The selective breakdown of frontal functions in patients with obsessive-compulsive disorder and in patients with schizophrenia: a double dissociation experimental finding.

In an our recent preliminary study, we reported the neuropsychological finding of a double dissociation in the frontal lobe functioning between 25 OCD patients and 25 schizophrenics. The first group performed normally in the Wisconsin Card Sorting Test (WCST), which is considered sensitive to Dorso-Lateral Prefrontal Cortex (DLPFC) dysfunctions and abnormally to the Object Alternation Test (OAT), which has been proposed as a tool sensitive to Orbito-Frontal Cortex (OFC); on the other hand, schizophrenics performed abnormally to the WCST and normally to the OAT. The present study, conducted on a new sample of 60 schizophrenic in-patients, 60 OCD in-patients and 30 normal subjects, matched according to age, educational level, handedness and duration of illness, confirms our preliminary data and it suggests a more selective impairment of OFC system in OCD and of DLPFC in schizophrenia. Moreover, schizophrenic patients with paranoid subtype showed worse WCST performance compared to non-paranoid subtype. Our results could open some interesting perspectives about the neuroanatomical systems involved in these two major psychiatric illnesses and so, about their pharmacological treatment, on the basis of the prominent catecholaminergic characterization of the DLPFC and, respectively, the cholinergic innervation of the OFC.