Effects of extensive practice on bradykinesia in Parkinson's disease: improvement, retention and transfer

We investigated the effects of extensive practice of rapid aiming on bradykinesia and, more specifically, generation of peak velocity, in discrete rapid aiming and in transfer to reach-to-grasp. Twenty-one participants (seven young adults, seven older adults, and seven adults with mild to moderate Parkinson's disease (PD) while on medication) engaged in eight practice periods per week for three weeks (> 700 trials), with changes in performance measured weekly. Retention was measured weekly for three weeks postpractice. Movement time decreased with one week of practice, primarily due to a decrease in time-to-peak velocity. With practice and after retention, the PD group generated peak velocity as consistently as both neurologically healthy groups, but remained more variable in time-to-peak velocity. Transfer was observed in the neurologically healthy groups, but not in the PD group. We concluded that short-term practice (one week in our paradigm) is sufficient for decreasing movement time, but more extensive practice is needed to improve consistency of rapid aiming performance for people with mild to moderate PD.