Motor sequence learning increases sleep spindles and fast frequencies in post-training sleep

Study Objectives: To investigate polysomnographic (PSG) sleep and NREM sleep characteristics, including sleep spindles and spectral activity involved in offline consolidation of a motor sequence learning task. Design: Counterbalanced within-subject design. Setting: Three weekly visits to the sleep laboratory. Participants: Fourteen healthy participants aged between 20 and 30 years (8 women). Interventions: Motor sequence learning (MSL) task or motor control (CTRL) task before sleep. Measurements and Results: Subjects were trained on either the MSL or CTRL task in the evening and retested 12 hours later the following morning on the same task after a night of PSG sleep recording. Total number and duration of sleep spindles and spectral power between 0.5 and 24 Hz were quantified during NREM sleep. After performing the MSL task, subjects exhibited a large increase in number and duration of sleep spindles compared to after the CTRL task. Higher sigma (σ; 13 Hz) and beta (β; 18-20 Hz) spectral power during the post-training night's sleep were also observed after the MSL task. Conclusions: These results provide evidence that sleep spindles are involved in the offline consolidation of a new sequence of finger movements known to be sleep dependent. Moreover, they expand on prior findings by showing that changes in NREM sleep following motor learning are specific to consolidation (and learning), and not to nonspecific motor activity. Finally, these data demonstrate, for the first time, higher fast rhythms (β frequencies) during sleep after motor learning.