Performance of a motor task learned on levodopa deteriorates when subsequently practiced off.

Area of Science:

• Neuroscience
• Motor Control
• Parkinson's Disease Research

Background:

• Dopamine's role in motor learning is complex.
• Its impact on motor learning retention is understudied.
• Animal models suggest practicing tasks in a dopamine-off state after learning in an on-state can impair performance.

Purpose of the Study:

• To investigate the effects of levodopa on motor task acquisition and retention in Parkinson's disease (PD).
• To examine how practicing motor tasks in the presence versus absence of levodopa influences performance over time.

Main Methods:

• Twenty individuals with PD (Hoehn and Yahr Stage 1.5-3) practiced three motor tasks over two weeks.
• Participants were divided into two groups: one practiced on levodopa then off, the other practiced off levodopa for both weeks.
• Tasks included alternate tapping, body movement to targets, and mirror drawing.

Main Results:

• For tapping and body movement tasks, practicing on levodopa during week 1 led to performance decline in week 2 when off levodopa.
• Subjects practicing off levodopa maintained or improved performance.
• For the mirror drawing task, levodopa initially hindered performance, but both groups showed similar practice-related improvements and retention.

Conclusions:

• Practicing speed-accuracy tasks learned on levodopa in an off state may lead to performance degradation.
• Levodopa may impede performance, but not necessarily the learning, of certain motor tasks in PD patients.