State-Dependent Cross-Brain Information Flow in Borderline Personality Disorder

A dual-brain therapeutic approach using noninvasive brain stimulation based on two-person neuroscience: A perspective review

Our actions and decisions in everyday life are heavily influenced by social interactions, which are dynamic feedback loops involving actions, reactions, and internal cognitive processes between individual agents. Social interactions induce interpersonal synchrony, which occurs at different biobehavioral levels and comprises behavioral, physiological, and neurological activities. Hyperscanning-a neuroimaging technique that simultaneously measures the activity of multiple brain regions-has provided a powerful second-person neuroscience tool for investigating the phase alignment of neural processes during interactive social behavior. Neural synchronization, revealed by hyperscanning, is a phenomenon called inter-brain synchrony- a process that purportedly facilitates social interactions by prompting appropriate anticipation of and responses to each other's social behaviors during ongoing shared interactions. In this review, I explored the therapeutic dual-brain approach using noninvasive brain stimulation to target inter-brain synchrony based on second-person neuroscience to modulate social interaction. Artificially inducing synchrony between the brains is a potential adjunct technique to physiotherapy, psychotherapy, and pain treatment- which are strongly influenced by the social interaction between the therapist and patient. Dual-brain approaches to personalize stimulation parameters must consider temporal, spatial, and oscillatory factors. Multiple data fusion analysis, the assessment of inter-brain plasticity, a closed-loop system, and a brain-to-brain interface can support personalized stimulation.

[Working in a team and mental health]

Humans have always naturally lived in groups, which has a significant impact on the well-being and mental stability of the individual. Various physiological processes are coregulated via the closeness of other persons. About one third of our adulthood is spent at work where social relationships often play an important role, because we are typically working with other individuals in groups or a team. In these situations, mutual support and successful cooperation can develop, which promotes the mental and physical health of the employees of a company ("social capital"). From various perspectives it becomes obvious that the quality of relationships at the workplace is a key factor for the satisfaction and health of individual employees as well as for the cohesion, resilience and performance of the entire team. This is confirmed by empirical findings that still need to be expanded, especially with respect to the neurobiological associations of the cooperation in teams and individual health.

Mobile cognition: imaging the human brain in the 'real world'

Cognitive neuroscience studies in humans have enabled decades of impactful discoveries but have primarily been limited to recording the brain activity of immobile participants in a laboratory setting. In recent years, advances in neuroimaging technologies have enabled recordings of human brain activity to be obtained during freely moving behaviours in the real world. Here, we propose that these mobile neuroimaging methods can provide unique insights into the neural mechanisms of human cognition and contribute to the development of novel treatments for neurological and psychiatric disorders. We further discuss the challenges associated with studying naturalistic human behaviours in complex real-world settings as well as strategies for overcoming them. We conclude that mobile neuroimaging methods have the potential to bring about a new era of cognitive neuroscience in which neural mechanisms can be studied with increased ecological validity and with the ability to address questions about natural behaviour and cognitive processes in humans engaged in dynamic real-world experiences.

The Pathogenesis of Borderline Personality Disorder: Evolution of Evidence and Treatment Implications for Two Prominent Models

Since Stern first started his work in 1938, the field has recognized several empirically supported models of the etiology of borderline personality disorder (BPD). Two such models are the Tripartite Model of the Development of BPD and the Biosocial Development Model of BPD. The Tripartite Model of the Development of BPD suggests that it is a combination of a hyperbolic temperament, traumatic childhood experiences, and an event or series of events that trigger the onset of BPD. Whereas the Biosocial Development Model of BPD elaborates on the work of Linehan's Biosocial Theory. This model suggests a combination of an emotionally vulnerable temperament and an invalidating environment cause BPD. Over 70 years of research support these models. This article covers a detailed description of each of these models, the decades of research supporting these models, similarities, differences, treatment implications, the latest research, and future directions.

Inter-brain plasticity as a biological mechanism of change in psychotherapy: A review and integrative model

Recent models of psychopathology and psychotherapy highlight the importance of interpersonal factors. The current review offers a biological perspective on these interpersonal processes by examining inter-brain synchrony—the coupling of brain activity between people interacting with one another. High inter-brain synchrony is associated with better relationships in therapy and in daily life, while deficits in the ability to achieve inter-brain synchrony are associated with a variety of psychological and developmental disorders. The review suggests that therapy improves patients’ ability to achieve such synchrony through inter-brain plasticity—a process by which recurring exposure to high inter-brain synchrony leads to lasting change in a person’s overall ability to synchronize. Therapeutic sessions provide repeated situations with high inter-brain synchrony. This can lead to a long-term increase in the ability to synchronize, first with the therapist, then generalized to other interpersonal relationships, ultimately leading to symptom reduction. The proposed inter-brain plasticity model offers a novel biological framework for understanding relational change in psychotherapy and its links to various forms of psychopathology and provides testable hypotheses for future research. Understanding this mechanism may help improve existing psychotherapy methods and develop new ones.

Directed coupling in multi-brain networks underlies generalized synchrony during social exchange

Advances in social neuroscience have made neural signatures of social exchange measurable simultaneously across people. This has identified brain regions differentially active during social interaction between human dyads, but the underlying systems-level mechanisms are incompletely understood. This paper introduces dynamic causal modeling and Bayesian model comparison to assess the causal and directed connectivity between two brains in the context of hyperscanning (h-DCM). In this setting, correlated neuronal responses become the data features that have to be explained by models with and without between-brain (effective) connections. Connections between brains can be understood in the context of generalized synchrony, which explains how dynamical systems become synchronized when they are coupled to each another. Under generalized synchrony, each brain state can be predicted by the other brain or a mixture of both. Our results show that effective connectivity between brains is not a feature within dyads per se but emerges selectively during social exchange. We demonstrate a causal impact of the sender's brain activity on the receiver of information, which explains previous reports of two-brain synchrony. We discuss the implications of this work; in particular, how characterizing generalized synchrony enables the discovery of between-brain connections in any social contact, and the advantage of h-DCM in studying brain function on the subject level, dyadic level, and group level within a directed model of (between) brain function.

Patient-clinician brain concordance underlies causal dynamics in nonverbal communication and negative affective expressivity

Patient-clinician concordance in behavior and brain activity has been proposed as a potential key mediator of mutual empathy and clinical rapport in the therapeutic encounter. However, the specific elements of patient-clinician communication that may support brain-to-brain concordance and therapeutic alliance are unknown. Here, we investigated how pain-related, directional facial communication between patients and clinicians is associated with brain-to-brain concordance. Patient-clinician dyads interacted in a pain-treatment context, during synchronous assessment of brain activity (fMRI hyperscanning) and online video transfer, enabling face-to-face social interaction. In-scanner videos were used for automated individual facial action unit (AU) time-series extraction. First, an interpretable machine-learning classifier of patients' facial expressions, from an independent fMRI experiment, significantly distinguished moderately painful leg pressure from innocuous pressure stimuli. Next, we estimated neural-network causality of patient-to-clinician directional information flow of facial expressions during clinician-initiated treatment of patients' evoked pain. We identified a leader-follower relationship in which patients predominantly led the facial communication while clinicians responded to patients' expressions. Finally, analyses of dynamic brain-to-brain concordance showed that patients' mid/posterior insular concordance with the clinicians' anterior insula cortex, a region identified in previously published data from this study¹, was associated with therapeutic alliance, and self-reported and objective (patient-to-clinician-directed causal influence) markers of negative-affect expressivity. These results suggest a role of patient-clinician concordance of the insula, a social-mirroring and salience-processing brain node, in mediating directional dynamics of pain-directed facial communication during therapeutic encounters.

Clinical Outcomes of Severe Forms of Early Social Stress

Early social stress, particularly severe but nevertheless frequent forms such as abuse and neglect, are among the major risk factors for the development of mental disorders. However, we only have very limited knowledge of the psychobiological disease mechanisms underlying the influence of early life stress and stress-related disorders during this vulnerable phase of life. Early stress can have long-lasting adverse effects on the brain and other somatic systems, e.g. through influences on brain development. In adulthood, the prior experience of abuse or neglect can result in complex clinical profiles. Besides conditions such as mood and anxiety disorders as well as posttraumatic stress disorder, substance use disorders (SUD) are among the most prevalent sequelae of early social stress. Current social stress further influences the development and maintenance of these disorders, e.g., by increasing the risk of relapses. In this chapter, we will first give an overview of currently used methods to assess the phenomenology and pathophysiology of stress-related disorders and then focus on the phenomenological and neurobiological background of the interaction between early social stress and SUD. We will give an overview of important insights from neuroimaging studies and will also highlight recent findings from studies using digital tools such as ecological momentary assessment or virtual reality to capture the influence of early social stress as well as current social stress in everyday life of persons with SUD.

[The domain "social processes" in the system of research domain criteria: current state and perspectives]

Soziale Prozesse und ihre Störungen, z. B. bei Autismusspektrumstörungen und psychotischen Störungen, sind seit jeher zentral für das Fach Psychiatrie. Die letzten Jahrzehnte haben zu beeindruckenden Fortschritten in unserem Verständnis der zugrunde liegenden neurobiologischen Grundlagen geführt, aber auch in der Art und Weise, wie wir soziale Prozesse untersuchen und analysieren. Seit ihrer Einführung bieten die Research Domain Criteria ein leistungsstarkes Rahmenwerk für die Operationalisierung und Unterteilung komplexer sozialer Prozesse in einer Weise, die sowohl neurobiologisch orientierte als auch klinische Ansätze zulässt. In diesem Artikel fassen wir die wichtigsten Erkenntnisse für jedes der vier grundlegenden Konstrukte der Domäne sozialer Prozesse zusammen und diskutieren sie: (a) Zugehörigkeit und Bindung, (b) soziale Kommunikation, (c) Wahrnehmung und Verständnis des Selbst und (d) Wahrnehmung und Verständnis anderer. Dabei heben wir insbesondere die klinische Relevanz der Erkenntnisse hervor, die auf dem Gebiet der sozialen Neurowissenschaften gewonnen wurden, und diskutieren die daraus resultierende zunehmende Bedeutung transdiagnostischer Konzepte in der angewandten Forschung. Schließlich stellen wir drei innovative Forschungsmethoden vor, die auf den sich beschleunigenden technologischen Fortschritten des letzten Jahrzehnts aufbauen und es zunehmend ermöglichen, komplexe soziale Interaktionen auch unter realistischeren und alltagsnäheren Bedingungen zu untersuchen.

[Neurobiological principles of borderline personality disorder: integration into the ICD-11 model of personality disorders]

BACKGROUND

Borderline personality disorder (BPD) is a severe mental disorder associated with far-reaching impairments in the self and interpersonal functioning. The broad database has contributed to the fact that BPD remains the only categorical personality diagnosis in ICD-11, even if coupled to the determination of the severity of impairments. Nevertheless, we need to deal with a dimensional conceptualization of personality disorders-which is also supported by neuroscientific findings-at the latest in 2022 when the ICD-11 comes into effect .

OBJECTIVE

This narrative review provides an overview of neuroscientific findings regarding impairments in self and interpersonal functioning in patients with BPD.

RESULTS

Alterations in the medial prefrontal cortex, temporoparietal junction and precuneus mediate deficits in self-referential thought processes and the mentalization of emotions and intentions of others. Enhanced connectivity between the amygdala and midline structures is associated with hypermentalization. At the same time, elevated insula activation seems to underlie the strengthened nonreflective parts of feelings of other people. Frontolimbic alterations are transdiagnostically associated with deficient emotional regulation and negative affectivity and alterations in reward and cognitive control regions are related to impulsivity.

CONCLUSION

Neuroscientific findings help to have a better understanding of the underlying mechanisms of central functional impairments in BPD and can support the transition to ICD-11 as well as the implementation of new interventions.

The role of impairments in self-other distinction in borderline personality disorder: A narrative review of recent evidence

Impairments in maintaining a differentiated sense of "self" and "other" are thought to be a central feature of borderline personality disorder (BPD). However, studies directly focusing on self-other distinction (SOD) in BPD are scarce, and these findings have not yet been integrated with novel insights into the neural mechanism involved in SOD. Here, we present a narrative review of recent behavioral and neuroimaging findings focusing on impairments in SOD in BPD. Behavioral findings of SOD at the embodied level provide preliminary evidence for impairments in multisensory integration in BPD. Furthermore, both behavioral and neuroscientific data converge to suggest that SOD impairments in BPD reflect an inability to shift between self and other representations according to task demands. Research also suggests that disruptions in infant-caregiver synchrony may play a role in the development of these impairments. Based on these findings, we present a new, integrative model linking impairments in SOD to reduced neural and behavioral synchrony in BPD. The implications of these findings for future research and clinical interventions are outlined.

A systematic review and meta-analysis of 'Systems for Social Processes' in borderline personality and substance use disorders

Deficits in social processing (SP) have been proposed to underpin interpersonal dysfunction in both Borderline Personality Disorder (BPD) and Substance Use Disorders (SUD). This study aimed to explore potential transdiagnostic cognitive and behavioral phenotypes of these disorders utilizing the NIMH Research Domain Criteria 'Systems for Social Processes'. A systematic review and meta-analysis of the published research was conducted on 134 studies identified through our database searches. Four meta-analyses were conducted, which revealed significant overlapping deficits in the ability to identify facial emotions and infer the mental states of others in both BPD and SUD. Further, people with BPD displayed a higher ostracism effect following perceived social exclusion. Systematically reviewed studies also revealed significant dysfunction amongst individuals with BPD and SUD across both self and other SP constructs, which were broadly similar in magnitude. Taken together, these results support the proposition that SP dysfunction may be considered a core transdiagnostic phenotype of BPD and SUD.

HyPyP: a Hyperscanning Python Pipeline for inter-brain connectivity analysis

The bulk of social neuroscience takes a 'stimulus-brain' approach, typically comparing brain responses to different types of social stimuli, but most of the time in the absence of direct social interaction. Over the last two decades, a growing number of researchers have adopted a 'brain-to-brain' approach, exploring similarities between brain patterns across participants as a novel way to gain insight into the social brain. This methodological shift has facilitated the introduction of naturalistic social stimuli into the study design (e.g. movies) and, crucially, has spurred the development of new tools to directly study social interaction, both in controlled experimental settings and in more ecologically valid environments. Specifically, 'hyperscanning' setups, which allow the simultaneous recording of brain activity from two or more individuals during social tasks, has gained popularity in recent years. However, currently, there is no agreed-upon approach to carry out such 'inter-brain connectivity analysis', resulting in a scattered landscape of analysis techniques. To accommodate a growing demand to standardize analysis approaches in this fast-growing research field, we have developed Hyperscanning Python Pipeline, a comprehensive and easy open-source software package that allows (social) neuroscientists to carry-out and to interpret inter-brain connectivity analyses.

Common and distinct brain functional alterations in pharmacotherapy treatment-naïve female borderline personality disorder patients with and without auditory verbal hallucinations: a pilot study

Auditory verbal hallucinations (AVHs) are experienced by approximately 25% of patients with borderline personality disorder (BPD). Despite the high incidence, the pathological features of AVH in BPD remain unclear. This study aimed to investigate whole-brain functional connectivity (FC), as measured by functional connectivity density (FCD), and its relationship with AVH in BPD. 65 pharmacotherapy treatment-naïve female BPD patients (30 with AVH and 35 without AVH), and 35 female healthy controls were investigated. Functional magnetic resonance imaging (fMRI) data were collected to assess whole-brain FC and functional connectivity density mapping (FCDM) was applied to the fMRI data to compute FCD features. Compared to the healthy controls, both BPD groups (BPD-AVH and BPD without AVH) exhibited significantly higher gFCD values in the bilateral prefrontal lobe, bilateral orbital lobule, and bilateral insula, and significantly lower gFCD values in the SMA, right anterior temporal lobule, and the ACC. These altered regions were significantly associated with AVH in the BPD subjects. Moreover, higher gFCD values were observed in the left posterior temporal lobule and posterior frontal lobule. Aberrant alterations also emerged in the left posterior temporal lobule and posterior frontal lobule, mainly in Broca and Wernicke regions. Nevertheless, there was no significant correlation between gFCD values and the severity of AVH as measured by the AVH scores. In summary, we have identified aberrations in the FC and brain metabolism of the aforementioned neural circuits/networks, which may provide new insights into BPD-AVH and facilitate the development of therapeutic approaches for treating AVH in BPD patients.

Subjektive Nebenwirkungsklagen von Borderline-Patienten – zwei Jahre nach einer tagesklinischen Behandlung

<b><i>Einleitung:</i></b> Die Erfassung von negativen Effekten (nE) von Psychotherapie (PT) ist wichtig, um Schwachstellen von PT zu identifizieren und die Behandlungsqualität zu verbessern. Studienziel ist, zu untersuchen, welche nE Patienten nach einer tagesklinischen Behandlung für Borderline-Persönlichkeitsstörungen (BPS) mit einem Dialektisch-Behavioralen Therapieschwerpunkt (DBT) beschreiben, welche Einflussfaktoren vorliegen und wie die Klagen inhaltlich zu verstehen sind. <b><i>Material und Methoden:</i></b> Katamnestisch wurden BPS-Patienten 22,6 Monate nach Therapieende befragt, an welche nE sie sich mit Bezug zu einer zwölfwöchigen ta­gesklinischen Behandlung erinnern. Messinstrumente wa­ren BDI, BSL-95 und INEP. <b><i>Ergebnisse:</i></b> 35 Frauen und 6 Männer antworteten (50% von 82). Im Mittel wurden 11,2 nE benannt, die subjektiv auf die DBT-Behandlung zurückgeführt wurden. 97,6% berichten von Verschlechterung ihres Befindens, 87,8% erinnern sich an Probleme in der therapeutischen Beziehung, 43,9% klagten über Verschlechterungen in der Beziehung, 70,7% über finanzielle Probleme in Folge der tagesklinischen Behandlung und 29,3% über Stigmatisierungserleben. Die Zahl der nE korrelierte mit höherem Alter zum Therapiestart (<i>p</i> &#x3c; 0,01) sowie höherer Symptomlast anhand der BSL-95 (<i>p</i> &#x3c; 0,01) bzw. BDI (<i>p</i> &#x3c; 0,01) zum Befragungszeitpunkt. <b><i>Diskussion:</i></b> Es konnte gezeigt werden, dass Patienten bei Vorlage des INEP über eine erheb­liche Rate an Negativerfahrungen im Rahmen der tages­klinischen Behandlung klagen. Der lange Rückerinne­rungszeitraum von 3 bis 51 Monaten und die Korrelation mit der aktuellen Symptomatik stellen die Validität der Antwort in Frage. Ergebnisse von Selbstratinginstrumenten zur Nebenwirkungserfassung bedürfen einer sehr sorgfältigen Interpretation.

A Multi-Brain Framework for Social Interaction

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

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

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

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.

Resilience and the brain: a key role for regulatory circuits linked to social stress and support

Given the high prevalence and burden of mental disorders, fostering the understanding of protective factors is an urgent issue for translational medicine in psychiatry. The concept of resilience describes individual and environmental protective factors against the backdrop of established adversities linked to mental illness. There is convergent evidence for a crucial role of direct as well as indirect adversity impacting the developing brain, with persisting effects until adulthood. Direct adversity may include childhood maltreatment and family adversity, while indirect social adversity can include factors such as urban living or ethnic minority status. Recently, research has begun to examine protective factors which may be able to buffer against or even reverse these influences. First evidence indicates that supportive social environments as well as trait-like individual protective characteristics might impact on similar neural substrates, thus strengthening the capacity to actively cope with stress exposure in order to counteract the detrimental effects evoked by social adversity. Here, we provide an overview of the current literature investigating the neural mechanisms of resilience with a putative social background, including studies on individual traits and genetic variation linked to resilience. We argue that the regulatory perigenual anterior cingulate cortex and limbic regions, including the amygdala and the ventral striatum, play a key role as crucial convergence sites of protective factors. Further, we discuss possible prevention and early intervention approaches targeting both the individual and the social environment to reduce the risk of psychiatric disorders and foster resilience.

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

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

[The importance of social neurosciences for psychiatry]

BACKGROUND

The social brain is dysfunctional in numerous stress-related psychiatric disorders.

OBJECTIVE

The definition of social brain networks and their susceptibility for social environmental stress. It is also reviewed how social brain networks are disrupted in schizophrenia, autism and conduct disorder.

MATERIAL AND METHODS

Literature search in PubMed.

RESULTS

The social brain consists of several subnetworks that act in concert to foster empathy. Interestingly, except for the mirror neuron system, the neural networks of the social brain have been reported to be vulnerable to social environmental stress and have also been highlighted as being compromised in psychiatric disorders. As an example, schizophrenia is related to dysfunction in social perception, mentalizing, and affiliation, whereas the most pronounced deficits in autism are seen during social perception and mentalizing. Patients with conduct disorder are more prone to dysfunction in perception, affiliation and aversion.

CONCLUSION

Social stress affects subnetworks also compromised in psychiatric disorders. Therefore, it is plausible that the social brain might mediate the association between social stress and psychiatric disorders. To advance ecological validity in social neuroscience, recent research has highlighted the role of hyperscanning and virtual reality as means by which a more naturalistic assessment of social interactions might be feasible.

Getting into sync: Data-driven analyses reveal patterns of neural coupling that distinguish among different social exchanges

In social interactions, each individual's brain drives an action that, in turn, elicits systematic neural responses in their partner that drive a reaction. Consequently, the brain responses of both interactants become temporally contingent upon one another through the actions they generate, and different interaction dynamics will be underpinned by distinct forms of between‐brain coupling. In this study, we investigated this by “performing functional magnetic resonance imaging on two individuals simultaneously (dual‐fMRI) while they competed or cooperated with one another in a turn‐based or concurrent fashion.” To assess whether distinct patterns of neural coupling were associated with these different interactions, we combined two data‐driven, model‐free analytical techniques: group‐independent component analysis and inter‐subject correlation. This revealed four distinct patterns of brain responses that were temporally aligned between interactants: one emerged during co‐operative exchanges and encompassed brain regions involved in social cognitive processing, such as the temporo‐parietal cortex. The other three were associated with competitive exchanges and comprised brain systems implicated in visuo‐motor processing and social decision‐making, including the cerebellum and anterior cingulate cortex. Interestingly, neural coupling was significantly stronger in concurrent relative to turn‐based exchanges. These results demonstrate the utility of data‐driven approaches applied to “dual‐fMRI” data in elucidating the interpersonal neural processes that give rise to the two‐in‐one dynamic characterizing social interaction.

The promise of two-person neuroscience for developmental psychiatry: using interaction-based sociometrics to identify disorders of social interaction

Social interactions are fundamental for human development, and disordered social interactions are pervasive in many psychiatric disorders. Recent advances in 'two-person neuroscience' have provided new tools for characterising social interactions. Accordingly, interaction-based 'sociometrics' hold great promise for developmental psychology and psychiatry, particularly in the early identification of social disorders.

DECLARATION OF INTEREST

None.

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

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

Social Impairments in Mental Disorders: Recent Developments in Studying the Mechanisms of Interactive Behavior

Most mental disorders are associated with impairments in social functioning. Paradigms developed to study social functioning in laboratory settings mostly put participants in a detached observer point of view. However, some phenomena are inherently interactive and studying full-blown reciprocal interactions may be indispensable to understand social deficits in psychopathology.

We conducted a narrative review on recent developments in the field of experimental clinical psychology and clinical social neuroscience that employs a second-person approach to studying social impairments in Autism Spectrum Disorder (ASD), Personality Disorder, Social Anxiety Disorder (SAD), and Schizophrenia.

Recent developments in methodological, analytical, and technical approaches, such as dual eye-tracking, mobile eye-tracking, live video-feed, hyperscanning, or motion capture allow for a more ecologically valid assessment of social functioning. In individuals with ASD, these methods revealed reduced sensitivity to the presence of a real interaction partner as well as diminished behavioral and neural synchronicity with interaction partners. Initial evidence suggests that interactive paradigms might be a powerful tool to reveal reduced interpersonal sensitivity in Personality Disorders and increased interpersonal sensitivity in individuals with SAD.

A shift towards adapting a second-person account has clearly benefitted research on social interaction in psychopathology. Several studies showed profound differences in behavioral and neural measures during actual social interactions, as compared to engaging participants as mere observers. While research using truly interactive paradigms is still in its infancy, it holds great potential for clinical research on social interaction.

We review studies adopting a second-person account of social interaction in clinical psychology.

Studies show profound differences between actual social interactions and mere observations.

The full extent of impairments in social functioning unfolds only in complex social interactions.

New methodological developments hold great potential for research on social interaction deficits.

Bidirectional signal exchanges and their mechanisms during joint attention interaction - A hyperscanning fMRI study

Social interactions are essential to our daily life. We tested the hypothesis that social interactions during joint attention (JA) require bidirectional communication, each with a different mechanism. We used a novel multivariate functional connectivity analysis, which enables obtaining directed pathways between four regions at each time-frequency point, with hyper-scanning MRI data of real-time JA interaction. Constructing multiple "4-regional directed pathways" and counting the number of times, regions engaged in feedforward or feedback processes in the 'sender' or the 'receiver brains, we obtained the following. (1) There were more regions in feedforward than in feedback processes (125 versus 99). (2) The right hemisphere was more involved in feedforward (74 versus 33), while the left hemisphere in feedback (66 versus 51). (3) The dmPFC was more engaged in feedforward (73 versus 44) while the TPJ in both (49 versus 45). (4) The dmPFC was more involved in the sending processes (i.e. initiation of feedforward and feedback) while the TPJ in the receiving processes. (5) JA interaction was involved with high MRI frequencies (0.04-0.1 Hz), while continues interactions by low MRI frequencies (0.01-0.04 Hz). (6) Initiation and responding to JA (i.e. IJA and RJA) evolved with composite neural systems: similar systems for pathways that included the dmPFC, vmPFC and the STS, and different systems for pathways that included the TPJ, vmPFC, PCC and the STS. These findings have important consequences in the basic understanding of social interaction and could help in diagnose and follow-up of social impairments.

Interplay between prior knowledge and communication mode on teaching effectiveness: Interpersonal neural synchronization as a neural marker

Teacher-student interaction allows students to combine prior knowledge with new information to develop new knowledge. It is widely understood that both communication mode and students' knowledge state contribute to the teaching effectiveness (i.e., higher students' scores), but the nature of the interplay of these factors and the underlying neural mechanism remain unknown. In the current study, we manipulated the communication modes (face-to-face [FTF] communication mode/computer-mediated communication [CMC] mode) and prior knowledge states (with vs. without) when teacher-student dyads participated in a teaching task. Using functional near-infrared spectroscopy, the brain activities of both the teacher and student in the dyads were recorded simultaneously. After teaching, perceived teacher-student interaction and teaching effectiveness were assessed. The behavioral results demonstrated that, during teaching with prior knowledge, FTF communication improved students' academic performance, as compared with CMC. Conversely, no such effect was found for teaching without prior knowledge. Accordingly, higher task-related interpersonal neural synchronization (INS) in the left prefrontal cortex (PFC) was found in the FTF teaching condition with prior knowledge. Such INS mediated the relationship between perceived interaction and students' test scores. Furthermore, the cumulative INS in the left PFC could predict the teaching effectiveness early in the teaching process (around 25-35 s into the teaching task) only in FTF teaching with prior knowledge. These findings provide insight into how the interplay between the communication mode and students' knowledge state affects teaching effectiveness. Moreover, our findings suggest that INS could be a possible neuromarker for dynamic evaluation of teacher-student interaction and teaching effectiveness.

[A selective review of recent research results in biological psychiatry]

In accordance with the motto of this year's German Society for Psychiatry, Psychotherapy and Psychosomatics (DGPPN) conference, this article surveys very recent developments in biological psychiatry and neurosciences that have the potential to open up new vistas for the psychiatry and psychotherapy of the future. The work reported includes progress in genome-wide association studies, the implications of these findings for psychiatric nosology and gene-environment interactions, new methods to characterize mechanisms of altered brain function in animal models and humans and the translation of these findings into new therapies. As a core methodology for the psychiatry of the future, biological and applied neuroscience approaches should benefit from sustained structural funding to ensure that these advances impact real-world patient care.

Borderline personality disorder

Caretakers are often intimidated or alienated by patients with borderline personality disorder (BPD), compounding the clinical challenges posed by the severe morbidity, high social costs and substantial prevalence of this disorder in many health-care settings. BPD is found in ∼1.7% of the general population but in 15-28% of patients in psychiatric clinics or hospitals and in a large proportion of individuals seeking help for psychological problems in general health facilities. BPD is characterized by extreme sensitivity to perceived interpersonal slights, an unstable sense of self, intense and volatile emotionality and impulsive behaviours that are often self-destructive. Most patients gradually enter symptomatic remission, and their rate of remission can be accelerated by evidence-based psychosocial treatments. Although self-harming behaviours and proneness to crisis can decrease over time, the natural course and otherwise effective treatments of BPD usually leave many patients with persistent and severe social disabilities related to depression or self-harming behaviours. Thus, clinicians need to actively enquire about the central issues of interpersonal relations and unstable identity. Failure to correctly diagnose patients with BPD leads to misleading pharmacological interventions that rarely succeed. Whether the definition of BPD should change is under debate that is linked to not fully knowing the nature of this disorder.