The influence of oxytocin administration on responses to infant faces and potential moderation by OXTR genotype

The neural basis of smile authenticity judgments and the potential modulatory role of the oxytocin receptor gene (OXTR)

Accurate perception of genuine vs. posed smiles is crucial for successful social navigation in humans. While people vary in their ability to assess the authenticity of smiles, little is known about the specific biological mechanisms underlying this variation. We investigated the neural substrates of smile authenticity judgments using functional magnetic resonance imaging (fMRI). We also tested a preliminary hypothesis that a common polymorphism in the oxytocin receptor gene (OXTR) rs53576 would modulate the behavioral and neural indices of accurate smile authenticity judgments. A total of 185 healthy adult participants (Neuroimaging arm: N = 44, Behavioral arm: N = 141) determined the authenticity of dynamic facial expressions of genuine and posed smiles either with or without fMRI scanning. Correctly identified genuine vs. posed smiles activated brain areas involved with reward processing, facial mimicry, and mentalizing. Activation within the inferior frontal gyrus and dorsomedial prefrontal cortex correlated with individual differences in sensitivity (d') and response criterion (C), respectively. Our exploratory genetic analysis revealed that rs53576 G homozygotes in the neuroimaging arm had a stronger tendency to judge posed smiles as genuine than did A allele carriers and showed decreased activation in the medial prefrontal cortex when viewing genuine vs. posed smiles. Yet, OXTR rs53576 did not modulate task performance in the behavioral arm, which calls for further studies to evaluate the legitimacy of this result. Our findings extend previous literature on the biological foundations of smile authenticity judgments, particularly emphasizing the involvement of brain regions implicated in reward, facial mimicry, and mentalizing.

Serum oxytocin levels in adolescents with conduct disorder associated with callous-unemotional traits

Background

Conduct disorder (CD) is a serious and common psychiatric disorder affecting children and adolescents. “Callous-unemotional traits” is a new specifier added to the diagnosis of CD in the DSM-5. The new specifier is thought to be associated with more severity and higher genetic load. Oxytocin is known to be related to interpersonal sympathy and social affection, and so its deficiency might be related to unemotionality. This work aims to explore the levels of serum oxytocin in adolescents with CD associated with callous-unemotional (CU) traits as compared to healthy control subjects. Twenty patients aged 12–18 years and 20 controls of the same age range were recruited. An Arabic-translated and validated version of Mini International Neuropsychiatric Interview for kids (MINI-kid) was used to confirm the diagnosis. The Youth Psychopathic Inventory-short version (YPI-short version) and the Inventory of Callous-Unemotional Traits (ICU), both parent and self-reports, were all translated into Arabic and validated by the authors and used to evaluate the sample. Evaluation of serum oxytocin level using ELISA technique was done.

Results

After statistical adjustment for differences in socioeconomic status, an adolescent with CD associated with CU traits showed low levels of serum oxytocin level as compared with the control group. Serum oxytocin levels were negatively correlated in a statistically significant degree with the unemotional, the callousness, and the uncaring subscores of ICU—self-report.

Conclusions

Low levels of serum oxytocin might play a potential role as a biomarker for CU traits and CD severity in adolescents with CD.

Associations between alcohol use and peripheral, genetic, and epigenetic markers of oxytocin in a general sample of young and older adults

INTRODUCTION

Human and nonhuman animal research suggests that greater oxytocin (OT) activity is protective against harmful substance use. Most research on this topic is preclinical, with few studies evaluating the association between substance use and individual differences in the human OT system. The present study sought to fill this gap by evaluating the relationship between alcohol use and multiple biological measures of OT activity in an overall low to moderate-drinking sample.

METHOD

As part of a larger study, generally healthy young (n = 51) and older (n = 53) adults self-reported whether they regularly used alcohol and how much alcohol they consumed per week. Participants also provided blood samples from which peripheral OT, and in an age-heterogeneous subset of participants (n = 56) variation in the oxytocin receptor gene (the OXTR rs53576 polymorphism) and OXTR DNA methylation levels (at cytosine-guanine dinucleotide sites -860, -924, -934), were obtained.

RESULTS

A-allele carriers of the OXTR rs53579 polymorphism were less likely to regularly consume alcohol. Among regular alcohol consumers, number of alcoholic drinks per week was positively associated with peripheral OT in regression models excluding observations of high influence (postdiagnostic models). Number of alcoholic drinks per week was consistently negatively associated with OXTR DNA methylation at site -860; and with OXTR DNA methylation at site -924 in postdiagnostic models.

CONCLUSIONS

The significant associations between alcohol use and individual differences in OT activity support the involvement of the OT system in alcohol use, which most likely reflect the role of OT when alcohol use is under control of its rewarding properties and/or the acute impacts of alcohol on the OT system. Additional research with markers of OT activity and alcohol use, particularly longitudinal, is needed to clarify the bidirectional effects of OT and alcohol use in moderate to harmful drinking and dependence.

Oxytocin and the Neurobiology of Prosocial Behavior

Humans are an unusually prosocial species, who engage in social behaviors that include altruism-whereby an individual engages in costly or risky acts to improve the welfare of another person-care, and cooperation. Current perspectives on the neurobiology of human prosociality suggest that it is deeply rooted in the neuroendocrine architecture of the social brain and emphasize the modulatory role of the neuropeptide hormone oxytocin. In this review, we provide a conceptual overview of the neurobiology of prosocial behavior with a focus on oxytocin's modulatory role in human prosociality. Specifically, we aim to encourage a better understanding of the peptide's susceptibility to diverse factors that produce heterogeneity in outcomes and the resulting methodological implications for measuring the behavioral effects of oxytocin in humans. After providing an overview of the state-of-the-art research on oxytocin's exogenous use, we elaborate on the peptide's modulatory role in the context of care-based altruism, cooperation, and conflict and discuss its potential for therapeutic interventions in psychiatric disorders characterized by social dysfunction.

Intranasal oxytocin administration but not peripheral oxytocin regulates behaviors of attachment insecurity: A meta-analysis

In light of the roles of oxytocin (OT) in social bonding and interpersonal relationship, studies have examined the roles of OT in human attachment, but by and large previous findings are inconsistent. Here, we conducted - meta-analyses to estimate the associations between peripheral OT level (e.g., blood and salivary OT) and attachment (i.e., attachment dimensions and behaviors of attachment insecurity) and examine the effects of intranasal OT administration on behaviors of attachment insecurity. The analyses indicated that: (1) Peripheral OT level was not significantly associated with attachment dimensions (e.g., attachment anxiety and attachment avoidance) and behaviors of attachment insecurity; (2) intranasal OT administration significantly reduced behaviors of attachment insecurity of neutral contexts, particularly behaviors of attachment avoidance. The findings suggest that intranasal OT administration is an available approach for reducing behaviors of attachment insecurity of interpersonal situations with ambiguous social cues, which implicates suggestions for therapeutic treatments of attachment-related dysfunctions.

Randomized clinical trial shows no substantial modulation of empathy-related neural activation by intranasal oxytocin in autism

Evidence suggests that intranasal application of oxytocin facilitates empathy and modulates its underlying neural processes, which are often impaired in individuals with autism spectrum disorders (ASD). Oxytocin has therefore been considered a promising candidate for the treatment of social difficulties in ASD. However, evidence linking oxytocin treatment to social behavior and brain function in ASD is limited and heterogeneous effects might depend on variations in the oxytocin-receptor gene (OXTR). We examined 25 male ASD patients without intellectual disability in a double-blind, cross-over, placebo-controlled fMRI-protocol, in which a single dose of oxytocin or placebo was applied intranasally. Patients performed three experiments in the MRI examining empathy for other's physical pain, basic emotions, and social pain. All participants were genotyped for the rs53576 single-nucleotide polymorphism of the OXTR. Oxytocin increased bilateral amygdala responsiveness during the physical pain task for both painful and neutral stimuli. Other than that, there were no effects of oxytocin treatment. OXTR genotype did not significantly interact with oxytocin treatment. Our results contribute to the growing body of empirical literature suggesting heterogenous effects of oxytocin administration in ASD. To draw clinically relevant conclusions regarding the usefulness of oxytocin treatment, however, empirical studies need to consider methods of delivery, dose, and moderating individual factors more carefully in larger samples.

Oxytocin-Trust Link in Oxytocin-Sensitive Participants and Those Without Autistic Traits

There have been numerous studies in which the biological role of oxytocin in trusting behavior has been investigated. However, a link between oxytocin and trust in humans was discovered only in one early study. We hypothesized that there is a large interindividual variation in oxytocin sensitivity, and that such variation is one reason for the doubt surrounding the role of oxytocin in trusting behavior. Here, in a double-blind, prospective, case-control study, we administered intranasal oxytocin to participants of trust and risk games. We measured salivary oxytocin concentration, relating it to the amount of money transferred among participants (a proxy for trust) and the autism-spectrum quotient (AQ). A one-sided Fisher’s exact test was performed to detect differences between the oxytocin and placebo groups in the proportions of investors who transferred the maximum amount of money. We discovered a tendency for participants who received oxytocin to transfer higher amounts of money to co-participants than those who received a placebo (P = 0.04). We also revealed a high degree of interindividual variation in salivary oxytocin concentrations after oxytocin administration. After stratifying the samples with respect to oxytocin sensitivity, oxytocin-sensitive participants in the oxytocin group also transferred higher amounts of money than those in the placebo group (P = 0.03), while such a tendency was not observed for oxytocin-insensitive participants (P = 0.34). Participants with lower AQ scores (less severe autistic traits) exhibited a greater tendency toward trusting behavior after oxytocin administration than did those with higher AQ scores (P = 0.02). A two-sample t-test that was performed to detect significant differences in the mean transfers between the oxytocin and placebo groups indicated no significant between-group difference in the mean transfers (P = 0.08). There are two possible interpretations of these results: First, there is no effect of oxytocin on trust in humans; second, the effects of oxytocin on trust in humans is person-dependent. However, the results should be interpreted with caution as the effect size was not larger than the minimal detectable effect size and the results were not statistically significant (P > 0.05) after Bonferroni corrections.

The influence of rs53576 polymorphism in the oxytocin receptor (OXTR) gene on empathy in healthy adults by subtype and ethnicity: a systematic review and meta-analysis

Empathy is essential for navigating complex social environments. Prior work has shown associations between rs53576, a single nucleotide polymorphism (SNP) located in the oxytocin receptor gene (OXTR), and generalized empathy. We undertook a systematic review and meta-analysis to assess the effects of rs53576 on subdomains of empathy, specifically cognitive empathy (CE) and affective empathy (AE), in healthy adults. Twenty cohorts of 8933 participants aged 18-98 were identified, including data from the Sydney Memory and Ageing Study, a cohort of older community adults. Meta-analyses found G homozygotes had greater generalized empathic abilities only in young to middle-aged adults. While meta-analyses of empathy subdomains yielded no significant overall effects, there were differential effects based on ethnicity. G homozygotes were associated with greater CE abilities in Asian cohorts (standardized mean difference; SMD: 0.09 [2.8·10^-3-0.18]), and greater AE performance in European cohorts [SMD: 0.12 (0.04-0.21)]. The current literature highlights a need for further work that distinguishes between genetic and ethnocultural effects and explores effects of advanced age on this relationship.

A variation in the infant oxytocin receptor gene modulates infant hippocampal volumes in association with sex and prenatal maternal anxiety

Genetic variants in the oxytocin receptor (OTR) have been linked to distinct social phenotypes, psychiatric disorders and brain volume alterations in adults. However, to date, it is unknown how OTR genotype shapes prenatal brain development and whether it interacts with maternal prenatal environmental risk factors on infant brain volumes. In 105 Finnish mother-infant dyads (44 female, 11-54 days old), the association of offspring OTR genotype rs53576 and its interaction with prenatal maternal anxiety (revised Symptom Checklist 90, gestational weeks 14, 24, 34) on infant bilateral amygdalar, hippocampal and caudate volumes were probed. A sex-specific main effect of rs53576 on infant left hippocampal volumes was observed. In boys compared to girls, left hippocampal volumes were significantly larger in GG-homozygotes compared to A-allele carriers. Furthermore, genotype rs53576 and prenatal maternal anxiety significantly interacted on right hippocampal volumes irrespective of sex. Higher maternal anxiety was associated both with larger hippocampal volumes in A-allele carriers than GG-homozygotes, and, though statistically weak, also with smaller right caudate volumes in GG-homozygotes than A-allele carriers. Our study results suggest that OTR genotype enhances hippocampal neurogenesis in male GG-homozygotes. Further, prenatal maternal anxiety might induce brain alterations that render GG-homozygotes compared to A-allele carriers more vulnerable to depression.

Lack of association of common polymorphisms linked to empathic behavior with self-reported trait empathy in healthy volunteers

BACKGROUND

In a previously specified sample of 421 healthy subjects, we found associations of a common oxytocin receptor (OXTR) polymorphism with self-reported trait empathy. In this study, we used this sample to explore polymorphisms in other genes which have been frequently linked to empathic behavior for associations with self-reported trait empathy: CD38 (CD38), involved in oxytocin secretion, the serotonin transporter (SLC6A4), the Catechol-O-Methyltransferase (COMT) and the corticotropin releasing hormone receptor 1 (CRHR1).

METHODS

We genotyped our sample for the following common polymorphisms: rs3796863 in the CD38 gene, 5-HTTLPR in the SLC6A4 gene, rs4680 in the COMT gene and rs242924 in the CRHR1 gene. Dispositional empathy was tested using Davis' Interpersonal Reactivity Index (IRI). We used a Bonferroni corrected alpha level of p = 0.002 to adjust for multiple comparisons.

RESULTS

None of the genotypes were associated with any of the IRI scales for the complete sample (n = 421) or for the sub-groups of male (n = 213) and female (n = 190) participants. Our sample of 421 participants achieved 95% power to detect effects greater than r = ±0.18. For smaller effects, however, false negatives could not be rejected with equal confidence as false positives.

CONCLUSIONS

We conclude that an association between the four polymorphisms with trait empathy measured by the IRI may not be present. We propose that the associations that have been found in other studies can be largely explained by differences in empathy-related constructs and measurements.

Intranasal oxytocin modulates brain responses to voice-identity recognition in typically developing individuals, but not in ASD

Faces and voices are prominent cues for person-identity recognition. Face recognition behavior and associated brain responses can be enhanced by intranasal administration of oxytocin. It is unknown whether oxytocin can also augment voice-identity recognition mechanisms. To find it out is particularly relevant for individuals who have difficulties recognizing voice identity such as individuals diagnosed with autism spectrum disorder (ASD). We conducted a combined behavioral and functional magnetic resonance imaging (fMRI) study to investigate voice-identity recognition following intranasal administration of oxytocin or placebo in a group of adults diagnosed with ASD (full-scale intelligence quotient > 85) and pairwise-matched typically developing (TD) controls. A single dose of 24 IU oxytocin was administered in a randomized, double-blind, placebo-controlled and cross-over design. In the control group, but not in the ASD group, administration of oxytocin compared to placebo increased responses to recognition of voice identity in contrast to speech in the right posterior superior temporal sulcus/gyrus (pSTS/G) - a region implicated in the perceptual analysis of voice-identity information. In the ASD group, the right pSTS/G responses were positively correlated with voice-identity recognition accuracy in the oxytocin condition, but not in the placebo condition. Oxytocin did not improve voice-identity recognition performance at the group level. The ASD compared to the control group had lower right pSTS/G responses to voice-identity recognition. Since ASD is known to have atypical pSTS/G, the results indicate that the potential of intranasal oxytocin to enhance mechanisms for voice-identity recognition might be variable and dependent on the functional integrity of this brain region.

A Novel Role of CD38 and Oxytocin as Tandem Molecular Moderators of Human Social Behavior

Oxytocin is an important modulator of human affiliative behaviors, including social skills, human pair bonding, and friendship. CD38 will be discussed as an immune marker and then in more detail the mechanisms of CD38 on releasing brain oxytocin. Mention is made of the paralogue of oxytocin, vasopressin, that has often overlapping and complementary functions with oxytocin on social behavior. Curiously, vasopressin does not require CD38 to be released from the brain. This review discusses the social salience hypothesis of oxytocin action, a novel view of how this molecule influences much of human social behaviors often in contradictory ways. The oxytocinergic-vasopressinergic systems are crucial modulators of broad aspects of human personality. Of special interest are studies of these two hormones in trust related behavior observed using behavioral economic games. This review also covers the role of oxytocin in parenting and parental attachment. In conclusion, the effects of oxytocin on human behavior depend on the individual's social context and importantly as well, the individual's cultural milieu, viz. East and West. ACRONYMS: ACC = Anterior Cingulate ADP = Adenosine diphosphate AQ = Autism Quotient cADPR = Cyclic ADP-ribose CNS = Central nervous system DA = Dopamine eQTLC = Expression Quantitative Trait Loci LC-NE = Locus Coeruleus-Norepinephrine MRI = Magnetic Resonance Imaging OFC = Orbitofrontal cortices OXT = Oxytocin RAGE = Receptor for advanced glycation end-products SARM1 = Sterile Alpha and toll/interleukin-1 receptor motif-containing 1 TRPM2= Transient Receptor Potential Cation Channel Subfamily M Member 2 AVP = Vasopressin.

The Role of Olfactory Genes in the Expression of Rodent Paternal Care Behavior

Olfaction is the dominant sensory modality in rodents, and is crucial for regulating social behaviors, including parental care. Paternal care is rare in rodents, but can have significant consequences for offspring fitness, suggesting a need to understand the factors that regulate its expression. Pup-related odor cues are critical for the onset and maintenance of paternal care. Here, I consider the role of olfaction in the expression of paternal care in rodents. The medial preoptic area shares neural projections with the olfactory and accessory olfactory bulbs, which are responsible for the interpretation of olfactory cues detected by the main olfactory and vomeronasal systems. The olfactory, trace amine, membrane-spanning 4-pass A, vomeronasal 1, vomeronasal 2 and formyl peptide receptors are all involved in olfactory detection. I highlight the roles that 10 olfactory genes play in the expression of direct paternal care behaviors, acknowledging that this list is not exhaustive. Many of these genes modulate parental aggression towards intruders, and facilitate the recognition and discrimination of pups in general. Much of our understanding comes from studies on non-naturally paternal laboratory rodents. Future studies should explore what role these genes play in the regulation and expression of paternal care in naturally biparental species.

Oxytocin modulation of self-referential processing is partly replicable and sensitive to oxytocin receptor genotype

Intranasal oxytocin (OXT) has been associated with effects on diverse social-emotional domains in humans, however progress towards a therapeutic application of OXT in disorders with social-emotion impairments is currently hampered by poor replicability. Limited statistical power and individual differences in biological factors, such as oxytocin receptor (OXTR) genetics, may have contributed to these variable findings. To this end, employing a validated oxytocin-sensitive trait judgment paradigm, we present a pharmaco-genetic study aiming at (1) replicating previous findings suggesting that intranasal oxytocin (24 IU) reduces the self-referential bias in a large sample of n = 170 male subjects, (2) determining whether variations in common receptor polymorphisms (rs237887, rs2268491, rs2254298, rs53576, rs2268498) influence sensitivity to oxytocin's behavioral effects. We confirmed that in the whole sample oxytocin influenced self-other distinction in terms of reduced decision time. However, oxytocin only influenced decision time in rs53576 G carriers, whereas effects on subsequent memory performance were only found in rs2268498 TT homozygotes. In summary, the current study partially replicates our previous findings showing that oxytocin reduces the self-referential bias and suggests that sensitivity to its effects in this domain are receptor genotype dependent.

Associations between oxytocin receptor gene (OXTR) polymorphisms, childhood trauma, and parenting behavior

Maternal oxytocin is connected to aspects of parenting including sensitivity, warmth, positive affect, and affectionate touch. Oxytocin receptor gene (OXTR) polymorphisms are associated with circulating oxytocin levels, altered brain activity, and parenting behaviors. This study aimed to replicate prior work on OXTR single-nucleotide polymorphisms (SNPs) rs1042778 and rs53576 in relation to maternal sensitivity, explore associations with other aspects of parenting (i.e., negative parenting), evaluate observational and self-report measures of parenting in relation to OXTR SNPs, and examine whether childhood trauma exposure moderates the relation between OXTR SNPs and parenting. Mothers (N = 100) were observed during 2 teaching interaction tasks with their 7-month-old infant, completed questionnaire and interview measures related to parenting and trauma history, and provided saliva specimens to derive OXTR genotypes. Mothers with OXTR rs1042778 TT genotypes demonstrated lower behavioral sensitivity, lower engagement, higher intrusiveness, and more frequent frightened/frightening behavior than mothers with TG or GG genotypes. Genotype interacted with childhood trauma history such that mothers who had experienced childhood trauma were more likely to demonstrate frightened/frightening behavior if they had the TT genotype on rs1042778 relative to the TG or GG genotype; however, small cell sizes for this interaction suggest replication is warranted. Contrary to expectations, mothers with the TT genotype on rs1042778 self-reported that they had less impaired bonding than mothers with TG or GG genotypes. Results are discussed with respect to prior work with oxytocin in lower versus higher risk samples, and the potential role of mothers' self-awareness in explaining discrepancies between results from observational versus self-report measures of parenting. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The expectant social mind: A systematic review of face processing during pregnancy and the effect of depression and anxiety

Pregnancy carries enormous changes in the psychological and neurophysiological domains. It has been suggested that pregnant women undergo a cognitive reorganization aimed at increasing the salience of social stimuli (i.e., the tendency of social cues to capture observer's attention, so that their processing results prioritized). The goal of the present work was to systematically review the empirical evidence of a change in face processing during pregnancy. Moreover, we explored whether face processing is associated with antenatal depression and anxiety and the extent to which this is part of a potential mechanism to explain detrimental effects of maternal psychopathology on infant outcomes. We identified 19 relevant studies and discussed them based on their methodological qualities. The results of the review suggest that even though it is not possible to draw firm conclusions, pregnancy is likely to be a plasticity window for face processing at the behavioral and neural levels. Evidence confirms the detrimental effect of depression and anxiety on face processing during pregnancy. Clinical implications for parenting interventions are discussed.

Genetics of human brain evolution

During the course of evolution the human brain has increased in size and complexity, ultimately these differences are the result of changes at the genetic level. Identifying and characterizing molecular evolution requires an understanding of both the genetic underpinning of the system as well as the comparative genetic tools to identify signatures of selection. This chapter aims to describe our current understanding of the genetics of human brain evolution. Primarily this is the story of the evolution of the human brain since our last common ape ancestor, but where relevant we will also discuss changes that are unique to the primate brain (compared to other mammals) or various other lineages in the evolution of humans more generally. It will focus on genetic changes that both directly affected the development and function of the brain as well as those that have indirectly influenced brain evolution through both prenatal and postnatal environment. This review is not meant to be exhaustive, but rather to begin to construct a general framework for understanding the full array of data being generated.

The Caring Continuum: Evolved Hormonal and Proximal Mechanisms Explain Prosocial and Antisocial Extremes

Implicit in the long-standing disagreements about whether humans’ fundamental nature is predominantly caring or callous is an assumption of uniformity. This article reviews evidence that instead supports inherent variation in caring motivation and behavior. The continuum between prosocial and antisocial extremes reflects variation in the structure and function of neurohormonal systems originally adapted to motivate parental care and since repurposed to support generalized forms of care. Extreme social behaviors such as extraordinary acts of altruism and aggression can often be best understood as reflecting variation in the neural systems that support care. A review of comparative, developmental, and neurobiological research finds consistent evidence that variations in caring motivations and behavior reflect individual differences in sensitivity to cues that signal vulnerability and distress and in the tendency to generalize care outward from socially close to distant others. The often complex relationships between caring motivation and various forms of altruism and aggression are discussed.

Oxytocin receptors (OXTR) and early parental care: An interaction that modulates psychiatric disorders

Oxytocin plays an important role in the modulation of social behavior in both typical and atypical contexts. Also, the quality of early parental care sets the foundation for long-term psychosocial development. Here, we review studies that investigated how oxytocin receptor (OXTR) interacts with early parental care experiences to influence the development of psychiatric disorders. Using Pubmed, Scopus and PsycInfo databases, we utilized the keyword "OXTR" before subsequently searching for specific OXTR single nucleotide polymorphisms (SNPs), generating a list of 598 studies in total. The papers were catalogued in a database and filtered for gene-environment interaction, psychiatric disorders and involvement of parental care. In particular, rs53576 and rs2254298 were found to be significantly involved in gene-environment interactions that modulated risk for psychopathology and the following psychiatric disorders: disruptive behavior, depression, anxiety, eating disorder and borderline personality disorder. These results illustrate the importance of OXTR in mediating the impact of parental care on the emergence of psychopathology.

Epigenetic Modification of OXTR is Associated with Openness to Experience

Oxytocin is a neuropeptide known to influence social and cognitive processing across several mammalian species. There currently exists a mixed and controversial pattern of evidence that oxytocin pathway genes confer individual differences in social cognition and personality in humans. Inconsistencies across studies may in part be explained by the presence of intermediary, epigenetic, variables that exist between genotype and phenotype. This study was designed to investigate the association between epigenetic modification of the Oxytocin Receptor Gene (OXTR), via DNA methylation, and Big-5 personality traits. Genetic data were collected via saliva samples and analyzed to quantify DNA methylation within the promoter region of OXTR. The results indicate that Openness to Experience is associated with OXTR DNA methylation, while controlling for the remaining Big-5 personality dimensions (Neuroticism, Extraversion, Agreeableness, and Conscientiousness) and sex and age. This finding provides additional support for models associating oxytocin with individual differences in personality and identity in humans.

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.

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.

The Role of Endogenous Oxytocin in Anxiolysis: Structural and Functional Correlates

BACKGROUND

Oxytocin is anxiolytic, and administration of synthetic oxytocin in humans reduces amygdala reactivity to negative stimuli. However, it is unknown whether endogenous oxytocin levels-which are heritable and stable across time-attenuate anxiety via similar mechanisms.

METHODS

In this study, we used plasma assays and structural and functional neuroimaging to examine potential anxiolytic effects of endogenous oxytocin in 73 participants.

RESULTS

We found that higher endogenous oxytocin levels are associated with reduced central amygdala volume and blood oxygen level-dependent activity in response to aversive stimuli. In contrast to previous reports, we found that oxytocin was not related to patterns of functional connectivity between the amygdala and other brain regions.

CONCLUSIONS

Together, our results underscore the importance of considering individual differences in participants' endogenous oxytocin with respect to anxiety-related neural activity and neuromorphology.

Psychophysiological effects of oxytocin on parent-child interactions: A literature review on oxytocin and parent-child interactions

Oxytocin (OT), often called the 'hormone of love' or 'hormone of attachment,' plays a fundamental role in the establishment and quality of parent-infant bonding. However, emerging evidence indicates that OT can also produce antisocial behavior. To clarify these effects, we review studies examining the role of endogenous and exogenous OT on several determinants of attachment: parental sensitivity, and bonding or synchrony in parent-child dyads. Contextual and individual factors moderating the effect of intranasal OT and its peripheral levels are also reviewed. Finally, potential therapeutic applications for OT and current limitations in human OT research are examined. This systematic literature review was based on the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, with two electronic databases and other bibliographic sources. We identified a total of 47 relevant studies for inclusion in our review. Most of the findings are in accordance with recent ideas that OT administration may increase parent-child prosocial interaction, showing that OT exerts beneficial effects on processes thought to promote bonding, sensitivity, and synchrony. However, we found that OT can induce antisocial behavior (e.g., anxiety) or adverse effects (modulation of maternal care recollections) that are moderated by different contextual (e.g., maltreatment level, presence of unfamiliar people) and individual (attachment style) factors. This review reinforces the importance of context- and individual-dependent factors, which must be taken into account when analyzing the psychophysiological effects of OT.

Intranasal oxytocin and a polymorphism in the oxytocin receptor gene are associated with human-directed social behavior in golden retriever dogs

The oxytocin system may play an important role in dog domestication from the wolf. Dogs have evolved unique human analogue social skills enabling them to communicate and cooperate efficiently with people. Genomic differences in the region surrounding the oxytocin receptor (OXTR) gene have previously been associated with variation in dogs' communicative skills. Here we have utilized the unsolvable problem paradigm to investigate the effects of oxytocin and OXTR polymorphisms on human-directed contact seeking behavior in 60 golden retriever dogs. Human-oriented behavior was quantified employing a previously defined unsolvable problem paradigm. Behaviors were tested twice in a repeated, counterbalanced design, where dogs received a nasal dose of either oxytocin or saline 45min before each test occasion. Buccal DNA was analysed for genotype on three previously identified SNP-markers associated with OXTR. The same polymorphisms were also genotyped in 21 wolf blood samples to explore potential genomic differences between the species. Results showed that oxytocin treatment decreased physical contact seeking with the experimenter and one of the three polymorphisms was associated with degree of physical contact seeking with the owner. Dogs with the AA-genotype at this locus increased owner physical contact seeking in response to oxytocin while the opposite effect was found in GG-genotype individuals. Hence, intranasal oxytocin treatment, an OXTR polymorphism and their interaction are associated with dogs' human-directed social skills, which can explain previously described breed differences in oxytocin response. Genotypic variation at the studied locus was also found in wolves indicating that it was present even at the start of dog domestication.

A 12-week randomized controlled trial of twice-daily intranasal oxytocin for social cognitive deficits in people with schizophrenia

Social cognition is impaired in people with schizophrenia and these deficits are strongly correlated with social functioning. Oxytocin is a hypothalamic peptide that contributes to maternal infant bonding and has diverse pro-social effects in adults. This study tested the hypothesis that 12weeks of intranasal oxytocin will improve social cognitive function in outpatients with schizophrenia and schizoaffective disorder. Sixty-eight eligible participants were randomized to oxytocin (24IU twice daily) or placebo. Social cognitive function was assessed using the Emotion Recognition-40, Brüne Theory of Mind, Reading the Mind in the Eyes test, Trustworthiness task and Ambiguous Intentions Hostility Questionnaire at baseline, 6weeks and 12weeks. In addition, social function was assessed using the Specific Levels of Functioning Scale and a role-play test, and psychopathology was assessed using the Positive and Negative Syndrome Scale (PANSS). Fifty-five participants completed the 12-week trial. The study found no evidence for a differential advantage of oxytocin over placebo on social cognition. Among secondary outcomes, there was a modest advantage for oxytocin over placebo on a component of social functioning, although there was also evidence that the placebo group outperformed the oxytocin group on the role-play task. No between-group differences emerged on measures of psychopathology in pre-specified comparisons, but oxytocin showed significant within-group reduction in PANSS negative symptoms and significant between-group improvement in negative symptoms in the schizophrenia subgroup. Further testing is needed to clarify whether oxytocin has therapeutic potential for social cognitive deficits and/or negative symptoms in people with schizophrenia.

Revisiting the impact of OXTR rs53576 on empathy: A population-based study and a meta-analysis

Oxytocin in the brain is related to empathy, which refers to the ability to understand and share others' internal states or responses. Previous studies have investigated the impact of OXTR rs53576, the most intensively examined polymorphism in the oxytocin receptor (OXTR) gene, on individual differences in empathy. However, these studies produced inconsistent results. In the current study, we reexamined the association of OXTR rs53576 with empathy in a relatively large population (N=1830) and also evaluated the association by a comprehensive meta-analysis (N=6631, 13 independent samples). The replication study indicated that OXTR rs53576 was indeed associated with individual differences in empathy. Individuals with a greater number of G alleles showed better empathic ability, particularly in fantasizing other's feelings and actions. The meta-analysis not only confirmed this association, but also indicated that the impact of this polymorphism was significant in both Europeans and Asians. These findings provide convincing evidence for the impact of OXTR rs53576 on empathy, highlighting the importance of OXTR gene in individuals' social cognition.

Genes Related to Oxytocin and Arginine-Vasopressin Pathways: Associations with Autism Spectrum Disorders

Autism spectrum disorder (ASD) is a highly heritable neurodevelopmental disorders characterized by impaired social interactions, communication deficits, and repetitive behavior. Although the mechanisms underlying its etiology and manifestations are poorly understood, several lines of evidence from rodent and human studies suggest involvement of the evolutionarily highly-conserved oxytocin (OXT) and arginine-vasopressin (AVP), as these neuropeptides modulate various aspects of mammalian social behavior. As far as we know, there is no comprehensive review of the roles of the OXT and AVP systems in the development of ASD from the genetic aspect. In this review, we summarize the current knowledge regarding associations between ASD and single-nucleotide variants of the human OXT-AVP pathway genes OXT, AVP, AVP receptor 1a (AVPR1a), OXT receptor (OXTR), the oxytocinase/vasopressinase (LNPEP), and ADP-ribosyl cyclase (CD38).

The neurobiological causes and effects of alloparenting

Alloparenting, defined as care provided by individuals other than parents, is a universal behavior among humans that has shaped our evolutionary history and remains important in contemporary society. Dysfunctions in alloparenting can have serious and sometimes fatal consequences for vulnerable infants and children. In spite of the importance of alloparenting, they still have much to learn regarding the underlying neurobiological systems governing its expression. Here, they review how a lack of alloparental behavior among traditional laboratory species has led to a blind spot in our understanding of this critical facet of human social behavior and the relevant neurobiology. Based on what is known, they draw from model systems ranging from voles to meerkats to primates to describe a conserved set of neuroendocrine mechanisms supporting the expression of alloparental care. In this review we describe the neurobiological and behavioral prerequisites, ontogeny, and consequences of alloparental care. Lastly, they identified several outstanding topics in the area of alloparental care that deserve further research efforts to better advance human health and wellbeing. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 214-232, 2017.

Vulnerability or Sensitivity to the Environment? Methodological Issues, Trends, and Recommendations in Gene-Environment Interactions Research in Human Behavior

Research on the potential role of gene-environment interactions (GxE) in explaining vulnerability to psychopathology in humans has witnessed a shift from a diathesis-stress perspective to differential susceptibility approaches. This paper critically reviews methodological issues and trends in this body of research. Databases were screened for studies of GxE in the prediction of personality traits, behavior, and mental health disorders in humans published between January 2002 and January 2015. In total, 315 papers were included. Results showed that 34 candidate genes have been included in GxE studies. Independent of the type of environment studied (early or recent life events, positive or negative environments), about 67-83% of studies have reported significant GxE interactions, which is consistent with a social susceptibility model. The percentage of positive results does not seem to differ depending on the gene studied, although publication bias might be involved. However, the number of positive findings differs depending on the population studied (i.e., young adults vs. older adults). Methodological considerations limit the ability to draw strong conclusions, particularly as almost 90% (n = 283/315) of published papers are based on samples from North America and Europe, and about 70% of published studies (219/315) are based on samples that were also used in other reports. At the same time, there are clear indications of methodological improvements over time, as is shown by a significant increase in longitudinal and experimental studies as well as in improved minimum genotyping. Recommendations for future research, such as minimum quality assessment of genes and environmental factors, specifying theoretical models guiding the study, and taking into account of cultural, ethnic, and lifetime perspectives, are formulated.

Differential effects of oxytocin on social sensitivity in two distinct breeds of dogs (Canis familiaris)

Dogs have been proven to show several human-analogue social behaviors, and recent research raises the possibility that the oxytocin system is related to these. However, despite dogs' general tendency to excel in the domain of social cognition, there is increasing evidence that dogs' ability to utilize human signals may vary with breed. Moreover, breeds may show differences not only in their 'inborn' communicative abilities, but also in their learning skills related to these. The aim of the present study was to explore breed differences and breed-specific effects of oxytocin administration on different aspects of social responsiveness. Dogs from two markedly different breeds, Border Collies (cooperative workers) and Siberian Huskies (independent workers) were tested. After having received intranasal administration of oxytocin or placebo, subjects participated in three behavioral tests measuring social responsiveness. Our results show that there are several behavioral differences between the two breeds and also that there are differential effects of the oxytocin treatment. Border Collies were in general more susceptible to the 'social' effects of oxytocin compared to Siberian Huskies: after oxytocin administration they (1) looked more at the experimenter in the 'Unreachable food' situation, (2) looked more at the owner and shifted their gaze more between the sound source and the owner in a potentially dangerous situation, and (3) looked longer at the experimenter's eyes in the 'Tolerance of prolonged eye contact' test. These findings suggest that selection for enhanced cooperative abilities, possibly complemented by the effect of different social environments the two breeds experience, affects dogs' performance in several behavioral tests and that the neurohormonal background differently modulates social behavior in different working breeds.

Oxytocin receptor gene variation rs53576 and alcohol abuse in a longitudinal population representative study

BACKGROUND

Oxytocin is an important regulator of social relationships and has been implicated in development of substance use and addiction. We examined the association of a variance in the oxytocin receptor gene (OXTR rs53576 polymorphism) with alcohol use in a population-representative sample, and potential moderation by social functioning.

METHODS

The analysis was carried out on the older birth cohort of the longitudinal Estonian Children Personality Behaviour and Health Study (ECPBHS), a cohort of initially 15 years old children (original n=593) recalled at ages 18 and 25. In all data collection waves the participants reported the frequency of consuming alcoholic beverages. Psychiatric interview was carried out at age 25 to assess the lifetime prevalence of substance use disorders. Adverse social interactions with teachers, classmates and family members were self-reported at ages 15 and 18. The minor (A) allele frequency was 0.37.

RESULTS

Males homozygous for the A allele (suggested to be associated with less efficient oxytocinergic functioning) were more frequent alcohol consumers at ages 15 and 18 and also more likely to have had alcohol abuse or addiction by age 25 compared to male G allele carriers. Alcohol use was not associated with the OXTR genotype in females. Both male and female AA homozygotes who had reported less favourable relations with their teachers at age 15 more likely had alcohol use disorder.

CONCLUSIONS

OXTR rs53576 polymorphism is associated with alcohol use and prevalence of alcohol use disorders in males, and this may be moderated by inferior interpersonal relationships.

The endocrinology of human caregiving and its intergenerational transmission

Variation in the quality of parental care has a tremendous impact on a child's social–emotional development. Research investigating the predictors of this variability in human caregiving behavior has mostly focused on learning mechanisms. Evidence is currently accumulating for the complementary underlying role of steroid hormones and neuropeptides. An overview is provided of the hormones and neuropeptides relevant for human caregiving behavior. Then the developmental factors are described that stimulate variability in sensitivity to these hormones and neuropeptides, which may result in variability in the behavioral repertoire of caregiving. The role of genetic variation in neuropeptide and steroid receptors, the role of testosterone and oxytocin during fetal development and parturition, and the impact of experienced caregiving in childhood on functioning of the neuroendocrine stress and oxytocin system are discussed. Besides providing a heuristic framework for further research on the ontogenetic development of human caregiving, a neuroendocrine model is also presented for the intergenerational transmission of caregiving practices. Insight into the underlying biological mechanisms that bring about maladaptive caregiving behavior, such as neglect and insensitive parenting, will hopefully result in more efficient approaches to reduce the high prevalence of such behavior and to minimize the impact on those affected.

Oxytocin efficacy is modulated by dosage and oxytocin receptor genotype in young adults with high-functioning autism: a 24-week randomized clinical trial

Recent studies have suggested that long-term oxytocin administration can alleviate the symptoms of autism spectrum disorder (ASD); however, factors influencing its efficacy are still unclear. We conducted a single-center phase 2, pilot, randomized, double-blind, placebo-controlled, parallel-group, clinical trial in young adults with high-functioning ASD, to determine whether oxytocin dosage and genetic background of the oxytocin receptor affects oxytocin efficacy. This trial consisted of double-blind (12 weeks), open-label (12 weeks) and follow-up phases (8 weeks). To examine dose dependency, 60 participants were randomly assigned to high-dose (32 IU per day) or low-dose intranasal oxytocin (16 IU per day), or placebo groups during the double-blind phase. Next, we measured single-nucleotide polymorphisms (SNPs) in the oxytocin receptor gene (OXTR). In the intention-to-treat population, no outcomes were improved after oxytocin administration. However, in male participants, Clinical Global Impression-Improvement (CGI-I) scores in the high-dose group, but not the low-dose group, were significantly higher than in the placebo group. Furthermore, we examined whether oxytocin efficacy, reflected in the CGI-I scores, is influenced by estimated daily dosage and OXTR polymorphisms in male participants. We found that >21 IU per day oxytocin was more effective than ⩽21 IU per day, and that a SNP in OXTR (rs6791619) predicted CGI-I scores for ⩽21 IU per day oxytocin treatment. No severe adverse events occurred. These results suggest that efficacy of long-term oxytocin administration in young men with high-functioning ASD depends on the oxytocin dosage and genetic background of the oxytocin receptor, which contributes to the effectiveness of oxytocin treatment of ASD.

Variation in the Oxytocin Receptor Gene Predicts Brain Region-Specific Expression and Social Attachment

BACKGROUND

Oxytocin (OXT) modulates several aspects of social behavior. Intranasal OXT is a leading candidate for treating social deficits in patients with autism spectrum disorder, and common genetic variants in the human OXTR gene are associated with emotion recognition, relationship quality, and autism spectrum disorder. Animal models have revealed that individual differences in Oxtr expression in the brain drive social behavior variation. Our understanding of how genetic variation contributes to brain OXTR expression is very limited.

METHODS

We investigated Oxtr expression in monogamous prairie voles, which have a well-characterized OXT system. We quantified brain region-specific levels of Oxtr messenger RNA and oxytocin receptor protein with established neuroanatomic methods. We used pyrosequencing to investigate allelic imbalance of Oxtr mRNA, a molecular signature of polymorphic genetic regulatory elements. We performed next-generation sequencing to discover variants in and near the Oxtr gene. We investigated social attachment using the partner preference test.

RESULTS

Our allelic imbalance data demonstrate that genetic variants contribute to individual differences in Oxtr expression, but only in particular brain regions, including the nucleus accumbens, where oxytocin receptor signaling facilitates social attachment. Next-generation sequencing identified one polymorphism in the Oxtr intron, near a putative cis-regulatory element, explaining 74% of the variance in striatal Oxtr expression specifically. Males homozygous for the high expressing allele display enhanced social attachment.

CONCLUSIONS

Taken together, these findings provide convincing evidence for robust genetic influence on Oxtr expression and provide novel insights into how noncoding polymorphisms in OXTR might influence individual differences in human social cognition and behavior.

Effects of oxytocin administration on spirituality and emotional responses to meditation

The oxytocin (OT) system, critically involved in social bonding, may also impinge on spirituality, which is the belief in a meaningful life imbued with a sense of connection to a Higher Power and/or the world. Midlife male participants (N = 83) were randomly assigned to receive intranasal OT or placebo. In exploratory analyses, participants were also genotyped for polymorphisms in two genes critical for OT signaling, the oxytocin receptor gene (OXTR rs53576) and CD38 (rs6449182 and rs3796863). Results showed that intranasal OT increased self-reported spirituality on two separate measures and this effect remained significant a week later. It also boosted participants' experience of specific positive emotions during meditation, at both explicit and implicit levels. Furthermore, the effect of OT on spirituality was moderated by OT-related genotypes. These results provide the first experimental evidence that spirituality, endorsed by millions worldwide, appears to be supported by OT.

Oxytocin and parent-child interaction in the development of empathy among children at risk for autism

This longitudinal study investigated whether variation in the oxytocin receptor gene (OXTR) and early parent-child interactions predicted later empathic behavior in 84 toddlers at high or low familial risk for autism spectrum disorder. Two well-studied OXTR single-nucleotide polymorphisms, rs53576 and rs2254298, were examined. Parent-child interaction was measured at 15 and 18 months of age during free play sessions. Empathy was measured at 24 and 30 months using a response to parental distress paradigm. While there was no direct association between parent-child interaction quality or OXTR and empathy, rs53576 moderated the relation between interaction quality and empathy. Results suggest that the interplay between OXTR and early parent-child interactions predicts individual differences in empathy in children at varying risk for atypical social development. Findings are consonant with a differential susceptibility model in which an OXTR variant may increase the social salience of interaction processes for specific allele carriers. These results increase our understanding of predictors of empathy development in young children with a wide range of social outcomes. (PsycINFO Database Record

Oxytocin Pathway Genes: Evolutionary Ancient System Impacting on Human Affiliation, Sociality, and Psychopathology

Oxytocin (OT), a nonapeptide signaling molecule originating from an ancestral peptide, appears in different variants across all vertebrate and several invertebrate species. Throughout animal evolution, neuropeptidergic signaling has been adapted by organisms for regulating response to rapidly changing environments. The family of OT-like molecules affects both peripheral tissues implicated in reproduction, homeostasis, and energy balance, as well as neuromodulation of social behavior, stress regulation, and associative learning in species ranging from nematodes to humans. After describing the OT-signaling pathway, we review research on the three genes most extensively studied in humans: the OT receptor (OXTR), the structural gene for OT (OXT/neurophysin-I), and CD38. Consistent with the notion that sociality should be studied from the perspective of social life at the species level, we address human social functions in relation to OT-pathway genes, including parenting, empathy, and using social relationships to manage stress. We then describe associations between OT-pathway genes with psychopathologies involving social dysfunctions such as autism, depression, or schizophrenia. Human research particularly underscored the involvement of two OXTR single nucleotide polymorphisms (rs53576, rs2254298) with fewer studies focusing on other OXTR (rs7632287, rs1042778, rs2268494, rs2268490), OXT (rs2740210, rs4813627, rs4813625), and CD38 (rs3796863, rs6449197) single nucleotide polymorphisms. Overall, studies provide evidence for the involvement of OT-pathway genes in human social functions but also suggest that factors such as gender, culture, and early environment often confound attempts to replicate first findings. We conclude by discussing epigenetics, conceptual implications within an evolutionary perspective, and future directions, especially the need to refine phenotypes, carefully characterize early environments, and integrate observations of social behavior across ecological contexts.

Primate paternal care: Interactions between biology and social experience

This article is part of a Special Issue "Parental Care".We review recent research on the roles of hormones and social experiences on the development of paternal care in humans and non-human primates. Generally, lower concentrations of testosterone and higher concentrations of oxytocin are associated with greater paternal responsiveness. Hormonal changes prior to the birth appear to be important in preparation for fatherhood and changes after the birth are related to how much time fathers spend with offspring and whether they provide effective care. Prolactin may facilitate approach and the initiation of infant care, and in some biparental non-human primates, it affects body mass regulation. Glucocorticoids may be involved in coordinating reproductive and parental behavior between mates. New research involving intranasal oxytocin and neuropeptide receptor polymorphisms may help us understand individual variation in paternal responsiveness. This area of research, integrating both biological factors and the role of early and adult experience, has the potential to suggest individually designed interventions that can strengthen relationships between fathers and their partners and offspring.

Neural, cognitive, and evolutionary foundations of human altruism

This article considers three forms of altruism from both a psychological and a neural perspective, with an emphasis on homologies that can be observed across species and potentially illuminate altruism's evolutionary origins. Kin-based altruism benefits biological relatives and, according to the theory of inclusive fitness, is ultimately beneficial to the altruist from a genetic standpoint. Kin selection adequately explains some altruistic behavior, but it is not applicable to much human altruism. Little is known about the neural processes that support it, but they may include cortical regions involved in processing autobiographical memory and the identities of familiar others. Reciprocity-based altruism is performed in expectation of future rewards and is supported by dopaminergic cortico-striatal networks that guide behavior according to anticipated rewards. Care-based altruism is aimed at improving the well-being of distressed and vulnerable individuals and is closely linked to empathic concern. This form of altruism is thought to rely on the subcortical neural systems that support parental care, particularly structures densely populated with receptors for the hormones oxytocin and vasopressin, including the amygdala, stria terminalis, and striatum. The amygdala may be a particularly important convergence point for care-based altruism because of its dual role in responding both to cues that signal infantile vulnerability and those that signal distress. Research on altruism continues to converge across disciplines, but more research linking molecular-level neural processes to altruistic behavior in humans and other species is needed, as is research on how various forms of altruism intersect. For further resources related to this article, please visit the WIREs website.

Genetic variation in CD38 and breastfeeding experience interact to impact infants' attention to social eye cues

Attending to emotional information conveyed by the eyes is an important social skill in humans. The current study examined this skill in early development by measuring attention to eyes while viewing emotional faces in 7-mo-old infants. In particular, we investigated individual differences in infant attention to eyes in the context of genetic variation (CD38 rs3796863 polymorphism) and experiential variation (exclusive breastfeeding duration) related to the oxytocin system. Our results revealed that, whereas infants at this age show a robust fear bias (increased attention to fearful eyes), their attention to angry and happy eyes varies as a function of exclusive breastfeeding experience and genetic variation in CD38. Specifically, extended exclusive breastfeeding duration selectively enhanced looking preference to happy eyes and decreased looking to angry eyes. Importantly, however, this interaction was impacted by CD38 variation, such that only the looking preferences of infants homozygous for the C allele of rs3796863 were affected by breastfeeding experience. This genotype has been associated with reduced release of oxytocin and higher rates of autism. In contrast, infants with the CA/AA genotype showed similar looking preferences regardless of breastfeeding exposure. Thus, differences in the sensitivity to emotional eyes may be linked to an interaction between the endogenous (CD38) and exogenous (breastfeeding) availability of oxytocin. These findings underline the importance of maternal care and the oxytocin system in contributing to the early development of responding to social eye cues.