Li Ziyang, Sheth Aarohi B, Sheth Bhavin R
University of Houston, Houston, TX, United States of America.
Carnegie Vanguard High School, Houston, TX, United States of America.
PLoS One. 2017 Oct 13;12(10):e0185681. doi: 10.1371/journal.pone.0185681. eCollection 2017.
What is the function of sleep in humans? One claim is that sleep consolidates learning. Slow wave activity (SWA), i.e. slow oscillations of frequency < 4 Hz, has been observed in electroencephalograms (EEG) during sleep; it increases with prior wakefulness and decreases with sleep. Studies have claimed that increase in SWA in specific regions of the sleeping brain is correlated with overnight improved performance, i.e. overnight consolidation, on a demanding motor learning task. We wondered if SWA change during sleep is attributable to overnight consolidation or to metabolic demand. Participants executed out-and-back movements to a target using a pen-like cursor with their dominant hand while the target and cursor position were displayed on a screen. They trained on three different conditions on separate nights, differing in the amount and degree of rotation between the actual hand movement direction and displayed cursor movement direction. In the no-rotation (NR) condition, there was no rotation. In the single rotation (SR) condition, the amount of rotation remained the same throughout, and performance improved both across pre-sleep training and after sleep, i.e. overnight consolidation occurred; in the random rotation (RR) condition, the amount of rotation varied randomly from trial to trial, and no overnight consolidation occurred; SR and RR were cognitively demanding. The average EEG power density of SWA for the first 30 min. of non-rapid eye movement sleep after training was computed. Both SR and RR elicited increase in SWA in the parietal region; furthermore, the topographic distribution of SWA in each was remarkably similar. No correlation was found between the overnight performance improvement on SR and the SWA change in the parietal region on measures of learning. Our results argue that regulation of SWA in early sleep is associated with high levels of cognitive effort during prior wakefulness, and not just overnight consolidation.
睡眠在人类中起到什么作用？一种观点认为睡眠能巩固学习效果。慢波活动（SWA），即频率<4赫兹的缓慢振荡，在睡眠期间的脑电图（EEG）中被观察到；它随着先前的清醒时间增加而增加，随着睡眠而减少。研究表明，睡眠大脑特定区域中SWA的增加与在一项要求较高的运动学习任务上夜间表现的改善相关，即夜间巩固。我们想知道睡眠期间SWA的变化是归因于夜间巩固还是代谢需求。参与者用优势手使用类似笔的光标向目标进行往返运动，同时目标和光标位置显示在屏幕上。他们在不同的夜晚在三种不同条件下进行训练，实际手部运动方向和显示的光标运动方向之间的旋转量和程度不同。在无旋转（NR）条件下，没有旋转。在单旋转（SR）条件下，旋转量始终相同，并且在睡前训练和睡眠后表现都有所改善，即发生了夜间巩固；在随机旋转（RR）条件下，每次试验的旋转量随机变化，没有发生夜间巩固；SR和RR都需要较高的认知能力。计算了训练后非快速眼动睡眠的前30分钟内SWA的平均脑电图功率密度。SR和RR都引起顶叶区域SWA的增加；此外，两者中SWA的地形分布非常相似。在SR上的夜间表现改善与学习测量中顶叶区域的SWA变化之间未发现相关性。我们的结果表明，早期睡眠中SWA的调节与先前清醒期间的高认知努力水平相关，而不仅仅是夜间巩固。
