Event-related functional magnetic resonance imaging of response inhibition in obsessive-compulsive disorder

Background: Obsessive-compulsive disorder (OCD) has been hypothesized to involve inhibitory control dysfunction related to abnormal frontal-striatal-thalamic-corticaI (FSTC) circuitry. Methods: We examined the neural substrates of response inhibition in adults with OCD using functional magnetic resonance imaging (fMRI) and a go/no-go task. Participants consisted of 12 adults with OCD and 14 healthy comparison subjects. Results: During response inhibition, healthy adults showed predominantly right-hemisphere activation including the right inferior frontal gyrus, whereas the patient group showed a more diffuse, bilateral pattern of activation. Furthermore, the OCD group demonstrated less activation than the comparison group in several right-hemisphere regions during response inhibition, including inferior and medial frontal gyri. Symptom severity was inversely correlated with activation in right orbitofrontal and anterior cingulate gyri and positively correlated with thalamic and posterior cortical activations. Neither depressed mood nor medication status could account for the results. Conclusions: These findings indicate that adults with OCD demonstrate underactivation of FSTC circuitry during response inhibition. Results suggest that the thalamus and related circuitry may play a role in the expression or intensity of OCD symptoms, whereas right frontal subregions may be involved in the suppression of symptoms.