Working memory functioning in medicated Parkinson's disease patients and the effect of withdrawal of dopaminergic medication

Cognitive impairments in Parkinson's disease (PD) could be explained by a c entral executive (CE) deficit in A. D. Baddeley's (1986) working memory mod el. To test this hypothesis, verbal, spatial, and double span tasks were gi ven to 12 medicated PD patients and control participants, with varying reca ll delays. The double span task was assigned to explore the coordinating an d integrating function of the CE, and lengthening the recall delay was expe cted to implicate more attentional resources. PD patients had lower spans r elative to controls in all tasks. However, the more specific implication of the CE was difficult to prove. One reason could be that PD patients were o n dopaminergic treatment when tested. To control this effect, 12 PD patient s on and off medication were studied in a second experiment using the same tasks. PD patients off medication had lower spans only in the double task; this result underlines the role of dopamine on working memory processes.