Abstract
Objective: fMRI scans of patients with obsessive-compulsive disorder (OCD) consistently show a hyperactivity of the insular cortex, a region responsible for disgust-processing, when confronted with symptom-triggering stimuli. This asks for an investigation of the role of disgust and the insula in OCD patients.Methods: Seventeen inpatients with OCD and 17 healthy controls (HC) underwent fMRI scanning. Whole-brain contrasts were calculated for “Disgust vs. Neutral” for both groups, plus an analysis of variance (ANOVA) to assess the interaction between group and condition. Additionally, the emotional dimensions of valence and arousal, along with the ability to cope, were assessed by picture ratings.Results: The picture ratings confirmed the patients’ heightened sensitivity to disgust with higher values for arousal and inability to cope, but not for valence. fMRI scans revealed no hyperactivity of the insula in patients compared to controls for the condition “Disgust vs. Neutral,” indicating no basic hypersensitivity to disgusting stimuli. Increased activity in the precuneus in controls for this condition might correspond to the downregulation of arousal.Conclusions: The absent differences in neural activity of the insula in patients compared to controls for the disgust-condition, but heightened activity for symptom-provoking conditions, suggests that the illness is due to an erroneous recruitment of the insula cortex for OCD-stimuli. The finding is interpreted within the framework of the neural reuse hypothesis.
Highlights
With a prevalence of 2%–3%, obsessive-compulsive disorder (OCD) is one of the most common psychiatric diseases and has a serious impact on the quality of life (Crino et al, 2005)
The aim of this study was to investigate if a heightened sensitivity to disgusting pictures can be found in our sample and if this hypersensitivity corresponds to differences in disgust processing in the brain in OCD patients
Patients scored significantly higher in arousal and assessed their ability to cope lower than controls for the disgusting pictures, but there was no difference in the rating of the valence (Table 1)
Summary
With a prevalence of 2%–3%, obsessive-compulsive disorder (OCD) is one of the most common psychiatric diseases and has a serious impact on the quality of life (Crino et al, 2005). Individuals with OCD experience a persistent intrusion of unwanted thoughts or images (obsessions) and/or the urge for repetitive, ritualistic behaviors or mental acts (compulsions) that need to be neutralized in order to reduce anxiety or distress (American Psychiatric Association, 2013). The aim of this study was to investigate if a heightened sensitivity to disgusting pictures can be found in our sample and if this hypersensitivity corresponds to differences in disgust processing in the brain in OCD patients. We were especially interested in the role of the insular cortex since this region has been identified as relevant for disgust processing (next to a variety of other functions) in patients as well as in healthy participants. Group differences were found in both functional imaging and lesion studies (e.g., Wright et al, 2004; Knowles et al, 2018), especially when highly disgusting stimuli were used (Oaten et al, 2018)
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