人们常常用“半睡半醒”形容犯困时做事准确度下降的情况。而一项最新研究显示，实验鼠的大脑的确可以出现这种状态，当大脑总体上还处于清醒状态时，某些局部区域脑电波的测量结果却表现出睡眠的特征。

新一期英国《自然》杂志刊登研究报告说，美国威斯康星大学麦迪逊分校等机构研究人员让一些实验鼠较长时期处于清醒状态，直到可能开始犯困的时候。这时虽然可以明显看到它们仍在活动，其脑电波在总体上也表现出清醒的特征，但用探针在其大脑中某些局部区域测量到的脑电波特征却显示其已睡着了。

研究人员托诺尼说，多次实验显示，这些睡眠区域出现的位置是随机的。他比喻说，这就像烧开水一样，在水快要沸腾的时候，就会有气泡随机地从各处冒出来，在实验鼠仍总体清醒但已犯困的时候，其大脑中一些区域开始随机地局部入睡。

这些局部入睡的大脑区域可能与活动能力有关，这较好地解释了在“半睡半醒”状态下做事准确度下降的情况。本次研究也显示，那些半睡半醒中的实验鼠，用爪子获取食物的准确度明显下降。

一些专家认为，这项研究结果提醒人们应该重新思考什么是睡眠，睡着和清醒可能不像通常认为的那样是两个截然分开的状态。既然醒着的时候可能有部分大脑区域入睡，那么睡着的时候也可能会有一些大脑区域处于清醒状态，对此深入研究或有助于解释梦游等现象。

原文出处：

Nature DOI： doi:10.1038/nature10009

Local sleep in awake rats

Vladyslav V. Vyazovskiy; Umberto Olcese; Erin C. Hanlon; Yuval Nir; Chiara Cirelli; Giulio Tononi

In an awake state, neurons in the cerebral cortex fire irregularly and electroencephalogram (EEG) recordings display low-amplitude, high-frequency fluctuations. During sleep, neurons oscillate between ‘on’ periods, when they fire as in an awake brain, and ‘off’ periods, when they stop firing altogether and the EEG displays high-amplitude slow waves. However, what happens to neuronal firing after a long period of being awake is not known. Here we show that in freely behaving rats after a long period in an awake state, cortical neurons can go briefly ‘offline’ as in sleep, accompanied by slow waves in the local EEG. Neurons often go offline in one cortical area but not in another, and during these periods of ‘local sleep’, the incidence of which increases with the duration of the awake state, rats are active and display an ‘awake’ EEG. However, they are progressively impaired in a sugar pellet reaching task. Thus, although both the EEG and behaviour indicate wakefulness, local populations of neurons in the cortex may be falling asleep, with negative consequences for performance.