The Effect of a Post‐Learning Nap on Motor Memory Consolidation in People With Parkinson's Disease: A Randomised Controlled Trial

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. Here, we investigated whether a post-learning nap-as compared to wakefulness-improves motor memory consolidation in Parkinson. Thirty-two people with Parkinson's disease and 32 healthy older adults learnt a finger-tapping sequence task before a nap or wake intervention (pseudo-randomised assignment). Consolidation was measured as the change in performance between pre- and post-intervention and at 24-h 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 association with performance change. The behavioural results suggest similar consolidation effects after sleep and wakefulness in both populations. Moreover, there was no effect of napping automaticity. Results also suggest positive associations between performance improvement and slow wave amplitude and slope in people with Parkinson's disease, and inconclusive associations between cross-frequency coupling and performance change in both populations. To conclude, napping did not have a beneficial effect on the consolidation of a finger-tapping task as compared to wakefulness in either people with Parkinson's disease or healthy older adults. Finally, in patients, sleep markers of plasticity were associated with performance improvements, implying that equivalent memory consolidation may be differently associated to sleep-related processes in Parkinson's and healthy ageing. Trial Registration: NCT04144283.