Problem solving in Parkinson's disease: comparison of performance on the Wisconsin and California Card Sorting Tests

Previous demonstrations that problem solving deficits may occur early in the course of Parkinson's disease (PD) have been taken to support the view that disturbances in the functioning of the frontal lobes are responsible for the initial cognitive deficits in this disease. However, no specific pattern of responding associated with poor problem solving by PD patients has been observed consistently. In an effort to clarify the nature of the problem solving deficits in PD we administered the Wisconsin Card Sorting Test (WCST) and the California Card Sorting Test (CCST), a new test which provides separate measures of concept generation, concept identification, and concept execution as well as several different measures of perseveration. On both tests PD patients of lower than normal mental status performed poorly and their patterns of performance resembled those previously described for patients with focal frontal lobe lesions, but PD patients of normal mental status performed normally. Because poor problem solving in association with increased perseverative responding was only observed for patients with global cognitive deficits these findings do not necessarily support the idea that frontal dysfunction is the principal cause of impaired cognition in PD. Although the overall pattern of results was similar for the WCST and the CCST, the CCST was more sensitive for detecting deficits than was the WCST.