Brief periods of NREM sleep do not promote early offline gains but subsequent on-task performance in motor skill learning

- Sleep modulates motor learning.
- Brief periods of NREM sleep do not promote early offline gains in motor learning.
- Brief periods of NREM sleep improve subsequent on-task performance in motor learning.
- Our findings inform the optimization of sleep-wake schedules for motor performance.
- Future work is needed to clarify sleep's impact on training-induced performance gains.
- Future work is needed to specify sleep's impact on detrimental on-task processes.

Sleep modulates motor learning, but its detailed impact on performance curves remains to be fully characterized. This study aimed to further determine the impact of brief daytime periods of NREM sleep on 'offline' (task discontinuation after initial training) and 'on-task' (performance within the test session) changes in motor skill performance (finger tapping task). In a mixed design (combined parallel group and repeated measures) sleep laboratory study (n = 17 'active' wake vs. sleep, n = 19 'passive' wake vs. sleep), performance curves were assessed prior to and after a 90 min period containing either sleep, active or passive wakefulness. We observed a highly significant, but state- (that is, sleep/wake)-independent early offline gain and improved on-task performance after sleep in comparison to wakefulness. Exploratory curve fitting suggested that the observed sleep effect most likely emerged from an interaction of training-induced improvement and detrimental 'time-on-task' processes, such as fatigue. Our results indicate that brief periods of NREM sleep do not promote early offline gains but subsequent on-task performance in motor skill learning.