The effect of a daytime 2-hour nap on complex motor skill learning

The present study examined whether three-ball cascade juggling was improved by sleep. To elucidate sleep functions related to motor memory consolidation, sleep EEG spectral analysis was performed for each recorded sleep stage. Sixteen female college students practiced juggling in the morning, and were tested immediately afterward. Eight of the subjects took a 2-hour nap after practice juggling (nap group), while another 8 stayed awake (control group). Juggling performance was then re-tested in the evening. Juggling performance improved after the 2-hour nap, while subjects in the control group did not show improvement. Slow oscillation, delta wave, and sigma wave EEG spectral power all increased significantly during non-REM sleep, especially during slow-wave sleep, after the post-motor learning nap (mNap) compared to an earlier baseline nap that preceded learning the task. Such EEG alterations have been suggested to relate to explicit declarative (hippocampus-dependent) memory consolidation; however, motor learning is considered to rely upon implicit procedural memory. We found that while sleep facilitated the consolidation of motor memory similar to that following real sport activities, the alterations in sleep EEG suggest that the initial motor learning of complex, highly coordinated 3-ball cascade juggling may involve substantial use of explicit memory.