fMRI of neuronal activation with symptom provocation in unmedicated patients with obsessive compulsive disorder

Background: Previous studies suggest that a neural circuit involving over-activation of cortical, paralimbic, limbic, and striatal structures may underlie OCD symptomatology, but results may have been limited by medication use in those studies. To address this, we examined the effects of symptom induction on fMRI neural activation in medication-free patients with OCD. Methods: Seven outpatients with OCD were exposed to individually tailored provocative and innocuous stimuli during fMRI scans. Self-ratings of OCD symptoms were performed prior to each scan and after exposure to stimuli. Images were analyzed as composite data sets and individually. Results: Stimulus presentation was associated with significant increases in OCD self-ratings. Significant activation was demonstrated in several regions of the frontal cortex (orbitofrontal, superior frontal, and the dorsolateral prefrontal); the anterior, medial and lateral temporal cortex; and the right anterior cingulate. Right superior frontal activation inversely correlated with baseline compulsion symptomatology and left orbitofrontal cortical activation was inversely associated with changes in OCD self-ratings following provocative stimuli. Conclusions: These results in unmedicated patients are consistent with those from previous studies with medicated patients and suggest that OCD symptomatology is mediated by multiple brain regions including the anterior cingulate as well as frontal and temporal brain regions.