Neural correlates of clinical symptoms and cognitive dysfunctions in obsessive-compulsive disorder

Although results from neuropsychological and neuroimaging studies have postulated the involvement of the frontal lobe and the subcortical brain regions in the pathophysiology of obsessive-compulsive disorder (OCD), neuroimaging studies have provided little evidence that cognitive abnormalities in patients with OCD are related to dysfunctions in these areas. This study was designed to determine whether the clinical features and cognitive deficits of OCD might be taken to reflect frontal-subcortical dysfunction. Fourteen patients with OCD and 14 case-matched normal subjects completed clinical and cognitive evaluation, including four sets of neuropsychological tests that assessed the executive functions and visual memory. Cerebral glucose metabolic rates were measured by using positron emission tomography (PET) with 18F-fluorodeoxyglucose. Behavioral and PET data were analyzed using statistical parametric mapping for group differences and behavioral-metabolic correlates. The right orbitofrontal cortex showed increased metabolic activity and the left parieto-occipital junction showed decreased metabolic activity in patients. Metabolism in the right hippocampus, the left putamen and the right parietal region was associated with the severity of obsessive-compulsive symptoms. Correlations between metabolic rates and neuropsychological test scores in the prefrontal cortex and the putamen occurred only in the patient group. These results suggest that patients with OCD have distinct features of brain metabolic activities for performing cognitive tasks as well as presenting obsessive-compulsive symptoms. In particular, the frontal-subcortical circuits might mediate not only symptomatic expression but also cognitive expression in patients with OCD.