Brain Synchronization Research Articles

Is the creativity of lovers better? A behavioral and functional near-infrared spectroscopy hyperscanning study

Love is an innate human emotion and an eternal theme in artistic and scientific works. However, the question of how love affects people’s behavior and the underlying neural mechanisms remains unanswered. This study examined the performance of lovers while solving group creative tasks and revealed the cognitive neural mechanisms of this process. We used a functional near-infrared spectroscopy (fNIRS)-based hyperscanning approach to measure simultaneously interpersonal brain synchronization in lover dyads and stranger (heterosexual) dyads during the realistic presented problem (RPP) task. The behavioral results found that originality and fluency in the lover dyads were significantly higher than in the stranger dyads. Moreover, compared to the stranger group, the behavioral index of cooperation was significantly higher in the lover dyads. Significantly increased interpersonal brain synchronization was observed at the frontopolar cortex (FPC) and right temporo- parietal (rTPJ) junction when the lover group was solving the RPP task. Furthermore, in the lover group, interpersonal brain synchronization was positively correlated with cooperation performance and RPP originality. These data indicate that lovers had more advantages in interaction and cooperation, and this contributed to the solving of group creative problems. Our findings provide the first cognitive neuroscience evidence for how romantic relationships affect creativity.

Synchronization and resilience in the Kuramoto white matter network model with adaptive state-dependent delays

White matter pathways form a complex network of myelinated axons that regulate signal transmission in the nervous system and play a key role in behaviour and cognition. Recent evidence reveals that white matter networks are adaptive and that myelin remodels itself in an activity-dependent way, during both developmental stages and later on through behaviour and learning. As a result, axonal conduction delays continuously adjust in order to regulate the timing of neural signals propagating between different brain areas. This delay plasticity mechanism has yet to be integrated in computational neural models, where conduction delays are oftentimes constant or simply ignored. As a first approach to adaptive white matter remodeling, we modified the canonical Kuramoto model by enabling all connections with adaptive, phase-dependent delays. We analyzed the equilibria and stability of this system, and applied our results to two-oscillator and large-dimensional networks. Our joint mathematical and numerical analysis demonstrates that plastic delays act as a stabilizing mechanism promoting the network’s ability to maintain synchronous activity. Our work also shows that global synchronization is more resilient to perturbations and injury towards network architecture. Our results provide key insights about the analysis and potential significance of activity-dependent myelination in large-scale brain synchrony.

Experience-Dependent Counselor-Client Brain Synchronization during Psychological Counseling.

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

Spectrally resolved EEG intersubject correlation reveals distinct cortical oscillatory patterns during free-viewing of affective scenes.

The analysis of the similarity of the brain response of different individuals using intersubject correlation (ISC) can be used to uncover the neural mechanisms behind the processing of complex audiovisual stimuli, and to understand how the brain works in real-life situations. Previous research on ISC reported anecdotal evidence of larger ISC during emotional scenes compared to neutral ones, but this effect has not been systematically investigated using standardized emotional movies. Moreover, the complex interplay between neuronal populations oscillating at different timescales was mainly studied through fMRI, thus with limited temporal resolution. This study aimed at showing how emotional movies synchronize brain activity in the main frequency bands characterizing cortical activity. Thirty-nine participants watched 18 movie clips selected from a standardized database of emotional movies (E-MOVIE) while their EEG activity was recorded. Spectrally resolved ISC was computed based on the coherence of homologous channels for each possible subject pair in the Delta, Alpha, and Gamma bands. Permutation-based statistics revealed that all emotional categories prompted larger ISC compared to the Neutral in each band. Moreover, high arousal erotic and fearful scenes prompted larger Delta-ISC and Gamma-ISC compared to the other categories. Finally, ISC topography followed a spatial gradient. At slower frequencies, ISC involved wider regions of the scalp, becoming more restricted to occipito-parietal regions at higher frequencies. Taken together, these results show that emotions trigger brain synchronization between individuals at multiple spatial and spectral scales. Different emotional states are reflected in specific topographical patterns of ISC in different frequency bands.

Different strategies, distinguished cooperation efficiency, and brain synchronization for couples: An fNIRS-based hyperscanning study.

IntroductionIndividuals may employ different strategies when cooperating with others. For example, when two participants are asked to press buttons simultaneously, they may press the buttons as quickly as possible (immediate response strategy) or press them in a delayed pattern (delayed response strategy). Despite recognition of interpersonal brain synchronization (IBS) as a fundamental neural mechanism of cooperation, it remains unclear how various strategies influence cooperative behavior and its neural activities.MethodsTo address this issue, 43 married couples were recruited to complete a button‐press cooperative task, during which IBS was recorded by functional near‐infrared spectroscopy hyperscanning.ResultsBehavioral results showed that couples who adopted a delayed response strategy performed better than those who adopted an immediate response strategy and those without any obvious strategy, and a new measure (cooperation coefficient) was used to index the level of cooperation. In addition, stronger IBS in the right frontal cortex was observed in the delayed response condition. The greater couples’ perceived parenting stress, the more likely they were to perform well in tasks and the stronger their brain synchronization, since they tended to choose the delayed response strategy.ConclusionThe delayed response strategy may better unify dyad partners’ response modes, trigger synchronized psychological processes, and enable their brains to become synchronized. The study extends understanding of cooperation by comparing the contributions of different strategies underlying cooperative behavior with corresponding neural evidence.

Frequency-specific neural synchrony in autism during memory encoding, maintenance and recognition.

Working memory impairment is associated with symptom severity and poor functional outcome in autistic individuals, and yet the neurobiology underlying such deficits is poorly understood. Neural oscillations are an area of investigation that can shed light on this issue. Theta and alpha oscillations have been found consistently to support working memory in typically developing individuals and have also been shown to be functionally altered in people with autism. While there is evidence, largely from functional magnetic resonance imaging studies, that neural processing underlying working memory is altered in autism, there remains a dearth of information concerning how sub-processes supporting working memory (namely encoding, maintenance and recognition) are impacted. In this study, we used magnetoencephalography to investigate inter-regional theta and alpha brain synchronization elicited during the widely used one-back task across encoding, maintenance and recognition in 24 adults with autism and 30 controls. While both groups performed comparably on the working-memory task, we found process- and frequency-specific differences in networks recruited between groups. In the theta frequency band, both groups used similar networks during encoding and recognition, but different networks specifically during maintenance. In comparison, the two groups recruited distinct networks across encoding, maintenance and recognition in alpha that showed little overlap. These differences may reflect a breakdown of coherent theta and alpha synchronization that supports mnemonic functioning, or in the case of alpha, impaired inhibition of task-irrelevant neural processing. Thus, these data provide evidence for specific theta and widespread alpha synchrony alterations in autism, and underscore that a detailed examination of the sub-processes that comprise working memory is warranted for a complete understanding of cognitive impairment in this population.

Age-related changes in the association of resting-state fMRI signal variability and global functional connectivity in non-demented healthy people

Research suggests that the aging relates to variability of resting-state fMRI (rs-fMRI) signal and the functional connectivity. However, the association between the spatial and temporal activity of resting-state fMRI signal was less documented. We recruited 477 healthy Han Chinese participants, who were separated into young, middle and old groups to investigate the relationship between the variability and global functional connectivity (gFC) in different age ranges using standard deviation (SD) of time series and gFC, respectively. Our analysis revealed the changing patterns during healthy aging: 1) 17 brain regions(Olfactory_L, Orbital_L etc.) were identified to have significant association of age with both SD and gFC respectively by linear regression analysis; 2) Two typical associations could be observed between SD and gFC: positive and negative correlations; 3) The variation ratio of SD to gFC was changing with age at the voxel level by using unsupervised clustering method. It is the first time to combine voxel-wise variability and gFC together for the study of age-related changes with rs-fMRI signal. This study may provide a new clue for understanding the synchronization of human brain based on SD and gFC due to the effect of aging.

Interpersonal brain synchronization with instructor compensates for learner's sleep deprivation in interactive learning

Recent advances shifted the focus on single-brain functioning toward two-brain communication during learning interactions, following the demonstration that interpersonal brain synchronization (IBS) can track instructor-learner information exchange. Here, we investigated (i) whether sleep deprivation (SD) that potentially impacts both social interactions and learning abilities modulates IBS, and (ii) conversely whether and to what extent IBS might compensate for SD-related learning deficits. Instructors (always with regular sleep, RS) were asked to teach numerical reasoning strategies to learners (either SD or RS), during which the activity of both brains was simultaneously recorded using functional near-infrared spectroscopy (fNIRS). SD learners initially performed below their baseline level, worse than RS learners, but learning improvement was comparable between RS and SD conditions after learning with the instructor. IBS within the instructor-learner dyads was higher in the SD (vs. RS) condition in the left inferior frontal cortex. In addition, clustered IBS (estimated by nonnegative matrix factorization) was correlated with performance improvement. Finally, Granger Causality analyses revealed biased causality with higher instructor-to-learner than learner-to-instructor directionality in brain signal processing. Together, these results indicate that SD-related learning deficits can to some extent be compensated via interactions with an instructor, as reflected by increased IBS and preserved learning ability. It suggests an essential role of the instructor in driving synchrony between teaching and SD learning brains during interactions.

Convolutional neural network for detection and classification of seizures in clinical data.

Epileptic seizure detection and classification in clinical electroencephalogram data still is a challenge, and only low sensitivity with a high rate of false positives has been achieved with commercially available seizure detection tools, which usually are patient non-specific. Epilepsy patients suffer from severe detrimental effects like physical injury or depression due to unpredictable seizures. However, even in hospitals due to the high rate of false positives, the seizure alert systems are of poor help for patients as tools of seizure detection are mostly trained on unrealistically clean data, containing little noise and obtained under controlled laboratory conditions, where patient groups are homogeneous, e.g. in terms of age or type of seizures. In this study authors present the approach for detection and classification of a seizure using clinical data of electroencephalograms and a convolutional neural network trained on features of brain synchronisation and power spectrum. Various deep learning methods were applied, and the network was trained on a very heterogeneous clinical electroencephalogram dataset. In total, eight different types of seizures were considered, and the patients were of various ages, health conditions and they were observed under clinical conditions. Despite this, the classifier presented in this paper achieved sensitivity and specificity equal to 0.68 and 0.67, accordingly, which is a significant improvement as compared to the known results for clinical data. Graphical abstract.

Creating while taking turns, the choice to unlocking group creative potential

This study aimed to examine how communication modes affect creative idea generation in groups. Three communication mode conditions were created: natural (N), turn-taking (T), and electronic brainstorming (E). Participants were randomly recruited and grouped in dyads to solve one alternative uses task (AUT) in each condition, during which functional near-infrared spectroscopy (fNIRS)-based hyperscanning was used to record interpersonal neural responses. No difference was observed in AUT fluency across the three conditions, but AUT uniqueness was higher in the T condition than in the E condition. In addition, AUT uniqueness, AUT fluency, and perspective-taking behaviours increased faster in the T condition than in the other conditions. The T condition also showed higher perspective-taking behaviours than did the other conditions. Moreover, fNIRS data showed higher interpersonal brain synchronisation (IBS) increments at the right angular gyrus in the T condition than in the other conditions, which positively predicted perspective-taking behaviours between individuals during group creativity tasks. These findings indicate that when group members create together while taking turns, both creative performance and interpersonal interaction processes can be stimulated.

Activity-dependent myelination: A glial mechanism of oscillatory self-organization in large-scale brain networks

Communication and oscillatory synchrony between distributed neural populations are believed to play a key role in multiple cognitive and neural functions. These interactions are mediated by long-range myelinated axonal fiber bundles, collectively termed as white matter. While traditionally considered to be static after development, white matter properties have been shown to change in an activity-dependent way through learning and behavior-a phenomenon known as white matter plasticity. In the central nervous system, this plasticity stems from oligodendroglia, which form myelin sheaths to regulate the conduction of nerve impulses across the brain, hence critically impacting neural communication. We here shift the focus from neural to glial contribution to brain synchronization and examine the impact of adaptive, activity-dependent changes in conduction velocity on the large-scale phase synchronization of neural oscillators. Using a network model based on primate large-scale white matter neuroanatomy, our computational and mathematical results show that such plasticity endows white matter with self-organizing properties, where conduction delay statistics are autonomously adjusted to ensure efficient neural communication. Our analysis shows that this mechanism stabilizes oscillatory neural activity across a wide range of connectivity gain and frequency bands, making phase-locked states more resilient to damage as reflected by diffuse decreases in connectivity. Critically, our work suggests that adaptive myelination may be a mechanism that enables brain networks with a means of temporal self-organization, resilience, and homeostasis.

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

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

Fronto-temporal theta phase-synchronization underlies music-evoked pleasantness

Listening to pleasant music engages a complex distributed network including pivotal areas for auditory, reward, emotional and memory processing. On the other hand, frontal theta rhythms appear to be relevant in the process of giving value to music. However, it is not clear to which extent this oscillatory mechanism underlies the brain interactions that characterize music-evoked pleasantness and its related processes. The goal of the present experiment was to study brain synchronization in this oscillatory band as a function of music-evoked pleasantness. EEG was recorded from 25 healthy subjects while they were listening to music and rating the experienced degree of induced pleasantness. By using a multilevel Bayesian approach we found that phase synchronization in the theta band between right temporal and frontal signals increased with the degree of pleasure experienced by participants. These results show that slow fronto-temporal loops play a key role in music-evoked pleasantness.

Fabry patient-reported outcome-gastrointestinal (FABPRO-GI): A new Fabry disease-specific gastrointestinal outcomes instrument

Alteration of brain activity synchrony has been shown in amyotrophic lateral sclerosis (ALS) using seed-based functional connectivity analysis. However, regional activity synchrony has not been characterized in ALS. The purpose of this study was to assess regional brain synchrony by calculating regional data coherence of resting state functional MRI (rsfMRI), as well as its correlations to clinical indices. Twelve ALS patients and 12 age- and sex-matched healthy controls underwent rsfMRI scans. Coherence measurement was performed in the sensory-motor network (SMN), a key brain network impaired by ALS. Decreased coherence was found in the superior medial SMN, which was surrounded by increased coherence in the peripheral SMN areas. Decreased regional coherence in the right postcentral gyrus/precentral gyrus/superior frontal gyrus was correlated with high disease severity as indicated by lower ALSFRS-r scores; meanwhile, enhanced regional coherence in left postcentral gyrus and inferior parietal cortex was related to longer disease duration. Finally, increased coherence in left postcentral gyrus corresponds to fast disease progression rate. These ALS-related SMN regional coherence alterations suggest using regional coherence as a potential marker for studying ALS and its progression.

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

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

Preferential interaction networks: A dynamic model for brain synchronization networks

In this work, we propose a weighted network model called a preferential interaction network (PIN), whose construction is based on mechanisms similar to those of the scale-free network model developed by Albert and Barabási. The PIN aims to reproduce the behaviour of real systems of fixed size in which stronger connections are reinforced over time. Its composition starts with a network with fixed nodes, and obeys two basic processes: firstly, an increase in the edge weights, and secondly, a preferential interaction is added. Preferential interaction is defined as the tendency whereby edges with larger weights are more likely to be chosen in a iteration. PIN has three parameters: the size of the network, the rate of increase of the weights, and the number of iterations. These parameters were used to fit the model to EEG brain synchronization networks of healthy subjects. The complementary cumulative distribution of weight in the model was compared to the corresponded distribution in EEG networks. The shape of the model distribution showed similar to those of the EEG data networks and the PIN model topology index are closer than a random null model, suggesting that a preferential interaction process represents the core of brain synchronization dynamics.

Examining the relationship between measures of autistic traits and neural synchrony during movies in children with and without autism

Children who have been diagnosed with autism spectrum disorder (ASD) often show a marked deficit in measures of social cognition. In autistic adults, measures of social cognition have been shown to relate to differences in brain synchronization (as measured by fMRI) when individuals are processing naturalistic stimuli, such as movies. However, whether children who differ in their degree of autistic traits, with or without a diagnosis of ASD, differ in their neural responses to movies has not yet been investigated. In the current study, neural synchrony, measured using fMRI, was examined in three groups of children aged 7 to 12, who differed with respect to scores on a measure of autistic traits associated with social impairment and whether or not they had been diagnosed with ASD. While watching the movie ‘Despicable Me’, those diagnosed with ASD had significantly less neural synchrony in areas that have been previously shown to be associated with social cognition (e.g. areas related to ‘theory of mind’), and plot following (e.g. the lateral prefrontal cortex), than those who did not have an ASD diagnosis. In contrast, two groups who differed in their degree of autistic traits, but did not have a diagnosis of ASD, showed no significant differences in neural synchrony across the whole brain. These results shed some light on how autistic traits may contribute to an individual’s conscious experience of the world, and how, for children with ASD, that experience may differ markedly from that of those without ASD.

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

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

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.

Abnormal synchronization of functional and structural networks in schizophrenia.

Synchronization is believed to play an important role in information processing of the brain. Mounting evidence supports the hypothesis that schizophrenia is related to impaired neural synchrony. However, most previous studies characterize brain synchronization from the perspective of temporal coordination of distributed neural activity, rather than network properties. Our aim was to investigate the network synchronization alterations in schizophrenia using publically available data. Resting-state functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) were performed in 96 schizophrenia patients and 120 healthy controls. The whole-brain functional and structural networks were constructed and analyzed using graph theoretical approaches. Inter-group differences in network synchronization were investigated. Both the binary and weighted functional networks of schizophrenia patients exhibited decreased synchronizability (increased eigenratio) than those of healthy controls. With respect to the structural binary networks, schizophrenia patients showed a trend towards excessive synchronizability (decreased eigenratio). In addition, the excessive synchronizability of the structural binary networks was associated with more severe negative symptoms in schizophrenia patients. Our findings provide novel biological evidence that schizophrenia involves a disruption of neural synchrony from the perspective of network properties.