Question

【题目】 We take showers and use the toilet every day to get rid of badly waste. Our brains also need to take a bath every day. How can they do it?

A 2013 study found the answer. Researchers at the LS 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 (CSF, 脑脊液), was found to increase dramatically (显著地) during sleep, washing away waste proteins that had been building up between brain cells in waking hours.

"This study shows that the brain has different functional stales 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.

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.

Researchers at Boston University, US, monitored (监测) the brain waves of 13 healthy adults who were sleeping, using accelerated MRI, which is capable of recording faster changes inside the brain than a regular MRI 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(与……一致) the rhythm of the brain's slow waves-an electrical activity that happens when we're in deep sleep.

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 (拼凑出) possible new explanations for misunderstood diseases.

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.

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."

【1】When the researchers studied the brains of mice, they found __________.

A.CSF in their brains went down when the mice slept

B.CSF carried away waste proteins in their brain during sleep

C.more waste proteins were produced in their brains when asleep

D.the more CSF was in their brains, the fewer waste proteins were

【2】What did the researchers discover when they monitored human brain waves?

A.The rhythm of the brain was slower than that of CSF.

B.The brains worked more slowly when asleep.

C.Brains were cleaned when blood flowed out.

D.It took 20 seconds for CSF to clean brains.

【3】Which of the following would be the best title for the passage?

A.Connecting Brain ActivitiesB.Cleaning in Your Dreams

C.Having a Good SleepD.Explaining Diseases

Answer 1

【答案】

【1】B

【2】D

【3】B

【解析】

文章大意：我们每天淋浴和使用厕所，以清除身体的严重废物。我们的大脑也需要每天洗澡，他们怎么能做到呢? 本文对此做了具体的说明。

【1】细节理解题。根据A kind of fluid in the brain, called cerebral spinal fluid (CSF, 脑脊液), was found to increase dramatically (显著地) during sleep, washing away waste proteins that had been building up between brain cells in waking hours. 大脑中的一种液体，即脑脊液，在睡眠期间会急剧增加，它会冲走在清醒时脑细胞之间积累起来的废物蛋白质。因此当研究人员研究老鼠的大脑时，发现脑脊液在睡眠中带走大脑中的废蛋白质。故答案选B。

【2】细节理解题。根据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(与……一致) the rhythm of the brain's slow waves-an electrical activity that happens when we're in deep sleep. 他们发现，每隔20秒，血液就从大脑中流出，为大量脑脊液进入大脑和“清洁”留出空间．这个周期正好与大脑慢波的节律（当我们进入深度睡眠时发生的一种电活动）相吻合。因此我们可知脑脊液用20秒清洗大脑，故答案选D。

【3】标题归纳题。通读全文，结合文章最后一段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年研究的领导者Nedergaard也对这些新发现感到兴奋。她在接受《科学美国人》采访时表示:“也许最重要的是，睡眠是一件严肃的事情。”“你真的需要睡觉来保持一个健康的大脑，因为它将电子活动与实际的‘家务’功能联系起来。” 可知本文主要介绍了在睡眠中是大脑本身如何自动清洁其中的废料，从而让我们在清醒的时候感觉状态很好的。故答案选B。