雅思阅读 006 · Why We Sleep

生物/心理主题。题型：T/F/NG + 填空。难度：中等（P2）。

正文 Passage

Sleep has long been a puzzle. Every animal with a nervous system sleeps, or at least rests in some way, yet the exact reason remains one of the great open questions of biology. For decades, scientists assumed that sleep was simply a period of rest — a time when the brain shut down to save energy. Modern research has shown that the opposite is true: during sleep, the brain is extraordinarily active, performing essential tasks that the waking day does not allow.

One of the most important functions of sleep is memory consolidation. During the day, we take in vast amounts of information — conversations, sights, sounds, skills. Much of this is discarded. But during deep sleep, the brain replays the experiences of the day, sorting what is worth keeping from what is not. Studies show that people who learn a task and then sleep perform significantly better the next day than those who stay awake.

Sleep also appears to be the brain's cleaning cycle. A decade ago, researchers discovered that during sleep, the spaces between brain cells widen, allowing a fluid called cerebrospinal fluid to flow through and wash away metabolic waste — including proteins linked to Alzheimer's disease. While we are awake, the cleaning system is largely inactive. This finding has led to the hypothesis that chronic sleep deprivation may be a contributing factor to dementia.

Not all sleep is the same. Sleep cycles through stages, from light dozing to deep slow-wave sleep to REM (rapid eye movement) sleep, in which most vivid dreams occur. Each stage serves a different purpose: deep sleep consolidates factual memory, while REM sleep appears to be involved in creativity and emotional processing. A good night's sleep is not eight hours of the same thing, but a carefully orchestrated sequence.

The implications for modern life are uncomfortable. We are the only species that deliberately deprives itself of sleep, and we pay a price. Studies link long-term sleep loss to obesity, diabetes, heart disease and weakened immunity. Even moderate sleep restriction — six hours a night, say — produces measurable impairments in attention and reaction time that are comparable to being drunk.

None of this is new advice, but the science behind it has never been clearer. Sleep is not a luxury. It is the foundation on which learning, health and emotional balance are built.

题目 Questions

Questions 1-5: T/F/NG

1. During sleep, the brain shuts down completely to save energy.

2. Sleep helps the brain decide which memories to keep.

3. Cerebrospinal fluid cleans the brain during waking hours.

4. REM sleep is associated with vivid dreams.

5. Six hours of sleep has no effect on attention.

Questions 6-10: Complete the notes. NO MORE THAN TWO WORDS.

• During (6) ____________ sleep, the brain replays the day's experiences.
• The brain's cleaning fluid is called (7) ____________.
• Proteins linked to (8) ____________ are washed away during sleep.
• (9) ____________ sleep is associated with creativity.
• Sleep loss is linked to obesity, diabetes and weakened (10) ____________.

答案 Answers

核心词汇

consolidation / cerebrospinal fluid / metabolic / Alzheimer's / dementia / REM / slow-wave / deprivation / chronic / immunity / orchestrate / hypothesis