Question

    Why would human beings waste a third of their lives sleeping when they could be doing more important things like looking after their families or working? Some scientists believe sleeping helps recharge the body, while others think it is important for strengthening newly-formed memories. Now, there is new evidence which suggests that the purpose of sleep may be to forget some of the millions of new things we learn each day.

The neurons (神经元) in the human brain consist of fibers called dendrites (树突). These grow as we learn new things and connect the brain's cells to each other at contact points called synapses (突触). The larger the dendrites become and the more cells they connect, the more information we store.

In 2003, Giulio Tononi and Chiara Cirelli, both biologists at the University of Wisconsin-Madison, suggested a new idea: The things our brains learn each day result in so many synapses that things start to get a little messy. Sleeping allows us to sort through the "noise" and dispense all the unnecessary information, leaving behind only the most important memories-

Recently, the university's research has provided direct evidence to support the theory. The experiment involved analyzing 6,920 synapses in the brain shavings from two groups of mice over a four — year period; one group had been allowed to sleep, while the other had been kept awake and entertained with toys. The researchers discovered that the brain shavings of the sleeping mice had nearly 20 percent fewer synapses than those that had been kept awake and entertained.

It was also evident during the study that the brain does not shave every synapse. 20% of neurons remained unchanged; these were most likely well-established memories. Therefore, although we may be sleeping to forget some of what we've learned, the brain "forgets" in a smart way.

Most researchers believe clearing our brains is not the only purpose of sleep. Resting our minds and bodies has also been found to help with other biological functions like strengthening our immunity. Though scientists may never agree on a single reason, they are all sure of one thing — a good night's rest is essential for our health. So try and spend at least a third of your day sleeping!

1.What will happen when we learn new things?

A.We tend to forget some key information.

B.We develop the ability to recharge the body.

C.The dendrites expand and connect brain's cells.

D.The neurons gather at what are called contact points.

2.Which of the following can replace the underlined word “dispense” in Paragraph 3?

A.Pick up. B.Get rid of.

C.Bring down. D.Pull out of.

3.What is the author's purpose of writing the text?

A.To prove a new theory.

B.To report a new discovery.

C.To show sleep good for memory.

D.To discuss how long one should sleep.

Answer

1.C

2.B

3.B

【解析】

本文为一篇说明文。文章介绍了睡眠的新研究：睡眠的目的可能是忘记我们每天学习的数百万新事物中的一些。

1.细节理解题。根据第二段These grow as we learn new things and connect the brain's cells to each other at contact points called synapses (突触).可知，当我们学习新事物时，这些神经元就会生长，并通过叫做突触的接触点将大脑细胞相互连接起来。由此可知，当我们学习新事物时，树突会扩张并连接大脑细胞。故选C项。

2.词义猜测题。根据后文leaving behind only the most important memories.(只留下最重要的信息)推测前文dispense意为“丢弃”，dispense all the unnecessary information意为“丢弃了不必要的信息”，B项“扔掉”与dispense意思相近。 故选B项。

3.推理判断题。结合全文及第一段Now, there is new evidence which suggests that the purpose of sleep may be to forget some of the millions of new things we learn each day.可知，文章介绍了睡眠的新研究：睡眠的目的可能是忘记我们每天学习的数百万新事物中的一些。由此推测，作者写这篇文章是为了报告一个有关睡眠的新发现。故选B项。