Cell子刊:“住宾馆睡不着”,或是“首夜效应”作祟
生物通 · 2016/05/01
很多人都有这样的感觉,当自己换了一个环境之后睡觉,无论怎样翻来覆去,就是睡不着,仿佛和床有了“代沟”,这种现象被人们称为“认床”。一直以来科学家们都是从心理学的角度来分析这一问题,那么其分子机制是什么呢?


很多人都有这样的感觉,当自己换了一个环境之后睡觉,无论怎样翻来覆去,就是睡不着,仿佛和床有了“代沟”,这种现象被人们称为“认床”。一直以来科学家们都是从心理学的角度来分析这一问题,那么其分子机制是什么呢?

来自布朗大学的一组研究人员最新报道的研究成果有助于解释这种“第一晚效应”,他们发现大脑中的一半脑半球会比其它时候更为活跃。这一研究成果公布在4月21日的Current Biology杂志上。

“这是一个有趣的发现,”哈佛医学院,麻省总医院的神经放射学家Steven Stufflebeam(未参与该项研究)说,“他们发现……脑半球在第一夜睡眠中会保持更加警惕的状态”。

所谓“第一晚效应”是指人们在一个新的地方第一晚入睡时,需要较长时间入睡,睡眠质量也会差,也有人将其称为认床。从人类开始睡在巢穴便出现这种现象,海洋哺乳动物和一些鸟类中也会出现这种情况。

“很早以前科学家们就发现第一晚效应,但我们不知道大脑中到底发生了什么?”文章作者之一Masako Tamaki说。

为了找到答案,Tamaki等人使用先进的神经影像技术对睡眠中的大脑采取快照,并收集志愿者处于新环境第一晚时的大脑活动。对这些志愿者采取的测量手段主要包括MRI和多导睡眠描记术。

研究人员集中关注的是慢波睡眠状态,而不是快速眼动 (REM) 睡眠。他们发现当志愿者者处于新环境的第一晚时,他们左侧大脑熟睡程度明显低于右侧,两侧大脑相同部位并未睡眠,显示不同程度的清醒状态。

检测“第一晚效应FNE”的方式之一是计算在新环境入睡所需的时间,这与两侧大脑半球的不对称程度有关,换句话说,志愿者两侧大脑半球不对称程度越大,他们入睡所需要的时间越长。

之后进行的研究也显示,在处于睡眠时期时,其左侧大脑半球对外部噪音更加敏感,不仅会刺激机体产生噪声应答反应,同时也使参与者易醒。当处于新环境第二晚时,左侧大脑半球对噪声的敏感性消失。由于FNE的存在,大家大多睡不好且第二天没精力,这对机体有什么好处呢?事实证明,不单单人类存在FNE。其他动物海洋哺乳动物和鸟类等都会在睡眠时保持大脑一侧半球的清醒,使它们时刻保持警惕,应对和规避风险。

下一步研究人员将会尝试了解第一晚效应与学习的关联。

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  • Night Watch in One Brain Hemisphere during Sleep Associated with the First-Night Effect in Humans

    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.

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