My apologies if this has already been posted.
Abstract from pubmed:

Brain Cogn. 2009 Mar;69(2):435-41. Epub 2008 Nov 8.
Benefits of physical exercise on executive functions in older people with Parkinson's disease.

Tanaka K, Quadros AC Jr, Santos RF, Stella F, Gobbi LT, Gobbi S.

UNESP, São Paulo State University at Rio Claro, SP, Brazil. katinhalua@yahoo.com.br

The benefits of physical exercise on cognitive functioning have been reported in the literature, but the potential benefits to slow the eventual decline in executive functioning (EF) caused by neurodegeneration from Parkinson's Disease (PD) have rarely been studied. Thus the objective of this study was to analyze the effects of a multimodal physical exercise program on EF in older people with Parkinson's disease. The EF of the older people was evaluated by neuropsychological testing, and for confounding variables such as attention, depressive symptoms and anxiety, before and after intervention. The 20 participants were assigned into Control (CG) and Trained (TG) Groups. The TG participated in generalized physical training for 6 months. The ANOVA showed a significant interaction (p<.05) that indicated a beneficial contribution of training on EF. No significant interactions were found in the results for confounding variables between groups and pre- and post-intervention, which supports the beneficial findings of physical exercise training on EF.