Orbitofrontal cortex dysfunction in obsessive-compulsive disorder? II. Olfactory quality discrimination in obsessive-compulsive disorder

Background: Olfactory quality discrimination is a putative marker of orbito frontal cortex function in mammals. As this portion of the cerebral cortex was repeatedly implicated in the pathophysiology of obsessive-compulsive di sorder (OCD) this study was designed in an attempt to quantify this behavio ural function in OCD patients. Methods and Results: Olfactory quality discr imination was compared in OCD patients and healthy controls. Thirty-two sub jects participated in the study: 16 (13 women and 3 men) medication free OC D outpatients and 16 sex and age matched healthy controls. Olfactory tests consisted of determination of detection thresholds to isoamyl acetate; and a three way forced choice quality discrimination task, using isoamyl acetat e, citral and eugenol as stimuli. No significant differences in sensitivity and performance of the quality discrimination task between the two groups were found. Within the OCD group the more severely affected patients (Y-BOC S>29) performed significantly better than the less severely affected (Y-BOC S<30) patients on the more difficult part of the quality discrimination tas k Within this subgroup of patients the correlation between performance on t he olfactory task and a previously reported alternation task tended to be n egative as compared to a significantly positive correlation in the control group. Conclusions: It seems that olfactory quality discrimination may prov e to be a useful noninvasive marker of prefrontal cortex function in OCD. F urthermore, the organization of functional modules within the orbitofrontal cortex, rather than a simple dysfunction, may prove to characterize OCD. ( C) 1999 Elsevier Science B.V. All rights reserved.