感动的表情图:人为什么会打哈欠?

打哈欠可以让人避免头脑发热

Yawning may activate a sinus "pump" that ventilates our brains. . 

打哈欠会牵动鼻窦，把空气“泵”向脑部……

Chinese paramilitary police officers in Beijing.

图：北京的中国预备役士兵

Photograph by Andy Wong, AP

摄影：美联社 Andy Wong

Christine Dell'Amore

作者：克里斯汀? 德拉摩尔

National Geographic News

国家地理新闻部

Published November 15, 2011

2011年11月15日发表

Yawning may help you keep a cool head—literally, a new study suggests. The findings might hold some hope for sufferers of insomnia, migraines, and even epilepsy.

打哈欠也许可以帮你保持头脑清醒——一项新的研究如是说。这个发现也许能给失眠、偏头痛甚至癫痫患者带来一些希望。

Though scientists have put forth various theories for yawning—from fatigue to lack of oxygen—none have held up to scrutiny.

    尽管科学家们已经为打哈欠寻了很多解释，比如疲劳、缺氧，等等，可是没有一种能经得起细细推敲。

"We can put a man on the moon, but we do not understand what the function of yawning is," said study co-author Gary Hack, of the University of Maryland School of Dentistry in Baltimore.

    本研究的其中一位作者嘉里?哈克说：“如今载人飞船都飞上月球了，可是我们却弄不明白打哈欠的作用是什么。”哈克任职于马里兰大学巴尔的摩口腔学院。

Now, Hack and co-author Andrew Gallup, of Princeton University, propose that yawning causes the walls of the maxillary sinus to expand and contract like a bellows, pumping air onto the brain, which lowers its temperature. Located in our cheekbones, the maxillary are the largest of four pairs of sinus cavities in the human head.

    哈克与来自普林斯顿大学的安德鲁?盖洛普，在他们合作发表的论文中提出了一个观点：打哈欠可以令上颌窦扩张和收缩，其作用就好像风箱一样，不断地将空气输送到脑部，从而降低了脑部的温度。上颌窦位于颧骨下方，是头部四对鼻窦中最大的。

Like a computer, the human brain is "exquisitely" sensitive to temperature and must stay cool to work efficiently, said Hack, whose previously collected data was combined with Gallup's in the new study, recently published in the journal Medical Hypotheses.

    哈克说，人类的大脑和电脑有点相似，对温度相当敏感，温度一高就没法高效运转了。最近医学核心刊物《医学假说》杂志发表了这项新的研究成果，里面包含了哈克早前收集的研究数据以及盖洛普的研究成果。

Sinus Solution?

解释鼻窦的功能？

In addition to potentially solving the mystery of yawning, the study may also reveal why we have sinuses, whose existence has also stumped scientists.

    除了有望解释哈欠的秘密，这项研究也有可能揭示人类为什么要有鼻窦这个器官，这是长久以来困扰科学家们的一个问题。

It's a "unified theory tying yawning, sinus ventilation, and brain cooling into a neat little package," Hack said.

    这项理论“将打哈欠、鼻窦通畅、脑部降温等问题用一个小小的数据包串在了一起，”哈克说道。

Ryan Soose—an ear, nose, and throat doctor as well as director of the University of Pittsburgh Medical Center's Division of Sleep Surgery—added, "The hypothesis that these two relatively unknown things may be directly related, to me, is very intriguing."

    Ryan Soose是耳鼻喉科医生同时也是匹兹堡大学医学中心睡眠外科的主任，他补充道：“两件本来关系不明的事物有可能直接相关，这一假说相当吸引我。”

Cadaverous Clues

尸检线索

In 2002 study co-author Hack and his team were dissecting a cadaver when they discovered that the back wall of the maxillary sinus was much thinner—and therefore more flexible—than described in many medical textbooks.

    在2002年的研究中，和他的团队通过尸体解剖发现上颌窦的后壁比众多医学教材上描述的要薄的多，这也就意味着它柔韧性更强，更加灵活。

The researchers postulated that, when the jaw moves, the sinus wall flexes, ventilating the sinuses. 

    研究者们假设，下颌运动时，鼻窦壁也会随之伸缩，令鼻窦中空气流通。

"I'd always kept that in the back of my mind, because yawning was an exaggerated jaw movement that would have an impact on this previously undescribed pump in humans," Hack said.

    “我很早就有过这一想法，因为打哈欠是一种夸张的下颌运动，这应该对人类的鼻窦有一些影响，而以前对鼻窦“泵”的作用却鲜有人提及，”哈克说。

Later, he came across the postdoctoral research of Princeton's Gallup, who in 2007 had become the first to suggest the brain-cooling theory for yawning.

    后来，他遇到了普林斯顿大学正在做博士后研究的盖洛普，后者于2007年首次提出了打哈欠的“大脑降温说”。

Since 2007, Gallup had tested the idea in both animals—many of which also yawn—and people. (Read "Beyond the Brain" in National Geographic magazine.)

    自2007年起，盖洛普就在人类和许多会打哈欠的动物身上验证了这一想法。

For instance, Gallup and his team had implanted probes into rats' brains and recorded brain-temperature changes before, during, and after the rats yawned.

    比方说，盖洛普和他的团队在老鼠大脑中植入探针，记录了老鼠在打哈欠之前、之中、之后等各个阶段脑部的温度变化。

The team discovered that brain temperature spikes in the run-up to a yawn, then starts to decline, and finally falls rapidly to pre-yawn temperature.

    他们发现，马上要打哈欠的那一刻，脑部温度达到峰值，然后就开始下降，最后快速降到打哈欠以前的温度。

This suggests yawns are triggered by an increase in brain temperature and "actually promote brain cooling," Gallup said.

    这表明，打哈欠这一举动是由脑部温度升高触发的，而且“确实有助于给脑部降温，”盖洛普说道。

Gallup had also studied two women who suffer from chronic bouts of excessive yawning. He had asked one of the patients—who could predict her "yawning attacks"—to take her own temperature before and after the episode, he said.

    盖洛普还对两名打哈欠过度频繁的慢性病人进行了研究。其中一人在“哈欠袭来”时能做出预判，于是盖洛普便让她在每次发作前后都测下自己的体温。

The results showed her body temperature rose before the yawn and fell afterward—"directly mirroring results of the rat-brain temperature study," Gallup said.

    结果显示，体温在打哈欠前升高，打完之后就回落——“完全与我们在小白鼠身上所做的研究结果一模一样，”盖洛普说。

However, "we do have to be cautious that there are only two subjects in [that] study."

    不过，“我们还是得保持冷静，毕竟针对人体的研究里只有两位受试者。”

Indeed, co-author Hack expects the brain-cooling yawning theory to be "very controversial—we're delving into an area that's not well understood."

    事实上，论文的另一作者哈克希望哈欠的“大脑降温说”能“引起激烈反响——毕竟我们正在探究一个并不大为人所知的领域。”

Yawning Theory May Influence Medicine

哈欠理论对医学的影响

Overall, understanding yawning could be a useful tool for diagnosing certain medical conditions, such as epilepsy and migraines, which are both preceded by excessive yawning, the scientists say.

    总的来说，明白了打哈欠的来龙去脉，可能有助于对诸如癫痫和偏头痛等病症的诊断，这些疾病发作之前都会出现打哈欠过度频繁的现象，科学家们如是说。

The University of Pittsburgh's Soose added that the discovery might someday aid doctors in treating patients with insomnia, the most common U.S. sleep disorder. Insomniacs often have trouble regulating their body temperatures, which must drop in order for sleep to occur. 

    匹兹堡大学的Soose还说，或许有朝一日这一发现可以帮助医治失眠患者，如今美国最常见的睡眠问题就是失眠。身患失眠症的人通常无法调节自己的体温，而温度降不下来的话是没法入睡的。

"You could envision some mechanism by which you could rinse or cool the sinuses to treat insomnia," Soose said. "It opens the doors to help treat insomnia in a different way."

    “将来可能会出现某种装置能通过冲洗鼻窦给它降温，从而治疗失眠症，”Soose说，“这为失眠症治疗开启了一扇新的大门。”

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相关阅读：

1. 你醒着，而你的大脑却在熟睡？

2. 人体探秘

3. Beyond the Brain

4. 老鼠可以改造得聪明绝顶——但类似的基因改造对人类不见得是好事？

5. 小测试——睡眠的秘密