The effect of a post-learning nap on motor memory consolidation in people with Parkinson’s disease: a randomised controlled trial
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Study Objectives
Motor memory consolidation is a process by which newly acquired skills become stable over time in the absence of practice. Sleep facilitates consolidation, yet it remains unknown whether sleep-dependent consolidation is intact in people with Parkinson’s disease (PD). Here, we investigated whether a post-learning nap - as compared to wakefulness - improves motor memory consolidation in PD.
Methods
Thirty-two people with PD and 32 healthy older adults (HOA) learnt a finger-tapping sequence task before being randomised to a nap or wake intervention. Consolidation was measured as the change in performance between pre- and post-intervention and at 24-hour retention. Automaticity was measured with dual-task cost, assessed at post-intervention and at post-night. Sleep architecture and electrophysiological markers of plasticity were extracted from the post-learning nap to assess their correlation with performance changes.
Results
The behavioural results provided weak evidence for similar consolidation effects after sleep and wakefulness in both PD and HOA, and showed no intervention effects. Napping also did not affect dual-task costs in PD or HOA. Results suggested positive correlations between performance improvements and slow wave amplitude and slope in PD, and opposite associations between cross-frequency coupling and performance change in PD and HOA.
Conclusions
Findings suggest that napping did not have a beneficial effect on the consolidation of a finger-tapping task over wakefulness in either PD or HOA groups. In PD, sleep markers of plasticity were associated with performance improvements, implying that equivalent memory consolidation between HOA and PD may be differently related to sleep-related processes.
Statement of significance
This is the first study to directly compare the effect of post-learning napping with wakefulness on motor memory consolidation in people with Parkinson’s disease (PD), and to show no beneficial effect of sleep as compared to wakefulness. Further, motor memory consolidation may be unaffected in early-to-mid stage PD as compared to healthy older adults (HOA). In PD, electrophysiological markers of plasticity during sleep were positively related to motor performance improvement, indicating that HOA and PD may achieve equivalent performance outcomes through different consolidation mechanisms.
