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) learned a finger-tapping sequence task before being randomized to a nap or wake intervention. Consolidation was measured as the change in performance between pre- and post-intervention and at 24-hours retention. Automaticity was measured with a dual-task assessed post-intervention and at retention. Sleep architecture and electrophysiological markers of plasticity were extracted from the experimental nap to assess their association with performance changes.
Results
Behavioural results provided weak evidence for equivalent benefit of sleep-dependent consolidation over wakefulness in both PD and HOA, and no difference of intervention effects between groups. Napping did not affect dual-task costs in PD or HOA. Results suggested positive associations between performance improvements and slow wave density, amplitude, slope, and spindle amplitude in PD and not in HOA.
Conclusions
A post-learning nap had similar effects in PD and HOA, yet the evidence remains inconclusive. Further, napping did not have a beneficial effect over wake in either group. In PD, sleep markers of plasticity were associated to performance improvements, suggesting that equivalent performance output between HOA and PD may be achieved using different consolidation mechanisms.
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), showing no beneficial effect of sleep as compared to wakefulness. Further, motor memory consolidation may be unaffected in PD as compared to heathy older adults. In PD, electrophysiological markers of plasticity during sleep were positively associated to motor performance improvement, indicating that HOA and PD may achieve equivalent performance outcomes through different consolidation mechanisms.
