Sleep Enhances Off-line Spatial and Temporal Motor Learning After Stroke

BACKGROUND: Individuals with chronic stroke demonstrate sleep-dependent off-line motor learning of a continuous tracking task. However, it remains unclear which aspects of learned movements are preferentially enhanced by sleep (ie, spatial accuracy and/or the time lag of tracking). OBJECTIVE: . The purpose of this study was to investigate whether spatial tracking accuracy, temporal tracking accuracy, or both are enhanced by sleep during off-line motor learning after stroke. METHODS: . Individuals with chronic stroke and control participants either practiced a continuous tracking task in the evening and underwent retention testing the following morning (sleep groups) or practiced the task in the morning and underwent retention testing in the evening (no-sleep groups). RESULTS: . Individuals with stroke who slept between practice and retention testing demonstrated off-line improvements in both spatial and temporal elements of tracking at retention. Participants with a stroke who stayed awake between practice and retention testing did not demonstrate off-line improvements in either spatial tracking accuracy or the time lag of tracking. Control participants did not demonstrate sleep- or time-dependent enhancement of either component of the movement task. Time of day of testing was not a factor in practice related changes in motor performance. CONCLUSION: This study provides the first evidence that sleep enhances motor learning through both improved spatial tracking accuracy and anticipation of upcoming movements, as demonstrated by a reduction in the time lag of tracking in individuals following stroke. We propose that the cerebellum and hippocampus are likely important neural correlates associated with sleep-dependent off-line motor skill learning.