Pavlovian disgust conditioning as a model for contamination-based OCD: Evidence from an analogue study

Conceptual-level disgust conditioning in contamination-based obsessive-compulsive disorder

Pavlovian fear conditioning and extinction represent learning mechanisms underlying exposure-based interventions. While increasing evidence indicates a pivotal role of disgust in the development of contamination-based obsessive-compulsive disorder (C-OCD), dysregulations in conditioned disgust acquisition and maintenance, in particular driven by higher-order conceptual processes, have not been examined. Here, we address this gap by exposing individuals with high (HCC, n = 41) or low (LCC, n = 41) contamination concern to a conceptual-level disgust conditioning and extinction paradigm. Conditioned stimuli (CS+) were images from one conceptual category partially reinforced by unconditioned disgust-eliciting stimuli (US), while images from another category served as non-reinforced conditioned stimuli (CS-). Skin conductance responses (SCRs), US expectancy and CS valence ratings served as primary outcomes to quantify conditioned disgust responses. Relative to LCC, HCC individuals exhibited increased US expectancy and CS+ disgust experience, but comparable SCR levels following disgust acquisition. Despite a decrease in conditioned responses from the acquisition phase to the extinction phase, both groups did not fully extinguish the learned disgust. Importantly, the extinction resilience of acquired disgust was more pronounced in HCC individuals. Together, our findings suggest that individuals with high self-reported contamination concern exhibit increased disgust acquisition and resistance to extinction. The findings provide preliminary evidence on how dysregulated disgust learning mechanism across semantically related concepts may contribute to C-OCD.

Neurocognitive mechanisms of mental imagery-based disgust learning

Disgust imagery represents a potential pathological mechanism for disgust-related disorders. However, it remains controversial as to whether disgust can be conditioned with disgust-evoking mental imagery serving as the unconditioned stimulus (US). Therefore, we examined this using a conditioned learning paradigm in combination with event-related potential (ERP) analysis in 35 healthy college students. The results indicated that the initial neutral face (conditioned stimulus, CS+) became more disgust-evoking, unpleasant, and arousing after pairing with disgust-evoking imagery (disgust CS+), compared to pairing with neutral (neutral CS+) and no (CS-) imagery. Moreover, we observed that mental imagery-based disgust conditioning was resistant to extinction. While the disgust CS + evoked larger P3 and late positive potential amplitudes than CS- during acquisition, no significant differences were found between disgust CS+ and neutral CS+, indicating a dissociation between self-reported and neurophysiological responses. Future studies may additionally acquire facial EMG as an implicit index of conditioned disgust. This study provides the first neurobiological evidence that associative disgust learning can occur without aversive physical stimuli, with implications for understanding how disgust-related disorders may manifest or deteriorate without external perceptual aversive experiences, such as in obsessive-compulsive disorder (OCD).

Is disgust more resistant to extinction than fear? A meta-analytic review of laboratory paradigms

Disgust can be acquired via evaluative conditioning; a process by which a neutral stimulus (conditioned stimulus; CS) comes to be evaluated as disgusting due to its pairing with an inherently disgusting stimulus (unconditioned stimulus; US). Research has shown that conditioned disgust responses are resistant to extinction which may have implications for disorders (i.e., contamination-based obsessive-compulsive disorder, specific phobias, and post-traumatic stress disorder) in which heightened disgust has been implicated. Importantly, extinction is the primary mechanism by which exposure therapies are thought to achieve symptom reduction for these disorders. Exposure therapies were originally modeled on fear extinction, whereas disgust extinction was largely overlooked until recently. Accordingly, differences in the degree to which learned disgust and fear can be attenuated via extinction learning remains unclear. The present investigation was a meta-analysis directly comparing the degree of extinction of conditioned disgust (n = 14) and conditioned fear (n = 14) in laboratory paradigms. Extinction was operationalized as the standardized mean difference (SMD) in evaluative ratings between the CS+ (the CS paired with the US) and CS- (the unpaired CS) after extinction training. Results of a subgroup analysis indicated that disgust (SMD = 0.52) was significantly more resistant to extinction than fear (SMD = 0.37). Additionally, a series of meta-regression analyses indicated that extinction was not influenced by important study characteristics (e.g., sex, age, number of conditioning and extinction trials). The findings suggest that extinction-based approaches may be less effective at attenuating learned disgust and research is needed to better optimize treatments for disgust-related disorders.

Conscious knowledge of CS-UCS contingency information affects extinction retrieval of conditioned disgust responses: Findings from an online de novo disgust conditioning task

Objective

The present study aimed to establish and develop an online de novo conditioning paradigm for the measurement of conditioned disgust responses. We further explored the effects of explicit instructions about the CS-UCS contingency on extinction learning and retrieval of conditioned disgust responses.

Method

The study included a sample of 115 healthy participants. Geometric figures served as conditioned stimuli (CS) and disgust-evoking pictures as unconditioned stimuli (UCS). During disgust conditioning, the CS+ was paired with the UCS (66% reinforcement) and the CS- remained unpaired; during extinction and retrieval, no UCS was presented. Half of the participants (n = 54) received instructions prior to the disgust extinction stating that the UCS will not be presented anymore. 1-2 days or 7-8 days later participants performed a retrieval test. CS-UCS contingency, disgust and valence ratings were used as dependent measures.

Results

Successful acquisition of conditioned disgust response was observed on the level of CS-UCS contingency, disgust and valence ratings. While some decline in valence and disgust ratings during the extinction stage was observed, contingency instructions did not significantly affect extinction performance. Retrieval one week later revealed that contingency instructions increased the discrimination of the CSs.

Conclusions

Extinction of conditioned disgust responses is not affected by explicit knowledge of the CS-UCS contingencies. However, contingency instructions prior to extinction seem to have a detrimental effect on long-term extinction retrieval.

Attenuating experimentally acquired disgust: Comparing counterconditioning, exposure and unconditioned stimulus revaluation

BACKGROUND AND OBJECTIVES

Disgust is implicated in the aetiology and maintenance of various psychopathologies such as anxiety disorders and obsessive-compulsive disorders. Despite its prominent role in psychopathology, little is known about how to effectively attenuate disgust. The study examined strategies to modify an experimentally acquired disgust response in a sample of undergraduate students.

METHODS

A conditioning paradigm was used where participants (N = 175) first underwent acquisition of disgust via repeated presentations of a neutral picture (functioning as conditioned stimulus + [CS+]) paired with a disgusting picture (functioning as unconditioned stimulus [US]). Participants were then randomly assigned to either an exposure (repeated presentation of CS-only trials), counterconditioning (pairing CS+ with pleasant pictures), US revaluation (pairing disgusting US with pleasant pictures) or a control (filler task) condition. We hypothesised that counterconditioning would attenuate evaluative learned disgust to the greatest extent, relative to exposure and US revaluation. Participants' evaluations of the pictures were attained with a disgust-pleasantness visual analogue scale.

RESULTS

Exposure, counterconditioning and US revaluation reduced disgusting US expectancies. However, experimental and control conditions did not differ in terms of attenuating disgust towards CS+.

LIMITATIONS

Measures of psychopathology and implicit evaluations of disgust were not collected. Modest power might have limited significance of the results.

CONCLUSIONS

No statistical support for the effectiveness of disgust attenuation following exposure nor counterconditioning were found. Findings for US revaluation are inconclusive. Implications for future research are discussed.

Treatment of disgust in specific emotional disorders

Although conditioning approaches have highlighted potential characteristics of disgust in anxiety disorders, obsessive-compulsive disorder (OCD), and posttraumatic stress disorder (PTSD), these findings have yet to be translated into evidence-based treatments. Examination of the literature suggests various indicators of disgust that predict treatment outcome in these disorders. However, mechanisms remain unclear because studies examining disgust during the course of treatment are limited. Increasingly, the field has moved toward experimental investigation of strategies that reduce disgust. While cognitive reappraisal and imagery techniques appear promising, such techniques have yet to be examined as anxiety disorder treatments in large-scale randomized clinical trials. The literature also points to novel approaches to treating disgust, ranging from an inhibitory-informed approach to exposure therapy to transcranial direct current stimulation. However, the development of novel treatment approaches will require more rigorous experimental psychopathology approaches that can further elucidate processes that contribute to the etiology and/or maintenance of disorders of disgust.

Pavlovian Disgust Conditioning and Generalization: Specificity and Associations With Individual Differences

Although studies have identified differences between fear and disgust conditioning, much less is known about the generalization of conditioned disgust. This is an important gap in the literature given that overgeneralization of conditioned disgust to neutral stimuli may have clinical implications. To address this knowledge gap, female participants (n = 80) completed a Pavlovian conditioning procedure in which one neutral food item (conditioned stimulus; CS+) was followed by disgusting videos of individuals vomiting (unconditioned stimulus; US) and another neutral food item (CS-) was not reinforced with the disgusting video. Following this acquisition phase, there was an extinction phase in which both CSs were presented unreinforced. Importantly, participants also evaluated generalization stimuli (GS+, GS-) that resembled, but were distinct from, the CS after each conditioning phase. As predicted, the CS+ was rated as significantly more disgusting and fear inducing than the CS- after acquisition and this pattern persisted after extinction. However, disgust ratings of the CS+ after acquisition were significantly larger than fear ratings. Participants also rated the GS+ as significantly more disgusting, but not fear inducing, than the GS- after acquisition. However, this effect was not observed after extinction. Disgust proneness did predict a greater increase in disgust and fear ratings of the CS+ relative to the CS- after acquisition and extinction. In contrast, trait anxiety predicted only higher fear ratings to the CS+ relative to the CS- after acquisition and extinction. Disgust proneness nor trait anxiety predicted the greater increase in disgust to the GS+ relative to the GS- after acquisition. These findings suggest that while conditioned disgust can generalize, individual difference variables that predict generalization remain unclear. The implications of these findings for disorders of disgust are discussed.

An experimental test of the effects of acute sleep deprivation on affect and avoidance

BACKGROUND AND OBJECTIVES

Avoidance and sleep have been identified as mechanisms involved in the development and maintenance of many mental health disorders. However, there has been little research into the relation between sleep and avoidance.

METHODS

To address this, a randomized controlled experiment using behavioral and self-report measures of affect and avoidance was conducted. Compared to a control group, we hypothesized that sleep-deprived individuals would demonstrate increased negative, and decreased positive, affectivity, more avoidance behavior toward a negatively valenced stimulus, as well as increased self-reported avoidance. Fifty-two healthy individuals ages 18-30 years old were randomly assigned to a full night of sleep deprivation or normal sleep. They completed a baseline and post-manipulation behavioral avoidance task (BAT) using a disgusting stimulus and self-reports of avoidance and state affect.

RESULTS

Repeated measures ANOVAs demonstrated negative affectivity and self-reported avoidance increased, and positive affectivity decreased, from pre-to post-manipulation in the sleep loss condition as expected. However, there were no effects of sleep deprivation on avoidance behaviors.

LIMITATIONS

This study emphasized internal validity over generalizability. Additionally, the at-home sleep deprivation limited researcher control over the overnight activities of participants.

CONCLUSIONS

Results replicate prior work on the affective consequences of sleep deprivation and highlight a discrepancy between the effect of sleep deprivation on behavioral avoidance toward a specific stimulus compared to self-reported cognitive and social avoidance behaviors.

Enhanced fear acquisition in individuals with evening chronotype. A virtual reality fear conditioning/extinction study

Circadian rhythms have received increasing attention within the context of mental disorders. Evening chronotype has been associated with enhanced risk to develop anxiety and post-traumatic stress disorder (PTSD). The classical fear conditioning paradigm is a powerful tool to reveal key mechanisms of anxiety and PTSD. We used this paradigm to study the neurocognitive basis of the association between chronotype and fear responses in healthy humans. 20 participants with evening chronotype and 20 controls (i.e., intermediate chronotype) completed a 2-day Pavlovian fear learning and extinction virtual reality task. Participants received fear conditioning, and extinction learning on day 1. Extinction memory recall was tested on day 2. To address interactions between chronotype and time of day of the fear conditioning, and extinction performance, half of the participants were tested in the morning, and the other half in the evening. Skin conductance response (SCR) and subjective fear ratings were measured as primary outcomes. Chronotype was established via the morningness-eveningness questionnaire (MEQ). We found an overall higher SCR for fear acquisition in participants with the evening chronotype profile, compared to controls. Moreover, the higher the MEQ scores -indicative of less eveningness - the lower the SCR was. No effects of chronotype were found for extinction and extinction recall. The higher vulnerability of the evening chronotype for anxiety and related disorders may thus be explained by enhanced fear acquisition of this group.

Functional Connectivity within the Frontal–Striatal Network Differentiates Checkers from Washers of Obsessive-Compulsive Disorder

Background: Obsessive-compulsive disorder (OCD) is a psychiatric disorder with high clinical heterogeneity manifested by the presence of obsessions and/or compulsions. The classification of the symptom dimensional subtypes is helpful for further exploration of the pathophysiological mechanisms underlying the clinical heterogeneity of OCD. Washing and checking symptoms are the two major symptom subtypes in OCD, but the neural mechanisms of the different types of symptoms are not yet clearly understood. The purpose of this study was to compare regional and network functional alterations between washing and checking OCD based on resting-state functional magnetic resonance imaging (rs-fMRI). Methods: In total, 90 subjects were included, including 15 patients in the washing group, 30 patients in the checking group, and 45 healthy controls (HCs). Regional homogeneity (ReHo) was used to compare the differences in regional spontaneous neural activity among the three groups, and local indicators were analyzed by receiver operating characteristic (ROC) curves as imaging markers for the prediction of the clinical subtypes of OCD. Furthermore, differently activated local brain areas, as regions of interest (ROIs), were used to explore differences in altered brain functioning between washing and checking OCD symptoms based on a functional connectivity (FC) analysis. Results: Extensive abnormalities in spontaneous brain activity involving frontal, temporal, and occipital regions were observed in the patients compared to the HCs. The differences in local brain functioning between checking and washing OCD were mainly concentrated in the bilateral middle frontal gyrus, right supramarginal gyrus, right angular gyrus, and right inferior occipital gyrus. The ROC curve analysis revealed that the hyperactivation right middle frontal gyrus had a better discriminatory value for checking and washing OCD. Furthermore, the seed-based FC analysis revealed higher FC between the left medial superior frontal gyrus and right caudate nucleus compared to that in the healthy controls. Conclusions: These findings suggest that extensive local differences exist in intrinsic spontaneous activity among the checking group, washing group, and HCs. The neural basis of checking OCD may be related to dysfunction in the frontal–striatal network, which distinguishes OCD from washing OCD.

Common and separable behavioral and neural mechanisms underlie the generalization of fear and disgust

Generalization represents the transfer of a conditioned responses to stimuli that resemble the conditioned stimulus (CS). Previous studies on generalization of defensive avoidance responses have primarily focused on fear and have neglected disgust generalization, which represents a key pathological mechanism in some anxiety disorders. In the present study we examined common and distinct mechanisms of fear and disgust generalization by means of a fear or disgust multi-CS conditioning and generalization paradigm with concomitant event-related potential (ERPs) acquisition in n = 62 subjects. We demonstrate that compared to fear, disgust-relevant generalized stimuli (GS) elicited larger expectancy ratings and longer reaction times (RTs) reflecting stronger ratings of 'risk'. On the electrophysiological level, increased P2 amplitudes were found in response to conditioned CS+ versus CS- across both domains, possibly reflecting higher motivational and attentional salience of aversive conditioned stimuli per se. Contingent negative variation (CNV) amplitude was significantly larger for disgust-CS+ than disgust-CS-, reflecting a stronger preparation of the disgust US. Additionally, we found that the contingent negative variation (CNV) fear generalization gradient, and CNV amplitude were increased with similarity to CS+. In contrast the CNV to disgust-GS did not differ and did not reflect disgust generalization. Together this may indicate that the CNV represents a highly fear-specific index for generalization learning. This study provides the first neurobiological evidence for common and distinct generalization learning in fear versus disgust suggesting that dysregulations in separable defensive avoidance mechanisms may underly different anxiety disorder subtypes.

A Current Learning Theory Approach to the Etiology and Course of Anxiety and Related Disorders

The authors describe how contemporary learning theory and research provide the basis for models of the etiology and maintenance of anxiety and related disorders. They argue that contemporary learning theory accounts for much of the complexity associated with individual differences in the development and course of these disorders. These insights from modern research on learning overcome the limitations of earlier behavioral approaches, which were overly simplistic and have been justifiably criticized. The authors show how considerations of early learning histories and temperamental vulnerabilities affect the short- and long-term likelihood that experiences with stressful events will lead to the development of anxiety disorders. They also discuss how contextual variables during and after stressful learning experiences influence the maintenance of anxiety disorder symptoms. Thus, contemporary learning models provide a rich and nuanced understanding of the etiology and course of anxiety and related disorders. Expected final online publication date for the Annual Review of Clinical Psychology, Volume 18 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Mechanisms and Effectiveness of Imagery Strategies in Reducing Disgust in Contamination-Related Obsessive–Compulsive Disorder: Comparing Imagery Rescripting, Imagery Self-compassion and Mood-Focused Imagery

Background

Strong feelings of disgust and anxiety are maintaining factors in contamination-related obsessive–compulsive disorder (C-OCD). To this day there are not many studies that investigated strategies for changing pathological disgust. In a previous study, it was shown that imagery rescripting could successfully change disgust. However, whether imagery rescripting or more general imagery processing, helps to reduce pathological disgust, remains unclear. Therefore, the aim of the present study was to investigate how successful imagery rescripting is in comparison to imagery self-compassion and a passive positive imagery condition in reducing disgust.

Methods

For this, the three strategies were compared to each other on 2 days (within-subject) in a laboratory experiment. The study included 24 subjects with diagnosed C-OCD, and 24 matched, healthy controls (between-subject).

Results

The results show that all three strategies changed disgust, they do not differ from each other and that different traits appear to influence the strategies’ success or failure. The theoretically derived underlying mechanisms of the strategies were found in an elaborate content analysis.

Conclusions

The present study provides first indications that imagery in general can help to change pathological disgust experience.

Fear conditioning and extinction in obsessive-compulsive disorder: A systematic review

Laboratory experiments using fear conditioning and extinction protocols help lay the groundwork for designing, testing, and optimizing innovative treatments for anxiety-related disorders. Yet, there is limited basic research on fear conditioning and extinction in obsessive-compulsive disorder (OCD). This is surprising because exposure-based treatments based on associative learning principles are among the most popular and effective treatment options for OCD. Here, we systematically review and critically assess existing aversive conditioning and extinction studies of OCD. Across 12 studies, there was moderate evidence that OCD is associated with abnormal acquisition of conditioned responses that differ from comparison groups. There was relatively stronger evidence of OCD's association with impaired extinction processes. This included multiple studies finding elevated conditioned responses during extinction learning and poorer threat/safety discrimination during recall, although a minority of studies yielded results inconsistent with this conclusion. Overall, the conditioning model holds value for OCD research, but more work is necessary to clarify emerging patterns of results and increase clinical translational utility to the level seen in other anxiety-related disorders. We detail limitations in the literature and suggest next steps, including modeling OCD with more complex conditioning methodology (e.g., semantic/conceptual generalization, avoidance) and improving individual-differences assessment with dimensional techniques.

Acquisition and maintenance of disgust reactions in an OCD analogue sample: Efficiency of extinction strategies through a counter-conditioning procedure

BACKGROUND

Obsessive-compulsive disorder (OCD) has long been considered as an anxiety disorder, disgust is the dominant emotion in contamination-based OCD. However, disgust seems resistant to exposure with response prevention partly due to the fact that disgust is acquired through evaluative conditioning.

AIMS

The present research investigates a counter-conditioning intervention in treating disgust-related emotional responses in two groups of individuals with high (High contamination concerns, HCC, n = 24) and low (Low contamination concerns LCC, n = 23) contamination concerns.

METHODS

The two groups completed a differential associative learning task in which neutral images were followed by disgusting images (conditioned stimulus; CS+), or not (CS-). Following this acquisition phase, there was a counter-conditioning procedure in which CS+ was followed by a very pleasant unconditional stimulus while CS- remained unreinforced.

RESULTS

Following counter-conditioning, both groups reported significant reduction in their expectancy of US occurrence and reported less disgust with CS+. For both expectancy and disgust, reduction was lower in the HCC group than in the LCC group. Disgust sensitivity was highly correlated with both acquisition and maintenance of the response acquired, while US expectation was predicted by anxiety.

CONCLUSION

Counter-conditioning procedure reduces both expectations and conditioned disgust.

Generalization gradients for fear and disgust in human associative learning

Previous research indicates that excessive fear is a critical feature in anxiety disorders; however, recent studies suggest that disgust may also contribute to the etiology and maintenance of some anxiety disorders. It remains unclear if differences exist between these two threat-related emotions in conditioning and generalization. Evaluating different patterns of fear and disgust learning would facilitate a deeper understanding of how anxiety disorders develop. In this study, 32 college students completed threat conditioning tasks, including conditioned stimuli paired with frightening or disgusting images. Fear and disgust were divided into two randomly ordered blocks to examine differences by recording subjective US expectancy ratings and eye movements in the conditioning and generalization process. During conditioning, differing US expectancy ratings (fear vs. disgust) were found only on CS-, which may demonstrated that fear is associated with inferior discrimination learning. During the generalization test, participants exhibited greater US expectancy ratings to fear-related GS1 (generalized stimulus) and GS2 relative to disgust GS1 and GS2. Fear led to longer reaction times than disgust in both phases, and the pupil size and fixation duration for fear stimuli were larger than for disgust stimuli, suggesting that disgust generalization has a steeper gradient than fear generalization. These findings provide preliminary evidence for differences between fear- and disgust-related stimuli in conditioning and generalization, and suggest insights into treatment for anxiety and other fear- or disgust-related disorders.

Design and Validation of Augmented Reality Stimuli for the Treatment of Cleaning Obsessive-Compulsive Disorder

Fear to contamination is an easy-to-provoke, intense, hard-to-control, and extraordinarily persistent fear. A worsening of preexisting psychiatric disorders was observed during the COVID-19 (coronavirus disease 2019) outbreak, and several studies suggest that those with obsessive-compulsive disorder (OCD) may be more affected than any other group of people. In the face of worsening OCD symptoms, there is a need for mental health professionals to provide the support needed not only to treat patients who still report symptoms, but also to improve relapse prevention. In this line, it is recommended to improve alternative strategies such as online consultations and digital psychiatry. The aim of this study is to develop augmented reality (AR) stimuli that are clinically relevant for patients with cleaning OCD and assess their efficiency to obtain emotionally significant responses. Four AR stimuli were developed: a plastic bag full of garbage, a piece of bread with mold, a dirty sports shoe, and a piece of rotten meat. All stimuli were shown to a clinical group (17 patients with cleaning OCD) and a control group (11 patients without OCD). Relevant results were the design of the AR stimuli. These stimuli were validated with the statistical difference in perceived anxiety in the meat stimuli between the clinical and control groups. Nevertheless, when looking at effect sizes, all stimuli present effect sizes from small (plastic bag) to large (meat), with both shoe and bread between small and medium effect sizes. These results are a valuable support for the clinical use of these AR stimuli in the treatment of cleaning OCD.

Behavioral avoidance tasks for eliciting disgust and anxiety in contamination fear: An examination of a test for a combined disgust and fear reaction

While research supports the role of disgust in contamination OCD, there is also an overlap with fear in motivating avoidance. The "heebie-jeebies" is an emotional response associated with fear and disgust that motivates avoidance of contact with skin-transmitted pathogens (e.g., parasites). This motivation aligns with characteristics of contamination OCD. From a screening of undergraduate students (N = 188), contamination fearful (n = 14), high trait-anxious (n = 14), and low trait-anxious (n = 18) groups were created. Participants engaged in disgust, fear, and "heebie-jeebies" behavioral avoidance tasks. Participants rated "heebie-jeebies" emotion, physical sensations, and behavioral urges. Duration or refusal of task was recorded. A significant interaction effect was found for disgust and anxiety. Participants with higher disgust reported higher "heebie-jeebies" emotion at high, but not low, levels of anxiety. Exploratory analyses revealed that many contamination fearful and high trait-anxious participants refused to complete the task. The interaction of disgust and anxiety significantly predicted the probability of refusal. Participants with higher disgust and anxiety were more likely to refuse to complete the task. Results suggest that the "heebie-jeebies" motivates avoidance of skin-transmitted pathogens. Future research is warranted to further investigate the "heebie-jeebies" and how it relates to contamination concerns.

The Role of Disgust in Eating Disorders

PURPOSE OF REVIEW

In current review, we evaluate the current literature examining the role of disgust in eating disorders (EDs), and provide a theoretical model designed to inform the study and treatment of disgust-based symptoms in EDs.

RECENT FINDINGS

Findings from this review suggest that aberrant disgust-conditioning processes represent promising but understudied mechanisms that may contribute to the risk and maintenance of core eating disorder (ED) psychopathology. In addition, preliminary evidence supports the use of interventions designed to target aversive disgust cues and disrupt maladaptive disgust-based conditioning that may maintain eating pathology. However, experimental studies designed to elucidate the role of disgust and aversive learning processes remain limited. Disgust is a promising risk and maintenance factor in EDs. Future systematic investigation is needed to examine disgust-based processes at a mechanistic level in order to better understand the links between disgust, avoidance behaviors, and EDs. Further investigation of the mechanistic role of disgust in EDs is warranted.

Fear Learning in Veterans With Combat-Related PTSD Is Linked to Anxiety Sensitivity: Evidence From Self-Report and Pupillometry

Several studies have observed heightened Pavlovian fear conditioning in PTSD. However, it is unclear how fear conditioning in PTSD is related to risk factors for the disorder, such as anxiety sensitivity. Fifty-one combat-exposed veterans (20 with PTSD, 31 without PTSD) completed a differential fear conditioning task in which one colored rectangle (CS+) predicted a loud scream (US), whereas a different colored rectangle (CS-) predicted no US. Veterans with PTSD were characterized by greater anxiety to the CS+ but not the CS- during acquisition and extinction, and greater US expectancy during the CS+ but not the CS- at extinction. Also, veterans with PTSD had greater pupil dilation to both CSs at extinction, but not at acquisition. Anxiety sensitivity was correlated with anxiety and US expectancy in response to the CS+, but not the CS-, at both acquisition and extinction, and also with pupil diameter to both the CS+ and CS- at extinction. Nearly all of these relations held when covarying for PTSD symptoms and trait anxiety. These findings suggest that increased fear conditioning in PTSD may be related to elevated anxiety sensitivity.

Attentional Processing of Disgust and Fear and Its Relationship With Contamination-Based Obsessive-Compulsive Symptoms: Stronger Response Urgency to Disgusting Stimuli in Disgust-Prone Individuals

Disgust has recently been characterized as a low-urgency emotion, particularly compared to fear. The aim of the present study is to clarify whether behavioral inhibition during disgust engagement is characteristic of a low-urgency emotion and thus indicates self-imposed attentional avoidance in comparison to fear. Therefore, 54 healthy participants performed an emotional go/no-go task with disgust- and fear-relevant as well as neutral pictures. Furthermore, heart rate activity and facial muscle activity on the fear-specific m. corrugator supercilli and the disgust-specific m. levator labii were assessed. The results partially support the temporal urgency hypothesis of disgust. The emotion conditions significantly differed in emotional engagement and in the facial muscle activity of the m. levator labii as expected. However, contrary to our expectations, no differences between the emotion conditions regarding behavioral inhibition as well as heart rate change could be found. Furthermore, individuals with a higher-trait disgust proneness showed faster reactions and higher activity of the m. levator labii in response to disgust stimuli. The results show that different trait levels influence attentional engagement and physiological parameters but have only a small effect on behavioral inhibition.

Examining Differences in Fear Learning in Patients With Obsessive-Compulsive Disorder With Pupillometry, Startle Electromyography and Skin Conductance Responses

Obsessive-compulsive disorder (OCD) is characterized by recurrent, persistent thoughts and repetitive behaviors causing stress and anxiety. In the associative learning model of OCD, mechanisms of fear extinction are supposed to partly underlie symptom development, maintenance and treatment of OCD, proposing that OCD patients suffer from rigid memory associations and inhibitory learning deficits. To test these assumptions, previous studies have used skin conductance and subjective ratings as readouts in fear conditioning paradigms, finding impaired fear extinction learning, impaired fear extinction recall or no differences between individuals with OCD and healthy controls. Against this heterogeneous background, we tested fear acquisition and extinction in 37 OCD patients and 56 healthy controls, employing skin conductance as well as pupillometry and startle electromyography. Extinction recall was also included in a subsample. We did not observe differences between groups in any of the task phases, except a trend toward higher startle amplitudes during extinction for OCD. Overall, sensitive readouts such as pupillometry and startle responses did not provide evidence for moderate-to-large inhibitory learning deficits using classical fear conditioning, challenging the assumption of generically impaired extinction learning and memory in OCD.

A Meta-Analysis on the Efficacy of Exposure-Based Treatment in Anxiety Disorders: Implications for Disgust

Despite of several meta-analyses indicating that exposure-based treatments (EBT) are successful in addressing anxiety and fear symptoms, less is known whether this is also the case for disgust, which also accompanies anxiety disorders. Therefore, the aim of the current meta-analysis was to compare the efficacy of EBT on disgust and anxiety (emotional distress), against control condition. This meta-analysis included a total of eight studies. Overall, there was a medium effect size (g = .57, 95% CI: .26 to .88, p < .001) for emotional distress; a medium effect size for anxiety (g = .79, 95% CI: .24 to 1.34, p = .005), yet a small effect size for disgust (g = .36, 95% CI: .05 to .68, p = .024). These findings prompt that current EBT are not tailored to address disgust symptoms accompanying many forms of anxiety disorders, although literature points more and more to a need in this respect. We also examined potential moderator variables (the year of publication, the number of exposure sessions, age of the sample, and gender composition). Additionally, we discussed several strengths and limitations, one of the most important being the small number of studies regarding the subject and their heterogeneity.

Green model to adapt classical conditioning learning in the hippocampus

Compared with the biological paradigms of classical conditioning, non-adaptive computational models are not capable of realistically simulating the biological behavioural functions of the hippocampal regions, because of their implausible requirement for a large number of learning trials, which can be on the order of hundreds. Additionally, these models did not attain a unified, final stable state even after hundreds of learning trials. Conversely, the output response has a different threshold for similar tasks in various models with prolonged transient response of unspecified status via the training or even testing phases. Accordingly, a green model is a combination of adaptive neuro-computational hippocampal and cortical models that is proposed by adaptively updating the whole weights in all layers for both intact networks and lesion networks using instar and outstar learning rules with adaptive resonance theory (ART). The green model sustains and expands the classical conditioning biological paradigms of the non-adaptive models. The model also overcomes the irregular output response behaviour by using the proposed feature of adaptivity. Further, the model successfully simulates the hippocampal regions without passing the final output response back to the whole network, which is considered to be biologically implausible. The results of the Green model showed a significant improvement confirmed by empirical studies of different tasks. In addition, the results indicated that the model outperforms the previously published models. All the obtained results successfully and quickly attained a stable, desired final state (with a unified concluding state of either "1" or "0") with a significantly shorter transient duration.

Linking Pavlovian Disgust Conditioning and Eating Disorder Symptoms: An Analogue Study

Although the experience of disgust is commonly endorsed among women with eating disorders, it remains unclear how to best model this emotion in relation to disordered eating. The present study sought to identify potential disgust conditioning abnormalities that may underlie the development of eating disorder symptoms. Individuals high and low in eating disorder symptoms (HED, n = 19; LED, n = 18) completed a Pavlovian conditioning procedure in which one neutral food item (conditioned stimulus; CS+) was followed by disgusting videos of individuals vomiting (unconditioned stimulus; US) and another neutral food item (CS-) was not reinforced with the disgusting video. Following this acquisition procedure, there was an extinction procedure in which both CSs were presented unreinforced. The results showed that ratings of disgust, fear, and willingness to eat the CS+ and CS- did not significantly vary as a function of the conditioning phase for the LED group. However, the HED group rated the CS+ as significantly more disgusting and fear inducing than the CS- after the acquisition phase and this pattern persisted after extinction. These conditioning effects were also observed to be significantly larger for disgust compared to fear. The HED group also reported being significantly less willing to eat the CS+ compared to the CS- after the acquisition phase and this pattern also persisted after extinction. In the full sample, only discriminant disgust responding after acquisition was associated with the amount of calorie consumption over the 24-hour period after conditioning. These findings suggest that eating disorder symptoms may result from a heightened proneness to associate disgusting outcomes with otherwise neutral food items. This pattern of disgust learning may reinforce food avoidance in eating disorders and appears to be difficult to fully unlearn.

The effects of exposure on the generalization of habituation on multiple indices of disgust

Examination of habituation to disgust-related stimuli has received limited experimental investigation. In this study, 38 undergraduates were divided into two groups. The vomit-blood (VB) group was first exposed to a realistic approximation of vomit and allowed to habituate to this stimulus, while the blood-vomit (BV) group was first allowed to habituate to a realistic approximation of blood. Following the habituation phase, each group underwent a short exposure to the unexposed stimuli (blood in the VB group, vomit in the BV group). Physiological and self-report assessments were collected during exposure. Self-report habituation was observed for both groups. In addition, only muscle tension at the levator labii and heart rate in the VB group demonstrated significant changes that could be interpreted as habituation. Consistent with previous literature, muscle tension at the levator labii appeared to be a unique indicator of disgust responding. Implications and suggestions for future research are discussed.

Disgust in Anxiety and Obsessive-Compulsive Disorders: Recent Findings and Future Directions

PURPOSE OF REVIEW

In the past 20 years, the role of disgust in anxiety disorders and obsessive-compulsive disorder (OCD) has been investigated with increasing precision. In this review, we examine recent evidence implicating disgust in anxiety and OCD, highlighting recent measurement and methodological improvements. Specific emphasis is placed on understanding the mechanisms that may account for the role of disgust in OCD and related disorders.

RECENT FINDINGS

Recent developments include clarification of the role of distinct disgust-relevant vulnerabilities in the etiology of anxiety and OCD, an improved understanding of the neurobiology of disgust processing in OCD, and an increased focus on disgust-related mechanisms that contribute to psychopathology, such as disgust-based learning and emotion regulation. Disgust proneness is increasingly linked with symptoms of anxiety and OCD. However, further examination of the mechanisms that account for the roles of distinct disgust-relevant vulnerabilities is needed, and studies that directly examine disgust during the course of treatment are limited. Increasingly, the field has moved toward experimental investigation of specific disgust-relevant mechanisms that influence the etiology and treatment of OCD and related anxiety disorders.

Cognitive mechanisms of disgust in the development and maintenance of psychopathology: A qualitative review and synthesis

A growing body of research has implicated disgust in various psychopathologies, especially anxiety-related disorders. Although the observed role of disgust in many disorders is robust, the mechanisms that may explain this role are unclear. Cutting-edge research in cognitive science has the potential to elucidate such mechanisms and consequently improve our understanding of how disgust contributes to the etiology and maintenance of psychopathology. In this qualitative review, we systematically assess cognitive bias mechanisms that have been linked to disgust and its disorders. This review suggests that disgust-related biases may be observed in memory, interpretation, judgment of expectancies, and attention, as well as at implicit levels. Of these cognitive domains, the most robust bias appears to be observed at the level of attention. However, reliable moderators of attentional biases for disgust have not yet been identified, and this bias has not been systematically linked to other levels of analysis. Despite these limitations, the available research indicates that attentional avoidance rather than orienting or maintenance may be the most characteristic of disgust. Attentional avoidance of disgust may have important implications for etiological and treatment models of disorders characterized by excessive disgust reactions. The implications for advancing such models are discussed in the context of a combined cognitive bias hypothesis.

Experimental modification of dysfunctional interpretations in individuals with contamination concerns

BACKGROUND AND OBJECTIVES

Dysfunctional interpretations of intrusive thoughts are implicated in the etiology and maintenance of Obsessive-Compulsive Disorder (OCD). Cognitive Bias Modification training for interpretations (CBM-I) has successfully modified dysfunctional interpretations in the context of several disorders, including OCD. However, research regarding CBM-I's impact on symptom reduction and behavior is mixed, which limits its clinical application. Further, support for the specific efficacy of CBM-I in individuals with contamination concerns is limited. The current study aimed to modify dysfunctional interpretations in individuals with contamination concerns, and examine the effect of the modification on both interpretation bias and performance on a behavioral approach task (BAT).

METHODS

Participants (N = 74) completed a word-sentence association task by indicating whether a threatening or benign word was related to an ambiguous scenario. The active condition received feedback designed to reduce maladaptive interpretations; the control condition received random feedback.

RESULTS

Findings revealed that the active-but not the control-condition showed a significant decrease in interpretation bias for threat cues. Analyses of behavioral effects indicated that when ceiling effects were accounted for, the active condition completed more BAT steps than the control condition (p = 0.06; d = 0.45).

LIMITATIONS

The current study is preliminary and requires replication with a clinical sample.

CONCLUSIONS

Completion of the CBM-I was beneficial for reducing dysfunctional interpretations relevant to naturally-occurring contamination concerns and, importantly, this reduction may help those individuals approach feared situations.

The effects of cognitive reappraisal on conditioned disgust in contamination-based OCD: An analogue study

Experimental research has shown that conditioned disgust is resistant to extinction, which may account for the slower habituation to disgust relative to fear in contamination-based obsessive-compulsive disorder (OCD). However, few studies have examined the efficacy of interventions that may attenuate conditioned disgust responses. Studies of cognitive reappraisal have demonstrated that reinterpreting a stimulus can alter emotional responding. This technique is based on cognitive theories which suggest that anxiety disorders arise from biased cognitions; therefore, changing a person's thoughts will elicit durable changes in emotional responses. Given the demonstrated effectiveness of cognitive reappraisal, the present study examined whether cognitive reappraisal would attenuate conditioned disgust responses. We conditioned participants high in contamination fear (n=55) using images of neutral food items (conditioned stimuli; CS) paired with videos of individuals vomiting (unconditioned stimuli; US) while we obtained subjective disgust reports. After conditioning, half of the participants were randomly assigned to cognitive reappraisal training aimed at decreasing their emotional response to the US and CS, while the other half received no such training. The findings showed that cognitive reappraisal participants demonstrated a reduction in learned disgust across sessions and further benefited from extinction. These findings suggest that cognitive reappraisal may be an effective strategy for attenuating learned disgust.