To investigate the neuro-mechanisms underpinning persistent avoidance in OCD patients

Many compulsions displayed by obsessive-compulsive disorder (OCD) patients serve to protect against perceived threat and can, therefore, be conceptualized as 'avoidance responses'. Exposure treatment with response prevention (ET+RP) is aimed at exposing patients to their obsessive thoughts and perceived threats while preventing engagement in compulsive avoidant responses. This induces extinction of threat perception and fearful arousal and hence reduces the motivation to avoid. While successful in many patients, however, as much as 40% dropout during treatment or display persistent avoidance after ET+RP. There is a clear need for treatment improvement for these often highly disabled patients.

Improving ET+RP outcomes requires a deeper understanding of the mechanisms that drive excessive and persistent avoidance in OCD patients. Psychological theories ascribe an important role to the relief that follows avoidance when the anticipated threat is successfully averted. This positive feeling arguably functions as a reward to reinforce the foregoing avoidance actions. Indeed, fMRI studies have found that the neurocircuitry of relief overlaps with that of reward, including the ventral tegmental area, ventral striatum and orbitofrontal cortex. Here, the authors will test the hypothesis that excessive-persistent avoidance is linked to exaggerated activation of the relief circuitry in OCD patients. For that purpose, we will acquire functional brain images of OCD patients in an MRI scanner and compare to healthy participants, while they participate in a computer task that is designed to model avoidance learning and relief.

Inclusion Criteria:

• Healthy volunteers 18-60 years old;
• Participants are motivated and give written informed consent;
• Adequate demand of Dutch language;
• Subjects have never participated in a fear conditioning task;
• Diagnosis of OCD (for OCD group only);
• Contraindications for the MRI exam.

Exclusion Criteria:

• Current neurological (e.g. Epilepsia), respiratory, cardiovascular, metabolic, gastrointestinal, endocrine (especially diabetes), renal or urinary diseases, psychiatric disorder or other relevant medical histories (except for OCD in the OCD group);
• Being pregnant or lactating;
• Alcohol intake greater than 14 alcoholic units per week (one alcoholic unit = 10 gr ethanol);
• History of cannabis use or any other drug of abuse during the 3 months prior to the study;
• The medical doctor has asked to the participant to stay away from stressful situations;
• Electronic implants (e.g., pacemaker);
• Pain or other condition of the hand or the wrist.

Healthy group: Mentally and medically healthy adults between 18 and 60 years, free from any current or previous medical or psychiatric condition.

OCD group: Same as the healthy group, except for the diagnosis of OCD and medication-free or with a stable medication regimen for at least 3 weeks prior to the study.