Oxytocin Enhances Basolateral Amygdala Activation and Functional Connectivity While Processing Emotional Faces: Preliminary Findings in Autistic Versus Non-Autistic Women

Neuroimaging and behavioral evidence of sex-specific effects of oxytocin on human sociality

Although the social role of oxytocin came to light due to sex-specific interactions such as mother-offspring bonding, current understanding of sex differences in the effects of oxytocin on human sociality is limited because of the predominance of all-male samples. With the increasing inclusion of females in intranasal oxytocin research, it is now possible to explore such patterns. Neuroimaging studies reveal relatively consistent sex-differential effects of oxytocin on the activation of brain regions associated with processing social stimuli - particularly the amygdala. Findings from behavioral research are varied but suggest that oxytocin more often facilitates social cognition and positive social interactions in males, with context-dependent effects in each sex. We discuss potential biological and psychological mechanisms underlying the reported sex differences, and conclude with considerations for future research and clinical applications of oxytocin.

The neurobiological mechanisms underlying the effects of exercise interventions in autistic individuals

Autism spectrum disorder is a pervasive and heterogeneous neurodevelopmental condition characterized by social communication difficulties and rigid, repetitive behaviors. Owing to the complex pathogenesis of autism, effective drugs for treating its core features are lacking. Nonpharmacological approaches, including education, social-communication, behavioral and psychological methods, and exercise interventions, play important roles in supporting the needs of autistic individuals. The advantages of exercise intervention, such as its low cost, easy implementation, and high acceptance, have garnered increasing attention. Exercise interventions can effectively improve the core features and co-occurring conditions of autism, but the underlying neurobiological mechanisms are unclear. Abnormal changes in the gut microbiome, neuroinflammation, neurogenesis, and synaptic plasticity may individually or interactively be responsible for atypical brain structure and connectivity, leading to specific autistic experiences and characteristics. Interestingly, exercise can affect these biological processes and reshape brain network connections, which may explain how exercise alleviates core features and co-occurring conditions in autistic individuals. In this review, we describe the definition, diagnostic approach, epidemiology, and current support strategies for autism; highlight the benefits of exercise interventions; and call for individualized programs for different subtypes of autistic individuals. Finally, the possible neurobiological mechanisms by which exercise improves autistic features are comprehensively summarized to inform the development of optimal exercise interventions and specific targets to meet the needs of autistic individuals.

Intranasal oxytocin as a treatment for anxiety and autism: From subclinical to clinical applications

Animal and human studies have demonstrated that intranasal oxytocin (OT) can penetrate the brain and induce cognitive, emotional, and behavioral changes, particularly in social functioning. Consequently, numerous investigations have explored the potential of OT as a treatment for anxiety and autism, conditions characterized by social deficits. Although both subclinical and clinical studies provide converging evidence of the therapeutic effects of OT in reducing anxiety levels and improving social symptoms in autism, results are not always consistent. Additionally, the pharmacological mechanism of OT requires further elucidation for its effective clinical application. Therefore, this review aims to examine the contentious findings concerning the effects of OT on anxiety and autism, offer interpretations of the inconsistent results from the perspectives of individual differences and varying approaches to OT administration, and shed light on the underlying mechanisms of OT. Ultimately, standardization of dosage, frequency of administration, formulation characteristics, and nasal spray devices is proposed as essential for future human studies and clinical applications of OT treatment.

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.

Autistic and non-autistic individuals show the same amygdala activity during emotional face processing

BACKGROUND

Autistic and non-autistic individuals often differ in how they perceive and show emotions, especially in their ability and inclination to infer other people's feelings from subtle cues like facial expressions. Prominent theories of autism have suggested that these differences stem from alterations in amygdala functioning and that amygdala hypoactivation causes problems with emotion recognition. Thus far, however, empirical investigations of this hypothesis have yielded mixed results and largely relied on relatively small samples.

METHODS

In a sample of 72 autistic and 79 non-autistic participants, we conducted a study in which we used the Hariri paradigm to test whether amygdala activation during emotional face processing is altered in autism spectrum disorder, and whether common mental disorders like depression, ADHD or anxiety disorders influence any potential alterations in activation patterns.

RESULTS

We found no evidence for differences in amygdala activation, neither when comparing autistic and non-autistic participants, nor when taking into account mental disorders or the overall level of functional impairment.

LIMITATIONS

Because we used one basic emotion processing task in a Dutch sample, results might not generalise to other tasks and other populations.

CONCLUSIONS

Our results challenge the view that autistic and non-autistic processing of emotional faces in the amygdala is vastly different and call for a more nuanced view of differences between non-autistic and autistic emotion processing.

Oxytocin effects on amygdala reactivity to angry faces in males and females with antisocial personality disorder

The amygdala is a key region in current neurocircuitry models of reactive aggression as it is crucially involved in detecting social threat and provocation. An increased amygdala reactivity to angry faces has been reported in aggression-prone individuals and the neuropeptide oxytocin (OT) could dampen anger-related amygdala reactivity in a number of mental disorders. One example is the antisocial personality disorder (ASPD) which has so far only been studied in limited numbers. To address the question whether OT can normalize amygdala hyperreactivity to emotional faces, we conducted a functional magnetic resonance imaging experiment with 20 men and 18 women with ASPD and 20 male and 20 female healthy control (HC) participants in a double-blind, randomized, placebo (PLC)-controlled within-subject design. Participants were exposed to an emotion classification task (fearful, angry, and happy faces) after receiving an intranasal dose (24 IU) of synthetic OT or PLC. We found OT to attenuate right amygdala hyperactivity to angry faces in participants with ASPD to such an extent that the intensity of amygdala activity in the ASPD group in the OT condition decreased to the level of amygdala activity in the PLC condition in the HC group. There was also a trend that OT effects were generally larger in women than in men. These findings suggest that OT differentially modulates the amygdala following social threatening or provoking cues in dependence of psychopathology (ASPD vs. HC) and sex (male vs. female). Particularly female ASPD patients could benefit from OT in the treatment of reactive aggression.