Movement programming in Parkinson's disease (PD) and Alzheimer's disease (AD)

Aim: Evaluate different performances in movement programming of PD and AD patients, in comparsion with normal controls. Patients: Ten PD patients (H&Y stage I-II) with bradykinesia as main sign and no cognitive impairment; 10 AD patients (CDR stage 1-2) with no parkinsonian sign and 17 age-matched controls. Methods: All subjects were instructed to make single, uncorrected horizontal movements with their dominants hands, as fast and accurate as possible on a digitizing table, without seeing their limbs. Target and starting location were always visible on a screen during the movement, while cursor position was either visible (visual feed-back, FB) or blanked (no FB). Results: In PD patients and controls, age correlated with a reduction of non-visual preprogramming phase and increase of FB. However, in PD patients visual FB worsened motor accuracy and speed. In AD patients, a correlation between age and preprogramming phase was no longer evident. Cognitive scores inversely correlated with preprogramming phase and directly with use of FB. Conclusion: Cognitive functions, and particulary working memory are deeply involved in motor programming. AD patients, owing to memory deficit, used mainly FB strategies. On the contrary, visual FB worsened motor accurancy and speed of PD patients.