Neurophysiological effects of acute oxytocin administration: systematic review and meta-analysis of placebo-controlled imaging studies

Oxytocin modulates hippocampal perfusion in people at clinical high risk for psychosis

Preclinical and human studies suggest that hippocampal dysfunction is a key factor in the onset of psychosis. People at Clinical High Risk for psychosis (CHR-P) present with a clinical syndrome that can include social withdrawal and have a 20-35% risk of developing psychosis in the next 2 years. Recent research shows that resting hippocampal blood flow is altered in CHR-P individuals and predicts adverse clinical outcomes, such as non-remission/transition to frank psychosis. Previous work in healthy males indicates that a single dose of intranasal oxytocin has positive effects on social function and marked effects on resting hippocampal blood flow. The present study examined the effects of intranasal oxytocin on hippocampal blood flow in CHR-P individuals. In a double-blind, placebo-controlled, crossover design, 30 CHR-P males were studied using pseudo-continuous Arterial Spin Labelling on 2 occasions, once after 40IU intranasal oxytocin and once after placebo. The effects of oxytocin on left hippocampal blood flow were examined in a region-of-interest analysis of data acquired at 22-28 and at 30-36 minutes post-intranasal administration. Relative to placebo, administration of oxytocin was associated with increased hippocampal blood flow at both time points (p = .0056; p = .034), although the effect at the second did not survive adjustment for the effect of global blood flow. These data indicate that oxytocin can modulate hippocampal function in CHR-P individuals and therefore merits further investigation as a candidate novel treatment for this group.

Clinical potential of oxytocin in autism spectrum disorder: current issues and future perspectives

The effects of oxytocin on social cognition and behavior have recently attracted considerable attention. In particular, oxytocin has been proposed as a novel therapeutic for psychiatric disorders with social deficits such as autism spectrum disorders. This review provides a brief overview of behavioral and neural responses to oxytocin manipulations in humans and animal models. Although the differences in findings between human and animal studies should be interpreted carefully, shared behavioral phenotypes have been recognized, such as social bonding, social responses, and recognition and usage of social cues. Previous literature suggests that the neural effects of oxytocin in humans and animals overlap in the prefrontal, limbic, and paralimbic cortices. Oxytocin-induced alterations in these regions may indicate a fundamental basis for how oxytocin modulates social behaviors and facilitate the discovery of new pharmaceutical targets for treating social deficits.

Variation in the Oxytocin Receptor Gene Is Associated With Social Cognition and ADHD

OBJECTIVE

Children with ADHD show substantial deficits in social cognitive abilities. Oxytocin, mediated through its specific receptor (OXTR), is involved in the regulation of social behavior and social cognition.

METHOD

The entire coding sequence of the human OXT and OXTR genes were sequenced to identify mutations and single nucleotide polymorphisms (SNPs) in 151 children with ADHD (ADHD-combined, n = 51; inattentive subtype, n = 50; ADHD-C plus conduct disorder [CD], n = 50; 11-18 years) and 100 healthy controls.

RESULTS

We examined the association of three detected SNPs of OXTR with social cognition deficits. A significant association was shown between the children with ADHD and children with CT/TT genotypes of rs4686302 (χ² = 3.695; p = .037). ADHD children with CT/TT genotype for the OXTR rs4686302 performed significantly lower on the facial emotion recognition task than those with CC genotype.

CONCLUSION

OXTR rs4686302 polymorphism was shown to be a genetic marker in social cognition deficits in ADHD children.

Evidence for intranasal oxytocin delivery to the brain: recent advances and future perspectives

The neuropeptide oxytocin plays an evolutionarily conserved role in mammalian social behavior. Despite striking effects on animal social behavior after intracerebroventricular drug delivery, this delivery mode is impractical in humans. Intranasal oxytocin delivery provides a noninvasive alternative to increase central oxytocin activity, and has shown promise as a treatment for psychiatric illnesses. Intranasal oxytocin delivery is purported to increase central oxytocin concentrations via channels surrounding trigeminal and olfactory nerve fibers, which may facilitate increased activity at central oxytocin receptors. This report outlines the evidence for intranasal oxytocin delivery increasing central concentrations or activity, identifies current knowledge gaps and highlights future research opportunities. Recent efforts to enhance intranasal oxytocin delivery via improved intranasal delivery technology and dose-ranging studies are discussed.

Oxytocin reduces neural activation in response to infant faces in nulliparous young women

Infant faces have distinctive features that together are described as baby schema, a configuration that facilitates caregiving motivation and behavior, and increases the perception of cuteness. In the current functional magnetic resonance imaging (fMRI) study, we investigated the effect of a within-subjects intranasal oxytocin administration (24 IU) and caregiving motivation on neural responses to infant faces of varying baby schema in 23 healthy nulliparous women. Overall, infant faces elicited activation in several brain regions involved in reward and salience processing, including the ventral tegmental area (VTA), putamen, amygdala, anterior cingulate cortex (ACC), and insula, and this activation was related to self-reported caregiving motivation. Critically, whereas we hypothesized enhanced neural caregiving-related responses after oxytocin administration, we observed reduced activation in the VTA, putamen and amygdala after oxytocin compared to placebo. In nulliparous women, oxytocin has been shown to reduce neural responses in the same regions in response to social stimuli using other paradigms. Oxytocin might affect neural activation toward social stimuli depending on elicited arousal and personal characteristics. The current study is the first to demonstrate this effect in response to infant faces and thereby adds to specify the role of oxytocin in human social information processing.

Pain, Parental Involvement, and Oxytocin in the Neonatal Intensive Care Unit

Preterm infants (PTI) typically experience many painful and stressful procedures or events during their first weeks of life in a neonatal intensive care unit, and these can profoundly impact subsequent brain development and function. Several protective interventions during this sensitive period stimulate the oxytocin system, reduce pain and stress, and improve brain development. This review provides an overview of the environmental risk factors experienced by PTI during hospitalization, with a focus on the effects of pain, and early maternal separation. We also describe the long-term adverse effects of the simultaneous experiences of pain and maternal separation, and the potential beneficial effects of maternal vocalizations, parental contact, and several related processes, which appear to be mediated by the oxytocin system.

Insular function in autism: Update and future directions in neuroimaging and interventions

The insular cortex, hidden within the lateral sulcus of the human brain, participates in a range of cognitive, affective, and sensory functions. Autism spectrum disorder (ASD), a neurodevelopmental condition affecting all of these functional domains, has increasingly been linked with atypical activation and connectivity of the insular cortices. Here we review the latest research linking atypical insular function to a range of behaviors characteristic of ASD, with an emphasis on neuroimaging findings in the domains of social cognition and executive function. We summarize some of the recent work linking the insula to interventions in autism, including oxytocin-based pharmacological treatments and music therapy. We suggest that future directions likely to yield significant insights into insular pathology in ASD include the analysis of the dynamics of this brain region. We also conclude that more basic research is necessary on the use of oxytocin pharmacotherapy, and larger studies addressing participant heterogeneity are needed on the use of music therapy in ASD. Long-term studies are needed to ascertain sustained effects of these interventions.

A Protective Mechanism against Illusory Perceptions Is Amygdala-Dependent

Most people have a clear sense of body ownership, preserving them from physical harm. However, perceptual body illusions - famously the rubber hand illusion (RHI) - can be elicited experimentally in healthy individuals. We hypothesize that the amygdala, a core component of neural circuits of threat processing, is involved in protective mechanisms against disturbed body perceptions. To test this hypothesis, we started by investigating two monozygotic human twin sisters with focal bilateral amygdala damage due to Urbach-Wiethe disease. Relative to 20 healthy women, the twins exhibited, on two occasions 1 year apart, augmented RHI responses in form of faster illusion onset and increased vividness ratings. Following up on these findings, we conducted a volumetric brain morphometry study involving an independent, gender-mixed sample of 57 healthy human volunteers (36 female, 21 male). Our results revealed a positive correlation between amygdala volume and RHI onset, i.e., the smaller the amygdala, the less time it took the RHI to emerge. This raised the question of whether a similar phenotype would result from experimental amygdala inhibition. To dampen amygdala reactivity, we intranasally administered the peptide hormone oxytocin to the same 57 individuals in a randomized trial before conducting the RHI. Compared with placebo, oxytocin treatment yielded enhanced RHI responses, again evident in accelerated illusion onset and increased vividness ratings. Together, the present series of experiments provides converging evidence for the amygdala's unprecedented role in reducing susceptibility to the RHI, thus protecting the organism from the potentially fatal threats of a distorted bodily self.SIGNIFICANCE STATEMENT Compelling evidence indicates that the amygdala is of vital importance for danger detection and fear processing. However, lethal threats can arise not only from menacing external stimuli but also from distortions in bodily self-perception. Intriguingly, the amygdala's modulatory role in such illusory body perceptions is still elusive. To probe the amygdala's involvement in illusory body experiences, we conducted a multi-methodological series of experiments in a rare human amygdala lesion model, complemented by a morphological and pharmaco-modulatory experiment in healthy volunteers. Our findings convergently suggest that the amygdala's integrity is indispensable for maintaining an unbiased, precise perception of our bodily self. Hence, the amygdala might shield us against distortions in self-perception and the resultant loss of behavioral control of our organism.

Oxytocin and vasopressin increase male-directed threats and vocalizations in female macaques

In a previous study, we reported that intranasal delivery of both oxytocin (OT) and arginine vasopressin (AVP) to male macaques relaxes spontaneous social interactions, flattens the existing dominance hierarchy, and increases behavioral synchrony with other monkeys. Here we report that intranasal OT and AVP administration modulates the behaviors of female macaque monkeys, but in robustly different ways from males. Most notably, both neuropeptides increase threatening and vocalization behaviors of females when they encounter males, and these behaviors effectively increase the social status of females over males. While OT and AVP heighten the confrontational nature of intersexual encounters, both peptides relax interactions between females. Finally, as previously reported for males, treating an individual female monkey with OT or AVP significantly modulates the behavior of her non-treated partner. Together, these findings show that OT and AVP can either inhibit or promote aggression, depending on sex and behavioral context, and call for a more careful, systematic examination of the functions of these neuropeptides in both sexes, especially in the context of therapeutics for human social disorders.

Oxytocin Modulates the Intrinsic Dynamics Between Attention-Related Large-Scale Networks

Attention and salience processing have been linked to the intrinsic between- and within-network dynamics of large-scale networks engaged in internal (default network [DN]) and external attention allocation (dorsal attention network [DAN] and salience network [SN]). The central oxytocin (OXT) system appears ideally organized to modulate widely distributed neural systems and to regulate the switch between internal attention and salient stimuli in the environment. The current randomized placebo (PLC)-controlled between-subject pharmacological resting-state fMRI study in N = 187 (OXT, n = 94; PLC, n = 93; single-dose intranasal administration) healthy male and female participants employed an independent component analysis approach to determine the modulatory effects of OXT on the within- and between-network dynamics of the DAN-SN-DN triple network system. OXT increased the functional integration between subsystems within SN and DN and increased functional segregation of the DN with both attentional control networks (SN and DAN). Whereas no sex differences were observed, OXT effects on the DN-SN interaction were modulated by autistic traits. Together, the findings suggest that OXT may facilitate efficient attention allocation by modulating the intrinsic functional dynamics between DN components and large-scale networks involved in external attentional demands (SN and DAN).

Oxytocin and Prader-Willi Syndrome

In the chapter, we explore the relationship between the peptide hormone, oxytocin (OT), and behavioral and metabolic disturbances observed in the genetic disorder Prader-Willi Syndrome (PWS). Phenotypic and genotypic characteristics of PWS are described, as are the potential implications of an abnormal OT system with respect to neural development including the possible effects of OT dysfunction on interactions with other regulatory mediators, including neurotransmitters, neuromodulators, and hormones. The major behavioral characteristics are explored in the context of OT dysfunction, including hyperphagia, impulsivity, anxiety and emotion dysregulation, sensory processing and interoception, repetitive and restrictive behaviors, and dysfunctional social cognition. Behavioral overlaps with autistic spectrum disorders are discussed. The implications of OT dysfunction on the mechanisms of reward and satiety and their possible role in informing behavioral characteristics are also discussed. Treatment implications and future directions for investigation are considered.

Oxytocin and brain activity in humans: A systematic review and coordinate-based meta-analysis of functional MRI studies

Oxytocin (OXT) is a neuropeptide which has a critical role in human social behaviour and cognition. Research investigating the role of OXT on functional brain changes in humans has often used task paradigms that probe socioemotional processes. Preliminary evidence suggests a central role of the amygdala in the social cognitive effects of intranasal OXT (IN-OXT), however, inconsistencies in task-design and analysis methods have led to inconclusive findings regarding a cohesive model of the neural mechanisms underlying OXT's actions. The aim of this meta-analysis was to systematically investigate these findings. A systematic search of PubMed, PsycINFO, and Scopus databases was conducted for fMRI studies which compared IN-OXT to placebo in humans. First, we systematically reviewed functional magnetic resonance imaging (fMRI) studies of IN-OXT, including studies of healthy humans, those with clinical disorders, and studies examining resting-state fMRI (rsfMRI). Second, we employed a coordinate-based meta-analysis for task-based neuroimaging literature using activation likelihood estimation (ALE), whereby, coordinates were extracted from clusters with significant differences in IN-OXT versus placebo in healthy adults. Data were included for 39 fMRI studies that reported a total of 374 distinct foci. The meta-analysis identified task-related IN-OXT increases in activity within a cluster of the left superior temporal gyrus during tasks of emotion processing. These findings are important as they implicate regions beyond the amygdala in the neural effects of IN-OXT. The outcomes from this meta-analysis can guide a priori predictions for future OXT research, and provide an avenue for targeted treatment interventions.

Oxytocin differentially modulates specific dorsal and ventral striatal functional connections with frontal and cerebellar regions

Interactions between oxytocin and the basal ganglia are central in current overarching conceptualizations of its broad modulatory effects on behavior. Whereas evidence from animal models emphasizes the critical role of the ventral striatum in the behavioral effects of oxytocin, region-specific contributions of the basal ganglia have not been systematically explored in humans. The present study combined the randomized placebo-controlled administration of oxytocin versus placebo in healthy men (n = 144) with fMRI-based resting-state functional connectivity to determine the modulatory role of oxytocin on the major basal ganglia pathways. Oxytocin specifically increased connectivity between ventral striatal and pallidal nodes with upstream frontal regions, whereas it decreased the strengths of downstream pathways between the dorsal striatum and posterior cerebellum. These pathways have previously been implicated in salience, reward and behavioral flexibility, thus shaping goal-directed behavior. Given the importance of aberrant striatal intrinsic organization in autism, addiction and schizophrenia the present findings may suggest new mechanistic perspectives for the therapeutic potential of oxytocin in these disorders.

Intranasal oxytocin in rhesus monkeys alters brain networks that detect social salience and reward

In primates, resting state functional neuroimaging (rsfcMRI) has identified several large-scale, intrinsic brain networks, including the salience network (SN), which is involved in detecting stimulus salience. Intranasal oxytocin (IN-OT) has been shown to modulate the salience and rewarding quality of social stimuli in mammals and numerous studies have shown that it can affect the functional connectivity between brain regions. Less is known, however, about how these effects unfold over time following IN-OT administration. This study used rsfcMRI in anesthetized rhesus macaques to track temporal changes in the functional connectivity between brain regions involved in the SN, including the anterior cingulate cortex (ACC), anterior insula (AI), amygdala (amy), and ventral striatum (vstr), lasting 3 hr after IN-OT or Placebo (saline) administration. We found significant temporal changes in the functional connectivity between all regions associated with treatment condition. IN-OT increased the functional connectivity between AI_vstr, ACC_amy (right hemisphere), ACC_vstr (left hemisphere), and amy_vstr (right hemisphere), but reduced the functional connectivity between ACC_AI, and the AI_amygdala. These results suggest that IN-OT may dampen salience detection in rhesus monkeys, consistent with previous findings of reduced social vigilance, while enhancing the connectivity between the SN and regions involved in processing reward.

Oxytocin enhances the pain-relieving effects of social support in romantic couples

Social support plays a vital role in physical and mental well-being. The neuropeptide hormone oxytocin (OXT) has been implicated in modulating pair-bonding and affiliative behaviors, but whether OXT contributes to the analgesic effects of a romantic partner's touch remains elusive. In the present randomized placebo-controlled, between-group, functional magnetic resonance imaging study involving 194 healthy volunteers (97 heterosexual couples), we tested the effects of intranasal OXT (24 IU) on handholding as a common mode of expressing emotional support in romantic couples. We scanned the subjects while brief electric shocks were administered. The subjects assumed that they received social support from either their romantic partner or an unfamiliar person. Unbeknown to the subject, in the partner and stranger support conditions, the same male experimenter always held the subject's left hand. Partner support was most effective in reducing the unpleasantness of electric shocks, and OXT further attenuated the unpleasantness across conditions. On the neural level, OXT significantly augmented the beneficial effects of partner support, as evidenced by a stronger decrease of neural responses to shocks in the anterior insula (AI), a stronger activity increase in the middle frontal gyrus (MFG), and a strengthened functional coupling between the AI and MFG. Our results support the notion that OXT specifically modulates the beneficial effects of social support in romantic couples by concomitantly reducing pain-associated activity and increasing activity linked to cognitive control and pain inhibition. We hypothesize that impaired OXT signaling may contribute to the experience of a lack of partner support.

Cognitive and neural facets of dissociation in a traumatized population

Dissociative phenomena are frequently experienced by psychologically traumatized people. However, little is known about the cognitive profiles of highly dissociative traumatized individuals, and corresponding patterns of neural connectivity when attentional networks are engaged in the context of emotion. One hundred seventeen traumatized women completed the multiscale dissociation inventory (MDI) and neuropsychological testing; MDI scores were used to classify high- and low-dissociative participants. Forty-six participants also underwent fMRI during performance of an attentional control task that incorporates emotionally distracting images (Affective Number Stroop; ANS). Compared to low-dissociative participants, high-dissociative participants demonstrated better performance on an executive functioning task (F1,111 = 4.64, p = .03), worse performance on a task of visual memory (F1,111 = 9.52, p = .003), and similar performance on all other neuropsychological measures. In addition, dissociative symptoms were negatively correlated with functional connectivity between the amygdala and right anterior insula in response to trauma-related ANS trials. These findings indicate that highly dissociative traumatized people experience difficulties with attentional control in the context of emotionally evocative stimuli, but in a neutral context, their overall cognitive profiles are similar to low-dissociative people. Highly dissociative participants also demonstrated weaker connectivity between the amygdala and insula in response to trauma-relevant images. Evocative, trauma-relevant stimuli appear to disrupt neutral networks involved with attention to salient cues and interoception in highly dissociative traumatized individuals. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Sex- and context-dependent effects of oxytocin on social sharing

We interact socially and form bonds with others because such experiences are rewarding. However, an insecure attachment style or social anxiety can reduce these rewarding effects. The neuropeptide oxytocin (OXT) may facilitate social interactions either by increasing their rewarding experience or by attenuating anxiety, although effects can be sex- and attachment-style dependent. In this study, 128 pairs of same-sex friends completed a social sharing paradigm in a double-blind, placebo-controlled, between-subject design with one friend inside an MRI scanner and the other in a remote behavioral testing room. In this way we could examine whether intranasal-OXT differentially modulated the emotional impact of social sharing and associated neural processing. Additionally, we investigated if OXT effects were modulated by sex and attachment style. Results showed that in women, but not men, OXT increased ratings for sharing stimuli with their friend but not with a stranger, particularly in the friend in the scanner. Corresponding neuroimaging results showed that OXT decreased both amygdala and insula activity as well as their functional connectivity in women when they shared with friends but had the opposite effect in men. On the other hand, OXT did not enhance responses in brain reward circuitry. In the PLC treated group amygdala responses in women when they shared pictures with their friend were positively associated with attachment anxiety and OXT uncoupled this. Our findings demonstrate that OXT facilitates the impact of sharing positive experiences with others in women, but not men, and that this is associated with differential effects on the amygdala and insula and their functional connections. Furthermore, OXT particularly reduced increased amygdala responses during sharing in individuals with higher attachment anxiety. Thus, OXT effects in this context may be due more to reduced anxiety when sharing with a friend than to enhanced social reward.

Oxytocin Facilitates Approach Behavior to Positive Social Stimuli via Decreasing Anterior Insula Activity

BACKGROUND

The neuropeptide oxytocin can extensively modulate human social behavior and affective processing, and its effects can be interpreted in terms of mediating approach-avoidance motivational processes. However, little is known about how oxytocin mediates approach-avoidance behavior and particularly the underlying neural mechanisms.

METHODS

In a randomized, double-blind, between-subject design, the present pharmaco-fMRI study used an approach-avoidance paradigm to investigate oxytocin's effects on approach-avoidance behavior and associated neural mechanisms.

RESULTS

Results revealed that oxytocin generally decreased activity in the right striatum irrespective of response (approach/avoidance) and social context, suggesting an inhibitory effect on motivational representation during both appetitive approach and aversive avoidance. Importantly, while on the behavioral level oxytocin selectively enhanced accuracy when approaching social positive stimuli, on the neural level it decreased left ventral and right dorsal anterior insula activity in response to social vs nonsocial positive stimuli compared with the placebo treatment. The left ventral anterior insula activity was negatively correlated with the corresponding accuracy difference scores in the oxytocin but not in the placebo group.

CONCLUSION

Given the role of the ventral anterior insula in emotional processing and the dorsal anterior insula in salience processing, the oxytocin-induced suppression of activity in these regions may indicate that oxytocin is acting to reduce interference from hyper-activity in core regions of the emotional and salience networks when approaching salient positive social stimuli and thereby to promote social interaction. Thus, oxytocin may be of potential therapeutic benefit for psychiatric disorders exhibiting avoidance of social stimuli.

Evaluation of the Social Motivation Hypothesis of Autism: A Systematic Review and Meta-analysis

Importance

The social motivation hypothesis posits that individuals with autism spectrum disorder (ASD) find social stimuli less rewarding than do people with neurotypical activity. However, functional magnetic resonance imaging (fMRI) studies of reward processing have yielded mixed results.

Objectives

To examine whether individuals with ASD process rewarding stimuli differently than typically developing individuals (controls), whether differences are limited to social rewards, and whether contradictory findings in the literature might be due to sample characteristics.

Data Sources

Articles were identified in PubMed, Embase, and PsycINFO from database inception until June 1, 2017. Functional MRI data from these articles were provided by most authors.

Study Selection

Publications were included that provided brain activation contrasts between a sample with ASD and controls on a reward task, determined by multiple reviewer consensus.

Data Extraction and Synthesis

When fMRI data were not provided by authors, multiple reviewers extracted peak coordinates and effect sizes from articles to recreate statistical maps using seed-based d mapping software. Random-effects meta-analyses of responses to social, nonsocial, and restricted interest stimuli, as well as all of these domains together, were performed. Secondary analyses included meta-analyses of wanting and liking, meta-regression with age, and correlations with ASD severity. All procedures were conducted in accordance with Meta-analysis of Observational Studies in Epidemiology guidelines.

Main Outcomes and Measures

Brain activation differences between groups with ASD and typically developing controls while processing rewards. All analyses except the domain-general meta-analysis were planned before data collection.

Results

The meta-analysis included 13 studies (30 total fMRI contrasts) from 259 individuals with ASD and 246 controls. Autism spectrum disorder was associated with aberrant processing of both social and nonsocial rewards in striatal regions and increased activation in response to restricted interests (social reward, caudate cluster: d = -0.25 [95% CI, -0.41 to -0.08]; nonsocial reward, caudate and anterior cingulate cluster: d = -0.22 [95% CI, -0.42 to -0.02]; restricted interests, caudate and nucleus accumbens cluster: d = 0.42 [95% CI, 0.07 to 0.78]).

Conclusions and Relevance

Individuals with ASD show atypical processing of social and nonsocial rewards. Findings support a broader interpretation of the social motivation hypothesis of ASD whereby general atypical reward processing encompasses social reward, nonsocial reward, and perhaps restricted interests. This meta-analysis also suggests that prior mixed results could be driven by sample age differences, warranting further study of the developmental trajectory for reward processing in ASD.

Imaging neuropeptide effects on human brain function

The discovery of prosocial effects of oxytocin (OT) opened new directions for studying neuropeptide effects on the human brain. However, despite obvious effects of OT on neural responses as reported in numerous studies, other peptides have received less attention. Therefore, we will only briefly summarize evidence of OT effects on human functional magnetic resonance imaging (fMRI) and primarily focus on OT's sister neuropeptide arginine-vasopressin by presenting our own coordinated-based activation likelihood estimation meta-analysis. In addition, we will recapitulate rather limited data on few other neuropeptides, including pharmacological and genetic fMRI studies. Finally, we will review experiments with external neuropeptide administration to patients afflicted with mental disorders, such as autism or schizophrenia. In conclusion, despite remaining uncertainty regarding the penetrance of exogenous neuropeptides through the blood-brain barrier, it is evident that neuropeptides simultaneously influence the activity of limbic and cortical areas, indicating that these systems have a good potential for therapeutic drug development. Hence, this calls for further systematic studies of a wide spectrum of known and less known neuropeptides to understand their normal function in the brain and, subsequently, to tackle their potential contribution for pathophysiological mechanisms of mental disorders.

Social Skills Deficits in Autism Spectrum Disorder: Potential Biological Origins and Progress in Developing Therapeutic Agents

Autism spectrum disorder is defined by two core symptoms: a deficit in social communication and the presence of repetitive behaviors and/or restricted interests. Currently, there is no US Food and Drug Administration-approved drug for these core symptoms. This article reviews the biological origins of the social function deficit associated with autism spectrum disorder and the drug therapies with the potential to treat this deficit. A review of the history of autism demonstrates that a deficit in social interaction has been the defining feature of the concept of autism from its conception. Abnormalities identified in early social skill development and an overview of the pathophysiology abnormalities associated with autism spectrum disorder are discussed as are the abnormalities in brain circuits associated with the social function deficit. Previous and ongoing clinical trials examining agents that have the potential to improve social deficits associated with autism spectrum disorder are discussed in detail. This discussion reveals that agents such as oxytocin and propranolol are particularly promising and undergoing active investigation, while other agents such as vasopressin agonists and antagonists are being activity investigated but have limited published evidence at this time. In addition, agents such as bumetanide and manipulation of the enteric microbiome using microbiota transfer therapy appear to have promising effects on core autism spectrum disorder symptoms including social function. Other pertinent issues associated with developing treatments in autism spectrum disorder, such as disease heterogeneity, high placebo response rates, trial design, and the most appropriate way of assessing effects on social skills (outcome measures), are also discussed.

Oxytocin Enhancement of Emotional Empathy: Generalization Across Cultures and Effects on Amygdala Activity

Accumulating evidence suggests that the neuropeptide oxytocin (OXT) can enhance empathy although it is unclear which specific behavioral and neural aspects are influenced, and whether the effects are modulated by culture, sex, and trait autism. Based on previous findings in Caucasian men, we hypothesized that a single intranasal dose of OXT would specifically enhance emotional empathy (EE) via modulatory effects on the amygdala in an Asian (Chinese) population and explored the modulatory role of sex and trait autism on the effects. We first conducted a double-blind, randomized between-subject design experiment using a modified version of the multifaceted empathy task to determine whether OXT’s facilitation of EE can be replicated in Chinese men (n = 60). To further explore neural mechanisms behind and potential sex differences, functional MRI and skin conductance measures were acquired in an independent experiment incorporating men and women (n = 72). OXT enhanced EE across experiments and sex, an effect that was accompanied by reduced amygdala activity and increased skin conductance responses. On the network level OXT enhanced functional coupling of the right amygdala with the insula and posterior cingulate cortex for positive valence stimuli but attenuated coupling for negative valence stimuli. The effect of OXT on amygdala functional connectivity with the insula was modulated by trait autism. Overall, our findings provide further support for the role of OXT in facilitating EE and demonstrate that effects are independent of culture and sex and involve modulatory effects on the amygdala and its interactions with other key empathy regions.

Divergent effects of oxytocin on (para-)limbic reactivity to emotional and neutral scenes in females with and without borderline personality disorder

Borderline personality disorder (BPD) patients’ hypersensitivity for emotionally relevant stimuli has been suggested be due to abnormal activity and connectivity in (para-)limbic and prefrontal brain regions during stimulus processing. The neuropeptide oxytocin has been shown to modulate activity and functional connectivity in these brain regions, thereby optimizing the processing of emotional and neutral stimuli. To investigate whether oxytocin would be capable of attenuating BPD patients’ hypersensitivity for such stimuli, we recorded brain activity and gaze behavior during the processing of complex scenes in 51 females with and 48 without BPD after intranasal application of either oxytocin or placebo. We found divergent effects of oxytocin on BPD and healthy control (HC) participants’ (para-)limbic reactivity to emotional and neutral scenes: Oxytocin decreased amygdala and insula reactivity in BPD participants but increased it in HC participants, indicating an oxytocin-induced normalization of amygdala and insula activity during scene processing. In addition, oxytocin normalized the abnormal coupling between amygdala activity and gaze behavior across all scenes in BPD participants. Overall, these findings suggest that oxytocin may be capable of attenuating BPD patients’ hypersensitivity for complex scenes, irrespective of their valence.

Oxytocin and vasopressin flatten dominance hierarchy and enhance behavioral synchrony in part via anterior cingulate cortex

The neuropeptides oxytocin (OT) and arginine vasopressin (AVP) influence social functions in many mammals. In humans and rhesus macaques, OT delivered intranasally can promote prosocial behavior in certain contexts. Yet the precise neural mechanisms mediating these behavioral effects remain unclear. Here we show that treating a group of male macaque monkeys intranasally with aerosolized OT relaxes their spontaneous social interactions with other monkeys. OT reduces differences in social behavior between dominant and subordinate monkeys, thereby flattening the status hierarchy. OT also increases behavioral synchrony within a pair. Intranasal delivery of aerosolized AVP reproduces the effects of OT with greater efficacy. Remarkably, all behavioral effects are replicated when OT or AVP is injected focally into the anterior cingulate gyrus (ACCg), a brain area linked to empathy and other-regarding behavior. ACCg lacks OT receptors but is rich in AVP receptors, suggesting exogenous OT may shape social behavior, in part, via nonspecific binding. Notably, OT and AVP alter behaviors of both the treated monkey and his untreated partner, consistent with enhanced feedback through reciprocal social interactions. These findings bear important implications for use of OT in both basic research and as a therapy for social impairments in neurodevelopmental disorders.

Neural substrates underlying the effects of oxytocin: a quantitative meta-analysis of pharmaco-imaging studies

The hypothalamic peptide oxytocin (OT) is crucial in social adaptation and used to treat emotional and social deficits. Here, we conducted a systematic, quantitative meta-analysis of functional-MRI studies intranasally administering OT (IN-OT) to uncover neural substrates underlying the IN-OT effects and to elucidate differential IN-OT effects between healthy and clinical populations. Meta-analyses were conducted on 66 IN-OT fMRI studies, stratified by psychopathology, valence and sex. IN-OT increased bilateral amygdala, caudate head, and superior temporal activity in healthy individuals and increased dorsal anterior cingulate activity in patients. Moreover, IN-OT decreased amygdala activity in both patients and healthy individuals but did so to a greater degree in patients than healthy individuals. The OT-increased amygdala activity was only found on the negative social and affective processes, whereas the OT-decreased amygdala activity was mainly contributed by contrasts on negative-valenced processes. IN-OT increased parahippocampal activity and decreased amygdala activity during negative socio-affective processing. During positive socio-affective processes, IN-OT increased caudate head activity. This study indicates convergent neural substrates and the underlying neuropsychological mechanisms for IN-OT effects on social and affective processes. The common and different effects of IN-OT on patients and healthy individuals and the modulation of OT effects by valence have critical implications.

Intranasal Oxytocin Selectively Modulates Large-Scale Brain Networks in Humans

A growing body of evidence indicates that the neuropeptide oxytocin (OT) alters the neural correlates of socioemotional and salience processing. Yet the effects of OT over important large-scale networks involved in these processes, such as the default mode (DM), ventral attention (VA), and cingulo-opercular (CO) networks, remain unknown. Therefore, we conducted a placebo-controlled crossover study with intranasal 24 IU OT in 38 healthy male subjects using a resting-state functional magnetic resonance imaging paradigm to investigate its impact over these three networks candidates. To understand the underlying mechanisms of the neuropeptide, we compared the intranetwork connectivity for each network candidate and also the internetwork connectivity across all networks between both treatment conditions. Based on the relevance of interindividual factors for OT effects, we correlated individual network changes with behavioral performance in a decision-making task and with impulsivity scores. Our results show that OT mainly alters connectivity in the VA, on one side reducing the coupling to regions that typically form the nodes of DM, an introspective and self-referential network, and on the other side increasing the coupling to the edges of the CO, which is involved in salience processing. The results of the internetwork analyses confirmed the specificity of the OT effects. Indeed, we observed significant correlations with the erroneous performance during decision-making but not with the obtained impulsivity scores. Overall, our data support that the modulation of functional connectivity within the VA is a basic mechanism by which OT directs attentional resources from internal to external cues, preparing the brain for context-dependent salience processing.

Endogenous testosterone and exogenous oxytocin influence the response to baby schema in the female brain

Nurturing behavior may be critically influenced by the interplay of different hormones. The neuropeptide oxytocin is known to promote maternal behavior and its reduction has been associated with postpartum depression risk and child neglect. Contrariwise, the observed decrease in testosterone level during early parenthood may benefit caretaking behavior, whereas increased testosterone may reduce attention to infants. Here we used functional magnetic resonance imaging to investigate the interactive influence of testosterone and oxytocin on selective attention to and neural processing of the baby schema (BS). 57 nulliparous women performed a target detection task with human faces with varying degree of BS following double-blinded placebo-controlled oxytocin administration in a between-subjects design. Our results support the idea that oxytocin enhances attention to the BS. Oxytocin had a positive effect on activation of the inferior frontal junction during identification of infant targets with a high degree of BS that were presented among adult distractors. Further, activation of the putamen was positively correlated with selective attention to the BS, but only in women with high endogenous testosterone who received oxytocin. These findings provide initial evidence for the neural mechanism by which oxytocin may counteract the negative effects of testosterone in the modulation of nurturing behavior.

Oxytocin promotes face-sensitive neural responses to infant and adult faces in mothers

Research utilizing intranasal oxytocin (OT) administration has shown that OT may increase attention and sensitivity to social cues, such as faces. Given the pivotal role of OT in parental behaviors across mammals, the paucity of intranasal OT research investigating responses to social cues in parents and particularly mothers of young children is a critical limitation. In the current study, we recorded cortical event-related potentials (ERPs) to investigate whether intranasal OT affects the early neural responses to emotional faces in mothers of 1-year-old infants. Using a double-blind, within-subjects design, mothers (n = 38) were administered intranasal OT and placebo on separate sessions and presented with happy and sad infant and adult faces while ERP components reflecting face-sensitive brain activation and attention allocation were measured. We hypothesized that ERP responses to faces would be larger in the OT condition and that the effects of OT on ERP responses would be more pronounced for infant faces. The amplitudes of the face-sensitive N170 ERP component were larger in the OT condition to infant and adult faces, but no clear support was found for the hypothesis that the responses to infant faces would be more susceptible to OT effects than the responses to adult faces. The attention-sensitive late positive potential (LPP) component was not modulated by intranasal substance condition. The results are in line with the view that OT acts to enhance the perceptual salience of social and emotional stimuli. Demonstrating such effects in mothers of young children encourages further investigation of the potential of intranasal OT to affect the perception of social cues relevant for parent-child interaction.

Deciphering the modulatory role of oxytocin in human altruism

Unlike any other species, humans frequently engage in altruistic behaviors by which they increase another individual's welfare even if this implies personal costs. The psychological motives underlying altruistic behaviors remain diverse, ranging from the ability to reciprocate trust and cooperation to bonding and empathizing with family members or even genetically unrelated others. This article explores the neuroendocrine architecture of altruism by emphasizing the crucial role of the evolutionarily highly conserved peptide hormone oxytocin as a modulator of cooperative behaviors including empathy-driven altruism. However, accumulating evidence suggests that oxytocin does not invariably facilitate cooperation but also produces protective or even defensive-aggressive responses in specific social contexts. In addition, we highlight the relevance of message frames as critical determinants of whether the peptide promotes altruism toward prosocial ends.

The effect of intranasal oxytocin on neural response to facial emotions in healthy adults as measured by functional MRI: A systematic review

Abnormalities in responses to human facial emotions are associated with a range of psychiatric disorders. Addressing these abnormalities may therefore have significant clinical applications. Previous meta-analyses have demonstrated effects of the neuropeptide oxytocin on behavioural response to facial emotions, and effects on brain, as measured by functional MRI. Evidence suggests that these effects may be mediated by sex and the role of eye gaze. However, the specific effect of oxytocin on brain response to facial emotions in healthy adults has not been systematically analysed. To address this question, this further systematic review was conducted. Twenty-two studies met our inclusion criteria. In men, oxytocin consistently attenuated brain activity in response to negative emotional faces, particularly fear, compared with placebo, while in women, oxytocin enhanced activity. Brain regions consistently involved included the amygdala, fusiform gyrus and anterior cingulate cortex. In some studies, oxytocin increased fixation changes towards the eyes with enhanced amygdala and/or fusiform gyrus activation. By enhancing understanding of emotion processing in healthy subjects, these pharmacoimaging studies provide a theoretical basis for studying deficits in clinical populations. However, progress to date has been limited by low statistical power, methodological heterogeneity, and a lack of multimodal studies.

Bumetanide for autism: more eye contact, less amygdala activation

We recently showed that constraining eye contact leads to exaggerated increase of amygdala activation in autism. Here, in a proof of concept pilot study, we demonstrate that administration of bumetanide (a NKCC1 chloride importer antagonist that restores GABAergic inhibition) normalizes the level of amygdala activation during constrained eye contact with dynamic emotional face stimuli in autism. In addition, eye-tracking data reveal that bumetanide administration increases the time spent in spontaneous eye gaze during in a free-viewing mode of the same face stimuli. In keeping with clinical trials, our data support the Excitatory/Inhibitory dysfunction hypothesis in autism, and indicate that bumetanide may improve specific aspects of social processing in autism. Future double-blind placebo controlled studies with larger cohorts of participants will help clarify the mechanisms of bumetanide action in autism.

Oxytocin selectively modulates brain processing of disgust in Huntington's disease gene carriers

People with Huntington's disease (HD) exhibit altered processing of emotional information, especially disgust and other negative emotions. These impairments are likely due to the effects of the disease on underlying brain networks. We examined whether oxytocin, when given intranasally, would normalise aberrant brain reactivity to emotional faces in participants with the gene-expansion for HD. In a double-blind placebo-controlled cross-over design, we measured brain activity, using functional magnetic resonance imaging, whilst nine medication-free HD carriers, and ten control participants viewed emotional (disgust, fear, angry, sad, surprise, happy) and neutral faces, following acute intranasal oxytocin (24IU) and placebo. Subjective mood changes were assessed before and after the neuroimaging on each visit. Permutation-based non-parametric statistical testing for the whole brain, showed significant group×drug interactions (p's<0.05, TFCE corrected) in areas of the left frontal pole, superior frontal, and middle frontal gyri cortically, and left putamen and thalamus sub-cortically. Parameter estimates extracted from the middle frontal gyrus and putamen showed that, under placebo, the HD group had lower brain activity to disgust stimuli, compared with controls. After intranasal oxytocin, the pattern of activation to disgust stimuli was normalised in the HD group to similar levels as controls; eight of the nine HD carriers showed increased response in the middle frontal gyrus, and seven of the nine HD carriers showed increased response in the putamen. The observed effects of oxytocin occurred in the absence of changes in subjective mood or state anxiety. These findings provide early evidence for a physiological role of oxytocin in the neuropathology of HD. Our findings are the first reported oxytocin effects in a neurodegenerative disease. Further research should examine the therapeutic benefits of oxytocin in alleviating emotional and social cognition deficits in HD and related disorders.

Effects of Intranasal Oxytocin on the Blood Oxygenation Level-Dependent Signal in Food Motivation and Cognitive Control Pathways in Overweight and Obese Men

Recent research indicates that the hypothalamic neuropeptide hormone oxytocin is a key central nervous system factor in the regulation of food intake and weight. However, the mechanisms underlying the anorexigenic effects of oxytocin in humans are unknown and critical to study to consider oxytocin as a neurohormonal weight loss treatment. We performed a randomized, double-blind, placebo-controlled crossover study with single-dose intranasal oxytocin (24 IU) in ten overweight or obese, otherwise healthy men. Following oxytocin/placebo administration, participants completed an established functional magnetic resonance imaging food motivation paradigm. We hypothesized that oxytocin would reduce the blood oxygenation level-dependent (BOLD) signal to high-calorie food vs non-food visual stimuli in the ventral tegmental area (VTA), the origin of the mesolimbic dopaminergic reward system. Following oxytocin administration, compared to placebo, participants showed bilateral VTA hypoactivation to high-calorie food stimuli. A secondary exploratory whole-brain analysis revealed hypoactivation in additional hedonic (orbitofrontal cortex, insula, globus pallidus, putamen, hippocampus, and amygdala) and homeostatic (hypothalamus) food motivation and hyperactivation in cognitive control (anterior cingulate and frontopolar cortex) brain regions following oxytocin administration vs placebo. Oxytocin administration reduces the BOLD signal in reward-related food motivation brain regions, providing a potential neurobiological mechanism for the anorexigenic oxytocin effects in humans. Furthermore, our data indicate that oxytocin administration reduces activation in homeostatic and increases activation in cognitive control brain regions critically involved in regulating food intake and resolving affective conflict, respectively. Future studies are required to link these changes in brain activation to oxytocin effects on food intake and weight.

Intranasal oxytocin, social cognition and neurodevelopmental disorders: A meta-analysis

Deficits in social cognition are pervasive and characteristic of neurodevelopmental disorders (NDDs). Clinical trials of intranasal oxytocin (IN-OT) to improve social cognition have yielded inconclusive results. The current study is a meta-analysis of randomized controlled trials (RCTs) considering the effect of IN-OT on social cognitive domains across a range of NDDs. Medline, PsychINFO and Scopus were searched for RCTs published through to July 25, 2017. Seventeen studies met inclusion criteria, comprising 466 participants with a NDD. Meta-analysis using a random-effects model, revealed that IN-OT had no significant effect on emotion recognition (Hedges' g=0.08), a moderate but non-significant effect on empathy (Hedges' g=0.49), and a small, significant effect on theory of mind (ToM) (Hedges' g=0.21). Meta-regression indicated that the effect of IN-OT on social cognition was not moderated by the diagnosis or age of participants, or the dose or frequency of IN-OT administration. The results highlight a need for more well-designed RCTs, as it remains difficult to draw conclusions about the potential for IN-OT to improve social cognition in NDDs. The promise of IN-OT should be considered tentative.

Oxytocin by intranasal and intravenous routes reaches the cerebrospinal fluid in rhesus macaques: determination using a novel oxytocin assay

Oxytocin (OT) is a potential treatment for multiple neuropsychiatric disorders. As OT is a peptide, delivery by the intranasal (IN) route is the preferred method in clinical studies. Although studies have shown increased cerebrospinal fluid (CSF) OT levels following IN administration, this does not unequivocably demonstrate that the peripherally administered OT is entering the CSF. For example, it has been suggested that peripheral delivery of OT could lead to central release of endogenous OT. It is also unknown whether the IN route provides for more efficient entry of the peptide into the CSF compared to the intravenous (IV) route, which requires blood-brain barrier penetration. To address these questions, we developed a sensitive and specific quantitative mass spectrometry assay that distinguishes labeled (d5-deuterated) from endogenous (d0) OT. We administered d5 OT (80 IU) to six nonhuman primates via IN and IV routes as well as IN saline as a control condition. We measured plasma and CSF concentrations of administered and endogenous OT before (t=0) and after (t=10, 20, 30, 45 and 60 min) d5 OT dosing. We demonstrate CSF penetrance of d5, exogenous OT delivered by IN and IV administration. Peripheral administration of d5 OT did not lead to increased d0, endogenous OT in the CSF. This suggests that peripheral administration of OT does not lead to central release of endogenous OT. We also did not find that IN administration offered an advantage compared to IV administration with respect to achieving greater CSF concentrations of OT.

Rebalancing the Addicted Brain: Oxytocin Interference with the Neural Substrates of Addiction

Drugs that act on the brain oxytocin (OXT) system may provide a much-needed treatment breakthrough for substance-use disorders. Targeting the brain OXT system has the potential to treat addiction to all major classes of addictive substance and to intervene across all stages of the addiction cycle. Emerging evidence suggests that OXT is able to interfere with such a wide range of addictive behaviours for such a wide range of addictive substances by rebalancing core neural systems that become dysregulated over the course of addiction. By improving our understanding of these interactions between OXT and the neural substrates of addiction, we will not only improve our understanding of addiction, but also our ability to effectively treat these devastating disorders.

Clinical and therapeutic role of mentalization in schizophrenia-a review

Recent empirical findings from clinical and genetic studies suggest that mentalization, a key area of social cognition, is a distinct construct, although it is closely related to the neurocognitive deficits and symptoms of schizophrenia. Mentalization contributes a great deal to impaired social functioning. Current measures often display methodological problems, and many aspects should be taken into account when assessing mentalization. Moreover, advances in cognitive and affective neurosciences have led to the development of more advanced behavioral methods to assess the relationship between cognitive functions, symptoms, and social cognition based on their underlying neural mechanisms. The development of assessment tools that better examine the neural circuitry of such relationships may lead to the development of new psychosocial and pharmacological treatments.

Intensive Care Unit Delirium and Intensive Care Unit-Related Posttraumatic Stress Disorder

Delirium is one of the most common behavioral manifestations of acute brain dysfunction in the intensive care unit (ICU) and is a strong predictor of worse outcome. Routine monitoring for delirium is recommended for all ICU patients using validated tools. In delirious patients, a search for all reversible precipitants is the first line of action and pharmacologic treatment should be considered when all causes have been ruled out, and it is not contraindicated. Long-term morbidity has significant consequences for survivors of critical illness and for their caregivers. ICU patients may develop posttraumatic stress disorder related to their critical illness experience.

Intranasal oxytocin increases neural responses to social reward in post-traumatic stress disorder

Therapeutic alliance and perceived social support are important predictors of treatment response for post-traumatic stress disorder (PTSD). Intranasal oxytocin administration may enhance treatment response by increasing sensitivity for social reward and thereby therapeutic alliance and perceived social support. As a first step to investigate this therapeutical potential, we investigated whether intranasal oxytocin enhances neural sensitivity to social reward in PTSD patients. Male and female police officers with (n = 35) and without PTSD (n = 37) were included in a double-blind, randomized, placebo-controlled cross-over fMRI study. After intranasal oxytocin (40 IU) and placebo administration, a social incentive delay task was conducted to investigate neural responses during social reward and punishment anticipation and feedback. Under placebo, PTSD patients showed reduced left anterior insula (AI) responses to social rewards (i.e. happy faces) compared with controls. Oxytocin administration increased left AI responses during social reward in PTSD patients, such that PTSD patients no longer differed from controls under placebo. Furthermore, in PTSD patients, oxytocin increased responses to social reward in the right putamen. By normalizing abberant insula responses and increasing putamen responses to social reward, oxytocin administration may enhance sensitivity for social support and therapeutic alliance in PTSD patients. Future studies are needed to investigate clinical effects of oxytocin.

The effects of adjunctive intranasal oxytocin in patients with schizophrenia

OBJECTIVES

Both human and animal studies have suggested that oxytocin may have therapeutic potential in the treatment of schizophrenia. We evaluated the effects of intranasal oxytocin on cognition and its predictive factors in Japanese patients with schizophrenia.

METHODS

Subjects were 16 chronic schizophrenia patients who underwent intranasal oxytocin treatment for 3 months and were assessed for changes in severity of clinical symptoms and cognitions. Fifteen of the 16 subjects underwent 3-Tesla magnetic resonance imaging.

RESULTS

Oxytocin significantly reduced scores on the positive and negative syndrome scale, especially on the negative symptoms. As for cognition, there was an improvement of the verbal fluency. Furthermore, the change of the negative score in positive and negative syndrome scale showed a negative correlation with the gray matter volumes of the right insula and left cingulate cortex.

CONCLUSIONS

Our results indicate that daily administration of intranasal oxytocin may be effective for ameliorating clinical symptoms and cognitive functions in chronic schizophrenia patients, and this improvement may be related to the gray matter volume of the right insula and left cingulate cortex.

Effects of oxytocin and vasopressin on the neural response to unreciprocated cooperation within brain regions involved in stress and anxiety in men and women

Anxiety disorders are characterized by hyperactivity in both the amygdala and the anterior insula. Interventions that normalize activity in these areas may therefore be effective in treating anxiety disorders. Recently, there has been significant interest in the potential use of oxytocin (OT), as well as vasopressin (AVP) antagonists, as treatments for anxiety disorders. In this double-blind, placebo-controlled, pharmaco- fMRI study, 153 men and 151 women were randomized to treatment with either 24 IU intranasal OT, 20 IU intranasal AVP, or placebo and imaged with fMRI as they played the iterated Prisoner's Dilemma game with same-sex human and computer partners. In men, OT attenuated the fMRI response to unreciprocated cooperation (CD), a negative social interaction, within the amygdala and anterior insula. This effect was specific to interactions with human partners. In contrast, among women, OT unexpectedly attenuated the amygdala and anterior insula response to unreciprocated cooperation from computer but not human partners. Among women, AVP did not significantly modulate the response to unreciprocated cooperation in either the amygdala or the anterior insula. However, among men, AVP attenuated the BOLD response to CD outcomes with human partners across a relatively large cluster including the amygdala and the anterior insula, which was contrary to expectations. Our results suggest that OT may decrease the stress of negative social interactions among men, whereas these effects were not found in women interacting with human partners. These findings support continued investigation into the possible efficacy of OT as a treatment for anxiety disorders.

Sex-dependent neural effect of oxytocin during subliminal processing of negative emotion faces

In line with animal models indicating sexually dimorphic effects of oxytocin (OXT) on social-emotional processing, a growing number of OXT-administration studies in humans have also reported sex-dependent effects during social information processing. To explore whether sex-dependent effects already occur during early, subliminal, processing stages the present pharmacological fMRI-study combined the intranasal-application of either OXT or placebo (n = 86-43 males) with a backward-masking emotional face paradigm. Results showed that while OXT suppressed inferior frontal gyrus, dorsal anterior cingulate and anterior insula responses to threatening face stimuli in men it increased them in women. In women increased anterior cingulate reactivity during subliminal threat processing was also positively associated with trait anxiety. On the network level, sex-dependent effects were observed on amygdala, anterior cingulate and inferior frontal gyrus functional connectivity that were mainly driven by reduced coupling in women following OXT. Our findings demonstrate that OXT produces sex-dependent effects even at the early stages of social-emotional processing, and suggest that while it attenuates neural responses to threatening social stimuli in men it increases them in women. Thus in a therapeutic context OXT may potentially produce different effects on anxiety disorders in men and women.

Oxytocin and Anxiety Disorders: Translational and Therapeutic Aspects

PURPOSE OF REVIEW

This review aims to evaluate the most recent literature examining the oxytocin (OXT) system's role in human anxiety by surveying various fields of preclinical and clinical research supporting this role, and queries whether the OXT system might be a target for novel anxiolytics.

RECENT FINDINGS

Evidence from the diverse body of literature presented here, from translational research, genetic and neuroimaging studies, to clinical trials of intranasal (IN) OXT reveals a positive association. In addition, some moderators (e.g., sex, specificities to cues) of OXT's anxiolytic effects can have an important influence on its outcomes, awaiting further research. Evidence for the role of OXT in regulating anxiety is undeniable. We expect that the diverse particularities of the OXT system will help broaden our understanding of anxiety and stress-related disorders. We conclude that OXT promises an enticing treatment option for human anxiety disorders especially those associated with socio-emotional dysfunctions.