The Social Salience Hypothesis of Oxytocin

Does oxytocin lead to emotional interference during a working memory paradigm?

BACKGROUND

Oxytocin administration may increase attention to emotional information. We hypothesized that this augmented emotional processing might in turn lead to interference on concurrent cognitive tasks. To test this hypothesis, we examined whether oxytocin administration would lead to heightened emotional interference during a working memory paradigm. Additionally, moderating effects of childhood maltreatment were explored.

METHODS

Seventy-eight healthy males received 24 IU of intranasal oxytocin or placebo in a randomized placebo-controlled double-blind between-subjects study. A working memory task was performed during which neutral, positive, and negative distractors were presented.

RESULTS

The main outcome observed was that oxytocin did not enhance interference by emotional information during the working memory task. There was a non-significant trend for oxytocin to slow down performance irrespective of distractor valence, while accuracy was unaffected. Exploratory analyses showed that childhood maltreatment was related to lower overall accuracy, but in the placebo condition only. However, the maltreated group sample size was very small precluding any conclusions on its moderating effect.

CONCLUSIONS

Despite oxytocin's previously proposed role in enhanced emotional processing, no proof was found that this would lead to reduced performance on a concurrent cognitive task. The routes by which oxytocin exerts its effects on cognitive and social-emotional processes remain to be fully elucidated.

Oxytocin and Olfaction

Social signals are identified through processing in sensory systems to trigger appropriate behavioral responses. Social signals are received primarily in most mammals through the olfactory system. Individuals are recognized based on their unique blend of odorants. Such individual recognition is critical to distinguish familiar conspecifics from intruders and to recognize offspring. Social signals can also trigger stereotyped responses like mating behaviors. Specific sensory pathways for individual recognition and eliciting stereotyped responses have been identified both in the early olfactory system and its connected cortices. Oxytocin is emerging as a major state modulator of sensory processing with distinct functions in early and higher olfactory brain regions. The brain state induced through Oxytocin influences social perception. Oxytocin acting on different brain regions can promote either exploration and recognition towards same- or other-sex conspecifics, or association learning. Region-specific deletion of Oxytocin receptors suffices to disrupt these behaviors. Together, these recent insights highlight that Oxytocin's function in social behaviors cannot be understood without considering its actions on sensory processing.

Oxytocin and Facial Emotion Recognition

The expression of emotion in faces serves numerous meaningful functions, such as conveying messages of danger or approach, facilitating communication, and promoting the formation of social bonds and relationships. The study of facial expressions of emotion has become integral to research in social psychology and social neuroscience, particularly with respect to the neuropeptide oxytocin. This chapter examines how oxytocin influences the processing of emotion in faces by reviewing intranasal administration studies of automatic processing, selective attention, and emotion recognition. Two important trends in the literature have been identified: exogenous oxytocin attenuates early attentional biases towards negative stimuli and increases selective attention and recognition of emotional cues in faces, particularly around the eyes. Both of these effects can be traced to well-delineated neural circuits involving amygdala, early visual processing areas, and reward circuits, and both purportedly facilitate approach-related behavior when affiliative opportunities are available. These data are integrated into a conceptual model incorporating contextual factors and moderating influences, as oxytocinergic effects on cognition and social behavior appear to vary in persons along indices of social competence, interpersonal sensitivity, and early adversity. Limitations of this literature and future directions for research are briefly discussed.

Preventing PTSD with oxytocin: effects of oxytocin administration on fear neurocircuitry and PTSD symptom development in recently trauma-exposed individuals

Background: Posttraumatic stress disorder (PTSD) is a debilitating psychiatric disorder which develops in approximately 10% of trauma-exposed individuals. Currently, there are few early preventive interventions available for PTSD. Intranasal oxytocin administration early posttrauma may prevent PTSD symptom development, as oxytocin administration was previously found to beneficially impact neurobiological (e.g. amygdala reactivity) and socio-emotional PTSD vulnerability factors. Objective: The overall aim of this dissertation was to investigate the potential of intranasal oxytocin administration as early preventive intervention for PTSD. Methods: We performed a functional magnetic resonance imaging (fMRI) study to assess the acute effects of a single administration of oxytocin on the functional fear neurocircuitry - consisting of the amygdala and (pre)frontal brain regions - in recently trauma-exposed emergency department patients (range n = 37-41). In addition, we performed a multicentre randomized double-blind placebo-controlled clinical trial (RCT) to assess the efficacy of repeated intranasal oxytocin administration early after trauma for preventing PTSD symptom development up to six months posttrauma (n = 107). Results: In our fMRI experiments we observed acutely increased amygdala reactivity to fearful faces and attenuated amygdala-ventromedial and ventrolateral prefrontal cortex functional connectivity after a single oxytocin administration in recently trauma-exposed individuals. However, in our RCT we found that repeated intranasal oxytocin administration early posttrauma reduced subsequent PTSD symptom development in recently trauma-exposed emergency department patients with high acute PTSD symptoms. Conclusions: These findings indicate that repeated intranasal oxytocin is a promising early preventive intervention for PTSD for individuals at increased risk for PTSD due to high acute symptom severity. Administration frequency dependent effects of oxytocin or the effects of oxytocin administration on salience processing may serve as explanatory frameworks for the contrasting oxytocin effects on anxiety-related measures in our clinical and neuroimaging studies.

Overview of Human Oxytocin Research

Social dysfunction is a core symptom of many psychiatric disorders and current medications have little or no remedial effects on this. Following on from extensive studies on animal models demonstrating that the neuropeptide oxytocin plays an important role in social recognition and bonding, human-based research has explored its therapeutic potential for social dysfunction in psychiatric disorders. Here we outline the historical background of this human-based research and some of the current methodological challenges it is facing. To date, research has primarily attempted to establish functional effects through measuring altered endogenous concentrations, observing effects of exogenous administration and by investigating the effects of polymorphisms and epigenetic modifications of the oxytocin receptor gene. We summarize some of the key findings on behavioral and neural effects that have been reported in healthy subjects in the context of social cognition which have provided encouragement that oxytocin could represent a promising therapeutic target. At the same time, we have identified a number of key areas where we urgently need further information about optimal dosing strategies and interactions with other peptide and transmitter systems. Finally, we have summarized current translational findings, particularly in the context of therapeutic outcomes of intranasal oxytocin administration in autism and schizophrenia. These clinical findings while somewhat varied in outcome do offer increasing cause for optimism that targeting the oxytocin system may provide a successful therapeutic approach for social dysfunction. However, future research needs to focus on the most effective treatment strategy and which types of individuals are likely to benefit most.

Oxytocin pathways in the intergenerational transmission of maternal early life stress

Severe stress in early life, such as childhood abuse and neglect, constitutes a major risk factor in the etiology of psychiatric disorders and somatic diseases. Importantly, these long-term effects may impact the next generation. The intergenerational transmission of maternal early life stress (ELS) may occur via pre-and postnatal pathways, such as alterations in maternal-fetal-placental stress physiology, maternal depression during pregnancy and postpartum, as well as impaired mother-offspring interactions. The neuropeptide oxytocin (OT) has gained considerable attention for its role in modulating all of these assumed transmission pathways. Moreover, central and peripheral OT signaling pathways are highly sensitive to environmental exposures and may be compromised by ELS with implications for these putative transmission mechanisms. Together, these data suggest that OT pathways play an important role in the intergenerational transmission of maternal ELS in humans. By integrating recent studies on gene-environment interactions and epigenetic modifications in OT pathway genes, the present review aims to develop a conceptual framework of intergenerational transmission of maternal ELS that emphasizes the role of OT.

Effects of Chronic Social Stress and Maternal Intranasal Oxytocin and Vasopressin on Offspring Interferon-γ and Behavior

Recent studies support the hypothesis that the adverse effects of early-life adversity and transgenerational stress on neural plasticity and behavior are mediated by inflammation. The objective of the present study was to investigate the immune and behavioral programing effects of intranasal (IN) vasopressin (AVP) and oxytocin (OXT) treatment of chronic social stress (CSS)-exposed F1 dams on F2 juvenile female offspring. It was hypothesized that maternal AVP and OXT treatment would have preventative effects on social stress-induced deficits in offspring anxiety and social behavior and that these effects would be associated with changes in interferon-γ (IFNγ). Control and CSS-exposed F1 dams were administered IN saline, AVP, or OXT during lactation and the F2 juvenile female offspring were assessed for basal plasma IFNγ and perseverative, anxiety, and social behavior. CSS F2 female juvenile offspring had elevated IFNγ levels and exhibited increased repetitive/perseverative and anxiety behaviors and deficits in social behavior. These effects were modulated by AVP and OXT in a context- and behavior-dependent manner, with OXT exhibiting preventative effects on repetitive and anxiety behaviors and AVP possessing preventative effects on social behavior deficits and anxiety. Basal IFNγ levels were elevated in the F2 offspring of OXT-treated F1 dams, but IFNγ was not correlated with the behavioral effects. These results support the hypothesis that maternal AVP and OXT treatment have context- and behavior-specific effects on peripheral IFNγ levels and perseverative, anxiety, and social behaviors in the female offspring of early-life social stress-exposed dams. Both maternal AVP and OXT are effective at preventing social stress-induced increases in self-directed measures of anxiety, and AVP is particularly effective at preventing impairments in overall social contact. OXT is specifically effective at preventing repetitive/perseverative behaviors, yet is ineffective at preventing deficits in overall social behavior.

Neuropeptide Regulation of Social Attachment: The Prairie Vole Model

Social attachments are ubiquitous among humans and integral to human health. Although great efforts have been made to elucidate the neural underpinnings regulating social attachments, we still know relatively little about the neuronal and neurochemical regulation of social attachments. As a laboratory animal research model, the socially monogamous prairie vole (Microtus ochrogaster) displays behaviors paralleling human social attachments and thus has provided unique insights into the neural regulation of social behaviors. Research in prairie voles has particularly highlighted the significance of neuropeptidergic regulation of social behaviors, especially of the roles of oxytocin (OT) and vasopressin (AVP). This article aims to review these findings. We begin by discussing the role of the OT and AVP systems in regulating social behaviors relevant to social attachments, and thereafter restrict our discussion to studies in prairie voles. Specifically, we discuss the role of OT and AVP in adult mate attachments, biparental care, social isolation, and social buffering as informed by studies utilizing the prairie vole model. Not only do these studies offer insight into social attachments in humans, but they also point to dysregulated mechanisms in several mental disorders. We conclude by discussing these implications for human health. © 2017 American Physiological Society. Compr Physiol 7:81-104, 2017.

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 chronic oxytocin on attention to dynamic facial expressions in infant macaques

Studies in a variety of species have reported enhanced prosocial effects after an acute administration of the neuromodulating hormone, oxytocin (OT). Although the exact mechanisms underlying these effects are not fully understood, there is broad interest in developing OT into a treatment for social deficits. Only a few studies, however, have examined the effects of OT if given repeatedly during early development, the period when early intervention is likely to have the greatest benefits for reversing the progression towards social impairment. Those studies, exclusively in rodents, report mixed results. Some have shown enhancement of prosocial behavior, including increased social exploration, but others have shown anti-social effects, including increased aggression. In the present study, infant rhesus macaques were treated with a high-frequency (3× per week) or low-frequency (1× per week) dose of intranasal oxytocin (IN-OT) or placebo (IN-saline) between two and six months of age, after which their reactions to dynamic facial expressions (neutral, lipsmacking and threats) were measured. Results showed that IN-OT, compared to placebo, increased the time monkeys spent viewing the expression videos, but selectively reduced attention to the eyes in neutral faces in a dose dependent manner. The mechanism for this non-prosocial effect may be that repeated IN-OT administration down-regulates the expression of OT receptors in brain regions important for regulating social attention. Consequently, our results raise questions about the efficacy of implementing chronic IN-OT as a pharmacotherapy for the treatment of social deficits, particularly if given early in development. More work is needed, not only to identify optimal treatment schedules, but also to understand how IN-OT exerts its influences on the brain and behavior.

Intranasal Oxytocin Enhances Connectivity in the Neural Circuitry Supporting Social Motivation and Social Perception in Children with Autism

Oxytocin (OT) has become a focus in investigations of autism spectrum disorder (ASD). The social deficits that characterize ASD may relate to reduced connectivity between brain sites on the mesolimbic reward pathway (nucleus accumbens; amygdala) that receive OT projections and contribute to social motivation, and cortical sites involved in social perception. Using functional magnetic resonance imaging and a randomized, double blind, placebo-controlled crossover design, we show that OT administration in ASD increases activity in brain regions important for perceiving social-emotional information. Further, OT enhances connectivity between nodes of the brain’s reward and socioemotional processing systems, and does so preferentially for social (versus nonsocial) stimuli. This effect is observed both while viewing coherent versus scrambled biological motion, and while listening to happy versus angry voices. Our findings suggest a mechanism by which intranasal OT may bolster social motivation—one that could, in future, be harnessed to augment behavioral treatments for ASD.

Contribution of oxytocin receptor polymorphisms to amygdala activation in schizophrenia spectrum disorders

BACKGROUND

Oxytocin has been proposed to mediate amygdala dysfunction associated with altered emotion processing in schizophrenia, but the contribution of oxytocin pathway genes is yet to be investigated.

AIMS

To identify potential different contributions of three oxytocin receptor polymorphisms (rs53576, rs237902 and rs2254298) between patients with schizophrenia spectrum disorders (SCZ), affective spectrum disorders (AD) and healthy controls (HC).

METHOD

In a total of 346 participants (104 with SCZ, 100 with AD, and 142 HC) underwent genotyping and functional magnetic resonance imaging (fMRI) during an emotional faces matching paradigm. Genetic association analyses were performed to test the possible effects on task-induced BOLD amygdala response to fearful/angry faces.

RESULTS

In participants with SCZ, the rs237902 G allele was associated with low amygdala activation (left hemisphere: b=-4.99, Bonferroni corrected P=0.04) and interaction analyses showed that this association was disorder specific (left hemisphere: Bonferroni corrected P=0.003; right hemisphere: Bonferroni corrected P=0.03). There were no associations between oxytocin polymorphisms and amygdala activation in the total sample, among AD patients or HC.

CONCLUSIONS

Rs237902 was associated with amygdala activation in response to fearful/angry faces only in patients with SCZ. Our findings indicate that the endogenous oxytocin system could serve as a contributing factor in biological underpinnings of emotion processing and that this contribution is disorder specific.

DECLARATION OF INTEREST

O.A.A. received speaker's honoraria from GSK, Otsuka, Lundbeck.

COPYRIGHT AND USAGE

© The Royal College of Psychiatrists 2016. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) licence.

Oxytocin and emotion processing

Since the observation that oxytocin has key effects on social decision making, research on this exciting neuropeptide has doubled in volume: hundreds of studies have pursued the promise of a specific oxytocin action on high-level cognition and social function with wide potential translational implications (from autism to social anxiety to dementia). Here we review the evidence on whether the complex behavioural effects observed in humans after exogenous oxytocin administration build on changes in basic emotional information processing, in particular emotional facial expressions recognition, and attention and memory for emotionally-valenced stimuli.We observe that recent studies confirm a facilitatory effect of oxytocin to more accurate emotion processing, irrespective of emotion type. However, it remains unclear whether this action precedes, is independent of or even secondary to the neuropeptide promoting a greater salience of social stimuli. Overall, this growing research area has shown that oxytocin produces behavioural and neurofunctional outcomes that are highly dependent on the experimental context and on individual differences (gender, personality, life experiences). This poses an exciting challenge for future experimental medicine designs to address and unpack complex interactions between individual and context characteristic, which is needed for the development of more precise clinical applications.

Common variant in OXTR predicts growth in positive emotions from loving-kindness training

Ample research suggests that social connection reliably generates positive emotions. Oxytocin, a neuropeptide implicated in social cognition and behavior, is one biological mechanism that may influence an individual's capacity to extract positive emotions from social contexts. Because variation in certain genes may indicate underlying neurobiological differences, we tested whether several SNPs in two genes related to oxytocin signaling would show effects on positive emotions that were context-specific, depending on sociality. For six weeks, a sample of mid-life adults (N=122) participated in either socially-focused loving-kindness training or mindfulness training. During this timespan they reported their positive emotions daily. Five SNPs within OXTR and CD38 were assayed, and each was tested for its individual effect on daily emotions. The hypothesized three-way interaction between time, training type, and genetic variability emerged: Individuals homozygous for the G allele of OXTR rs1042778 experienced gains in daily positive emotions from loving-kindness training, whereas individuals with the T allele did not experience gains in positive emotions with either training. These findings are among the first to show how genetic differences in oxytocin signaling may influence an individual's capacity to experience positive emotions as a result of a socially-focused intervention.

Oxytocin enhances gaze-following responses to videos of natural social behavior in adult male rhesus monkeys

Gaze following is a basic building block of social behavior that has been observed in multiple species, including primates. The absence of gaze following is associated with abnormal development of social cognition, such as in autism spectrum disorders (ASD). Some social deficits in ASD, including the failure to look at eyes and the inability to recognize facial expressions, are ameliorated by intranasal administration of oxytocin (IN-OT). Here we tested the hypothesis that IN-OT might enhance social processes that require active engagement with a social partner, such as gaze following. Alternatively, IN-OT may only enhance the perceptual salience of the eyes, and may not modify behavioral responses to social signals. To test this hypothesis, we presented four monkeys with videos of conspecifics displaying natural behaviors. Each video was viewed multiple times before and after the monkeys received intranasally either 50 IU of OT or saline. We found that despite a gradual decrease in attention to the repeated viewing of the same videos (habituation), IN-OT consistently increased the frequency of gaze following saccades. Further analysis confirmed that these behaviors did not occur randomly, but rather predictably in response to the same segments of the videos. These findings suggest that in response to more naturalistic social stimuli IN-OT enhances the propensity to interact with a social partner rather than merely elevating the perceptual salience of the eyes. In light of these findings, gaze following may serve as a metric for pro-social effects of oxytocin that target social action more than social perception.

Influence of oxytocin on emotion recognition from body language: A randomized placebo-controlled trial

The neuropeptide 'oxytocin' (OT) is known to play a pivotal role in a variety of complex social behaviors by promoting a prosocial attitude and interpersonal bonding. One mechanism by which OT is hypothesized to promote prosocial behavior is by enhancing the processing of socially relevant information from the environment. With the present study, we explored to what extent OT can alter the 'reading' of emotional body language as presented by impoverished biological motion point light displays (PLDs). To do so, a double-blind between-subjects randomized placebo-controlled trial was conducted, assessing performance on a bodily emotion recognition task in healthy adult males before and after a single-dose of intranasal OT (24 IU). Overall, a single-dose of OT administration had a significant effect of medium size on emotion recognition from body language. OT-induced improvements in emotion recognition were not differentially modulated by the emotional valence of the presented stimuli (positive versus negative) and also, the overall tendency to label an observed emotional state as 'happy' (positive) or 'angry' (negative) was not modified by the administration of OT. Albeit moderate, the present findings of OT-induced improvements in bodily emotion recognition from whole-body PLD provide further support for a link between OT and the processing of socio-communicative cues originating from the body of others.

Oxytocin enhances inter-brain synchrony during social coordination in male adults

Recent brain imaging research has revealed oxytocin (OT) effects on an individual's brain activity during social interaction but tells little about whether and how OT modulates the coherence of inter-brain activity related to two individuals' coordination behavior. We developed a new real-time coordination game that required two individuals of a dyad to synchronize with a partner (coordination task) or with a computer (control task) by counting in mind rhythmically. Electroencephalography (EEG) was recorded simultaneously from a dyad to examine OT effects on inter-brain synchrony of neural activity during interpersonal coordination. Experiment 1 found that dyads showed smaller interpersonal time lags of counting and greater inter-brain synchrony of alpha-band neural oscillations during the coordination (vs control) task and these effects were reliably observed in female but not male dyads. Moreover, the increased alpha-band inter-brain synchrony predicted better interpersonal behavioral synchrony across all participants. Experiment 2, using a double blind, placebo-controlled between-subjects design, revealed that intranasal OT vs placebo administration in male dyads improved interpersonal behavioral synchrony in both the coordination and control tasks but specifically enhanced alpha-band inter-brain neural oscillations during the coordination task. Our findings provide first evidence that OT enhances inter-brain synchrony in male adults to facilitate social coordination.

The Role of Oxytocin in Parenting and as Augmentative Pharmacotherapy: Critical Issues and Bold Conjectures

Despite the sometimes heated debate about the validity of human oxytocin studies, experimental oxytocin research with intranasal administration is a growing field with promising preliminary findings. The effects of intranasally administered oxytocin compared to placebo on brain neural activity have been supported in animal studies and in human studies of neural resting state. In several studies, oxytocin sniffs have been shown to lead to down-regulation of amygdala activation in response to infant attachment vocalisations. Meta-analytic evidence shows that oxytocin enhances the salience of (emotional) stimuli, lowers stress and arousal, and elevates empathic concern and tender care, in particular for offspring and in-group members. Less firm evidence points at the amnestic effects of oxytocin. We also note that the average effect sizes of oxytocin experiments are small to modest, and that most studies include a small number of subjects and thus are seriously underpowered, which implies a high risk for publication bias and nonreplicability. Nevertheless, we argue that the power of within-subjects experiments with oxytocin has been underestimated. Much more work is needed, however, to create a firm knowledge base of the neural and behavioural effects of oxytocin. Human oxytocin research is still taking place in the context of discovery, in which bold conjectures are being generated. In the context of justification, these conjectures should subsequently be subjected to stringent attempts at refutations before we jump to theoretical or clinical conclusions. For this context of justification, we propose a multisite multiple replications project on the social stimuli salience enhancing effect of oxytocin. Clinical application of oxytocin is premature. Meta-analytically, the use of oxytocin in clinical groups tends to show only effectiveness in changing symptomatology in individuals with autism spectrum disorders but, even then, it is not yet a validated therapy and its use is premature because safety and long-term side-effects have not been sufficiently studied, in particular in children.

Distinct oxytocin effects on belief updating in response to desirable and undesirable feedback

Humans update their beliefs upon feedback and, accordingly, modify their behaviors to adapt to the complex, changing social environment. However, people tend to incorporate desirable (better than expected) feedback into their beliefs but to discount undesirable (worse than expected) feedback. Such optimistic updating has evolved as an advantageous mechanism for social adaptation. Here, we examine the role of oxytocin (OT)-an evolutionary ancient neuropeptide pivotal for social adaptation-in belief updating upon desirable and undesirable feedback in three studies (n = 320). Using a double-blind, placebo-controlled between-subjects design, we show that intranasally administered OT (IN-OT) augments optimistic belief updating by facilitating updates of desirable feedback but impairing updates of undesirable feedback. The IN-OT-induced impairment in belief updating upon undesirable feedback is more salient in individuals with high, rather than with low, depression or anxiety traits. IN-OT selectively enhances learning rate (the strength of association between estimation error and subsequent update) of desirable feedback. IN-OT also increases participants' confidence in their estimates after receiving desirable but not undesirable feedback, and the OT effect on confidence updating upon desirable feedback mediates the effect of IN-OT on optimistic belief updating. Our findings reveal distinct functional roles of OT in updating the first-order estimation and second-order confidence judgment in response to desirable and undesirable feedback, suggesting a molecular substrate for optimistic belief updating.

Cyclic ADP-Ribose and Heat Regulate Oxytocin Release via CD38 and TRPM2 in the Hypothalamus during Social or Psychological Stress in Mice

Hypothalamic oxytocin (OT) is released into the brain by cyclic ADP-ribose (cADPR) with or without depolarizing stimulation. Previously, we showed that the intracellular free calcium concentration ([Ca²⁺]_i) that seems to trigger OT release can be elevated by β-NAD⁺, cADPR, and ADP in mouse oxytocinergic neurons. As these β-NAD⁺ metabolites activate warm-sensitive TRPM2 cation channels, when the incubation temperature is increased, the [Ca²⁺]_i in hypothalamic neurons is elevated. However, it has not been determined whether OT release is facilitated by heat in vitro or hyperthermia in vivo in combination with cADPR. Furthermore, it has not been examined whether CD38 and TRPM2 exert their functions on OT release during stress or stress-induced hyperthermia in relation to the anxiolytic roles and social behaviors of OT under stress conditions. Here, we report that OT release from the isolated hypothalami of male mice in culture was enhanced by extracellular application of cADPR or increasing the incubation temperature from 35°C to 38.5°C, and simultaneous stimulation showed a greater effect. This release was inhibited by a cADPR-dependent ryanodine receptor inhibitor and a nonspecific TRPM2 inhibitor. The facilitated release by heat and cADPR was suppressed in the hypothalamus isolated from CD38 knockout mice and CD38- or TRPM2-knockdown mice. In the course of these experiments, we noted that OT release differed markedly between individual mice under stress with group housing. That is, when male mice received cage-switch stress and eliminated due to their social subclass, significantly higher levels of OT release were found in subordinates compared with ordinates. In mice exposed to anxiety stress in an open field, the cerebrospinal fluid (CSF) OT level increased transiently at 5 min after exposure, and the rectal temperature also increased from 36.6°C to 37.8°C. OT levels in the CSF of mice with lipopolysaccharide-induced fever (+0.8°C) were higher than those of control mice. The TRPM2 mRNA levels and immunoreactivities increased in the subordinate group with cage-switch stress. These results showed that cADPR/CD38 and heat/TRPM2 are co-regulators of OT secretion and suggested that CD38 and TRPM2 are potential therapeutic targets for OT release in psychiatric diseases caused by social 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.

The effect of oxytocin on the anthropomorphism of touch

One of the leading hypotheses regarding the mechanism underlying the social effects of oxytocin (OT) is the "social salience hypothesis", which proposes that OT alters the attentional salience of social cues in a context-dependent manner. Recently, OT was implicated in the process of anthropomorphism; specifically, OT was found to increase the tendency to ascribe social meaning to inanimate stimuli. However, the precise component of social interaction that contributes to this effect remains unclear. Because OT plays a role in the response to touch, whether or not objects are touching in a social context may represent the prominent trigger. Given that OT plays a major role in both anthropomorphism and touch, it is reasonable to assume that OT enhances anthropomorphism specifically for non-human touch, further clarifying its role in altering the perceptual salience of social cues. Here, we examined whether intranasal delivery of OT influences anthropomorphism for touch in inanimate objects. To that end, we implicitly measured the emotional reactions of participants (N=51) to photos that depicted two humans or two inanimate objects either touching or not touching. We asked them to rate whether they will include each photo in an emotional album and found that OT treatment increased the likelihood of inclusion in an emotional album to photos that contain touch, particularly between inanimate objects. In a follow-up experiment we found that the more human the inanimate objects were perceived, the more included they were in the emotional album. Our findings demonstrate that OT can enhance the social meaning of touch between two inanimate objects and advance our understanding of the mechanisms underlying the ability of OT to anthropomorphize environmental cues.

Oxytocin blurs the self-other distinction during trait judgments and reduces medial prefrontal cortex responses

The neuropeptide oxytocin (OXT) may act either to increase or blur the distinction between self and other and thereby promote either more selfish or altruistic behaviors. To attempt to distinguish between these two possibilities we performed a double-blind, between-subject, placebo-controlled design study to investigate the effect of intranasal OXT on self and other (mother, classmate, or stranger) trait judgments in conjunction with functional magnetic resonance imaging. Results showed that OXT reduced response times for making both self and other judgments, but also reduced the accuracy of their subsequent recall, thereby abolishing the normal self-bias observed in this task. OXT also abolished the positive correlation between response and self-esteem scale scores seen in the PLC group, suggesting that its effects were strongest in individuals with higher levels of self-esteem. A whole-brain functional magnetic resonance imaging analysis revealed that OXT also reduced responses during both self and other trait judgments in the dorsal (dmPFC) and ventral (vmPFC) medial prefrontal cortex. A subsequent region of interest analysis revealed that behavioral performance and self-esteem scale scores were associated with dmPFC activation and its functional connectivity with the anterior cingulate and between the vmPFC and posterior cingulate. Thus overall, while OXT may improve speed of decision making in self -vs. other trait judgments it also blunts the normal bias towards remembering self-attributes and reduces mPFC responses and connectivity with other cortical midline regions involved in self-processing. This is consistent with the view that OXT can reduce self-centered behavior. Hum Brain Mapp 37:2512-2527, 2016. © 2016 Wiley Periodicals, Inc.