[Spatial-temporal parameters of ballistic arm abduction in normal subjects and patients with Parkinson's disease]

Spatio-temporal parameters of ballistic arm abduction movements were studied in healthy control subjects and in patients with Parkinson's disease. Arm abduction was performed during a step-tracking task. Patients showed longer reaction times, slower mean velocities and lesser accuracy, with a marked tendency to undershooting. In patients, "ballistic" movements (taken as initial movements completed within a mean reaction time or less) were fewer and more inaccurate. Moreover, their motor performance was greatly impaired in motor tasks including slight expected perturbations during the movement: evident changes in velocity or even arrests, together with inability to overcome the obstacle were observed. The motor performance of all tested subjects did not differ significantly in visual open-loop conditions. The present results: i) support the hypothesis that Parkinsonism interferes with the generation of accurate ballistic actions and ii) contribute to the understanding of bradykinesia.