Tamaki Masako, Bang Ji Won, Watanabe Takeo, Sasaki Yuka
Department of Cognitive, Linguistic, and Psychological Sciences, Brown University, 190 Thayer Street, Box 1821, Providence, RI 02912, USA.
Department of Cognitive, Linguistic, and Psychological Sciences, Brown University, 190 Thayer Street, Box 1821, Providence, RI 02912, USA.
Curr Biol. 2016 May 9;26(9):1190-4. doi: 10.1016/j.cub.2016.02.063. Epub 2016 Apr 21.
We often experience troubled sleep in a novel environment [1]. This is called the first-night effect (FNE) in human sleep research and has been regarded as a typical sleep disturbance [2-4]. Here, we show that the FNE is a manifestation of one hemisphere being more vigilant than the other as a night watch to monitor unfamiliar surroundings during sleep [5, 6]. Using advanced neuroimaging techniques [7, 8] as well as polysomnography, we found that the temporary sleep disturbance in the first sleep experimental session involves regional interhemispheric asymmetry of sleep depth [9]. The interhemispheric asymmetry of sleep depth associated with the FNE was found in the default-mode network (DMN) involved with spontaneous internal thoughts during wakeful rest [10, 11]. The degree of asymmetry was significantly correlated with the sleep-onset latency, which reflects the degree of difficulty of falling asleep and is a critical measure for the FNE. Furthermore, the hemisphere with reduced sleep depth showed enhanced evoked brain response to deviant external stimuli. Deviant external stimuli detected by the less-sleeping hemisphere caused more arousals and faster behavioral responses than those detected by the other hemisphere. None of these asymmetries were evident during subsequent sleep sessions. These lines of evidence are in accord with the hypothesis that troubled sleep in an unfamiliar environment is an act for survival over an unfamiliar and potentially dangerous environment by keeping one hemisphere partially more vigilant than the other hemisphere as a night watch, which wakes the sleeper up when unfamiliar external signals are detected.
我们在新环境中常常会经历睡眠困扰[1]。在人类睡眠研究中，这被称为首夜效应（FNE），并被视为一种典型的睡眠障碍[2 - 4]。在此，我们表明，首夜效应是一个半球比另一个半球在睡眠期间更警觉，像夜间值班一样监测不熟悉环境的一种表现[5, 6]。使用先进的神经成像技术[7, 8]以及多导睡眠图，我们发现第一次睡眠实验阶段的短暂睡眠障碍涉及睡眠深度的区域间半球不对称[9]。与首夜效应相关的睡眠深度半球不对称在清醒休息时参与自发内心想法的默认模式网络（DMN）中被发现[10, 11]。不对称程度与入睡潜伏期显著相关，入睡潜伏期反映入睡难度，是首夜效应的一项关键指标。此外，睡眠深度降低的半球对异常外部刺激的诱发脑反应增强。睡眠较少的半球检测到的异常外部刺激比另一个半球检测到的引发更多觉醒和更快的行为反应。在随后的睡眠阶段，这些不对称均不明显。这些证据支持了这样一种假设，即在不熟悉的环境中睡眠困扰是一种通过让一个半球比另一个半球在夜间值班时保持部分更警觉来在不熟悉且潜在危险的环境中生存的行为，当检测到不熟悉的外部信号时会唤醒睡眠者。
