SPECIFIC COGNITIVE DEFICITS IN TESTS SENSITIVE TO FRONTAL-LOBE DYSFUNCTION IN OBSESSIVE-COMPULSIVE DISORDER

Forty patients with obsessive-compulsive disorder (OCD) were compared to matched healthy controls on neuropsychological tests which are sens itive to frontal lobe dysfunction. On a computerized version of the To wer of London test of planning, the patients were no different from he althy controls in the accuracy of their solutions. However, when they made a mistake, they spent more time than the controls in generating a lternative solutions or checking that the next move would be correct. The results suggest that OCD patients have a selective deficit in gene rating alternative strategies when they make a mistake. In a separate attentional set-shifting task, OCD patients were impaired in a simple discrimination learning task and showed a continuous cumulative increa se in the number who failed at each stage of the task, including the c rucial extra-dimensional set shifting stage. This suggests that OCD pa tients show deficits in both acquiring and maintaining cognitive sets. The cognitive deficits in OCD may be summarized as: (i) being easily distracted by other competing stimuli; (ii) excessive monitoring and c hecking of the response to ensure a mistake does not occur; and (iii) when a mistake does occur, being more rigid at setting aside the main goal and planning the necessary subgoals. Both studies support the evi dence of fronto-striatal dysfunction in OCD and the results are discus sed in terms of an impaired Supervisory Attentional System.