Salivary Oxytocin Concentrations Research Articles

Negative association between basal oxytocin and oxytocin changes after repetitive transcranial magnetic stimulation in patients with treatment-resistant depression

Repetitive transcranial magnetic stimulation (rTMS) is a neuromodulator effective for treating depressive symptoms in patients with treatment-resistant depression (TRD). One of the multiple mechanisms for its antidepressant effects proposed is related to the hypothalamus. Oxytocin is a neuropeptide synthesized in the hypothalamus that affects human behavior and psychology, including social and affiliative behaviors, stress regulation, and fear and emotion processing. There have been no reports on the relationship between rTMS and oxytocin for the treatment of TRD. Therefore, we aimed to investigate changes in salivary oxytocin concentrations in patients with TRD before and after 6 weeks of rTMS treatment. A total of 28 patients with TRD who received rTMS at Saga University Hospital between August 2013 and August 2020 were included. Although rTMS treatment significantly improved 24-item Hamilton Depression Rating Scale scores, rTMS treatment did not change mean salivary oxytocin after 6 weeks of treatment in patients with TRD. Multiple regression analysis revealed that the change in salivary oxytocin levels after rTMS treatment was negatively associated with basal oxytocin levels before rTMS treatment, suggesting that rTMS treatment tends to decrease oxytocin levels in patients with depression with high basal oxytocin levels while increasing them in those with low basal levels. These findings suggest that rTMS treatment improved depressive symptoms through mechanisms other than the modulatory effect on oxytocin levels in patients with TRD, while there is room for further studies to confirm these findings using a larger patient sample size and/or a sham rTMS procedure.

Do pet dogs reciprocate the receipt of food from familiar and unfamiliar conspecifics?

Reciprocity is one of the most prominent explanations for the evolution of stable cooperation. Although reciprocity has been studied for decades in numerous animal species and behavioural contexts, its underlying proximate mechanisms remain unclear. Domestic dogs provide a useful model species for the study of proximate mechanisms, though there are currently inconsistent findings regarding dogs' propensity to reciprocate. Here, we investigated whether, after minimal training, pet dogs would press a button, which remotely controlled a food dispenser, to deliver food to an enclosure occupied by a helpful conspecific that had provided them with food or an unhelpful conspecific that had not provided them with food. We included an asocial control condition in which the enclosure was unoccupied and a social facilitation control in which the food delivery mechanism was non-functional. Whether subjects were familiar with the helpful and unhelpful conspecifics was also varied. In addition, to investigate potential mechanisms underlying reciprocity, we measured subjects salivary oxytocin concentration before and after they experienced the helpful and unhelpful acts. There was no effect of the previous helpfulness or the familiarity of the partner on the number of times subjects pressed the button. However, there was also no effect of the presence of a partner or the operationality of the food delivery mechanism on the number of button presses, indicating that subjects were not pressing the button to provision the partner. Moreover, the experience of the helpful or unhelpful act did not influence subjects' salivary oxytocin concentration. Variation in findings of reciprocity across studies appears to correspond with differing training protocols. Subjects' understanding of the task in the current study may have been constrained by the limited training received. Additional tests to verify subjects' understanding of such tasks are warranted in future studies.

Validation of two immunoassays for oxytocin measurements in human saliva.

The objective of this research was to develop and validate two immunoassays for oxytocin measurement in human saliva, one using a monoclonal and the other a polyclonal antibody against oxytocin, whose affinity for oxytocin was tested by an antibody mapping epitope analysis. These assays were analytically validated and used to compare oxytocin concentrations with those obtained with a commercial kit before and after the extraction or reduction/alkylation (R/A) treatments to saliva samples. The assays were also used to evaluate changes in salivary oxytocin concentrations following a physical effort and an induced psychological stress, which have previously been described as situations that cause an increase in salivary oxytocin. Both assays showed to be precise and accurate in the validation studies, and the antibodies used showed a defined binding region in case of the monoclonal antibody, whereas the polyclonal antibody showed binding events through all the oxytocin sequence. Although the monoclonal and polyclonal assays showed a positive correlation, they give results in a different range of magnitude. Both assays showed significant increases in oxytocin concentrations when applied after the physical effort and the psychological stress. This study shows that a variability in the reported values of oxytocin can occur depending on the assay and indicates that the use of different types of antibodies can give a different range of values when measuring oxytocin in saliva.

Stress during the COVID-19 Pandemic Moderates Pain Perception and Momentary Oxytocin Levels.

Self-reported pain levels have been associated with increased stress levels during the COVID-19 pandemic. Less is known about the long-term effects of stress on individuals' physical and emotional pain levels and their associations with the neuropeptide hormone oxytocin. We aimed to predict momentary pain through individual stress levels and momentary oxytocin levels at genuinely high-stress phases, namely during COVID-related lockdowns. In a cross-sectional (n = 254) and a longitudinal (n = 196) assessment during lockdowns in Germany, participants completed a 2-day ecological momentary assessment (EMA) protocol (collecting six saliva samples on two consecutive days each and simultaneously reporting on stress, physical, and emotional pain levels) in 2020, as well as one year later, in 2021. Hierarchical linear modeling revealed significant positive associations between individuals' stress levels and physical pain, both cross-sectionally (b = 0.017; t(103) = 3.345; p = 0.001) and longitudinally (b = 0.009; t(110) = 2.025; p = 0.045). Similarly, subjective stress ratings showed significant positive associations with emotional pain on a within-person (b = 0.014; t(63) = 3.594; p < 0.001) as well as on a between-person (b = 0.026; t(122) = 5.191; p < 0.001) level. Participants further displayed significantly lower salivary oxytocin when experiencing higher levels of emotional pain (b = -0.120; t(163) = -2.493; p = 0.014). In addition, high-stress levels significantly moderated the association between physical pain and salivary oxytocin (b = -0.012; t(32) = -2.150; p = 0.039). Based on mechanistic and experimental research, oxytocinergic mechanisms have long been suggested to modulate pain experiences, however, this has not yet been investigated in everyday life. Our data, which was collected from a large sample experiencing continued stress, in this case, during the COVID-19 pandemic, suggests that individuals experience more intense physical pain and elevated stress levels, as shown by particularly low salivary oxytocin concentrations.

Salivary oxytocin concentration correlates with plasma oxytocin concentration in patients undergoing induction of labor

Salivary oxytocin concentration has been used as a proxy for plasma oxytocin, but whether a correlation exists in the context of labor is unknown. This study aimed to measure the correlation between oxytocin concentration in plasma and saliva in patients undergoing induction of labor.

Salivary oxytocin in autistic patients and in patients with intellectual disability.

Assessing the role of oxytocin (OT) in the regulation of social interaction is a promising area that opens up new opportunities for studying the mechanisms of developing autism spectrum disorders (ASD). To assess the correlation between the salivary OT level and age-related and psychopathological symptoms of children with intellectual disability (ID) and ASD. We used the clinical and psychopathological method to assess the signs of ASD based on International Classification of Diseases (ICD-10), the severity of ASD was specified by the selected Russian type version "Childhood Autism Rating Scale" (CARS). Patients of both groups had an IQ score below 70 points. The median and interquartile range of salivary OT levels in patients with ID and ASD were 23.897 [14.260-59.643] pg/mL, and in the group ID without ASD - Me = 50.896 [33.502-83.774] pg/mL (p = 0.001). The severity of ASD on the CARS scale Me = 51.5 [40.75-56.0] score in the group ID with ASD, and in the group ID without ASD-at the level of Me = 32 [27.0-38.0] points (p < 0.001). According to the results of correlation-regression analysis in the main group, a direct correlation was established between salivary OT level and a high degree of severity of ASD Rho = 0.435 (p = 0.005). There was no correlation between the salivary OT level and intellectual development in the group ID with ASD, Rho = 0.013 (p = 0.941) and we have found a relationship between oxytocin and intellectual development in the group ID without ASD, Rho = 0.297 (p = 0.005). There was no correlation between salivary OT and age, ASD and age. The results of this study indicate that patients in the group ID with ASD demonstrated a lower level of salivary OT concentration and a direct relationship between the maximum values of this indicator and the severity of autistic disorders, in contrast to patients in the group ID without ASD.

Salivary Cortisol, but Not Oxytocin, Varies With Social Challenges in Domestic Pigs: Implications for Measuring Emotions.

Animals respond to inherently rewarding or punishing stimuli with changes in core affective states, which can be investigated with the aid of appropriate biomarkers. In this study we evaluate salivary cortisol (sCORT) and salivary oxytocin (sOXT) concentrations under baseline conditions and in response to two negatively- and two positively-valenced social challenges in 75 young pigs (Sus scrofa domesticus), housed and tested in eight social groups. We predicted that: (1) Relative to baseline, weaning and brief social isolation would be associated with increases in sCORT, due to psychosocial stress, and reductions in sOXT, due to a lack of opportunities for social support; and (2) Opportunities for social play, and reunions with group members after a separation would be associated with weaker sCORT responses, and increases in sOXT concentrations compared to baseline and to negative social challenges. Testing and sample collection occurred between 28 and 65 days of age and involved a within-subject design, in which every subject was sampled multiple times in neutral (baseline), negative and positive social contexts. We also recorded behavioral data and measured rates of agonism, play and affiliative interactions in the different contexts, prior to saliva sampling. As expected, negative social challenges were associated with robust cortisol responses. Relative to baseline, pigs also had higher sCORT responses to positive social challenges, although these differences were only significant during reunions. Salivary oxytocin concentrations did not differ between the different social conditions, although sOXT was lowest during the brief social isolation. Behavioral analyses confirmed predictions about the expected changes in social interactions in different social contexts, with increases in agonism following weaning, increases in coordinated locomotor play in the play context and high rates of affiliative interactions during reunions. Relative sCORT reactivity to different contexts may reflect the intensity of emotional responses, with greater increases occurring in response to challenges that involve more psychosocial stress. Our results suggest that sOXT is not a reliable indicator of emotional valence in pigs, although more research is needed to characterize sOXT responses to various challenges with and without access to social support.

Salivary oxytocin and touch in everyday life: Results from an EMA study during Covid-19 lockdown

BackgroundAffectionate touch is important in human social life. Previous research demonstrated that touch is associated with release of endogenous oxytocin and has calming and stress reducing effects. Less is known about the impact of Covid-19-related lockdown on psychobiological outcomes in everyday life. We, thus, focused on the relationship between daily social touch and oxytocin levels during Covid-19 lockdown.Methods173 women and 74 men (age: M=32.6, SD=13.1) participated in ecological momentary assessment on two consecutive days during Covid-19 pandemic in Spring 2020. At 6 timepoints per day participants collected saliva samples and simultaneously reported subjective momentary burden, mood and social interactions, including social touch. Concentrations of salivary oxytocin, cortisol, and alpha amylase were analyzed using enzyme linked immunoassay.ResultsHierarchical linear model (HLM) analyzes showed a significantly negative association between social touch intensity and self-reported burden levels (t=-2.683; p=.007) as well as positive association with oxytocin concentrations (t=2.476; p=.013).ConclusionsThese preliminary finding show that individuals experiencing intense social touch have higher salivary oxytocin concentrations and report less burden in their everyday life. While further analyses within this study are being conducted, these results suggest that oxytocin might play a mediating role between social touch and the individual's well-being.

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.

Ejaculate Collection Influences the Salivary Oxytocin Concentrations in Breeding Male Pigs.

Simple SummaryThis study aimed to evaluate how the process of ejaculate collection affects oxytocin concentrations in saliva of boars used in artificial insemination. Saliva samples of 33 boars were collected the day before ejaculate collection, during the ejaculation time, and two hours after ejaculate collection. Free oxytocin and oxytocin linked to proteins were quantified in these saliva samples. Oxytocin concentrations during the ejaculation time were higher than the day before with oxytocin linked to proteins showing higher differences. In addition, younger boars, boars with higher libido intensity and boars of the Pietrain breed showed higher values of oxytocin in saliva during ejaculation than the day before. This study demonstrated that ejaculation influences the salivary oxytocin concentrations boars.The objective of the present study was to evaluate the possible changes of oxytocin concentrations in saliva during and after ejaculate collection in breeding boars usually used in artificial insemination programs. Saliva samples of 33 boars were collected the day before ejaculate collection (DB), during the ejaculation time (T0) and two hours after ejaculate collection (T2). Free oxytocin and oxytocin linked to proteins concentrations were measured by two methods previously developed and validated for saliva of pigs. Younger boars, boars with higher libido intensity and boars of the Pietrain breed showed higher values of oxytocin in saliva during ejaculation than the day before. In addition, boars with higher libido showed higher concentrations two hours after ejaculate collection than during the day before. These changes were of higher magnitude and significance when oxytocin linked to proteins was measured. In conclusion, this study demonstrated for the first time that ejaculation influences the salivary oxytocin concentrations in breeding boars, although this influence varies according to age, libido and breed.

The Effects of Essential Oil on Salivary Oxytocin Concentration in Postmenopausal Women.

Objectives: The aim of this study was to find essential oils that have increased the oxytocin concentration in postmenopausal women. Methods: Fifteen postmenopausal women participated in this study and the effects of 10 different essential oils were investigated. The essential oils included rose otto, sweet orange, lavender, neroli, frankincense, jasmine absolute, ylang ylang, roman chamomile, clary sage, and Indian sandalwood. The subjects were exposed to the control first for 20 min, followed by exposure to an essential oil for 20 min. Each subject received exposure to only a single kind of essential oil per day. Saliva was collected four times for each patient: immediately before and immediately after control exposure, and immediately before and immediately after essential oil exposure. The oxytocin concentration in the saliva was measured using a competitive ELISA kit. Results: The results showed that salivary oxytocin concentrations increased significantly more after exposure to lavender, neroli, jasmine absolute, roman chamomile, clary sage, and Indian sandalwood than after exposure to the control odor. Conclusions: The aroma of certain essential oils may elicit increased secretion of oxytocin in postmenopausal women. This study suggests that olfactory stimulation with any of a number of essential oils increases salivary oxytocin concentrations, which may inhibit aging-induced reduction in muscle mass and function in women.

Effects of Human–Dog Interactions on Salivary Oxytocin Concentrations and Heart Rate Variability: A Four-Condition Cross-Over Trial

ABSTRACTDog ownership is often advocated for its potential benefits to human health, with changes to oxytocin and autonomic nervous system (ANS) activity proposed as possible underlying mechanisms. The aims of the current study were to a) examine the effect of two common types of human–dog interactions (dog-walking and affiliative interactions) on salivary oxytocin concentrations and heart rate variability (HRV, an indicator of ANS activity), and b) investigate any putative moderating role for the strength of human–dog attachment on such responses. Twenty-nine dog owners completed a four-condition random-order cross-over trial: dog-walking (DW); walking without the dog (W); affiliative human–dog interaction (H-DI); and resting without the dog (C). Each condition was performed for approximately 15 minutes. Saliva and HRV samples were collected before and after each condition. Linear mixed models were used to analyze data, with the participant considered a random effect; condition, order of conditions, and condition duration as fixed effects. Oxytocin concentrations were not significantly different following any of the four conditions. HRV was significantly reduced following DW (mean change HF HRV = –0.37, 95% CI = –0.70, –0.04) and W (mean change HF HRV = –0.49, 95% CI = –0.81, –0.17). Considering moderation by the strength of the human–dog bond, pairwise comparisons revealed that, compared with W, DW elicited an increase in oxytocin concentrations (mean change 9.32 pg/mL, 95% CI = 6.52, 12.12) and HRV (mean change SDRR = 0.41, 95% CI = 0.19, 0.63) in owners with lower levels of attachment. These owners also displayed increased oxytocin concentrations following H-DI (mean change 3.90 pg/mL, 95% CI = 1.48, 6.32), compared with C. Overall, we did not find a consistent pattern for positive oxytocin or HRV responses to human–dog interactions. The strength of owner–dog attachment was found to have a moderating effect, suggesting that human–dog interactions may elicit greater physiological responses in low-attachment individuals.

Maternal responsivity and oxytocin in opioid-dependent mothers.

Although prenatal opioid exposure and postnatal withdrawal (neonatal abstinence syndrome) are associated with infant neurobehavioral deficits, little is known about the impact of continued maternal opioid treatment in the postnatal period on maternal responsivity and relationship to mother's oxytocin release during dyadic interactions in the Still Face paradigm. Mother and infant dyads (N=14) were recruited and comprised of mothers on opioid replacement throughout pregnancy and postpartum (opioid-exposed group, n=7) and a demographically controlled, non-exposed group (n=7). Salivary oxytocin was collected following 10min of infant separation before and immediately after a 6-min Still Face paradigm. Oxytocin measures correlated strongly with sensitive and prosocial maternal behaviors in response to infant initiation. Opioid-exposed compared to non-exposed mothers had significantly lower pre-test to post-test rise in salivary oxytocin concentration level as well as fewer sensitive behaviors during the reunion condition of the Still Face paradigm. Maternal opioid dependence during early infancy may impair maternal responsivity and sensitivity through suppression of the oxytocin reflex to infant stimulation.

Effects of Lactobacillus reuteri-containing lozenges on healing after surgical removal of mandibular third molars: a randomised controlled trial.

We investigated the effect of probiotic supplements on oral wound healing, swelling, pain and discomfort after surgical removal of mandibular third molars. A second aim was to evaluate if the intervention could influence the concentrations of oxytocin in saliva. Sixty-four consecutive volunteers (18-34 years) were enrolled to a double-blind randomised placebo-controlled trial with two parallel arms. Following surgery, the patients were asked to take three lozenges per day containing two strains of Lactobacillus reuteri (DSM 17938 and ATCC PTA 5289) or placebo for two weeks. The clinical healing and extra-oral swelling were scored two weeks post-operatively. Samples of wound exudate were cultivated for the presence of Staphylococcus aureus and β-haemolytic streptococci. Salivary oxytocin concentrations were analysed from pre- and post-surgery samples using ELISA technique. Compliance and the subjective perception of swelling, pain and discomfort were reported daily through visual analogue scales in a logbook. All patients except three completed the protocol and the postoperative course was uneventful in most cases. Minor extra-oral swellings were noted in five patients, but none required antibiotic treatment. At the 2-week follow-up, there were no significant differences in clinical wound healing index, extra-oral swelling, bacterial growth or salivary oxytocin levels between the groups. The self-reported data unveiled, however, a significantly reduced sense of swelling, in particular during the second week after surgery in the probiotic test group (P<0.05). Likewise, significantly fewer nights with disturbed sleep and fewer days with sick-leave from work were reported among the participants in the test group (P<0.05). No differences were found in the post-operative use of analgesics. In conclusion, we found no significant influence of probiotic supplements on objective wound healing after surgical extraction of impacted mandibular third molars. However, since the patients' perceived significant post-operative ameliorations, further studies are needed to explore the patient's value of the intervention.

Increase in salivary oxytocin and decrease in salivary cortisol after listening to relaxing slow-tempo and exciting fast-tempo music.

Relaxation and excitation are components of the effects of music listening. The tempo of music is often considered a critical factor when determining these effects: listening to slow-tempo and fast-tempo music elicits relaxation and excitation, respectively. However, the chemical bases that underlie these relaxation and excitation effects remain unclear. Since parasympathetic and sympathetic nerve activities are facilitated by oxytocin and glucocorticoid, respectively, we hypothesized that listening to relaxing slow-tempo and exciting fast-tempo music is accompanied by increases in the oxytocin and cortisol levels, respectively. We evaluated the change in the salivary oxytocin and cortisol levels of participants listening to slow-tempo and fast-tempo music sequences. We measured the heart rate (HR) and calculated the heart rate variability (HRV) to evaluate the strength of autonomic nerve activity. After listening to a music sequence, the participants rated their arousal and valence levels. We found that both the salivary oxytocin concentration and the high frequency component of the HRV (HF) increased and the HR decreased when a slow-tempo music sequence was presented. The salivary cortisol level decreased and the low frequency of the HRV (LF) to HF ratio (LF/HF) increased when a fast-tempo music sequence was presented. The ratio of the change in the oxytocin level was correlated with the change in HF, LF/HF and HR, whereas that in the cortisol level did not show any correlation with indices of autonomic nerve activity. There was no correlation between the change in oxytocin level and self-reported emotions, while the change in cortisol level correlated with the arousal level. These findings suggest that listening to slow-tempo and fast-tempo music is accompanied by an increase in the oxytocin level and a decrease in the cortisol level, respectively, and imply that such music listening-related changes in oxytocin and cortisol are involved in physiological relaxation and emotional excitation, respectively.

Salivary Oxytocin Concentration Changes during a Group Drumming Intervention for Maltreated School Children.

Many emotionally-disturbed children who have been maltreated and are legally separated from their parents or primary caregivers live in group homes and receive compulsory education. Such institutions provide various special intervention programs. Taiko-ensou, a Japanese style of group drumming, is one such program because playing drums in a group may improve children’s emotional well-being. However, evidence for its efficacy has not been well established at the biological level. In this study, we measured salivary levels of oxytocin (OT), a neuropeptide associated with social memory and communication, in three conditions (recital, practice, and free sessions) in four classes of school-aged children. Following the sessions, OT concentrations showed changes in various degrees and directions (no change, increases, or decreases). The mean OT concentration changes after each session increased, ranging from 112% to 165%. Plasma OT concentrations were equally sensitive to drum playing in school-aged boys and girls. However, the difference between practice and free play sessions was only significant among elementary school boys aged 8–12 years. The results suggest that younger boys are most responsive to this type of educational music intervention.

Choir versus Solo Singing: Effects on Mood, and Salivary Oxytocin and Cortisol Concentrations.

The quantification of salivary oxytocin (OXT) concentrations emerges as a helpful tool to assess peripheral OXT secretion at baseline and after various challenges in healthy and clinical populations. Both positive social interactions and stress are known to induce OXT secretion, but the relative influence of either of these triggers is not well delineated. Choir singing is an activity known to improve mood and to induce feelings of social closeness, and may therefore be used to investigate the effects of positive social experiences on OXT system activity. We quantified mood and salivary OXT and cortisol (CORT) concentrations before, during, and after both choir and solo singing performed in a randomized order in the same participants (repeated measures). Happiness was increased, and worry and sadness as well as salivary CORT concentrations were reduced, after both choir and solo singing. Surprisingly, salivary OXT concentrations were significantly reduced after choir singing, but did not change in response to solo singing. Salivary OXT concentrations showed high intra-individual stability, whereas salivary CORT concentrations fluctuated between days within participants. The present data indicate that the social experience of choir singing does not induce peripheral OXT secretion, as indicated by unchanged salivary OXT levels. Rather, the reduction of stress/arousal experienced during choir singing may lead to an inhibition of peripheral OXT secretion. These data are important for the interpretation of future reports on salivary OXT concentrations, and emphasize the need to strictly control for stress/arousal when designing similar experiments.

Salivary Oxytocin Concentration Associates with the Subjective Feeling of Body Ownership during the Rubber Hand Illusion.

Oxytocin is a hormone of the posterior pituitary that promotes lactation, maternal bonding, and birth. Recent studies have shown that oxytocin may modulate social recognition in both sexes, and thus it may be related to empathy. Brain regions that are associated with social recognition and empathy (e.g., the insular cortex) are activated in the rubber hand illusion (RHI), which involves illusory ownership of a rubber hand caused by brush strokes applied synchronously to both a rubber hand and one of the participant's hand, which is hidden from view. It is intriguing to examine whether oxytocin modulates plastic changes in body representation, such as the changes occurring in the RHI. In the present study, we investigated the relationship between salivary oxytocin concentration and the feeling of rubber hand ownership. Brush strokes were applied synchronously or asynchronously to the participant's hand and a rubber hand on different days. Salivary oxytocin was measured before and after the behavioral tasks. We found that participants who had high concentrations of salivary oxytocin tended to feel strong ownership of the rubber hand. We also found that the participants with a high autism spectrum quotient (AQ) score who particularly felt difficulties in social skills and communications tended to feel weak rubber hand ownership. We observed that illusory body ownership was closely linked to social communications and a related neuroendocrine basis. The results of the present study suggest that an individual's salivary oxytocin concentration can predict the extent to which the individual experiences the RHI; furthermore, oxytocin might modulate the sensation of body ownership.

Salivary oxytocin concentrations in response to running, sexual self-stimulation, breastfeeding and the TSST: The Regensburg Oxytocin Challenge (ROC) study

Intranasal oxytocin (OXT) application is emerging as a potential treatment for socio-emotional disorders associated with abnormalities in OXT system (re-) activity. The crucial identification of patients with such abnormalities could be streamlined by the assessment of basal and stimulus-induced OXT concentrations in saliva, using a simple, stress-free sampling procedure (i.e. an OXT challenge test). We therefore established the Regensburg Oxytocin Challenge (ROC) test to further validate salivary OXT concentrations as a practical, reliable and sensitive biomarker.OXT concentrations were quantified by radioimmunoassay in samples collected at home by healthy adult male and female volunteers before and after running (“Run”) or sexual self-stimulation (“Sex”). In lactating women, salivary OXT concentrations were quantified before, during and after breastfeeding. Salivary OXT along with salivary cortisol and heart rate were monitored in healthy adult participants undergoing the Trier Social Stress Test (TSST).The home-based “Run” and “Sex” challenges as well as the laboratory-based TSST caused quantifiable, rapid, and consistent increases in salivary OXT (approximately 2.5-fold after 10–15min), which were similar for men and women. Breastfeeding did not result in measurably increased salivary OXT levels, probably because the short pulses of OXT release characteristic for lactation were missed.Taken together, ROC tests reliably assess the responsiveness of the OXT system (i.e., the increase in salivary OXT concentrations as compared to basal levels) to challenges such as “Run“ and “Sex“ at home or psychosocial stress (TSST) in the laboratory. Further studies with larger sample numbers are essentially needed in order to reveal individual differences in ROC test outcomes depending on, for example, genetic or environmental factors.

A human tendency to anthropomorphize is enhanced by oxytocin

In the course of human evolution, the brain has evolved into a highly sensitive detector of social signals. As a consequence of this socially driven adaptation, humans display a tendency to anthropomorphize, that is they attribute social meaning to non-social agents. The evolutionarily highly conserved hypothalamic peptide oxytocin (OXT) has been identified as a key factor attaching salience to socially relevant cues, but whether it contributes to spontaneous anthropomorphism is still elusive. In the present study involving 60 healthy female participants, we measured salivary OXT concentrations and explored the effect of a single intranasal dose of synthetic OXT (24 IU) or placebo (PLC) on anthropomorphic tendencies during participants׳ verbal descriptions of short video clips depicting socially and non-socially moving geometric shapes. Our results show that endogenous OXT concentrations at baseline positively correlated with the attribution of animacy to social stimuli. While intranasal OXT had no modulatory effect on arousal ratings and did not make the participants more talkative, the treatment boosted anthropomorphic descriptions specifically for social stimuli. In conclusion, we here provide first evidence indicating that spontaneous anthropomorphism in women is facilitated by oxytocin, thereby enabling a context-specific upregulation of the propensity to anthropomorphize environmental cues.