Oxytocin modulates local topography of human functional connectome in healthy men at rest

How does oxytocin modulate human behavior?

While the highly evolutionarily conserved hypothalamic neuropeptide, oxytocin (OT) can influence cognitive, emotional and social functions, and may have therapeutic potential in disorders with social dysfunction, it is still unclear how it acts. Here, we review the most established findings in both animal model and human studies regarding stimuli which evoke OT release, its primary functional effects and the mechanisms whereby exogenous administration influences brain and behavior. We also review progress on whether OT administration can improve social symptoms in autism spectrum disorder and schizophrenia and consider possible impediments to translational success. Importantly, we emphasize that OT acting via its extensive central or peripheral receptors primarily influences behavior indirectly through neuromodulatory interactions with classical transmitters and other peptides which themselves can independently influence behavior. We also emphasize that exogenous administration studies increasingly demonstrate peripheral effects of OT may be of greater importance than originally thought, especially involving the vagus. Overall, we propose a hierarchical model whereby OT's neuromodulatory actions influence behavior across interconnected functional domains and ultimately help to promote survival, security and sociability. Initially, OT potently facilitates attention to salient social and other important stimuli and additionally modulates cognitive, emotional and reward processing in a person- and context-dependent manner to promote interpersonal social understanding, attraction and bonds on the one hand and social group cohesion through increased conformity, altruistic punishment and moral emotions on the other. OT also increases co-operation and protection across both social domains. We hope this review and model will promote further research and help aid future translation success.

The pharmacodynamic modulation effect of oxytocin on resting state functional connectivity network topology

Introduction

Neuroimaging studies have demonstrated that intranasal oxytocin has extensive effects on the resting state functional connectivity of social and emotional processing networks and may have therapeutic potential. However, the extent to which intranasal oxytocin modulates functional connectivity network topology remains less explored, with inconsistent findings in the existing literature. To address this gap, we conducted an exploratory data-driven study.

Methods

We recruited 142 healthy males and administered 24 IU of intranasal oxytocin or placebo in a randomized controlled double-blind design. Resting-state functional MRI data were acquired for each subject. Network-based statistical analysis and graph theoretical approaches were employed to evaluate oxytocin's effects on whole-brain functional connectivity and graph topological measures.

Results

Our results revealed that oxytocin altered connectivity patterns within brain networks involved in sensory and motor processing, attention, memory, emotion and reward functions as well as social cognition, including the default mode, limbic, frontoparietal, cerebellar, and visual networks. Furthermore, oxytocin increased local efficiency, clustering coefficients, and small-world propensity in specific brain regions including the cerebellum, left thalamus, posterior cingulate cortex, right orbitofrontal cortex, right superior frontal gyrus, left inferior frontal gyrus, and right middle orbitofrontal cortex, while decreasing nodal path topological measures in the left and right caudate.

Discussion

These findings suggest that intranasal oxytocin may produce its functional effects through influencing the integration and segregation of information flow within small-world brain networks, particularly in regions closely associated with social cognition and motivation.

Connectome dysfunction in patients at clinical high risk for psychosis and modulation by oxytocin

Abnormalities in functional brain networks (functional connectome) are increasingly implicated in people at Clinical High Risk for Psychosis (CHR-P). Intranasal oxytocin, a potential novel treatment for the CHR-P state, modulates network topology in healthy individuals. However, its connectomic effects in people at CHR-P remain unknown. Forty-seven men (30 CHR-P and 17 healthy controls) received acute challenges of both intranasal oxytocin 40 IU and placebo in two parallel randomised, double-blind, placebo-controlled cross-over studies which had similar but not identical designs. Multi-echo resting-state fMRI data was acquired at approximately 1 h post-dosing. Using a graph theoretical approach, the effects of group (CHR-P vs healthy control), treatment (oxytocin vs placebo) and respective interactions were tested on graph metrics describing the topology of the functional connectome. Group effects were observed in 12 regions (all pFDR < 0.05) most localised to the frontoparietal network. Treatment effects were found in 7 regions (all pFDR < 0.05) predominantly within the ventral attention network. Our major finding was that many effects of oxytocin on network topology differ across CHR-P and healthy individuals, with significant interaction effects observed in numerous subcortical regions strongly implicated in psychosis onset, such as the thalamus, pallidum and nucleus accumbens, and cortical regions which localised primarily to the default mode network (12 regions, all pFDR < 0.05). Collectively, our findings provide new insights on aberrant functional brain network organisation associated with psychosis risk and demonstrate, for the first time, that oxytocin modulates network topology in brain regions implicated in the pathophysiology of psychosis in a clinical status (CHR-P vs healthy control) specific manner.

Intranasal Oxytocin Modulates Decision-Making Depending on Outcome Predictability-A Randomized Within-Subject Controlled Trial in Healthy Males

Oxytocin (OT) has been extensively studied with regard to its socio-cognitive and -behavioral effects. Its potential as a therapeutic agent is being discussed for a range of neuropsychiatric conditions. However, there is limited evidence of its effects on non-social cognition in general and decision-making in particular, despite the importance of these functions in neuropsychiatry. Using a crossover/within-subject, blinded, randomized design, we investigated for the first time if intranasal OT (24 IU) affects decision-making differently depending on outcome predictability/ambiguity in healthy males. The Iowa Gambling Task (IGT) and the Cambridge Risk Task (CRT) were used to assess decision-making under low outcome predictability/high ambiguity and under high outcome probability/low ambiguity, respectively. After administration of OT, subjects performed worse and exhibited riskier performance in the IGT (low outcome predictability/high ambiguity), whereas they made borderline-significant less risky decisions in the CRT (high outcome probability/low ambiguity) as compared to the control condition. Decision-making in healthy males may therefore be influenced by OT and adjusted as a function of contextual information, with implications for clinical trials investigating OT in neuropsychiatric conditions.

Emerging trends in the delivery of nanoformulated oxytocin across Blood-Brain barrier

Neurological diseases are related to the central nervous system disorders and considered as serious cases. Several drugs are used to treat neurological diseases; however, to date the main issue is to design a therapeutic model which can cross the blood-brain-barrier (BBB) easily. The delivery of neuropeptides into the brain lays as one of the important routes for treating neurological disorders. Neuropeptides have been demonstrated as potential therapeutics for neurological disorders. Among numerous neuropeptides, the oxytocin (OT) hormone is of particular interest as it serves as a neurotransmitter in the brain as well as its role as a hormone. OT has a wide-range of activities in the brain and has a key role in cognitive, neuroendocrine, and social functions. However, OT does not cross the BBB readily coupled with its half-life in the blood being too short. The current literature reveals that the delivery of OT by nanoparticle-based drug delivery system (DDS) improves its efficacy. Nanoparticle based DDS are considered important tools for the targeted delivery of drugs to the brain as they lower toxicity of the drug and improve the drug efficacy. Nanoparticles are advantageous candidates for biomedical applications due to their distinctive characteristics such as quantum effects, large surface area and their ability to carry and transport the drug to its target site. OT can be delivered through oral and intranasal routes, but the bioavailability of OT inside the brain can further be enhanced by the delivery using nanoparticles. The application of nano-based delivery system not only improves the penetration of OT inside brain but also increases its half-life by the application of encapsulation and extended release. The aim of current review is to provide an overview of nanoparticle-based drug-delivery systems for the delivery of OT inside brain.

Heterogeneity in response to repeated intranasal oxytocin in schizophrenia and autism spectrum disorders: A meta-analysis of variance

Intranasal oxytocin (OT) has been suggested as a putative adjunctive treatment for patients with schizophrenia and autism spectrum disorders (ASD). Here, we examine available evidence from trials investigating the effects of repeated administrations of intranasal OT on the core symptoms of patients with schizophrenia and ASD, focusing on its therapeutic efficacy and heterogeneity of response (meta-ANOVA). Repeated administration of intranasal OT does not improve most of the core symptoms of schizophrenia and ASD, beyond a small tentative effect on schizophrenia general symptoms. However, we found significant moderator effects for dose in schizophrenia total psychopathology and positive symptoms, and percentage of included men and duration of treatment in schizophrenia general symptoms. We found evidence of heterogeneity (increased variance) in the response of schizophrenia negative symptoms to intranasal OT compared with placebo, suggesting that subgroups of responsive and non-responsive patients might coexist. For other core symptoms of schizophrenia, or any of the core symptom dimensions in ASD, the response to repeated treatment with intranasal OT did not show evidence of heterogeneity.