Reward Circuitry and Motivational Deficits in Social Anxiety Disorder: What Can Be Learned From Mouse Models?

SAUSI: a novel assay for measuring social anxiety and motivation

Social anxiety is one of the most prevalent mental health disorders, though the underlying neurobiology is poorly understood. Progress in understanding the etiology of social anxiety has been hindered by the lack of comprehensive tools to assess social anxiety in model systems. Here, we created a new behavioral task - Selective Access to Unrestricted Social Interaction (SAUSI), which combines elements of social motivation, hesitancy, decision-making, and free interaction to enable the wholistic assessment of social anxiety-like behaviors in mice. Using this novel assay, we found that social isolation-induced social anxiety-like behaviors in female mice are largely driven by increases in social fear, social hesitancy, and altered ultrasonic vocalizations. Deep learning analyses were able to computationally identify a unique behavioral footprint underlying the state produced by social isolation, demonstrating the compatibility of modern computational approaches with SAUSI. Finally, we compared the results of SAUSI to traditionally social assays including the 3-chamber sociability assay and the resident intruder task. This revealed that behavioral changes induced by isolation were highly context dependent, and that while fragments of social anxiety measured in SAUSI were replicable across other tasks, a wholistic assessment was not obtainable from these alternative assays. Our findings debut a novel task for the behavioral toolbox - one which overcomes limitations of previous assays, allowing for both social choice as well as free interaction, and offers a new approach for assessing social anxiety in rodents.

Age-dependent alterations in the coordinated development of subcortical regions in adolescents with social anxiety disorder

Subcortical brain regions play essential roles in the pathology of social anxiety disorder (SAD). While adolescence is the peak period of SAD, the relationships between altered development of the subcortical regions during this period and SAD are still unclear. This study investigated the age-dependent alterations in structural co-variance among subcortical regions and between subcortical and cortical regions, aiming to reflect aberrant coordination during development in the adolescent with SAD. High-resolution T1-weighted images were obtained from 76 adolescents with SAD and 67 healthy controls (HC), ranging from 11 to 17.9 years. Symptom severity was evaluated with the Social Anxiety Scale for Children (SASC) and the Depression Self Rating Scale for Children (DSRS-C). Structural co-variance and sliding age-window analyses were used to detect age-dependent group differences in inter-regional coordination patterns among subcortical regions and between subcortical and cortical regions. The volume of the striatum significantly correlated with SAD symptom severity. The SAD group exhibited significantly enhanced structural co-variance among key regions of the striatum (putamen and caudate). While the co-variance decreased with age in healthy adolescents, the co-variance in SAD adolescents stayed high, leading to more apparent group differences in middle adolescence. Moreover, the striatum's mean structural co-variance with cortical regions decreased with age in HC but increased with age in SAD. Adolescents with SAD suffer aberrant developmental coordination among the key regions of the striatum and between the striatum and cortical regions. The degree of incoordination is age-dependent, which may represent a neurodevelopmental trait of SAD.

Male mice engaging differently in emotional eating present distinct plasmatic and neurological profiles

Objective: Stressed individuals tend to turn to calorie-rich food, also known as 'comfort food' for the temporary relief it provides. The emotional eating drive is highly variable among subjects. Using a rodent model, we explored the plasmatic and neurobiological differences between 'high and low emotional eaters' (HEE and LEE).Methods: 40 male mice were exposed for 5 weeks to a protocol of unpredictable chronic mild stress. Every 3 or 4 days, they were submitted to a 1-h restraint stress, immediately followed by a 3-h period during which a choice between chow and chocolate sweet cereals was proposed. The dietary intake was measured by weighing. Plasmatic and neurobiological characteristics were compared in mice displaying high vs low intakes.Results: Out of 40 mice, 8 were considered as HEE because of their high post-stress eating score, and 8 as LEE because of their consistent low intake. LEE displayed higher plasma corticosterone and lower levels of NPY than HEE, but acylated and total ghrelin were similar in both groups. In the brain, the abundance of NPY neurons in the arcuate nucleus of the hypothalamus was similar in both groups, but was higher in the ventral hippocampus and the basal lateral amygdala of LEE. The lateral hypothalamus LEE had also more orexin (OX) positive neurons. Both NPY and OX are orexigenic peptides and mood regulators.Discussion: Emotional eating difference was reflected in plasma and brain structures implicated in emotion and eating regulation. These results concur with the psychological side of food consumption.

Neurobiological mechanisms of dialectical behavior therapy and Morita therapy, two psychotherapies inspired by Zen

Psychotherapy is a learning process. Updating the prediction models of the brain may be the mechanism underlying psychotherapeutic changes. Although developed in different eras and cultures, dialectical behavior therapy (DBT) and Morita therapy are influenced by Zen principles, and both emphasize the acceptance of reality and suffering. This article reviews these two treatments, their common and distinct therapeutic factors, and their neuroscientific implications. Additionally, it proposes a framework that includes the predictive function of the mind, constructed emotions, mindfulness, therapeutic relationship, and changes enabled via reward predictions. Brain networks, including the Default Mode Network (DMN), amygdala, fear circuitry, and reward pathways, contribute to the constructive process of brain predictions. Both treatments target the assimilation of prediction errors, gradual reorganization of predictive models, and creation of a life with step-by-step constructive rewards. By elucidating the possible neurobiological mechanisms of these psychotherapeutic techniques, this article is expected to serve as the first step towards filling the cultural gap and creating more teaching methods based on these concepts.

Social anxiety inhibits needs repair following exclusion in both relational and non-relational reward contexts: The mediating role of positive affect

The pain of social exclusion can motivate people to capitalize on opportunities to reconnect with others and repair their self-esteem and feelings of belongingness. This effect is often diminished for those with high social anxiety (HSA). Prior research suggests this may be due to their diminished capacity for recognizing and emotionally responding to relational reward cues. We investigated whether non-relational success experiences in the aftermath of exclusion may be an alternative means of repairing threatened self-esteem and belongingness in HSA individuals. In a preregistered, online study, we threatened belongingness and self-esteem in 422 participants by excluding them in a Cyberball game and then assigned them to one of three conditions: Relational Repair, Non-Relational Repair, or a No-Repair control condition. Results showed that both repair contexts facilitated needs repair relative to the no-repair control condition, and mediation analyses suggested this effect was driven by increased positive affect (PA). HSA individuals were less likely to restore needs regardless of condition and this effect appeared to be driven by low PA. Findings emphasize the critical role of PA for restoring threatened needs in the aftermath of exclusion and suggest that HSA inhibits needs repair processes across both relational and non-relational reward contexts.

Psychedelic Therapy's Transdiagnostic Effects: A Research Domain Criteria (RDoC) Perspective

Accumulating clinical evidence shows that psychedelic therapy, by synergistically combining psychopharmacology and psychological support, offers a promising transdiagnostic treatment strategy for a range of disorders with restricted and/or maladaptive habitual patterns of emotion, cognition and behavior, notably, depression (MDD), treatment resistant depression (TRD) and addiction disorders, but perhaps also anxiety disorders, obsessive-compulsive disorder (OCD), Post-Traumatic Stress Disorder (PTSD) and eating disorders. Despite the emergent transdiagnostic evidence, the specific clinical dimensions that psychedelics are efficacious for, and associated underlying neurobiological pathways, remain to be well-characterized. To this end, this review focuses on pre-clinical and clinical evidence of the acute and sustained therapeutic potential of psychedelic therapy in the context of a transdiagnostic dimensional systems framework. Focusing on the Research Domain Criteria (RDoC) as a template, we will describe the multimodal mechanisms underlying the transdiagnostic therapeutic effects of psychedelic therapy, traversing molecular, cellular and network levels. These levels will be mapped to the RDoC constructs of negative and positive valence systems, arousal regulation, social processing, cognitive and sensorimotor systems. In summarizing this literature and framing it transdiagnostically, we hope we can assist the field in moving toward a mechanistic understanding of how psychedelics work for patients and eventually toward a precise-personalized psychedelic therapy paradigm.

Mindfulness-Based Stress Reduction Specifically Improves Social Anhedonia Among Adults with Chronic Stress

This randomized controlled trial examined the effects of mindfulness on anhedonic symptoms in a sample of adults reporting high levels of chronic stress. Meditation-naïve adults (N = 68, Mage = 32, 62% female) were randomized to either an 8-week group-based MBSR intervention (N = 35), or a waitlist control group (N = 33). We hypothesized that changes in mindfulness would mediate the relationship between condition and changes in anhedonic symptoms. Additionally, the present study aimed to determine if other theoretically linked mechanisms (i.e., stress, negative affect [NA], depression) were involved in producing changes in anhedonic symptoms. Results provided evidence for full mediation of the effect of MBSR on social anhedonia through its essential mechanism of ΔMindfulness. These results highlight specificity of anhedonic symptoms targeted by MBSR, with social anhedonia symptoms being modified by changes in mindfulness whereas other anhedonic domains were not. The specificity of effects to the social anhedonia domain may be in part due to the group-based nature of MBSR. Additionally, although associative relationships were present for stress, depression, NA, and anhedonic symptoms, no mediational relationships emerged. Results presented here should be evaluated in light of study limitations, such as the reliance on self-report measures as well as a lack of information regarding cultural or geographic diversity.

Contributions of childhood abuse and neglect to reward neural substrates in adolescence

BACKGROUND

Childhood adverse experiences may come to bear particularly during adolescence, when neural reward systems are developing rapidly and psychopathology spikes. Despite prior work differentiating threat- (abuse) vs. deprivation- (neglect) related adversity, no research has yet identified their relative nor interactive contributions to reward neural substrates during adolescence. In the present study, we leveraged a diverse sample of adolescents with different childhood adversity profiles to examine neural responses to reward in relation to varying degrees of abuse vs. neglect.

METHODS

Adolescents (N = 45; 23 females; mean age = 14.9 years, SD = 1.9) completed a child-friendly monetary incentive delay task during fMRI acquisition. The self-report Childhood Trauma Questionnaire assessed childhood abuse and neglect. Whole brain ANCOVA analyses evaluated reward anticipation (reward vs. no reward expected) and feedback (hitting vs. missing the target with a reward vs. no reward) in relation to abuse and neglect dimensions.

RESULTS

Whole-brain analyses revealed that abuse, adjusted for neglect, is associated with greater differences between task conditions (reward vs. no reward, hit vs. miss) in regions associated with threat/emotion regulation (prefrontal and temporal cortices, as well as posterior regions including fusiform and posterior cingulate/precuneus). Additionally, level of neglect modulated neural response associated with abuse in prefrontal and temporoparietal regions, such that youths with high levels of both abuse and neglect showed qualitatively different, more exaggerated neural patterns compared to youths with elevated adversity in only one dimension.

CONCLUSIONS

Our findings suggest that early experiences of abuse and neglect have a long developmental reach resulting in reward-related neural alterations in adolescence. Moreover, our results bolster theoretical conceptualizations of adversity along threat and deprivation dimensions and provide evidence that "adding up" adverse life events may not be sufficient to capture the qualitatively different neural profiles produced by differing combinations of types of adversity, which may in turn necessitate different treatment approaches.

Binge-like Alcohol Exposure in Adolescence: Behavioural, Neuroendocrine and Molecular Evidence of Abnormal Neuroplasticity… and Return

Binge alcohol consumption among adolescents affects the developing neural networks underpinning reward and stress processing in the nucleus accumbens (NAc). This study explores in rats the long-lasting effects of early intermittent exposure to intoxicating alcohol levels at adolescence, on: (1) the response to natural positive stimuli and inescapable stress; (2) stress-axis functionality; and (3) dopaminergic and glutamatergic neuroadaptation in the NAc. We also assess the potential effects of the non-intoxicating phytocannabinoid cannabidiol, to counteract (or reverse) the development of detrimental consequences of binge-like alcohol exposure. Our results show that adolescent binge-like alcohol exposure alters the sensitivity to positive stimuli, exerts social and novelty-triggered anxiety-like behaviour, and passive stress-coping during early and prolonged withdrawal. In addition, serum corticosterone and hypothalamic and NAc corticotropin-releasing hormone levels progressively increase during withdrawal. Besides, NAc tyrosine hydroxylase levels increase at late withdrawal, while the expression of dopamine transporter, D1 and D2 receptors is dynamically altered during binge and withdrawal. Furthermore, the expression of markers of excitatory postsynaptic signaling—PSD95; Homer-1 and -2 and the activity-regulated spine-morphing proteins Arc, LIM Kinase 1 and FOXP1—increase at late withdrawal. Notably, subchronic cannabidiol, during withdrawal, attenuates social- and novelty-induced aversion and passive stress-coping and rectifies the hyper-responsive stress axis and NAc dopamine and glutamate-related neuroplasticity. Overall, the exposure to binge-like alcohol levels in adolescent rats makes the NAc, during withdrawal, a locus minoris resistentiae as a result of perturbations in neuroplasticity and in stress-axis homeostasis. Cannabidiol holds a promising potential for increasing behavioural, neuroendocrine and molecular resilience against binge-like alcohol harmful effects.

Reconnecting in the Face of Exclusion: Individuals with High Social Anxiety May Feel the Push of Social Pain, but not the Pull of Social Rewards

Background

Previous research has shown that high levels of trait social anxiety (SA) disrupt the social repair processes following a painful social exclusion, but the cognitive mechanisms involved in these processes and how trait SA may disrupt them remain unknown.

Methods

We conducted a preregistered study on Prolific participants (N = 452) who were assigned to experience either social exclusion or inclusion and were then exposed to follow-up opportunities for social reconnection.

Results

Moderated mediation analyses revealed that irrespective of levels of SA, participants responded to social pain with heightened approach motivation and greater downstream positive affect. Exploratory analyses revealed that heightened desire to affiliate was driven by increased curiosity and attention to social rewards. Moreover, higher SA was associated with lower overall desire to affiliate and this relationship between SA and affiliation was mediated by diminished reward responsiveness.

Conclusions

Findings highlight the roles of goal pursuit and social reward responsiveness in social repair and how high levels of trait SA may disrupt these processes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10608-021-10263-z.

Protocol for quantitative assessment of social cooperation in mice

Social cooperation in rodents was recently validated in rats, and we recently successfully applied a modified automated analysis to mice. Here, we describe a detailed procedure for using this paradigm in mice that relies on reward-based mutual communication that is automatically detected by a software algorithm embedded in the custom-made equipment. We also describe exemplary results of analyses in mice as a guide to broader neuroscience research applications employing transgenic knockout mice modeling neuropsychiatric disorders and mice of various ages.

For complete details on the use and execution of this protocol, please refer to Han et al. (2020).

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Detailed protocol for performing customized social cooperation tests in mice

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Detailed guidelines for analyzing social cooperation in mice

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Troubleshooting of the most common pitfalls associated with the procedure

Microbiota-gut-brain axis as a regulator of reward processes

Our gut harbours trillions of microorganisms essential for the maintenance of homeostasis and host physiology in health and disease. In the last decade, there has been a growing interest in understanding the bidirectional pathway of communication between our microbiota and the central nervous system. With regard to reward processes there is accumulating evidence from both animal and human studies that this axis may be a key factor in gating reward valence. Focusing on the mesocorticolimbic pathway, we will discuss how the intestinal microbiota is involved in regulating brain reward functions, both in natural (i.e. eating, social or sexual behaviours) and non-natural reinforcers (drug addiction behaviours including those relevant to alcohol, psychostimulants, opioids and cannabinoids). We will integrate preclinical and clinical evidence suggesting that the microbiota-gut-brain axis could be implicated in the development of disorders associated with alterations in the reward system and how it may be targeted as a promising therapeutic strategy. Cover Image for this issue: https://doi.org/10.1111/jnc.15065.