Enhancement of learning: Does sleep benefit motor skill memory consolidation?

Abstract

Purpose: It remains unclear how the brain best recovers from neurologic injury and how to optimally focus rehabilitation approaches to maximize this recovery. Recent research has indicated that sleep may augment this recovery. Sleep has been shown to benefit memory consolidation for certain motor skills, but it remains unclear if this relationship exists for explicit, continuous, goal-directed motor skills with rehabilitation applications. We aimed to determine the neurobehavioral relationship between finger-tracking skill development and sleep following skill training in young, healthy subjects. Methods: Forty subjects were recruited to receive motor skill training in the morning (n=20) or the evening (n=20). Measures of skill and cortical excitability were collected before and after training. Following training, each group had a post-training interval consisting of waking activity or an interval containing sleep. After this twelve-hour interval, skill performance and cortical excitability were reassessed. Subjects underwent another twelve-hour interval containing either waking activity or a sleep episode and came back for a second assessment, twenty-four hours after training. A subset of subjects (n=10) underwent the same procedures except the training period involved simple, repeated movement of the finger. Results: Skill performance improved after training and then continued to improve offline during the first post-training interval. Improvement was not enhanced by sleep during this interval. Cortical excitability was not substantially altered by training but was related to level of skill performance at follow-up assessment. Sleep quality was also found to be related to level of skill at follow-up assessments. The skilled training period did not lead to significantly improved performance compared to simple movement activity. Discussion: These data suggest that sleep is not required for offline memory enhancement for a continuous, visuospatial finger-tracking skill. These findings are in agreement with recent literature indicating the type of motor skill trained may determine the beneficial effect of sleep on post-training information processing. These results, combined with related studies in patient populations, provide a foundation to evaluate the relationship between sleep, changes in neural activity, and the time course of continuous visuospatial motor skill learning in individuals following neurologic insult.