Just as our bodies produce waste every day – which is why we need to shower and use the toilet – our brains produce harmful waste proteins. But how can our brains “shower” themselves?
正如我們的身體每天都會產(chǎn)生廢物 —— 這也是我們需要洗澡、上廁所的原因 —— 我們的大腦也會產(chǎn)生有害的廢棄蛋白質(zhì)。但是我們的大腦又是如何“清潔”自己的呢？

A 2013 study found the answer. Researchers at the US University of Rochester studied the brains of mice and discovered that they cleaned themselves while the mice slept. A kind of fluid in the brain, called cerebral spinal fluid, was found to increase dramatically during sleep, washing away waste proteins that had been building up between brain cells in waking hours.
一項2013年的研究找到了答案。美國羅切斯特大學(xué)的研究人員們對老鼠的大腦進(jìn)行了研究，發(fā)現(xiàn)老鼠在睡眠時會對大腦進(jìn)行自我清潔。他們發(fā)現(xiàn)，老鼠的大腦內(nèi)有種名為腦脊液的液體，在睡眠時會顯著增加，“清洗”掉清醒時大腦細(xì)胞間堆積的廢棄蛋白質(zhì)。

“This study shows that the brain has different functional states when asleep and when awake,” Maiken Nedergaard, the lead researcher, told NBC News. It also explains why we can’t seem to think clearly after a sleepless night while a good night’s sleep leaves us feeling sharp and refreshed.
“該研究表明，大腦在睡眠和清醒時的功能狀態(tài)有所不同，”該研究首席研究員梅肯·內(nèi)德加德在接受美國全國廣播公司新聞頻道采訪時如此表示。研究也解釋了失眠之后我們似乎無法清晰思考，而一夜安眠卻讓我們感到清醒振作的原因。

Now a new study, published on Oct 31 in Science, digs a little deeper into our brains’ self-cleaning procedure. Instead of mice, this time humans were the test subjects.
去年10月31日發(fā)表于《科學(xué)》期刊上的一項新研究進(jìn)一步探究了我們大腦的自我清潔過程。這一次的實驗對象不是老鼠，而是人類。

Researchers at Boston University, US, monitored the brain waves of 13 healthy adults who were sleeping, using accelerated fMRI, which is capable of recording faster changes inside the brain than a regular fMRI machine. They found that every 20 seconds, blood flowed out of the brain, making room for a large amount of CSF to come in and “clean”. This cycle coincided with the rhythm of the brain’s slow waves – an electrical activity that happens when we’re in deep sleep.
美國波士頓大學(xué)的研究人員通過增強(qiáng)性磁共振成像監(jiān)測了13名健康成年人睡眠時的腦電波，和普通的功能性磁共振成像儀器相比，這種技術(shù)能夠捕捉到腦內(nèi)更快的變化。他們發(fā)現(xiàn)，每隔20秒血液會流出大腦，從而讓腦脊液流入，進(jìn)行“清潔”。這一循環(huán)與大腦慢波頻率一致 —— 這是種我們進(jìn)入深度睡眠才會發(fā)生的腦電活動。

It’s still unknown how these brain activities are connected. But the mere fact that they are connected is exciting enough, since it allows researchers to piece together possible new explanations for misunderstood diseases.
這些大腦活動有何關(guān)聯(lián)仍是未解之謎。但這些活動具有相關(guān)性的事實足以令人感到興奮，因為這或許能讓研究人員們拼湊出對于遭到誤解的疾病的新解釋。

For example, slow-wave sleep has been proven to play a role in strengthening our memories. This may explain why people with Alzheimer’s often have fewer and weaker slow brainwaves. Based on this new study, there could be one more explanation for diseased brains: They are not clean.
比如，經(jīng)過證實，慢波睡眠對于增強(qiáng)記憶起著關(guān)鍵作用。這或許解釋了為何阿爾茨海默癥患者的大腦慢波往往更少、更微弱?；谶@項新研究，大腦的發(fā)病原因或許又多了一個解釋：不夠“干凈”。

Nedergaard, leader of the 2013 study, is also excited about the new findings. “Maybe the most important take-home message is that sleep is a serious thing,” she told Scientific American. “You really need to sleep to keep a healthy brain because it links electrical activity to a practical ‘housekeeping’ function.”
2013年那項研究的首席研究員內(nèi)德加德也對這些新發(fā)現(xiàn)感到興奮?！盎蛟S最重要的關(guān)鍵信息就是睡眠很重要，”她在接受《科學(xué)美國人》雜志采訪時表示?！澳愕拇_需要通過睡眠來保持大腦健康，因為這將大腦的‘清掃’功能與腦電活動聯(lián)系了起來?！?/span>

以上文章內(nèi)容選自《21世紀(jì)學(xué)生英文報高中版》，詳情請見《21世紀(jì)學(xué)生英文報高中版》高三701期