Core, social and moral disgust are bounded: A review on behavioral and neural bases of repugnance in clinical disorders

Different Disgust Domains Specifically Relate to Mental and Contact Contamination Fear in Obsessive-Compulsive Disorder: Evidence From a Path Analytic Model in an Italian Clinical Sample

Both contact contamination (CC) and mental contamination (MC) fears-which combined represent the most common manifestation of obsessive-compulsive disorder (OCD)-have been widely associated with disgust propensity. However, extant research explored this relationship using measures assessing only pathogen-related disgust, not taking into account the potential role played by sexual and moral disgust, despite literature about MC suggesting that this might be particularly relevant. In Study 1, the psychometric properties of the Italian version of the Three Domains of Disgust Scale (TDDS) were assessed in a large Italian community sample. Exploratory and confirmatory factor analyses confirmed the three-factor structure of the TDDS. The scale also showed good internal consistency and construct validity. In Study 2, the differential patterns of relationships between CC and MC and the three disgust domains were explored in an Italian clinical OCD sample using a path analytic approach. The TDDS-Pathogen subscale was a unique predictor of CC while the TDDS-Sexual subscale was a unique predictor of MC, after controlling for anxiety and depression. Surprisingly, the TDDS-Moral subscale was not a predictor of either domain of contamination fear. Limitations and clinical implications are discussed.

Insula H-coil deep transcranial magnetic stimulation in severe and enduring anorexia nervosa (SE-AN): a pilot study

INTRODUCTION

Anorexia nervosa (AN) is a complex disorder of unknown etiology, characterized by obsessions and compulsions around body shape, weight, and calorie intake. In the course of AN, 10%-30% will recover, while the rest will develop a treatment-resistant course with a high mortality rate due to AN-related complications. The insula is a region in the brain of considerable interest to its role in gustatory modulation, feeding behavior, and processing of interoceptive stimuli.

OBJECTIVE

Recent advances in the neurophysiology of AN suggest insula dysfunction as a potential biomarker for people with severe and enduring AN (SE-AN). Deep transcranial magnetic stimulation (dTMS) is of particular interest in SE-AN because of its ability to target deep areas of the brain.

DESIGN

We conducted a pilot study to investigate the feasibility and safety of insula dTMS in subjects with SE-AN.

RESULTS

We found that dTMS is a safe and well-tolerated treatment. We also found a reduction in AN-related obsessions and compulsions, as well as depression and anxiety scores from baseline to the end of the trial. Due to small sample size, the results of this study should be interpreted with great caution.

DISCUSSION

The results suggest that dTMS is safe and well tolerated and may be of some clinical interest in patients with SE-AN. However, to determine the true efficacy of dTMS for SE-AN, there is a need to conduct a randomized controlled trial comparing real versus sham dTMS in a larger number of AN subjects.

Emotional Roles of Mono-Aminergic Neurotransmitters in Major Depressive Disorder and Anxiety Disorders

A growing body of researches support a role for dysfunction of serotoninergic, noradrenergic, and dopaminergic systems in the neurobiological processes involved in major depression disorder (MDD) and anxiety disorders (ADs). The physiological changes underlying abnormal signaling of 5-HT, NE, and DA may be due to either reduced presynaptic release of these neurotransmitters or aberrant signal transductions, and thus contributing to the alterations in regulation or function of receptors and/or impaired intracellular signal processing. Animal models demonstrate crucial responsiveness to disturbance of 5-HT, NE, and DA neurotransmissions. Postmortem and biochemical studies have shown altered concentrations of 5-HT, NE, and DA metabolites in brain regions that contribute importantly to regulation of mood and motivation in patients with MDD or ADs. Neuroimaging studies have found abnormal 5-HT, NE, and DA receptors binding and regulation in regard to receptor numbers. Medications that act on 5-HT, NE, and DA neurons or receptors, such as SSRIs and SNRIs, show efficacy in both MDD and ADs. The overlapping treatment response presumably suggests a common mechanism underlying the interaction of these disorders. In this paper, we reviewed studies from multiple disciplines to interpret the role of altered 5-HT, NE and DA mono-amine neurotransmitter functions in both MDD and ADs.

Moral Violations and the Experience of Disgust and Anger

Disgust is a natural defensive emotion that has evolved to protect against potential sources of contamination and has been recently linked to moral judgements in many studies. However, that people often report feelings of disgust when thinking about feces or moral transgressions alike does not necessarily mean that the same mechanisms mediate these reactions. The present study used functional magnetic resonance imaging (n = 22) to investigate whether core and moral disgusts entrain common neural systems. We provide evidence that: (i) activation of overlapping brain regions between core and moral disgust is the result of content overlap in the vignettes—core disgust elicitors—across conditions, and not from moral violations per se, and (ii) moral residue (i.e., the remaining or “residual” activation after the influence of core disgust elicitors have been taken into account) produced a pattern of activation that is more consistent with moral anger, than one of “residual disgust.” These findings run contrary to the premise that our “moral center” is connected to the area of the brain in which physical revulsion is located.

The effect of hunger and satiety in the judgment of ethical violations

Human history is studded with instances where instinctive motivations take precedence over ethical choices. Nevertheless, the evidence of any linking between motivational states and morality has never been systematically explored. Here we addressed this topic by testing a possible linking between appetite and moral judgment. We compared moral disapproval ratings (MDR) for stories of ethical violations in participants under fasting and after having eaten a snack. Our results show that subjective hunger, measured via self-reported rating, reduces MDR for ethical violations. Moreover, the higher the disgust sensitivity the higher the MDR for ethical violations. This study adds new insights to research on physiological processes influencing morality by showing that appetite affects moral disapproval of ethical violations.

Early bilateral and massive compromise of the frontal lobes

The frontal lobes are one of the most complex brain structures involved in both domain-general and specific functions. The goal of this work was to assess the anatomical and cognitive affectations from a unique case with massive bilateral frontal affectation. We report the case of GC, an eight-year old child with nearly complete affectation of bilateral frontal structures and spared temporal, parietal, occipital, and cerebellar regions. We performed behavioral, neuropsychological, and imaging (MRI, DTI, fMRI) evaluations. Neurological and neuropsychological examinations revealed a mixed pattern of affected (executive control/abstraction capacity) and considerably preserved (consciousness, language, memory, spatial orientation, and socio-emotional) functions. Both structural (DTI) and functional (fMRI) connectivity evidenced abnormal anterior connections of the amygdala and parietal networks. In addition, brain structural connectivity analysis revealed almost complete loss of frontal connections, with atypical temporo-posterior pathways. Similarly, functional connectivity showed an aberrant frontoparietal network and relative preservation of the posterior part of the default mode network and the visual network. We discuss this multilevel pattern of behavioral, structural, and functional connectivity results. With its unique pattern of compromised and preserved structures and functions, this exceptional case offers new constraints and challenges for neurocognitive theories.

Body odour disgust sensitivity predicts authoritarian attitudes

Authoritarianism has resurfaced as a research topic in political psychology, as it appears relevant to explain current political trends. Authoritarian attitudes have been consistently linked to feelings of disgust, an emotion that is thought to have evolved to protect the organism from contamination. We hypothesized that body odour disgust sensitivity (BODS) might be associated with authoritarianism, as chemo-signalling is a primitive system for regulating interpersonal contact and disease avoidance, which are key features also in authoritarianism. We used well-validated scales for measuring BODS, authoritarianism and related constructs. Across two studies, we found that BODS is positively related to authoritarianism. In a third study, we showed a positive association between BODS scores and support for Donald Trump, who, at the time of data collection, was a presidential candidate with an agenda described as resonating with authoritarian attitudes. Authoritarianism fully explained the positive association between BODS and support for Donald Trump. Our findings highlight body odour disgust as a new and promising domain in political psychology research. Authoritarianism and BODS might be part of the same disease avoidance framework, and our results contribute to the growing evidence that contemporary social attitudes might be rooted in basic sensory functions.

The Perception of Time Is Underestimated in Adolescents With Anorexia Nervosa

Research has revealed reduced temporal discounting (i.e., increased capacity to delay reward) and altered interoceptive awareness in anorexia nervosa (AN). In line with the research linking temporal underestimation with a reduced tendency to devalue a reward and reduced interoceptive awareness, we tested the hypothesis that time duration might be underestimated in AN. Our findings revealed that patients with AN displayed lower timing accuracy in the form of timing underestimation compared with controls. These results were not predicted by clinical, demographic factors, attention, and working memory performance of the participants. The evidence of a temporal underestimation bias in AN might be clinically relevant to explain their abnormal motivation in pursuing a long-term restrictive diet, in line with the evidence that increasing the subjective temporal proximity of remote future goals can boost motivation and the actual behavior to reach them.

A call to action: Managing the neural pathway of disgust, bias, prejudice, and discrimination that fuels stigma

Stigma has long been cited as a barrier to individuals seeking treatment for alcohol and other drug use-related problems. This paper focuses on the foundation upon which stigma sits: the brain-based, neural and structural engine of prejudice and stereotyping, processes that lead to stigma. Research findings on the neural underpinnings of disgust, prejudice, bias, and discrimination are discussed. This commentary suggests the need to promote increased awareness of the neural drivers of stigma as a basis for managing responses to persons who use substances. The commentary challenges the use of the term "stigma," calling for a new approach in lieu of foisting a badge of dishonor upon this population.

A lesion model of envy and Schadenfreude: legal, deservingness and moral dimensions as revealed by neurodegeneration

The study of moral emotions (i.e. Schadenfreude and envy) is critical to understand the ecological complexity of everyday interactions between cognitive, affective, and social cognition processes. Most previous studies in this area have used correlational imaging techniques and framed Schadenfreude and envy as unified and monolithic emotional domains. Here, we profit from a relevant neurodegeneration model to disentangle the brain regions engaged in three dimensions of Schadenfreude and envy: deservingness, morality, and legality. We tested a group of patients with behavioural variant frontotemporal dementia (bvFTD), patients with Alzheimer’s disease, as a contrastive neurodegeneration model, and healthy controls on a novel task highlighting each of these dimensions in scenarios eliciting Schadenfreude and envy. Compared with the Alzheimer’s disease and control groups, patients with bvFTD obtained significantly higher scores on all dimensions for both emotions. Correlational analyses revealed an association between envy and Schadenfreude scores and greater deficits in social cognition, inhibitory control, and behaviour disturbances in bvFTD patients. Brain anatomy findings (restricted to bvFTD and controls) confirmed the partially dissociable nature of the moral emotions’ experiences and highlighted the importance of socio-moral brain areas in processing those emotions. In all subjects, an association emerged between Schadenfreude and the ventral striatum, and between envy and the anterior cingulate cortex. In addition, the results supported an association between scores for moral and legal transgression and the morphology of areas implicated in emotional appraisal, including the amygdala and the parahippocampus. By contrast, bvFTD patients exhibited a negative association between increased Schadenfreude and envy across dimensions and critical regions supporting social-value rewards and social-moral processes (dorsolateral prefrontal cortex, angular gyrus and precuneus). Together, this study provides lesion-based evidence for the multidimensional nature of the emotional experiences of envy and Schadenfreude. Our results offer new insights into the mechanisms subsuming complex emotions and moral cognition in neurodegeneration. Moreover, this study presents the exacerbation of envy and Schadenfreude as a new potential hallmark of bvFTD that could impact in diagnosis and progression.

Assessment of social behavior directed toward sick partners and its relation to central cytokine expression in rats

Acute illness not only reduces the expression of social behavior by sick rodents, but can also lead to avoidance responses when detected by healthy, would-be social partners. When healthy animals interact with a sick partner, an intriguing question arises: does exposure to a sick conspecific elicit an anticipatory immune response that would facilitate defense against future infection? To address this question, healthy adult male Sprague-Dawley rats (N=64) were given a brief social interaction (30min) with a partner that was either sick (250μg/kg injection with lipopolysaccharide [LPS] 3h prior to test) or healthy (sterile saline injection). During this exposure, social behavior directed toward the healthy or sick conspecific was measured. Additionally, the impact of housing condition was assessed, with rats group- or isolate-housed. Immediately after social interaction, brains were harvested for cytokine assessments within socially-relevant brain structures (olfactory bulb, amygdala, hippocampus and PVN). As expected, behavioral results demonstrated that (i) there was a robust suppression of social interaction directed against sick conspecifics; and (ii) isolate-housing generally increased social behavior. Furthermore, examination of central cytokine expression in healthy experimental subjects revealed a modest increase in TNF-α in rats that interacted with a sick social partner, but only in the olfactory bulb. Among the LPS-injected partners, expected increases in IL-1β, IL-6, and TNF-α expression were observed across all brain sites. Moreover, IL-1β and IL-6 expression was exacerbated in LPS-injected partners that interacted with isolate-housed experimental subjects. Together, these data replicate and extend our prior work showing that healthy rats avoid sick conspecifics, and provide preliminary evidence for an anticipatory cytokine response when rats are exposed to a sick partner. These data also provide new evidence to suggest that recent housing history potently modulates cytokine responses evoked by LPS.

Mapping the sequence of brain events in response to disgusting food

Warning signals indicating that a food is potentially dangerous may evoke a response that is not limited to the feeling of disgust. We investigated the sequence of brain events in response to visual representations of disgusting food using a dynamic image analysis. Functional MRI was acquired in 30 healthy subjects while they were watching a movie showing disgusting food scenes interspersed with the scenes of appetizing food. Imaging analysis included the identification of the global brain response and the generation of frame-by-frame activation maps at the temporal resolution of 2 s. Robust activations were identified in brain structures conventionally associated with the experience of disgust, but our analysis also captured a variety of other brain elements showing distinct temporal evolutions. The earliest events included transient changes in the orbitofrontal cortex and visual areas, followed by a more durable engagement of the periaqueductal gray, a pivotal element in the mediation of responses to threat. A subsequent core phase was characterized by the activation of subcortical and cortical structures directly concerned not only with the emotional dimension of disgust (e.g., amygdala-hippocampus, insula), but also with the regulation of food intake (e.g., hypothalamus). In a later phase, neural excitement extended to broad cortical areas, the thalamus and cerebellum, and finally to the default mode network that signaled the progressive termination of the evoked response. The response to disgusting food representations is not limited to the emotional domain of disgust, and may sequentially involve a variety of broadly distributed brain networks. Hum Brain Mapp 39:369-380, 2018. © 2017 Wiley Periodicals, Inc.

Salivary secretion and disgust: A pilot study

Although a direct link has been established between self-experienced disgust and salivary secretion, it is unclear whether this physiological index is modulated by the social experience of disgust (i.e., exposure to the facial expression of disgust). We tested this issue in a pilot study by collecting salivary samples in a group of 20 healthy humans watching pictures of faces expressing disgust. Moreover, we tried to replicate previous evidence by testing saliva secretion in response to pictures of unpalatable (i.e., rotten) food and non-gustatory disgusting stimuli (i.e., disgusting insects). Overall, our analysis shows a general reduction of saliva secretion in response to disgust stimuli, compared to their positive counterparts, although further analyses for specific stimulus categories indicated that this difference was statistically significant only for food pictures. The non-significance of the face and insect categories might be due to insufficient power of our small sample. Overall, a general reduction of saliva secretion for different disgust-related stimuli suggests a shared mechanism of encoding, in line with theories of neural reuse.

Increased Subjective Distaste and Altered Insula Activity to Umami Tastant in Patients with Bulimia Nervosa

The aim of this study was to examine differences in brain neural activation in response to monosodium glutamate (MSG), the representative component of umami, between patients with bulimia nervosa (BN) and healthy women (HW) controls. We analyzed brain activity after ingestion of an MSG solution using functional magnetic resonance imaging (fMRI) in a group of women with BN (n = 18) and a group of HW participants (n = 18). Both groups also provided a subjective assessment of the MSG solution via a numerical rating scale. The BN group subjectively rated the MSG solution lower in pleasantness and liking than the control group, although no difference in subjective intensity was noted. The fMRI results demonstrated greater activation of the right insula in the BN group versus the control group. Compared with the HW controls, the BN patients demonstrated both altered taste perception-related brain activity and more negative hedonic scores in response to MSG stimuli. Different hedonic evaluation, expressed as the relative low pleasing taste of umami tastant and associated with altered insula function, may explain disturbed eating behaviors, including the imbalance in food choices, in BN patients.