Wisconsin Card Sorting Test in Parkinson's disease: diffusion tensor imaging.

It is generally assumed that executive dysfunctions in Parkinson's disease (PD) are caused by degeneration of the basal ganglia or frontal cortex or both. However, there have been few studies investigating the relationship between executive dysfunctions and cerebral pathological change. The objective of this study was to evaluate various cognitive functions in non-demented patients with PD, and to compare the fractional anisotropy (FA) values of PD patients with and without executive dysfunction.Twenty-one consecutive non-demented patients with PD were enrolled in this study. Patients were divided into two groups on the basis of their Wisconsin Card Sorting Test score.There was significant FA reduction in the left parietal white matter in the group in which the number of categories achieved was 2.Accumulating evidence suggests that conventional 'frontal' tasks correlate with both frontal lobe and parietal lobe function, and we suggest that pathological changes in the left parietal lobe may cause, in part, disturbances in executive tasks in PD.