SynopsisForty patients with obsessive–compulsive disorder (OCD) were compared to matched healthy controls on neuropsychological tests which are sensitive to frontal lobe dysfunction. On a computerized version of the Tower of London test of planning, the patients were no different from healthy controls in the accuracy of their solutions. However, when they made a mistake, they spent more time than the controls in generating alternative solutions or checking that the next move would be correct. The results suggest that OCD patients have a selective deficit in generating 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 increase in the number who failed at each stage of the task, including the crucial extra-dimensional set shifting stage. This suggests that OCD patients 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 checking 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 evidence of fronto-striatal dysfunction in OCD and the results are discussed in terms of an impaired Supervisory Attentional System.
Specific cognitive deficits in tests sensitive to frontal lobe dysfunction in obsessive–compulsive disorder
