我们知道，大脑从来没有停止过工作，即使在深度睡眠的时候，我们的大脑仍然在活动。问题是，大脑在做什么，有没有不做什么的时候？一个新研究揭示，当你意识模糊的时候，大脑就自动停止了同自己的交流。此时，“大脑分裂成了不能互相交流的独立的小岛。”这个过程允许大脑皮质回路消除干扰性神经键，并且让大脑皮质回路重归正常，为接下来的一天做准备。这种皮质活动性的降低，也许还可以解释为什么在睡眠之后执行各种任务效率都会有所提高。-你的大脑从来没有停止过工作。但是一个新的研究揭示，当你意识模糊的时候，大脑就自动停止了同自己的交流。
长久以来，科学家们只知道在深度睡眠时人的大脑仍然在活动。但是大脑在做什么？没做什么？在意识清楚时与不清楚时，两者的差异是什么呢？这是科学家们一直想知道的。
当我们是清醒的时候，大脑的各个部分通过神经元及化学介质在整个大脑网络中不断的进行通信。就像由客户机、路由器与服务器组成的Internet，各个不同的计算机在不断的进行数据交流。
然而在深度睡眠的时候，大脑的不同节点之间就都失去了联系。
“大脑分裂成了不能互相交流的独立的小岛。”威斯康星麦迪逊大学的研究小组组长Giulio Tononi说。
Tononi的团队采用了一种非侵入性方式对大脑各个被选定的部位进行刺激，通过对被试大脑上安装电极进行监测，以确定每个刺激所触发的大脑其它部位的反应。
在清晨，当被试在做梦的时候，在他们大脑所监测到的信号与他们清醒时很相似。但是在深夜，当被试处于深度睡眠的时候，监测结果就大大的不同了。
“在晚上深度睡眠的早期，反应是短期的并且根本不会传播。”Tononi说
科学家们长期都被意识问题所迷惑，这个新的发现表明了意识是依靠大脑对信息的整合能力，Tononi说。
Tononi的同事Marcello Massimini表示，大脑在这个阶段的区域化状态，能使平时帮助连接形成思考的神经突触们得到休息。
Massimini对科学在线说：“这个过程允许大脑皮质回路消除干扰性神经键，并且让大脑皮质回路重归正常，为接下来的一天做准备。”皮质活动性的降低也许还可以解释为什么在睡眠之后执行各种任务效率都会有所提高。
用于管理实验的机器是全新的，它产生一个磁场来提供刺激。Tononi的团队希望这是同类研究中第一个能够帮助研究者们更好的了解大脑的意识以及特殊病变的研究。
本研究的详细内容将发表于9月30日的《科学》杂志。
附原文：
Your brain never stops working. But it does cease talking to itself when you lose consciousness, a new study shows.
Scientists have long wondered what the brain does and doesn’t do during deep sleep. It remains active, they know. So what’s the difference between consciousness and the lack of it?
When we’re awake, different parts of the brain use chemicals and nerve cells to communicate constantly across the entire network, similar to the perpetual flow of data between all the different computers, routers and servers that make up the Internet.
In the deepest part of sleep, however, the various nodes of your cranial Internet all lose their connections.
“The brain breaks down into little islands that can’t talk to one another,” said study leader Giulio Tononi of the University of Wisconsin-Madison.
Tononi’s team used a non-invasive procedure to activate select parts of the brain. Subjects had electrodes attached to their heads to monitor how each stimulation triggered reactions elsewhere.
In the early morning, when subjects were dreaming, signals careened around the noggin similarly to when they were awake. But at night, during deeper sleep, the picture was much different.
“During deep sleep early in the night,” Tononi said, “the response is short-lived and doesn’t propagate at all.”
Consciousness has long mystified scientists. The new finding suggests that it depends on the brain’s ability to integrate information, Tononi says.
The compartmentalization might also help the brain’s synapses, which make all the connections that give us thought, to take a break, according to Tononi’s colleague, Marcello Massimini.
“This process would allow cortical circuits to eliminate noisy synapses and renormalize in order to be ready for the next day,” Massimini told LiveScience. The reduced activity might also help explain why performance in various tasks improves after sleep, he said.
The machine used to conduct the experiments is new. It generates a magnetic field to provide stimulation, and Tononi’s team expects this to be the first of many similar studies that will help researchers better understand the mind and specific disorders of the brain.
The study is detailed in the Sept. 30 issue of the journal Science.
By Robert Roy Britt
译者：罗禹(Roger)
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