved in bilingual language production. A group of unbalanced Chinese-English bilinguals undertook an 8-day cued picture naming training during which they named pictures in either of their languages based on visually presented cues. Participants' brain activation was scanned before and after the training in the same task. Behavioral results revealed a significant training effect such that switch costs were reduced after training. fMRI results showed that after training, activation of brain areas associated with cognitive control including the anterior cingulated cortex and the caudate was reduced. Besides, the activation reduction in the left dorsal anterior cingulated cortex positively correlated with the reduction in switch costs in response time and this training effect could be transferred to untrained stimuli. These findings suggest that neural correlates of cognitive control, especially that of the conflict monitoring process, in bilingual language production could be modulated by short-term language switching training. Hum Brain Mapp 38:5859-5870, 2017. © 2017 Wiley Periodicals, Inc.