便秘会导致肠胃炎:解开呵欠的面纱：大脑冷却剂

如果你的头脑过热，那么很有可能很快就打个呵欠。根据一项新的研究表明，打呵欠的主要原因就是控制大脑温度。

The finding solves several mysteries about yawning, such as why it's most commonly done just before and after sleeping, why certain diseases lead to excessive yawning, and why breathing through the nose and cooling off the forehead often stop yawning.

这项结论解决的许多关于呵欠的谜题，比如说为什么大多数呵欠都发生在睡前或刚睡醒时，为什么某些疾病会引起过多的呵欠，以及为何通过鼻孔呼吸和冷却前额通常会制止呵欠的产生。

The key yawn instigator appears to be brain temperature.

打呵欠最关键的诱因就是大脑的温度。

"Brains are like computers," Andrew Gallup, a researcher in the Department of Biology at Binghamton University who led the study, told Discovery News. "They operate most efficiently when cool, and physical adaptations have evolved to allow maximum cooling of the brain." 

“大脑工作起来就像是台计算机，”一名宾厄姆敦大学生理学系的研究员，同时也领导着这项研究的安德鲁·盖洛普告诉Discovery News，“它们在冷却的状态下运行才能发挥最大的效率，而机体适应机制也发展为最大限度的使大脑冷却。”

He and colleagues Michael Miller and Anne Clark analyzed yawning in parakeets as representative vertebrates because the birds have relatively large brains, live wild in Australia, which is subject to frequent temperature swings, and, most importantly, do not engage in contagious yawning, as humans and some other animals do.

他和同事迈克尔·米勒，安妮·克拉克将长尾小鹦鹉作为分析呵欠的脊椎动物的代表，因为这种鸟儿拥有相对而言较大的大脑，并野生在温度频繁变化的澳大利亚，最重要的一点是，它们不会像人和其他动物那样出现呵欠传染啊

Contagious yawning is thought to be an evolved mechanism for keeping groups alert so they "remain vigilant against danger," Gallup said.

呵欠传染被认为是进化出来用于保持群体的警惕性使群体“在危险面前保持警觉，”盖洛普说。

For the study, the scientists exposed parakeets to three different conditions: increasing temperature, high temperature and a moderate control temperature. While the frequency of yawns did not increase during the latter two conditions, it more than doubled when the researchers increased the bird's ambient temperature.

为了完成试验，科学家们将长尾小鹦鹉暴露在三种不同的状况下：温度上升，持续高温和适当控制的温度。但鸟儿们的呵欠在后两种情况下并没有增多，而当提升鸟儿周围的温度时，它们的呵欠增加了两倍多。

A paper on the findings has been accepted for publication in the journal Animal Behavior.

关于这项结论的论文已经被《动物行为》杂志接受出版。

"Based on the brain cooling hypothesis, we suggest that there should be a thermal window in which yawning should occur," Gallup said. "For instance, yawning should not occur when ambient temperatures exceed body temperature, as taking a deep inhalation of warm air would be counterproductive. In addition, yawning when it is extremely cold may be maladaptive, as this may send unusually cold air to the brain, which may produce a thermal shock."

“根据大脑冷却假设，我们认为存在一个气窗促使呵欠产生，”盖洛普说。“举个例子，呵欠在环境温度超过体温时不大可能发生，因为这时候深吸一口热空气只能帮倒忙。另外，在极度寒冷的时候打呵欠也许不大合适，因为这时通常会将冷空气送到大脑，从而使大脑发生热冲击。”

The parakeets yawned as predicted. 

长尾小鹦鹉们的呵欠和预测的一致。

It's now believed yawning operates like a radiator for birds and mammals.

现在他们明白了呵欠对于鸟类和哺乳类来说起到了散热器的作用。

If air in the atmosphere is cooler than brain and body temperatures, taking it in quickly cools facial blood that, in turn, cools the brain and may even alter blood flow. Prior studies reveal yawning leads to a heightened state of arousal, so a morning yawn may function somewhat like a cup of coffee in providing a jolt of energy.

如果环境空气的温度比大脑和身体的温度低，把它快速吸入可以冷却面部血液，当然，也为大脑甚至血液循环降了温。先前的实验揭示呵欠可以产生一种加强的激励状态，所以早晨的一个呵欠也许就像一杯醒脑的咖啡那样提供少许的能量。

The new findings also explain why tired individuals often yawn, since both exhaustion and sleep deprivation have been shown to increase deep brain temperatures, again prompting a yawn-driven cool down. Yawning additionally appears to facilitate transitional states of the brain, such as going from sleep to waking periods.

这个新发现也解释了为什么疲惫的人经常打呵欠，因为疲劳和睡眠匮乏的出现提升了大脑深度的温度，所以呵欠降温再次发挥作用。呵欠还起到了使大脑状态过度顺畅的作用，比如从睡眠状态到清醒状态切换时。

Gordon Gallup, Jr., a State University of New York at Albany psychologist, did not work on the study, but, as Andrew Gallup's father, paid close attention to the research. The senior Gallup also happens to be a leading expert on the science of yawning and other widespread evolved traits.

小戈登·盖洛普是一名来自位于奥尔巴尼的纽约州立大学的心理学家，他并没有参与这次研究，但作为安德鲁·盖洛普的父亲，他对这项实验进行了紧密的关注。巧合的是，老盖洛普也是一名主持对呵欠和其他引发广泛关注的特质进行研究的专家。

"It is interesting to note that instances of excessive yawning in humans may be indicative of brain cooling problems," Gallup, Jr., told Discovery News, pointing out that patients with multiple sclerosis often experience bouts of excessive yawning "and MS involves thermoregulatory dysfunction."

“人们过多的呵欠也许表明大脑制冷的问题，这个观点很有意思，”老盖洛普告诉Discovery News，同时指出罹患多发性硬化症的病人经常出现过多呵欠的症状，“而多发性硬化症和体温调节功能障碍有关。”

"Bouts of excessive yawning often precede the onset of seizures in epileptic patients, and predict the onset of headaches in people who suffer from migraines," he added.

“过多呵欠的症状经常是癫痫病人病情发作的先兆，而且可以预测头痛病人偏头痛的发作，”他补充道。

In the future, researchers may focus more on brain temperature and its role in diseases and their symptoms. But the new study on yawning changes the popular notion that yawns are mere signs of boredom.

在将来，研究人员也许会关注大脑温度和它在疾病预知方面所扮演的角色。但是这项新的关于呵欠的研究改变了大众对呵欠的看法——只不过是无聊的表现。

On the contrary, as Gallup said, "yawning more accurately reflects a mechanism that maintains attention, and therefore should be looked at as a compliment!"

与此相反的是，如同盖洛普所言，“打呵欠更准确的说是反映出维持注意力的机制，那样的话对人打呵欠应该看作对他的赞美才对！”