Vasopressin needs an audience: neuropeptide elicited stress responses are contingent upon perceived social evaluative threats

Social anxiety is associated with greater peripheral oxytocin reactivity to psychosocial stress

To date, it has been difficult to establish reliable biomarkers associated with specific forms of psychopathology. Social anxiety, for example, is associated with inconsistent biological responses to psychosocial stress on markers including cortisol and salivary alpha-amylase. Thus, it is critical that studies identify more reliable biomarkers that index patterns associated with social anxiety. Two potential candidates are the neuropeptides oxytocin and vasopressin, which have been implicated in stress responsivity across species. Studies have demonstrated a reliable increase in oxytocin, and a surrogate marker for vasopressin, following engagement in the most widely used lab-based psychosocial stress paradigm: the Trier Social Stress Test (TSST). However, no study has examined whether social anxiety moderates peripheral oxytocin or vasopressin reactivity to psychosocial stress. In 101 young adult participants, dimensionally assessed social anxiety was associated with greater plasma oxytocin, but not vasopressin, reactivity to the TSST. Results were maintained following the inclusion of depression as a covariate. Findings suggest that studying changes in peripheral oxytocin concentrations may be a method of differentiating individuals with higher levels of social anxiety.

Natura Non Facit Saltus: The Adaptive Significance of Arginine Vasopressin in Human Affect, Cognition, and Behavior

Hormones coordinate internal bodily systems with cognition, affect, and behavior, and thereby influence aspects of social interactions including cooperation, competition, isolation, and loneliness. The adaptive significance and contextuality of oxytocin (OXT) and testosterone (T) have been well-studied, but a unified theory and evolutionary framework for understanding the adaptive functions of arginine vasopressin (AVP) remain undeveloped. We propose and evaluate the hypothesis that AVP mediates adaptive variation in the presence and strength of social and sociosexual salience, attention and behavior specifically in situations that involve combinations of cooperation with conflict or competition. This hypothesis can help to explain the ancestral, original functions of AVP-like peptides, and their continuity with the current roles of AVP, for humans, in male-male competition, male-male reciprocity, male-to-female pair bonding, female-female interactions, social integration, and social attention and anxiety. In this context, social isolation and loneliness may be mediated by reduced abilities or interests in navigation of social opportunities and situations, due in part to low AVP levels or reactivity, and in part to reductions in levels of OXT-mediated social reward.

Empathy Modulates the Effect of Stress Reactivity on Generous Giving

How does acute stress influence the degree to which we cooperate with others? Research on the effects of stress on social decision-making is guided by two seemingly contrasting theories. Acute stress may trigger a Fight-or-Flight response, manifested by increased anxiety, and more egocentric or selfish behavior. Alternatively, according to the Tend-and-Befriend model, acute stress may induce affiliative behaviors, marked by increased prosociality in an effort to seek and receive social support and protection. Extant studies on the topic do not provide consistent support for either pattern of behavior, with studies showing evidence for both Fight-or-Flight or Tend-and-Befriend like responses. One possibility, may be the nature of social responses to stressful situations differ as a function of the individual. In the current study, we demonstrate an example of such a person-by-situation interaction, showing that acute stress can cause either pro-social or selfish responses, contingent on individual differences in trait empathy. One hundred and twenty three participants (60 F) were assessed for trait empathy using the Interpersonal Reactivity Index; consequently, they underwent either the Trier Social Stress Test-a well-validated paradigm for eliciting acute psychosocial stress-or a non-stress inducing control condition. Following exposure to either the stress or control condition, participants played a one-shot Dictator Game to evaluate their generosity levels. Statistical analyses revealed that acute stress by itself did not affect the amount transferred in the Dictator Game. Rather, individual differences in trait empathy moderated the effects of stress on giving. Elevations in stress-induced cortisol resulted in more generous behavior, but only in individuals high in empathy. In contrast, in individuals low in empathy, a greater rise in stress-induced cortisol resulted in more selfish behavior. Effects were more pronounced in females than males. Our findings highlight the necessity of integrating personality traits as important moderators of the link between stress and sociality.

Alterations in oxytocin and vasopressin in men with problematic pornography use: The role of empathy

BACKGROUND

Addictive behaviors share clinical, genetic, neurobiological and phenomenological parallels with substance addictions. Despite the prevalence of compulsive sexual behaviors, particularly problematic pornography use (PPU), how neuroendocrine systems relate to PPU is not well understood. Preclinical studies demonstrate alterations in oxytocin and arginine vasopressin (AVP) function in animal models of addiction, but no human study has tested their involvement in PPU.

METHOD

Participants included 122 males; 69 reported PPU, and 53 were demographically-matched participants without PPU. Plasma oxytocin and AVP levels and oxytocin-to-AVP balance were measured at baseline. Salivary oxytocin was assessed at baseline and in response to four videos depicting neutral/positive social encounters. Participants reported on empathy and psychiatric symptoms.

RESULTS

Baseline plasma AVP levels were elevated in men with PPU, and the ratio of oxytocin-to-vasopressin suggested AVP dominance. Men with PPU reacted with greater oxytocin increases to presentation of neutral/positive social stimuli. Decreased empathic tendencies were found in men with PPU, and this reduced empathy mediated links between oxytocin and pornography-related hypersexuality. Structural equation modeling revealed three independent paths to pornography-related hypersexuality; two direct paths via increased AVP and higher psychiatric symptoms and one indirect path from oxytocin to pornography-related hypersexuality mediated by diminished empathy.

CONCLUSIONS

Findings are among the first to implicate neuropeptides sustaining mammalian attachment in the pathophysiology of pornography-related hypersexuality and describe a neurobiological mechanism by which oxytocin-AVP systems and psychiatric symptomatology may operate to reduce empathy and lead to pornography-related hypersexuality.

Social evaluation under stress: Does acute stress affect social attributions and eye gaze?

Acute stress has been found to elicit pro-social, anti-social or null responses in humans. The causes for these contradicting findings are currently poorly understood, and may rise from subjects' characteristics, such as sex or hormonal status, as well as stimuli-based traits, such as group membership. In the current study, 120 subjects performed either the Trier Social Stress Test or a control (non-stress inducing) condition, followed by ranking displayed faces according to several attributes (e.g., trustworthiness, attractiveness, dominance). Participants' eye gaze was also tracked while viewing facial stimuli. We examined how acute stress interacts with participants' sex, female participants' hormonal status (hormonal contraceptives, early-follicular phase and mid-luteal phase), and the observed faces’ social group (ethnicity-based in-group or out-groups). In general, frequentist and Bayesian analyses showed that acute stress exposure did not affect social attributions or gaze behavior, nor did it interact with subjects' sex or the group membership of the observed faces. Interestingly, sub-group analyses showed that in females, acute stress interacted with hormonal status to yield heterogenous anti-social effects, such as post-stress reductions in perceived trustworthiness in the early-follicular phase, and lower perceived attractiveness in the mid-luteal phase. Given the small sample sizes for the sub-groups, these results should be viewed as preliminary until further replicated. Our results highlight the necessity for large-scale studies, particularly in females, to further refine existing theories regarding the nature and contexts by which acute stress elicits changes in social cognition and behavior.

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Bayesian analysis showed that stress did not broadly affect social attributions.

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However, females' hormonal status may interact with stress to modulate attributions.

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Attributions were highly biased against out-group members, regardless of stress.

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Stress also did not influence patterns of eye gaze to faces.

HPA Axis in the Pathomechanism of Depression and Schizophrenia: New Therapeutic Strategies Based on Its Participation

The hypothalamic-pituitary-adrenal (HPA) axis is involved in the pathophysiology of many neuropsychiatric disorders. Increased HPA axis activity can be observed during chronic stress, which plays a key role in the pathophysiology of depression. Overactivity of the HPA axis occurs in major depressive disorder (MDD), leading to cognitive dysfunction and reduced mood. There is also a correlation between the HPA axis activation and gut microbiota, which has a significant impact on the development of MDD. It is believed that the gut microbiota can influence the HPA axis function through the activity of cytokines, prostaglandins, or bacterial antigens of various microbial species. The activity of the HPA axis in schizophrenia varies and depends mainly on the severity of the disease. This review summarizes the involvement of the HPA axis in the pathogenesis of neuropsychiatric disorders, focusing on major depression and schizophrenia, and highlights a possible correlation between these conditions. Although many effective antidepressants are available, a large proportion of patients do not respond to initial treatment. This review also discusses new therapeutic strategies that affect the HPA axis, such as glucocorticoid receptor (GR) antagonists, vasopressin V1B receptor antagonists and non-psychoactive CB1 receptor agonists in depression and/or schizophrenia.

Specification of oxytocinergic and vasopressinergic circuits in the developing mouse brain

Oxytocin (OXT) and arginine vasopressin (AVP) support a broad range of behaviors and homeostatic functions including sex-specific and context-appropriate social behaviors. Although the alterations of these systems have been linked with social-related disorders such as autism spectrum disorder, their formation and developmental dynamics remain largely unknown. Using novel brain clearing techniques and 3D imaging, we have reconstructed the specification of oxytocinergic and vasopressinergic circuits in the developing mouse brain with unprecedented cellular resolution. A systematic quantification indicates that OXT and AVP neurons in the hypothalamus display distinctive developmental dynamics and high cellular plasticity from embryonic to early postnatal stages. Our findings reveal new insights into the specification and consolidation of neuropeptidergic systems in the developing CNS.

Evolution of stress responses refine mechanisms of social rank

Social rank functions to facilitate coping responses to socially stressful situations and conditions. The evolution of social status appears to be inseparably connected to the evolution of stress. Stress, aggression, reward, and decision-making neurocircuitries overlap and interact to produce status-linked relationships, which are common among both male and female populations. Behavioral consequences stemming from social status and rank relationships are molded by aggressive interactions, which are inherently stressful. It seems likely that the balance of regulatory elements in pro- and anti-stress neurocircuitries results in rapid but brief stress responses that are advantageous to social dominance. These systems further produce, in coordination with reward and aggression circuitries, rapid adaptive responding during opportunities that arise to acquire food, mates, perch sites, territorial space, shelter and other resources. Rapid acquisition of resources and aggressive postures produces dominant individuals, who temporarily have distinct fitness advantages. For these reasons also, change in social status can occur rapidly. Social subordination results in slower and more chronic neural and endocrine reactions, a suite of unique defensive behaviors, and an increased propensity for anxious and depressive behavior and affect. These two behavioral phenotypes are but distinct ends of a spectrum, however, they may give us insights into the troubling mechanisms underlying the myriad of stress-related disorders to which they appear to be evolutionarily linked.

Intranasal vasopressin modulates resting state brain activity across multiple neural systems: Evidence from a brain imaging machine learning study

Arginine vasopressin (AVP), a neuropeptide with widespread receptors in brain regions important for socioemotional processing, is critical in regulating various mammalian social behavior and emotion. Although a growing body of task-based brain imaging studies have revealed the effects of AVP on brain activity associated with emotion processing, social cognition and behaviors, the potential modulations of AVP on resting-state brain activity remain largely unknown. Here, the current study addressed this issue by adopting a machine learning approach to distinguish administration of AVP and placebo, employing the amplitude of low-frequency fluctuation (ALFF) as a measure of resting-state brain activity. The brain regions contributing to the classification were then subjected to functional connectivity and decoding analyses, allowing for a data-driven quantitative inference on psychophysiological functions. Our results indicated that ALFF across multiple neural systems were sufficient to distinguish between AVP and placebo at individual level, with the contributing regions distributed across the social cognition network, sensorimotor regions and emotional processing network. These findings suggest that the role of AVP in socioemotional functioning recruits multiple brain networks distributed across the whole brain rather than specific localized neural pathways. Beyond these findings, the current data-driven approach also opens a novel avenue to delineate neural underpinnings of various neuropeptides or hormones.

Association of Copeptin With Sense of Coherence in Individuals With Varying Degrees of Glucose Intolerance

OBJECTIVE

This study aimed to examine the association of serum copeptin levels, a surrogate marker of arginine-vasopressin secretion with sense of coherence (SOC) among individuals with varying degrees of glucose intolerance.

METHODS

The study was conducted in 120 age- and sex-matched individuals who were divided equally into three groups. Group A included individuals with normal glucose tolerance; group B, individuals with prediabetes (impaired glucose tolerance and/or impaired fasting glucose); and group C, individuals with newly detected diabetes mellitus (NDDM). SOC, perceived stress scale (PSS), copeptin, anthropometry, glycated hemoglobin, insulin, and salivary cortisol were measured in all study participants.

RESULTS

The SOC score was found to be significantly lower in group C compared with group A (p < .001) and group B (p = .006). The PSS score was found to be significantly higher in group C compared with group A (p = .002). No significant difference was found between PSS scores of groups B and C (p = .25). Copeptin levels were found to be significantly higher in group C compared with group A (p = .016). Copeptin levels in group C did not differ significantly from those in group B (p = .056). There was a significant negative correlation between serum copeptin levels and SOC in the NDDM group C (r = 0.31, p = .048) and overall (r = 0.19, p = .037). In multiple regression analysis, SOC emerged as the variable with the strongest association with 2-hour postprandial plasma glucose and glycated hemoglobin.

CONCLUSION

Individuals with NDDM displayed significantly higher serum copeptin levels that inversely correlated with SOC, a global measure of stress coping ability.

A systematic review of the Trier Social Stress Test methodology: Issues in promoting study comparison and replicable research

Since its development in 1993, the Trier Social Stress Test (TSST) has been used widely as a psychosocial stress paradigm to activate the sympathetic nervous system and hypothalamic-pituitary-adrenal axis (HPAA) stress systems, stimulating physiological functions (e.g. heart rate) and cortisol secretion. Several methodological variations introduced over the years have led the scientific community to question replication between studies. In this systematic review, we used the Preferred Reporting Items of Systematic Reviews and Meta-Analysis (PRISMA) to synthesize procedure-related data available about the TSST protocol to highlight commonalities and differences across studies. We noted significant discrepancies across studies in how researchers applied the TSST protocol. In particular, we highlight variations in testing procedures (e.g., number of judges, initial number in the arithmetic task, time of the collected saliva samples for cortisol) and discuss possible misinterpretation in comparing findings from studies failing to control for variables or using a modified version from the original protocol. Further, we recommend that researchers use a standardized background questionnaire when using the TSST to identify factors that may influence physiological measurements in tandem with a summary of this review as a protocol guide. More systematic implementation and detailed reporting of TSST methodology will promote study replication, optimize comparison of findings, and foster an informed understanding of factors affecting responses to social stressors in healthy people and those with pathological conditions.

A novel perceptual trait: gaze predilection for faces during visual exploration

Humans are social animals and typically tend to seek social interactions. In our daily life we constantly move our gaze to collect visual information which often includes social information, such as others’ emotions and intentions. Recent studies began to explore how individuals vary in their gaze behavior. However, these studies focused on basic features of eye movements (such as the length of movements) and did not examine the observer predilection for specific social features such as faces. We preformed two test-retest experiments examining the amount of time individuals fixate directly on faces embedded in images of naturally occurring scenes. We report on stable and robust individual differences in visual predilection for faces across time and tasks. Individuals’ preference to fixate on faces could not be explained by a preference for fixating on low-level salient regions (e.g. color, intensity, orientation) nor by individual differences in the Big-Five personality traits. We conclude that during visual exploration individuals vary in the amount of time they direct their gaze towards faces. This tendency is a trait that not only reflects individuals’ preferences but also influences the amount of information gathered by each observer, therefore influencing the basis for later cognitive processing and decisions.

Association of Polymorphism of Arginine-Vasopressin Receptor 1A (AVPR1a) Gene With Trust and Reciprocity

Oxytocin (OXT) is known to play an important role in trust, whereas the involvement of other peptide hormones has not been evaluated. In this study, we focused on microsatellite polymorphisms in the intron of the arginine-vasopressin receptor 1a (AVPR1a) gene and examined whether the association between the repeat lengths in the intron of AVPR1a is associated with trust and reciprocity in humans. Four-hundred and thirty-three participants played the trust game, answered the attitudinal trust question, and their buccal cells were collected. Results showed that men with a short form of AVPR1a tend to send more money to the opponent, even if there is a possibility of being betrayed by the opponent. Additionally, people with a short form of AVPR1a tended to return money to the opponent who trusts them. However, attitudinal trust was not associated with AVPR1a. These results indicate that arginine-vasopressin receptor 1a plays an important role in trust and reciprocal behaviors.

Vasopressin enhances human preemptive strike in both males and females

The neuropeptide arginine vasopressin (AVP), which is known to modulate a wide range of social behaviors in animals, has been identified as a modulator of various negative responses to social stimuli in humans. However, behavioral evidence directly supporting its involvement in human defensive aggression has been rare. We investigated the effect of intranasal AVP on defensive aggression in a laboratory experiment, using an incentivized economic game called the “preemptive strike game” (PSG). Participants played PSG individually (1 on 1) as well as in pairs (2 on 2) under either AVP or saline. We observed that exogenous but not basal AVP modulated the attack rate in PSG for both male and female participants. A model-based analysis of the aggregation of individual attack preferences into pair decisions revealed that the AVP effect on defensive aggression occurred mainly at the individual level and was not amplified at the pair level. Overall, these results present the first evidence that intranasal AVP promotes human defensive aggression for both males and females in a bilateral situation where each party can potentially damage the resources of the other party. These findings also parallel accumulating evidence from non-human animals concerning AVP’s involvement in territorial defense against potential intruders.

Anxiety-like behavior and neuropeptide receptor expression in male and female prairie voles: The effects of stress and social buffering

Strong social support can negate negative health outcomes - an effect defined as 'social buffering'. In the present study, using the socially monogamous prairie vole (Microtus ochrogaster), we examined whether the presence of a bonded partner during a stressful event can reduce stress responses. Adult, pair-bonded female and male voles were assigned into experimental groups that were either handled (Control), experienced a 1-h immobilization (IMO) stress alone (IMO-Alone), or experienced IMO with their partner (IMO-Partner). Thereafter, subjects were tested for anxiety-like behavior, and brain sections were subsequently processed for oxytocin receptor (OTR) and vasopressin V1a-type receptor (V1aR) binding. Our data indicate that while IMO stress significantly decreased the time that subjects spent in the open arms of an elevated plus maze, partner's presence prevented this behavioral change - this social buffering on anxiety-like behavior was the same for both male and female subjects. Further, IMO stress decreased OTR binding in the nucleus accumbens (NAcc), but a partner's presence dampened this effect. No effects were found in V1aR binding. These data suggest that the neuropeptide- and brain region-specific OTR alterations in the NAcc may be involved in both the mediation and social buffering of stress responses. Some sex differences in the OTR and V1aR binding were also found in selected brain regions, offering new insights into the sexually dimorphic roles of the two neuropeptides. Overall, our results suggest a potential preventative approach in which the presence of social interactions during a stressor may buffer typical negative outcomes.

Individual variation in plasma oxytocin and vasopressin levels in relation to the development of combat-related PTSD in a large military cohort

In an attempt to decrease the risk of developing mental health problems after military deployment, it is important to find biological markers to identify those at risk. Oxytocin (OT) and arginine vasopressin (AVP) are potential biomarkers for the development of posttraumatic stress disorder (PTSD) because they are involved in the regulation of stress and anxiety. Therefore, the aim was to examine whether plasma OT (pOT) and AVP (pAVP) levels before and after deployment are biomarkers for the development of posttraumatic stress symptoms over time in addition to other known risk factors. This study is part of a large prospective cohort study on candidate markers for stress-related mental health symptoms and resiliency after deployment to a combat zone; Prospective Research in Stress-related Military Operations (PRISMO; N = 907). Data was collected prior to deployment and follow-ups were performed at 1 and 6 months, and 1, 2, and 5 years post-deployment. Blood samples were collected in the first three assessments. The levels of pOT and pAVP were not significantly related to the development of PTSD symptoms over time. The results confirm that age, the experience of early life trauma, combat-related stressors and the presence of depressive symptoms are predictive for the development of PTSD symptoms over time. These findings showed that peripherally measured OT and AVP currently do not qualify as useful susceptibility biomarkers for the development of PTSD symptoms over time in military men after combat.

Associations Between Vocal Symptoms and Genetic Variants in the Oxytocin Receptor and Arginine Vasopressin 1A Receptor Gene

PURPOSE

Oxytocin and arginine vasopressin are associated with different aspects of the stress response. As stress is regarded as a risk factor for vocal symptoms, we wanted to explore the association between the oxytocin receptor gene (OXTR) and arginine vasopressin 1A receptor gene (AVPR1A) single-nucleotide polymorphisms (SNPs) and vocal symptoms. We also wanted to explore whether such effects might be mediated by cortisol because oxytocin and vasopressin are associated with cortisol levels.

METHOD

A population-based sample (N = 657) of Finnish twins (born 1961-1989) completed a web questionnaire on the occurrence of vocal symptoms. A total of 170 participants submitted saliva samples for hormone analysis. A total of 20 OXTR and AVPR1A SNPs were analyzed.

RESULTS

Three OXTR polymorphisms (rs2270465, rs2268493, rs7632287) and 2 AVPR1A polymorphisms (rs1587097, rs1042615) showed nominal effects (p < .05) on vocal symptoms, of which 1 (rs1587097) remained significant after correcting for multiple testing (p = .003). We found potential mediation of the effect of the OXTR rs2268493 polymorphism on vocal symptoms through levels of cortisol.

CONCLUSIONS

The associations between variants of OXTR and AVPR1A and vocal symptoms indicate that oxytocin and vasopressin might influence vocal symptoms. The effect of oxytocin seems to be partly mediated through cortisol actions.

Intranasal Oxytocin and Vasopressin Modulate Divergent Brainwide Functional Substrates

The neuropeptides oxytocin (OXT) and vasopressin (AVP) have been identified as modulators of emotional social behaviors and associated with neuropsychiatric disorders characterized by social dysfunction. Experimental and therapeutic use of OXT and AVP via the intranasal route is the subject of extensive clinical research. However, the large-scale functional substrates directly engaged by these peptides and their functional dynamics remain elusive. By using cerebral blood volume (CBV) weighted fMRI in the mouse, we show that intranasal administration of OXT rapidly elicits the transient activation of cortical regions and a sustained activation of hippocampal and forebrain areas characterized by high oxytocin receptor density. By contrast, intranasal administration of AVP produced a robust and sustained deactivation in cortico-parietal, thalamic and mesolimbic regions. Importantly, intravenous administration of OXT and AVP did not recapitulate the patterns of modulation produced by intranasal dosing, supporting a central origin of the observed functional changes. In keeping with this notion, hippocampal local field potential recordings revealed multi-band power increases upon intranasal OXT administration. We also show that the selective OXT-derivative TGOT reproduced the pattern of activation elicited by OXT and that the deletion of OXT receptors does not affect AVP-mediated deactivation. Collectively, our data document divergent modulation of brainwide neural systems by intranasal administration of OXT and AVP, an effect that involves key substrates of social and emotional behavior. The observed divergence calls for a deeper investigation of the systems-level mechanisms by which exogenous OXT and AVP modulate brain function and exert their putative therapeutic effects.

Dose-Dependent and Lasting Influences of Intranasal Vasopressin on Face Processing in Men

Arginine vasopressin (AVP) and related peptides have diverse effects on social behaviors in vertebrates, sometimes promoting affiliative interactions and sometimes aggressive or antisocial responses. The type of influence, in at least some species, depends on social contexts, including the sex of the individuals in the interaction and/or on the levels of peptide within brain circuits that control the behaviors. To determine if AVP promotes different responses to same- and other-sex faces in men, and if those effects are dose dependent, we measured the effects of two doses of AVP on subjective ratings of male and female faces. We also tested if any influences persist beyond the time of drug delivery. When AVP was administered intranasally on an initial test day, 20 IU was associated with decreased social assessments relative to placebo and 40 IU, and some of the effects persisted beyond the initial drug delivery and appeared to generalize to novel faces on subsequent test days. In single men, those influences were most pronounced, but not exclusive, for male faces, whereas in coupled men they were primarily associated with responses to female faces. Similar influences were not observed if AVP was delivered after placebo on a second test day. In a preliminary analysis, the differences in social assessments observed between men who received 20 and 40 IU, which we suggest primarily reflect lowered social assessments induced by the lower dose, appeared most pronounced in subjects who carry what has been identified as a risk allele for the V1a receptor gene. Together, these results suggest that AVP's effects on face processing, and possibly other social responses, differ according to dose, depend on relationship status, and may be more prolonged than previously recognized.

Mate-choice copying, social information processing, and the roles of oxytocin

Social and sexual behaviors, including that of mate choice, are dependent on social information. Mate choice can be modified by prior and ongoing social factors and experience. The mate choice decisions of one individual can be influenced by either the actual or potential mate choice of another female or male. Such non-independent mate choice, where individuals gain social information and socially learn about and recognizes potential mates by observing the choices of another female or male, has been termed "mate-choice copying". Here we first briefly review how, why, and under what circumstances individuals engage in mate-choice copying. Secondly, we review the neurobiological mechanisms underlying mate-choice copying. In particular, we consider the roles of the nonapeptide, oxytocin, in the processing of social information and the expression of mate-choice copying.

Effects of d-amphetamine upon psychosocial stress responses

Psychostimulant drugs alter the salience of stimuli in both laboratory animals and humans. In animals, stimulants increase rates of responding to conditioned incentive stimuli, and in humans, amphetamine increases positive ratings of emotional images. However, the effects of stimulants on real-life emotional events have not been studied in humans. In this study, we examined the effect of d-amphetamine on responses to acute psychosocial stress using a public speaking task. Healthy volunteers (N=56) participated in two experimental sessions, one with a psychosocial stressor (the Trier Social Stress Test) and one with a non-stressful control task. They were randomly assigned to receive d-amphetamine (5 mg n=18, 10 mg n=20) or placebo (n=18) on both sessions under double blind conditions. Salivary cortisol, subjective mood, and vital signs were measured at regular intervals during the session. Subjects also provided cognitive appraisals of the tasks before and after their performances. Amphetamine produced its expected mood and physiological effects, and the Trier Social Stress Test produced its expected effects on cortisol and mood. Although neither dose of amphetamine altered cardiovascular or hormonal responses to stress, amphetamine (10 mg) increased participants' pre-task appraisals of how challenging the task would be, and it increased post-task ratings of self-efficacy. Paradoxically, it also increased ratings of how stressful the task was, and prolonged aversive emotional responses. These findings suggest that amphetamine differentially affects stress response components: it may increase participants' appraisals of self-efficacy without dampening the direct emotional or physiological responses to the stress.

Oxytocin, but not vasopressin, impairs social cognitive ability among individuals with higher levels of social anxiety: a randomized controlled trial

Individuals with social anxiety are characterized by a high degree of social sensitivity, which can coincide with impairments in social cognitive functioning (e.g. theory of mind). Oxytocin (OT) and vasopressin (AVP) have been shown to improve social cognition, and OT has been theorized as a potential therapeutic agent for individuals with social anxiety disorder. However, no study has investigated whether these neuropeptides improve social cognitive ability among socially anxious individuals. In a randomized, double-blind, placebo controlled, between-subjects design we investigated whether social anxiety moderated the effects of OT or AVP (vs placebo) on social working memory (i.e. working memory that involves manipulating social information) and non-social working memory. OT vs placebo impaired social working memory accuracy in participants with higher levels of social anxiety. No differences were found for non-social working memory or for AVP vs placebo. Results suggest that OT administration in individuals with higher levels of social anxiety may impair social cognitive functioning. Randomized-controlled trial registration: NCT01680718.

Oxytocin modulates behavioral and physiological responses to a stressor in marmoset monkeys

Social isolation is a major source of stress and can lead to activation of the hypothalamic-pituitary-adrenal (HPA) axis. The presence of a close social partner can reduce the magnitude of the HPA-axis response during a stressor, a phenomenon known as social buffering. The oxytocin (OXT) system has been identified as one candidate for mediating social buffering due to its role in the facilitation of social bonding and the expression of prosocial behavior. The goal of the present study was to determine whether the OXT system contributes to social buffering of HPA-axis activity in response to stressor exposure in marmoset monkeys (Callithrix jacchus). Male and female marmosets experienced a standardized psychogenic stressor with and without their long-term mate under OXT-treatments (Pro(8)-OXT, Leu(8)-OXT, OXT antagonist, and saline); we assessed HPA-axis activity by measuring urinary cortisol across the stressor. We found that blocking, but not augmenting, the OXT system altered patterns of cortisol and proximity behavior in response to a stressor. We demonstrated that (1) the presence of a mate during a stressor significantly attenuated HPA-axis activity in female, but not male, marmosets; (2) male, but not female, marmosets treated with an OXT antagonist had significantly higher HPA-axis activity across the stressor than when they were treated with saline, suggesting that the OXT system may reduce the stressor-induced rise in cortisol levels; (3) male and female marmosets treated with an OXT antagonist spent significantly less time in close proximity to their mate during the first 30 min of the stressor than when they were treated with saline, suggesting that the OXT system may be important for the expression of partner-seeking behavior during a stressor. Thus, the OXT system and social context differentially influenced how the HPA-axis responded to a stressor in male and female marmosets, and may modulate HPA-axis activity by promoting the expression of proximity behavior with a close social partner.

Salivary Oxytocin and Vasopressin Levels in Police Officers With and Without Post-Traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is characterised by symptoms associated with maladaptive fear and stress responses, as well as with social detachment. The neuropeptides oxytocin (OT) and arginine vasopressin (AVP) have been associated with both regulating fear and neuroendocrine stress responsiveness and social behaviour. However, there is only limited evidence for dysregulated peripheral OT and AVP levels in PTSD patients. The present study aimed to investigate basal salivary OT and AVP levels in trauma-exposed male and female police officers with and without PTSD. Saliva samples were collected during rest and OT and AVP levels were determined using a radioimmunoassay. Men and women were analysed separately, having adjusted for differences in trauma history, and for hormonal contraception use in women. The results showed that male PTSD patients had lower basal salivary OT levels, and did not differ in AVP levels compared to male trauma-exposed healthy controls after adjusting for childhood emotional abuse. There were no significant differences in basal salivary OT and AVP levels in women. Our findings indicate potential dysfunctioning of the OT system in male PTSD patients. Future studies are needed to replicate these findings and to further unravel the relationship between the OT and AVP systems, sex, trauma history and PTSD.

An attempt to identify single nucleotide polymorphisms contributing to possible relationships between personality traits and oxytocin-related genes

BACKGROUND

The neuropeptides oxytocin and vasopressin play a central role in social behavior. Trials with intranasal oxytocin have been conducted and many indicate that the hormone facilitates affiliative behavior and trust. Intranasal oxytocin administration is suggested as a treatment option for psychiatric illnesses with altered sociability as a core symptom and the effects may be due to differences in variants of oxytocin- and vasopressin-related genes. The purpose of the present study was to investigate the endogenous oxytocin system by exploring the relationship between variants in the oxytocin gene factors and personality traits closely related to trust, anxiety and social behavior.

METHODS

72 single nucleotide polymorphisms (SNPs) in the genes coding for oxytocin (OXT), vasopressin (AVP), the oxytocin receptor (OXTR) and CD38 (CD38), including polymorphisms reported earlier to be related to social phenotypes and novel SNPs, were investigated in 196 healthy subjects. Association analysis between these variants and 3 personality traits (agreeableness, neuroticism and extraversion) measured by the Neuroticism-Extraversion-Openness Five-Factor Inventory was performed.

RESULTS

We found 7 nominally significant associations for personality traits: agreeableness [rs857240 (AVP, p = 0.0075), rs2270463 (OXTR, p = 0.047)], neuroticism [rs3756242 (CD38, p = 0.024), rs13104011 (CD38, p = 0.024), rs6816486 (CD38, p = 0.024), rs7655635 (CD38, p = 0.034)] and extraversion [rs237878 (OXTR, p = 0.019)]. None of these associations remained significant after the Bonferroni correction (p threshold = 2.31 × 10(-4)).

CONCLUSION

Our results do not contradict the hypothesis of associations between personality traits and oxytocin-related gene variants; however, there are no statistically significant associations after correcting for multiple testing, warranting replication in larger samples.

Vasopressin, but not oxytocin, increases empathic concern among individuals who received higher levels of paternal warmth: A randomized controlled trial

BACKGROUND

Empathy improves our ability to communicate in social interactions and motivates prosocial behavior. The neuropeptides arginine vasopressin and oxytocin play key roles in socioemotional processes such as pair bonding and parental care, which suggests that they may be involved in empathic processing.

METHODS

We investigated how vasopressin and oxytocin affect empathic responding in a randomized, double-blind, placebo controlled, between-subjects study design. We also examined the moderating role of parental warmth, as reported in the early family environment, on empathic responding following vasopressin, oxytocin, or placebo administration.

RESULTS

Among participants who reported higher levels of paternal warmth (but not maternal warmth), vasopressin (vs. placebo and oxytocin) increased ratings of empathic concern after viewing distressing and uplifting videos. No main or interaction effects were found for individuals who received oxytocin.

CONCLUSIONS

Vasopressin has a role in enhancing empathy among individuals who received higher levels of paternal warmth.

TRIAL REGISTRATION

NCT01680718.

Changes in social functioning and circulating oxytocin and vasopressin following the migration to a new country

Prior studies have reported associations between plasma oxytocin and vasopressin and markers of social functioning. However, because most human studies have used cross-sectional designs, it is unclear whether plasma oxytocin and vasopressin influences social functioning or whether social functioning modulates the production and peripheral release of these peptides. In order to address this question, we followed individuals who experienced major changes in social functioning subsequent to the migration to a new country. In this study, 59 new international students were recruited shortly after arrival in the host country and reassessed 2 and 5 months later. At each assessment participants provided information on their current social functioning and blood samples for oxytocin and vasopressin analysis. Results indicated that changes in social functioning were not related to changes in plasma oxytocin. Instead, baseline oxytocin predicted changes in social relationship satisfaction, social support, and loneliness over time. In contrast, plasma vasopressin changed as a function of social integration. Baseline vasopressin was not related to changes in social functioning over time. These results emphasize the different roles of plasma oxytocin and vasopressin in responses to changes in social functioning in humans.

Oxytocin and vasopressin receptor polymorphisms interact with circulating neuropeptides to predict human emotional reactions to stress

Oxytocin (OT) and a polymorphism (rs53576) in the oxytocin receptor gene (OXTR) have been independently associated with stress reactivity, whereas oxytocin's sister peptide, arginine vasopressin (AVP) and polymorphisms in the vasopressin receptor gene (AVPR1A) have been independently associated with aggressive behavior. In this study, 68 men and 98 women were genotyped for the OXTR rs53576 polymorphism and the AVPR1A RS1 polymorphism. Baseline and poststressor levels of plasma OT, plasma AVP, positive affect, and anger were assessed. Women, but not men, with high levels of poststressor OT and the GG genotype of rs53576 felt the most positive affect after the stressor. Men, but not women, with high levels of poststressor AVP and the 320 allele of the RS1 polymorphism reported more poststressor anger than noncarriers. These data constitute the first evidence that oxytocin and vasopressin receptor genes interact with levels of OT and AVP to predict sex-specific emotional stress responses.

Sex differences in the neural and behavioral response to intranasal oxytocin and vasopressin during human social interaction

Both oxytocin (OT) and vasopressin (AVP) are known to modulate social behavior, and dysfunction in both systems has been postulated as a potential cause of certain psychiatric disorders that involve social behavioral deficits. In particular, there is growing interest in intranasal OT as a potential treatment for certain psychiatric disorders, and preliminary pre-clinical and clinical studies suggest efficacy in alleviating some of the associated symptoms. However, the vast majority of research participants in these studies have been male, and there is evidence for sexually differentiated effects of nonapeptides in both humans and non-human animals. To date, no study has investigated the effect of intranasal OT on brain function in human males and females within the same paradigm. Previously, in a randomized, placebo-controlled, double-blind fMRI study, we reported effects of intranasal OT and AVP on behavior and brain activity of human males as they played an interactive social game known as the Prisoner's Dilemma Game. Here, we present findings from an identical study in human females, and compare these with our findings from males. Overall, we find that both behavioral and neural responses to intranasal OT and AVP are highly sexually differentiated. In women, AVP increased conciliatory behavior, and both OT and AVP caused women to treat computer partners more like humans. In men, AVP increased reciprocation of cooperation from both human and computer partners. However, no specific drug effects on behavior were shared between men and women. During cooperative interactions, both OT and AVP increased brain activity in men within areas rich in OT and AVP receptors and in areas playing a key role in reward, social bonding, arousal and memory (e.g., the striatum, basal forebrain, insula, amygdala and hippocampus), whereas OT and AVP either had no effect or in some cases actually decreased brain activity in these regions in women. OT treatment rendered neural responses of males more similar to responses of females in the placebo group and vice versa, raising the prospect of an inverted u-shaped dose response to central OT levels. These findings emphasize the need to fully characterize the effects of intranasal OT and AVP in both males and females and at multiple doses before widespread clinical application will be warranted.

Interaction of stress, corticotropin-releasing factor, arginine vasopressin and behaviour

Stress mediates the activation of a variety of systems ranging from inflammatory to behavioral responses. In this review we focus on two neuropeptide systems, corticotropin-releasing factor (CRF) and arginine vasopressin (AVP), and their roles in regulating stress responses. Both peptides have been demonstrated to be involved in anxiogenic and depressive effects, actions mediated in part through their regulation of the hypothalamic-pituitary-adrenal axis and the release of adrenocorticotropic hormone. Because of the depressive effects of CRF and AVP, drugs modifying the stress-associated detrimental actions of CRF and AVP are under development, particularly drugs antagonizing CRF and AVP receptors for therapy in depression.

Biological and psychological markers of stress in humans: focus on the Trier Social Stress Test

Validated biological and psychological markers of acute stress in humans are an important tool in translational research. The Trier Social Stress Test (TSST), involving public interview and mental arithmetic performance, is among the most popular methods of inducing acute stress in experimental settings, and reliably increases hypothalamic-pituitary-adrenal axis activation. However, although much research has focused on HPA axis activity, the TSST also affects the sympathetic-adrenal-medullary system, the immune system, cardiovascular outputs, gastric function and cognition. We critically assess the utility of different biological and psychological markers, with guidance for future research, and discuss factors which can moderate TSST effects. We outline the effects of the TSST in stress-related disorders, and if these responses can be abrogated by pharmacological and psychological treatments. Modified TSST protocols are discussed, and the TSST is compared to alternative methods of inducing acute stress. Our analysis suggests that multiple readouts are necessary to derive maximum information; this strategy will enhance our understanding of the psychobiology of stress and provide the means to assess novel therapeutic agents.

Effects of arginine vasopressin on musical working memory

Previous genetic studies showed an association between variations in the gene coding for the 1a receptor of the neuro-hormone arginine vasopressin (AVP) and musical working memory (WM). The current study set out to test the influence of intranasal administration (INA) of AVP on musical as compared to verbal WM using a double blind crossover (AVP—placebo) design. Two groups of 25 males were exposed to 20 IU of AVP in one session, and 20 IU of saline water (placebo) in a second session, 1 week apart. In each session subjects completed the tonal subtest from Gordon's “Musical Aptitude Profile,” the interval subtest from the “Montreal Battery for Evaluation of Amusias (MBEA),” and the forward and backward digit span tests. Scores in the digit span tests were not influenced by AVP. In contrast, in the music tests there was an AVP effect. In the MBEA test, scores for the group receiving placebo in the first session (PV) were higher than for the group receiving vasopressin in the first session (VP) (p < 0.05) with no main Session effect nor Group × Session interaction. In the Gordon test there was a main Session effect (p < 0.05) with scores higher in the second as compared to the first session, a marginal main Group effect (p = 0.093) and a marginal Group × Session interaction (p = 0.88). In addition we found that the group that received AVP in the first session scored higher on scales indicative of happiness, and alertness on the positive and negative affect scale, (PANAS). Only in this group and only in the music test these scores were significantly correlated with memory scores. Together the results reflect a complex interaction between AVP, musical memory, arousal, and contextual effects such as session, and base levels of memory. The results are interpreted in light of music's universal use as a means to modulate arousal on the one hand, and AVP's influence on mood, arousal, and social interactions on the other.

Winning and losing in public: audiences direct future success in Japanese quail

Among vertebrates, winning a fight enhances the probability of future victories and vice versa and the role of post-conflict testosterone in mediating this 'winner effect' is widely accepted. In a series of staged fights of Japanese quail (Coturnix japonica) we tested both opponents' pre-fight and post-conflict testosterone, behavior and dominance status after returning to their social groups. We found that the presence of a familiar mixed-sex audience during the encounter modulated both the testosterone response and the long-term success after a fighting experience. 'Public losers' but not 'public winners' lacked a post-conflict testosterone response, whereas without an audience both winners and losers increased testosterone metabolite levels. Long-lasting winner and loser effects exclusively occurred when the performance information was perceived by a mixed-sex audience. In further experiments we manipulated the testosterone responsiveness of either the loser or the winner. An artificial post-conflict testosterone surge after having lost a fight effectively reversed the loser effect in Japanese quail. In contrast, the 'winner effect' was not changed by blocking testosterone after the fight. Overall, male Japanese quails' post-conflict testosterone was connected to the audiences and thus, own or the observers' perception of the challenge rather than to winning or losing a fight.

Posttraumatic stress disorder and partner-specific social cognition: a pilot study of sex differences in the impact of arginine vasopressin

Posttraumatic stress disorder (PTSD) is associated with problems in intimate relationships, partly due to deficits in social cognition. In this study, the role of arginine vasopressin (AVP) in the link between PTSD and partner-specific social cognition was examined. Participants were 24 individuals from 12 heterosexual couples in which at least one partner exhibited clinically significant PTSD symptoms. Attention to partner expressions of anger was examined as an indicator of distress and need for affiliative behaviors to repair the relationship bond. AVP administration improved the speed of men's attentional engagement with their partners' expressions of anger and alleviated the negative impact of PTSD on this social cognitive process. Further, men's morning urinary AVP levels were negatively correlated with their PTSD severity. No such effects were found among women or for attention to unfamiliar men's or women's anger expressions. Thus, the AVP system may function in the relationship problems associated with PTSD.

Intranasal oxytocin attenuates the cortisol response to physical stress: a dose-response study

INTRODUCTION

Intranasal oxytocin attenuates cortisol levels during social stress inductions. However, no research to date has documented the dose-response relation between intranasal oxytocin administration and cortisol, and researchers examining intranasal oxytocin have not examined the cortisol response to physical stress. We therefore examined the effects of 24IU and 48IU of intranasal oxytocin on the cortisol response to vigorous exercise.

METHOD

Seventeen males participated in a randomized, placebo-controlled, double-blind, and within-subject experiment. Participants engaged in vigorous exercise for 60min following the administration of placebo or intranasal oxytocin on three occasions. Saliva samples and mood ratings were collected at eight intervals across each session.

RESULTS

Salivary cortisol concentrations changed over time, peaking after 60min of exercise (quadratic: F(1,16)=7.349, p=.015, partial η(2)=.32). The 24IU dose of oxytocin attenuated cortisol levels relative to placebo (F(1,16)=4.496, p=.05, partial η(2)=.22) and the 48IU dose, although the latter fell just short of statistical significance (F(1,16)=3.054, p=.10, partial η(2)=.16). There was no difference in the cortisol response to exercise in participants who were administered 48IU of intranasal oxytocin relative to placebo. Intranasal oxytocin had no effect on mood.

CONCLUSION

This is the first study to demonstrate that the effect of intranasal oxytocin on salivary cortisol is dose-dependent, and that intranasal oxytocin attenuates cortisol levels in response to physical stress. Future research using exogenous oxytocin will need to consider the possibility of dose-response relations.

Neurophysiological mechanisms underlying affiliative social behavior: insights from comparative research

Humans are intensely social animals, and healthy social relationships are vital for proper mental health (see Lim and Young, 2006). By using animal models, the behavior, mental, and physiological processes of humans can be understood at a level that cannot be attained by studying human behavior and the human brain alone. The goals of this review are threefold. First, we define affiliative social behavior and describe the primary relationship types in which affiliative relationships are most readily observed--the mother-infant bond and pair-bonding. Second, we summarize neurophysiological studies that have investigated the role of neurohypophyseal nanopeptides (oxytocin and vasopressin) and the catecholamine dopamine in regulating affiliative social behavior and the implications of said research for our understanding of human social behavior. Finally, we discuss the merits and limitations of the using a comparative approach to enhance our understanding of the mechanisms underlying human affiliative social behavior.

The animal and human neuroendocrinology of social cognition, motivation and behavior

Extensive animal and recent human research have helped inform neuroendocrinological models of social cognition, motivation and behavior. In this review, we first summarize important findings regarding oxytocin, arginine vasopressin and testosterone in the domains of affiliation, social cognition, aggression and stress/anxiety. We then suggest ways in which human research can continue to profit from animal research, particularly by exploring the interactive nature of neuromodulatory effects at neurochemical, organismic and contextual levels. We further propose methods inspired by the animal literature for the ecologically valid assessment of affiliative behavior in humans. We conclude with suggestions for how human research could advance by directly assessing specific social cognitive and motivational mechanisms as intermediate variables. We advocate a more comprehensive look at the distinct networks identified by social neuroscience and the importance of a motivational state, in addition to approach and avoidance, associated with quiescence and homeostatic regulation.

Vasopressin selectively impairs emotion recognition in men

The biological mechanisms underlying empathy, the ability to recognize emotions and to respond to them appropriately, are only recently becoming better understood. This report focuses on the nonapeptide arginine-vasopressin (AVP), which plays an important role in modulating social behavior in animals, especially promoting aggressive behavior. Towards clarifying the role of AVP in human social perception we used the Reading of the Mind in the Eyes Test and intranasal administration of AVP to show that AVP leads to a significant decrease in emotion recognition. Moreover, when comparing photos of males vs. females, all viewed by males, AVP had an effect on gender-matched photos only. Furthermore, the effect of AVP was restricted to recognition of negative emotions while leaving recognition of positive emotions unaffected. The current report emphasizes the selective role of AVP in male emotional perception and empathy, a core element in all human social interactions.

The Neurogenetics of Nice

Oxytocin, vasopressin, and their receptor genes influence prosocial behavior in the laboratory and in the context of close relationships. These peptides may also promote social engagement following threat. However, the scope of their prosocial effects is unknown. We examined oxytocin receptor ( OXTR) polymorphism rs53576, as well as vasopressin receptor 1a ( AVPR1a) polymorphisms rs1 and rs3 in a national sample of U.S. residents ( n = 348). These polymorphisms interacted with perceived threat to predict engagement in volunteer work or charitable activities and commitment to civic duty. Specifically, greater perceived threat predicted engagement in fewer charitable activities for individuals with A/A and A/G genotypes of OXTR rs53576, but not for G/G individuals. Similarly, greater perceived threat predicted lower commitment to civic duty for individuals with one or two short alleles for AVPR1a rs1, but not for individuals with only long alleles. Oxytocin, vasopressin, and their receptor genes may significantly influence prosocial behavior and may lie at the core of the caregiving behavioral system.

Oxytocin and social motivation

Humans are fundamentally social creatures who are ‘motivated’ to be with others. In this review we examine the role of oxytocin (OT) as it relates to social motivation. OT is synthesized in the brain and throughout the body, including in the heart, thymus, gastrointestinal tract, as well as reproductive organs. The distribution of the OT receptor (OTR) system in both the brain and periphery is even more far-reaching and its expression is subject to changes over the course of development. OTR expression is also sensitive to changes in the external environment and the internal somatic world. The OT system functions as an important element within a complex, developmentally sensitive biobehavioral system. Other elements include sensory inputs, the salience, reward, and threat detection pathways, the hypothalamic-pituitary-gonadal axis, and the hypothalamic-pituitary-adrenal stress response axis. Despite an ever expanding scientific literature, key unresolved questions remain concerning the interplay of the central and peripheral components of this complex biobehavioral system that dynamically engages the brain and the body as humans interact with social partners over the course of development.

Sociality, Pathogen Avoidance, and the Neuropeptides Oxytocin and Arginine Vasopressin

Both humans and nonhumans have evolved a variety of mechanisms to recognize pathogen threat and a variety of adaptive behavioral responses to minimize exposure to it. Because social interactions facilitate the spread of infection among individuals, the ability to recognize and avoid infected and potentially infected individuals is crucial. The neuropeptides oxytocin (OT) and arginine vasopressin (AVP) are involved in mediating various facets of social behavior, including social recognition and responses to salient social threats. Results of studies with rodents have revealed that OT and AVP are also associated with the olfactory-mediated recognition and avoidance of actually or potentially infected individuals. The evidence reviewed here suggests that OT and AVP likely play parallel roles in modulating the recognition and avoidance of socially relevant pathogen threat in both humans and rodents.

Oxytocin and vasopressin in the human brain: social neuropeptides for translational medicine

The neuropeptides oxytocin (OXT) and arginine vasopressin (AVP) are evolutionarily highly conserved mediators in the regulation of complex social cognition and behaviour. Recent studies have investigated the effects of OXT and AVP on human social interaction, the genetic mechanisms of inter-individual variation in social neuropeptide signalling and the actions of OXT and AVP in the human brain as revealed by neuroimaging. These data have advanced our understanding of the mechanisms by which these neuropeptides contribute to human social behaviour. OXT and AVP are emerging as targets for novel treatment approaches--particularly in synergistic combination with psychotherapy--for mental disorders characterized by social dysfunction, such as autism, social anxiety disorder, borderline personality disorder and schizophrenia.