BACKGROUND AND AIMS: The observation of every-day problems in decision making in patients with obsessive-compulsive disorder (OCD) is reflected by their inclusion in psychometric scales for OCD. Experimentalstudiesin OCD patients did not consistently find deficits in DM, however. Our aim was to minimize the hypothesized influence of working memory capacity, reward/punishment processing upon feedback, planning and strategy on action selection performance and neural correlates thereof using fMRI. METHODS: We conducted an event-related 3T-fMRI study in 12 unmedicated OCD patients and 10 healthy controls. We used a forced-choice reaction time (RT) paradigm with parametrically increasing number of choice alternatives to be indicated by button press (0–4). Choices were based on abstract stimuli and rules, with no feedback provided. RESULTS: As expected both groups showed nearly errorless task performance and increasing RTs with increasing number of choice alternatives (0–4). This effect was paralleled by a parametrically increasing recruitment of a bilateral parieto-premotor-prefrontal cortical network and the cerebellum in all subjects. However, we did not observe any group differences applying a P=0.05 threshold with correction for multiple comparisons in SPM8. Analoguously, patients with OCD did not differ from controls regarding error rate or RT. CONCLUSIONS: Using a “purified” action selection paradigm we suggest that forming and executing simple decisions without switching contingencies and without delivering reward or punishment is unimpaired in OCD, both in behavioural and neural terms. Further studies will need to determine which additional task requirements associated with action selection may be responsible for observable deficits.
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