A Causal Role for Gastric Rhythm in Human Disgust Avoidance

Ingestible pills reveal gastric correlates of emotions

Although it is generally held that gastrointestinal (GI) signals are related to emotions, direct evidence for such a link is currently lacking. One of the reasons why the internal milieu of the GI system is poorly investigated is because visceral organs are difficult to access and monitor. To directly measure the influence of endoluminal markers of GI activity on the emotional experience, we asked a group of healthy male participants to ingest a pill that measured pH, pressure, and temperature of their GI tract while they watched video clips that consistently induced disgust, fear, happiness, sadness, or a control neutral state. In addition to the objective physiological markers of GI activity, subjective ratings of perceived emotions and visceral (i.e. gastric, respiratory and cardiac) sensations were recorded, as well as changes in heart rate (HR), heart rate variability (HRV) and spontaneous eyes blinks as non-gastric behavioral and autonomic markers of the emotional experience. We found that when participants observed fearful and disgusting video clips, they reported to perceive not only cardiac and respiratory sensations but also gastric sensations, such as nausea. Moreover, we found that there was a clear relation between the physiology of the stomach and the perceived emotions. Specifically, when disgusting video clips were displayed, the more acidic the pH, the more participants reported feelings of disgust and fear; the less acidic the pH, the more they reported happiness. Complementing the results found in the deep gastric realm, we found that disgusting stimuli induced a significant increase in HRV compared to the neutral scenarios, and together with fearful video clips a decrease in HR. Our findings suggest that gastric signals contribute to unique emotional states and that ingestible pills may open new avenues for exploring the deep-body physiology of emotions.

Long-term disgust habituation with limited generalisation in care home workers

Countless workers handle bodily effluvia and body envelope violations every working day, and consequentially face deeply unpleasant levels of disgust. Understanding if and how they adapt can help inform policies to improve worker satisfaction and reduce staff turnover. So far, limited evidence exist that self-reported disgust is reduced (or lower to begin with) among those employed in high-disgust environments. However, it is unclear if this is due to demand effects or translates into real behavioural changes. Here, we tested healthcare assistants (N = 32) employed in UK care homes and a control sample (N = 50). We replicated reduced self-reported pathogen disgust sensitivity in healthcare workers compared to controls. We also found it negatively correlated with career duration, suggesting long-term habituation. Furthermore, we found that healthcare assistants showed no behavioural disgust avoidance on a web-based preferential looking task (equivalent to eye tracking). Surprisingly, this extended to disgust elicitors found outside care homes, suggesting generalisation of disgust habituation. While we found no difference between bodily effluvia (core disgust) and body envelope violations (gore disgust), generalisation did not extend to other domains: self-reported sexual and moral disgust sensitivity were not different between healthcare assistants and the control group, nor was there a correlation with career duration. In sum, our work confirms that people in high-frequency disgust employment are less sensitive to pathogen disgust. Crucially, we provide preliminary evidence that this is due to a process of long-term habituation with generalisation to disgust-elicitors within the pathogen domain, but not beyond it.

Thermosensation and emotion: Thermosensory accuracy in a dynamic thermal matching task is linked to depression and anxiety symptomatology

Interoception is related to the generation of bodily feelings and the awareness of ourselves as 'sentient beings', informing the organism about its bodily needs to guarantee survival. Previous studies have reported links among interoception, emotion processing, and mental health. For example, the alignment of interoceptive dimensions (i.e., accuracy, sensibility, awareness) can predict emotional symptoms, such as anxiety. Here, we aimed to investigate the relationship between the perception of a certain type of skin-mediated interoceptive signal, i.e., thermosensation, and self-reported depression, anxiety, and stress. One hundred seventy participants completed the Depression Anxiety Stress Scale (DASS-21) and a dynamic thermal matching task, a static temperature detection task, and a heartbeat counting task. Our results revealed that self-reported anxiety and depression were related to the perception of temperature on hairy and non-hairy skin, respectively: higher anxiety was related to better performance on the thermal matching task on the forearm, while higher depression was related to poorer performance on dynamic and static temperature tasks on the palm. Discrepancies between thermosensory accuracy and sensibility measures ('trait prediction error') were related to heightened anxiety, in line with previous studies. No significant correlations were found between DASS-21 scores and heartbeat counting accuracy. In conclusion, this study suggests that individual differences in thermosensory perception in different areas of the body are associated with self-reported anxiety and depression.

Larval Wound Therapy: Possibilities and Potential Limitations-A Literature Review

Patient-centered care (PCC) is recognized as a standard in healthcare for determining high quality. Honoring patients' values, experiences, needs, and preferences in devising, coordinating, and delivering care underscores the enhancement of the therapeutic rapport between patients and healthcare providers. Wound treatment involves a multi-stage process encompassing diagnostics and local wound dressing, which reduces the risk of infection through a coordinated interdisciplinary team. Within this team, nurses undertake specific professional functions and roles. The implementation of local therapy using innovative and scientifically substantiated methods may be hindered by a deficit of knowledge or inappropriate knowledge among staff and patients themselves. This study presents the challenges concerning the care of patients with chronic wounds treated using Lucilia sericata larvae, based on a review of the current scientific literature. A critical analysis of the literature spanning from 2002 to 2022 was conducted using the Medline, PubMed, Cochrane, and Termedia databases, employing keywords such as "maggot debridement therapy" in relation to acceptance and perception. As a result of the preliminary selection, 472 papers were identified, of which 12 publications were included in the development of this concept. The acquired data were organized and presented in the concluding section in the form of tables, accompanied by descriptions and references to individual studies. Negative psychological and somatic sensations were among the most prominent challenges among patients treated with Maggot Debridement Therapy (MDT). Pain related to peripheral ischemia or infection in this group of patients requires pain prophylaxis, including hyperalgesia and allodynia, in order to improve method tolerance. On the other hand, augmenting patients' understanding of MDT diminishes negative emotions, reinforces positive behaviors, and mitigates anxiety levels. MDT constitutes an effective and safe method. Its widespread use for chronic wounds requires substantial knowledge among healthcare professionals and patient education, along with that of their caregivers, to develop a positive attitude.

A transdiagnostic meta-analysis of acute augmentations to psychological therapy

At least half of all patients with mental health disorders do not respond adequately to psychological therapy. Acutely enhancing particular biological or psychological processes during psychological therapy may improve treatment outcomes. However, previous studies are confined to specific augmentation approaches, typically assessed within single diagnostic categories. Our objective was to assess to what degree acute augmentations of psychological therapy reduce psychiatric symptoms and estimate effect sizes of augmentation types (for example, brain stimulation or psychedelics). We searched Medline, PsycINFO and Embase for controlled studies published between database inception and 25 May 2022. We conducted a preregistered random-effects meta-analysis (PROSPERO CRD42021236403). We identified 108 studies (N = 5,889). Acute augmentation significantly reduced the severity of mental health problems (Hedges' g = -0.27, 95% CI: [-0.36, -0.18]; P < 0.0001), particularly for the transdiagnostic dimensions 'Fear' and 'Distress'. This result survived a trim-and-fill analysis to account for publication bias. Subgroup analyses revealed that pharmacological, psychological and somatic augmentations were effective, but to varying degrees. Acute augmentation approaches are a promising route to improve outcomes from psychological therapy.

Vagus nerve stimulation increases stomach-brain coupling via a vagal afferent pathway

BACKGROUND

Maintaining energy homeostasis is vital and supported by vagal signaling between digestive organs and the brain. Previous research has established a gastric network in the brain that is phase synchronized with the rhythm of the stomach, but tools to perturb its function were lacking.

OBJECTIVE

To evaluate whether stomach-brain coupling can be acutely increased by non-invasively stimulating vagal afferent projections to the brain.

METHODS

Using a single-blind randomized crossover design, we investigated the effect of acute right-sided transcutaneous auricular vagus nerve stimulation (taVNS) versus sham stimulation on stomach-brain coupling.

RESULTS

In line with preclinical research, taVNS increased stomach-brain coupling in the nucleus of the solitary tract (NTS) and the midbrain while boosting coupling across the brain. Crucially, in the cortex, taVNS-induced changes in coupling occurred primarily in transmodal regions and were associated with changes in hunger ratings as indicators of the subjective metabolic state.

CONCLUSIONS

taVNS increases stomach-brain coupling via an NTS-midbrain pathway that signals gut-induced reward, indicating that communication between the brain and the body is effectively modulated by vago-vagal signaling. Such insights may help us better understand the role of vagal afferents in orchestrating the recruitment of the gastric network which could pave the way for novel neuromodulatory treatments.

Relationship Between Sensitivity to Disgust and Irritable Bowel Syndrome: A Study on Healthy Individuals

OBJECTIVE

Irritable bowel syndrome (IBS) is a psychosomatic gastrointestinal disorder involving the dysfunctional activation of specific brain regions crucial for interoception and disgust processing. Yet, no study has ever investigated the link between this socio-affective/visceral experience and IBS.

METHOD

The present study investigated whether disgust sensitivity and disgust propensity, which can be socially relevant, relate with IBS symptoms in a nonclinical population.105 healthy participants were asked to complete the Disgust Propensity and Sensitivity Scale-Revised (DPSS-R), the Irritable Bowel Syndrome-Quality of Life Measure (IBS-QOL), and the Chronic Urticaria Quality of Life Measure (CU-Q2OL), as control condition.

RESULTS

Results showed higher disgust sensitivity scores in individuals with high IBS-QOL score, compared to individuals with low IBS-QOL score. The correlation analysis corroborates this result by showing a positive relationship between disgust sensitivity and respective IBS-QOL scores.

CONCLUSIONS

This research provides new insights into understanding the etiopathogenesis of IBS, suggesting the relevance of a socially relevant personality trait such as disgust sensitivity as a potential trigger and / or predisposition factor for this chronic inflammatory disease.

Interoceptive pathways to understand and treat mental health conditions

An increasing recognition that brain and body are dynamically coupled has enriched our scientific understanding of mental health conditions. Peripheral signals interact centrally to influence how we think and feel, generating our sense of the internal condition of the body, a process known as interoception. Disruptions to this interoceptive system may contribute to clinical conditions, including anxiety, depression, and psychosis. After reviewing the nature of interoceptive disturbances in mental health conditions, this review focuses on interoceptive pathways of existing and putative mental health treatments. Emerging clinical interventions may target novel peripheral treatment mechanisms. Future treatment development requires forward- and back-translation to uncover and target specific interoceptive processes in mental health to elucidate their efficacy relative to interventions targeting other factors.

Lessons learned developing and testing family-based interoceptive exposure for adolescents with low-weight eating disorders

BACKGROUND

Anorexia nervosa (AN) usually develops in early adolescence and is characterized by high rates of morbidity and mortality. Family-based therapy (FBT) is the leading evidence-based treatment for adolescents with AN, but not all patients experience sufficient improvement. The purpose of this manuscript is to describe the development and subsequent experience with a Family-Based Interoceptive Exposure (FBT-IE) for adolescents with a broader form of low-weight eating disorders.

METHODS

The novel IE-based behavioral intervention is a six-session family-based treatment module designed to directly target and modify disgust by altering the prefrontal regulation of the insula response to aversive stimuli by decreasing visceral sensitivity (e.g., bloating). Each session teaches a new skill regarding tolerating distress to visceral sensations associated with disgust and an in-vivo "IE exercise," in which the family is provided with a meal replacement shake of unknown content and caloric density.

RESULTS

In this novel treatment, the patient learns to tolerate disgust in the context of a challenging food stimulus as a way to increase consumption of restricted foods outside of session.

CONCLUSION

We discuss successes and challenges executing this treatment with patients with low-weight eating disorders and propose future directions for the intervention.

Influence of visual food cues on autonomic activity and craving

In this study, we tested the hypothesis that autonomic control of the stomach is related to craving and is modulated by visual food cues. Twenty-nine healthy human participants were shown pictures of either high- or low-appeal food, as well as non-food pictures, and were asked to rate how much they wanted to eat each item using a 7-point Likert scale. Simultaneously, the electrogastrogram, electrocardiogram, electrodermal activity, respiration rate, and pupil diameter were recorded. After the ingestion of a 500-kcal liquid meal, participants were asked to perform the task a second time. Despite changes in craving ratings, we did not find changes in the amplitude of the gastric rhythm, but we found increases in pupil diameter for the high appeal food pictures. Moreover, craving ratings were mostly related to increases in pupil and tonic electrodermal activity, compatible with an increase in arousal and a heightened motivational response to food.

MouseView.js: Reliable and valid attention tracking in web-based experiments using a cursor-directed aperture

Psychological research is increasingly moving online, where web-based studies allow for data collection at scale. Behavioural researchers are well supported by existing tools for participant recruitment, and for building and running experiments with decent timing. However, not all techniques are portable to the Internet: While eye tracking works in tightly controlled lab conditions, webcam-based eye tracking suffers from high attrition and poorer quality due to basic limitations like webcam availability, poor image quality, and reflections on glasses and the cornea. Here we present MouseView.js, an alternative to eye tracking that can be employed in web-based research. Inspired by the visual system, MouseView.js blurs the display to mimic peripheral vision, but allows participants to move a sharp aperture that is roughly the size of the fovea. Like eye gaze, the aperture can be directed to fixate on stimuli of interest. We validated MouseView.js in an online replication (N = 165) of an established free viewing task (N = 83 existing eye-tracking datasets), and in an in-lab direct comparison with eye tracking in the same participants (N = 50). Mouseview.js proved as reliable as gaze, and produced the same pattern of dwell time results. In addition, dwell time differences from MouseView.js and from eye tracking correlated highly, and related to self-report measures in similar ways. The tool is open-source, implemented in JavaScript, and usable as a standalone library, or within Gorilla, jsPsych, and PsychoJS. In sum, MouseView.js is a freely available instrument for attention-tracking that is both reliable and valid, and that can replace eye tracking in certain web-based psychological experiments.

Interoception and Obsessive-Compulsive Disorder: A Review of Current Evidence and Future Directions

Disrupted interoceptive processes are present in a range of psychiatric conditions, and there is a small but growing body of research on the role of interoception in obsessive-compulsive disorder (OCD). In this review, we outline dimensions of interoception and review current literature on the processing of internal bodily sensations within OCD. Investigations in OCD utilizing objective measures of interoception are limited and results mixed, however, the subjective experience of internal bodily sensations appears to be atypical and relate to specific patterns of symptom dimensions. Further, neuroimaging investigations suggest that interoception is related to core features of OCD, particularly sensory phenomena and disgust. Interoception is discussed in the context of treatment by presenting an overview of existing interventions and suggesting how modifications aimed at better targeting interoceptive processes could serve to optimize outcomes. Interoception represents a promising direction for multi-method research in OCD, which we expect, will prove useful for improving current interventions and identifying new treatment targets.

Deontological Guilt and Disgust Sensitivity Modulate Moral Behaviour

OBJECTIVE

Deontological Guilt (DG), and Altruistic Guilt (AG) emerge from the appraisal of violating an internalized rule or an altruistic principle, respectively. DG is strictly connected with Disgust Sensitivity and plays a key role in the development and maintenance of Obsessive-Compulsive Disorder (OCD). Previous studies investigated how DG affects responses to hypothetical moral dilemmas, however how DG and Disgust Sensitivity interact modulating moral behavior is still unknown.

METHODS

STUDY 1. 46 healthy participants performed an ecological paradigm in which people can spontaneously decide to lie to obtain a reward (egoistic lie) or give it away (altruistic lie) after three emotional inductions: DG, AG or neutral. Furthermore, OCD traits, Morality, Guilt Propensity and Disgust Sensitivity were assessed by means of questionnaires. STUDY 2. 27 participants from the original sample were retested during the COVID-19 lockdown in Italy to ascertain whether the pandemic modified traits related to morality, disgust, guilt or OCD symptoms and whether these changes modulated moral behavior (measured by a task in which cheating was associated to higher pay-offs).

RESULTS

STUDY 1. Compared to the neutral, after the DG induction participants produced less altruistic and more egoistic lies. This effect was stronger in participants with high Disgust Sensitivity. STUDY 2. During the COVID-19 lockdown participants became more sensitive to the Authority pillar of the Moral Foundations and more sensitive to Disgust: this increment in deontological morality affected (im) moral behavior depending on changes in Disgust Sensitivity.

CONCLUSIONS

Our data suggest that people with high Disgust Sensitivity are more affected by deontological inductions which translate to higher immorality, supposedly by lowering their moral self-image. These results might have important clinical implications as they suggest that addressing Disgust Sensitivity in therapy, might also decrease the effect of guilt on patients' behavior.

Disgust: Internal Context Matters

Novel research suggests the rhythms in our stomachs can influence our response to disgusting stimuli. Monetary reward will only encourage people to engage with disgusting stimuli after a peripherally acting drug alters gastric signals.