Contribution of night and day sleep vs. simple passage of time to the consolidation of motor sequence and visuomotor adaptation learning

Abstract

There is increasing evidence supporting the notion that the contribution of sleep to consolidation of motor skills depends on the nature of the task used in practice. We compared the role of three post-training conditions in the expression of delayed gains on two different motor skill learning tasks: finger tapping sequence learning (FTSL) and visuomotor adaptation (VMA). Subjects in the DaySleep and ImmDaySleep conditions were trained in the morning and at noon, respectively, afforded a 90-min nap early in the afternoon and were re-tested 12 h post-training. In the NightSleep condition, subjects were trained in the evening on either of the two learning paradigms and re-tested 12 h later following sleep, while subjects in the NoSleep condition underwent their training session in the morning and were re-tested 12 h later without any intervening sleep. The results of the FTSL task revealed that post-training sleep (day-time nap or night-time sleep) significantly promoted the expression of delayed gains at 12 h post-training, especially if sleep was afforded immediately after training. In the VMA task, however, there were no significant differences in the gains expressed at 12 h post-training in the three conditions. These findings suggest that "off-line" performance gains reflecting consolidation processes in the FTSL task benefit from sleep, even a short nap, while the simple passage of time is as effective as time in sleep for consolidation of VMA to occur. They also imply that procedural memory consolidation processes differ depending on the nature of task demands.

Fig. 1

Motor skill learning paradigms and protocols. (a) Finger tapping sequence learning task (FTSL) (b) Visuomotor adaptation learning task (VMA) (c) Experimental design. Subjects in the NightSleep condition were trained in the evening on either the FTSL or the VMA task, and re-tested 12 h post-training (12 h PT) after a night of sleep. In the NoSleep condition, subjects were trained on either the FTSL or the VMA task in the morning and re-tested at 12 h PT. In the DaySleep condition, subjects were trained on either the FTSL or the VMA task in the morning. At noon, subjects afforded a 90-min nap and were re-tested at 12 h PT. In the ImmDaySleep condition, subjects were trained on the FTSL task at noon and afforded a 90-min nap immediately after the training period. They were then re-tested at 8 h PT

Fig. 2

FTSL task performance changes (mean group speed and accuracy) during the first 12 or 8 h after a single training session. NoSleep group (a) participants stayed awake after training at 09:00 AM, performance of the trained sequence was re-tested at 09:00 PM; no napping was afforded. NightSleep group (b) after training at 09:00 PM subjects had a normal night sleep, performance of the trained sequence was re-tested at 09:00 AM. DaySleep group (c) after training at 09:00 AM, subjects were allowed a 90 min day-time afternoon nap and the performance of the trained sequence was re-tested at 09:00 PM. ImmDaySleep group (d) after training at 12:00 PM subjects had 90 min day-time afternoon sleep. Performance of the trained sequence was re-tested at 09:00 PM. Baseline (Pre–test), immediate post-training (0 h PT), 8 or 12 h (8 or 12 h PT) scores for speed (upper panels) and accuracy (lower panels) are shown. Bars S.E.M, *p < 0.05. A slope of the regression line fitted to the accuracy data points

Fig. 3

Individual normalized gains in performance speed for the FTSL task. The difference in each participant's average performance 8 or 12 h post-training from his/her own average 0 h PT performance speed, normalized to the 0 h PT performance. Black squares individual normalized gains, white circles means of normalized gains. Data for participants in the four groups, NoSleep, NightSleep, DaySleep and ImmDaySleep is shown

Fig. 4

VMA task performance changes (white triangles mean group accuracy, black rhombs mean group speed) during the first 12 h after a single training session. Each data point refers to the group mean performance in successive blocks, each block representing mean performance on 64 trials. The delayed improvements are not apparent from the graphs because the scale of the overall improvement in performance starting from the baseline is relatively large, thus, the minor delayed post-training improvements of 3–4% are hardly distinguishable. NoSleep group (a) after training at 09:00 AM, performance of the trained sequence was re-tested at 09:00 PM; no napping was afforded. NightSleep group (b) after training at 09:00 PM subjects had a normal night sleep, performance of the trained sequence was re-tested at 09:00 AM. DaySleep group (c) after training at 09:00 AM, subjects were allowed a 90 min day-time afternoon nap and the performance of the trained sequence was re-tested at 09:00 PM. Bars SEM

Fig. 5

Individual normalized gains in performance speed and accuracy for the VMA task. The difference in each participant's average performance at 0 and 12 post-training from his/her own average 0 h PT performance, normalized to the 0 h PT performance. Circles means of normalized gains, squares individual normalized gains. Data for participants in the three groups, NoSleep, NightSleep and DaySleep is shown