Does trait anxiety influence effects of oxytocin on eye-blink startle reactivity? A randomized, double-blind, placebo-controlled crossover study

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.

Oxytocin Differentially Modulates Amygdala Responses during Top-Down and Bottom-Up Aversive Anticipation

The ability to successfully regulate negative emotions such as fear and anxiety is vital for mental health. Intranasal administration of the neuropeptide oxytocin (OXT) has been shown to reduce amygdala activity but to increase amygdala-prefrontal cortex connectivity during exposure to threatening stimuli suggesting that it may act as an important modulator of emotion regulation. The present randomized, between-subject, placebo-controlled pharmacological study combines the intranasal administration of OXT with functional magnetic resonance imaging (fMRI) during an explicit emotion regulation paradigm in 65 healthy male participants to investigate the modulatory effects of OXT on both bottom-up and top-down emotion regulation. OXT attenuates the activation in the posterior insular cortex and amygdala during anticipation of top-down regulation of predictable threat stimuli in participants with high trait anxiety. In contrast, OXT enhances amygdala activity during the bottom-up anticipation of unpredictable threat stimuli in participants with low trait anxiety. OXT may facilitate top-down goal-directed attention by attenuating amygdala activity in high anxiety individuals, while promoting bottom-up attention/vigilance to unexpected threats by enhancing amygdala activity in low anxiety individuals. OXT may thus have the potential to promote an adaptive balance between bottom-up and top-down attention systems depending on an individual's trait anxiety level.

An updated field guide for snark hunting: Comparative contributions to behavioral neuroendocrinology in the era of model organisms

Studying neuroendocrine behavioral regulatory mechanisms in a variety of species across vertebrate groups is critical for determining how they work in natural contexts, how they evolved, and ultimately what can be generalized from them, potentially even to humans. All of the above are difficult, at best, if work within our field is exclusively done in traditional laboratory organisms. The importance of comparative approaches for understanding the relationships between hormones and behavior has been recognized and advocated for since our field's inception through a series of papers centered upon a poetic metaphor of Snarks and Boojums, all of which have articulated the benefits that come from studying a diverse range of species and the risks associated with a narrow focus on "model organisms." This mini-review follows in the footsteps of those powerful arguments, highlighting some of the comparative work since the latest interactions of the metaphor that has shaped how we think about three major conceptual frameworks within our field, two of them formalized - the Organization/Activation Model of sexual differentiation and the Social Brain Network - and one, context-dependency, that is generally associated with virtually all modern understandings of how hormones affect behavior. Comparative approaches are broadly defined as those in which the study of mechanism is placed within natural and/or evolutionary contexts, whether they directly compare different species or not. Studies are discussed in relation to how they have either extended or challenged generalities associated with the frameworks, how they have shaped subsequent work in model organisms to further elucidate neuroendocrine behavioral regulatory mechanisms, and how they have stimulated work to determine if and when similar mechanisms influence behavior in our own species.

Oxytocin biases eye-gaze to dynamic and static social images and the eyes of fearful faces: associations with trait autism

A key functional effect of intranasal oxytocin with potential therapeutic relevance for autism-spectrum disorder is its reported facilitation of attention towards social stimuli, notably the eye region of faces. In the current randomized placebo-controlled within-subject experiment on 40 healthy males, we investigated the robustness of this facilitation of attention by intranasal oxytocin (24IU) towards social cues. Eye-tracking measures of preference for dynamic and static social vs. non-social stimuli were taken in four different paradigms where autistic individuals tend to exhibit reduced interest in social stimuli. Additionally, we investigated whether oxytocin increases attention towards the eyes relative to other salient face regions in an emotional face paradigm. Results showed that the time spent viewing both dynamic and static social vs. non-social stimuli was negatively associated with trait autism and significantly increased following intranasal oxytocin. For face stimuli, oxytocin primarily increased gaze towards the eyes of fearful expression faces but not for other face emotions. Overall, our findings demonstrate that oxytocin significantly shifts gaze preference towards social vs. non-social stimuli and to the eyes of fearful faces. Importantly, oxytocin appears generally to shift attention more towards salient social stimuli of particular relevance in the context of autism providing further support for its potential therapeutic use in autism-spectrum disorder.

Pupil dilation as an implicit measure of appetitive Pavlovian learning

Appetitive Pavlovian conditioning is a learning mechanism of fundamental biological and pathophysiological significance. Nonetheless, its exploration in humans remains sparse, which is partly attributed to the lack of an established psychophysiological parameter that aptly represents conditioned responding. This study evaluated pupil diameter and other ocular response measures (gaze dwelling time, blink duration and count) as indices of conditioning. Additionally, a learning model was used to infer participants' learning progress on the basis of their pupil dilation. Twenty-nine healthy volunteers completed an appetitive differential delay conditioning paradigm with a primary reward, while the ocular response measures along with other psychophysiological (heart rate, electrodermal activity, postauricular and eyeblink reflex) and behavioral (ratings, contingency awareness) parameters were obtained to examine the relation among different measures. A significantly stronger increase in pupil diameter, longer gaze duration and shorter eyeblink duration was observed in response to the reward-predicting cue compared to the control cue. The Pearce-Hall attention model best predicted the trial-by-trial pupil diameter. This conditioned response was corroborated by a pronounced heart rate deceleration to the reward-predicting cue, while no conditioning effect was observed in the electrodermal activity or startle responses. There was no discernible correlation between the psychophysiological response measures. These results highlight the potential value of ocular response measures as sensitive indices for representing appetitive conditioning.

Oxytocin Facilitates Empathic- and Self-embarrassment Ratings by Attenuating Amygdala and Anterior Insula Responses

The hypothalamic neuropeptide oxytocin has been reported to enhance emotional empathy in association with reduced amygdala activation, although to date studies have not investigated empathy for individuals expressing self-conscious, moral emotions which engage mentalizing as well as emotion processing networks. In the current randomized, double-blind placebo controlled functional MRI experiment in 70 male and female subjects we have therefore investigated the effects of intranasal oxytocin (40 IU) on behavioral and neural responses to embarrassment experienced by others or by self. Results showed that oxytocin significantly increased ratings of both empathic and self-embarrassment and concomitantly decreased skin conductance response, activation in the right amygdala and insula but not in the medial prefrontal cortex. The amygdala effects of oxytocin were associated with the magnitude of the skin conductance response and trait anxiety scores. Overall our results demonstrate that oxytocin increases ratings of self- and other embarrassment and that this is associated with reduced physiological arousal and activity in neural circuits involved in emotional arousal. The neural effects of oxytocin were more pronounced stronger in individuals with high trait anxiety suggesting that it may particularly reduce their anxiety in embarrassing situations.

Oxytocin facilitates adaptive fear and attenuates anxiety responses in animal models and human studies-potential interaction with the corticotropin-releasing factor (CRF) system in the bed nucleus of the stria terminalis (BNST)

Despite its relatively well-understood role as a reproductive and pro-social peptide, oxytocin (OT) tells a more convoluted story in terms of its modulation of fear and anxiety. This nuanced story has been obscured by a great deal of research into the therapeutic applications of exogenous OT, driving more than 400 ongoing clinical trials. Drawing from animal models and human studies, we review the complex evidence concerning OT's role in fear learning and anxiety, clarifying the existing confusion about modulation of fear versus anxiety. We discuss animal models and human studies demonstrating the prevailing role of OT in strengthening fear memory to a discrete signal or cue, which allows accurate and rapid threat detection that facilitates survival. We also review ostensibly contrasting behavioral studies that nonetheless provide compelling evidence of OT attenuating sustained contextual fear and anxiety-like behavior, arguing that these OT effects on the modulation of fear vs. anxiety are not mutually exclusive. To disambiguate how endogenous OT modulates fear and anxiety, an understudied area compared to exogenous OT, we survey behavioral studies utilizing OT receptor (OTR) antagonists. Based on emerging evidence about the role of OTR in rat dorsolateral bed nucleus of stria terminalis (BNST) and elsewhere, we postulate that OT plays a critical role in facilitating accurate discrimination between stimuli representing threat and safety. Supported by human studies, we demonstrate that OT uniquely facilitates adaptive fear but reduces maladaptive anxiety. Last, we explore the limited literature on endogenous OT and its interaction with corticotropin-releasing factor (CRF) with a special emphasis on the dorsolateral BNST, which may hold the key to the neurobiology of phasic fear and sustained anxiety.