RESPONSE-INHIBITION DEFICITS IN OBSESSIVE-COMPULSIVE DISORDER - AN INDICATOR OF DYSFUNCTION IN FRONTOSTRIATAL CIRCUITS

Abnormalities in the orbital prefrontal cortex and its ventral striata l target fields are believed to be involved in causing obsessive and c ompulsive symptoms. Lesions to this brain circuitry result in a select ive disturbance in suppressing responses to irrelevant stimuli. This d isturbance might underlie the apparent inhibitory deficit suggested by the symptomatology of obsessive-compulsive disorder (OCD). Oeulomotor tests were administered to 12 medication-free, nondepressed patients with OCD aged 18 to 44 y and 12 matched healthy controls to assess the ability to suppress responses and to execute delayed responses voliti onally. Patients with OCD had more response-suppression failures than controls when peripheral visual targets were presented close to centra l fixation. No significant case-control differences were observed on t he delayed-response task. A basic disturbance of neurobehavioral inhib ition in OCD may underlie the repetitive behavior that characterizes t he illness and be related to abnormalities in orbital prefrontal ventr al striatal circuits.