IELTS Reading 練習 6 睡眠科學（含題目+詳解）

The Science of Sleep

For most of recorded history, sleep was regarded as a passive state — essentially a temporary switching-off of the brain. Research since the 1950s has overturned this view entirely. Sleep is now understood as a highly structured, metabolically active process, during which the brain carries out tasks that cannot easily be performed while the body is awake.

A typical adult moves through four to six sleep cycles per night, each lasting approximately 90 minutes. Each cycle contains two principal phases. During non-rapid-eye-movement (NREM) sleep, the brain's electrical activity slows and the body cools slightly; this stage is associated with physical restoration, growth-hormone release and immune regulation. During rapid-eye-movement (REM) sleep, by contrast, brain activity resembles that of wakefulness, but skeletal muscles are temporarily paralysed. Most vivid dreaming occurs during this phase.

One of the most significant discoveries of the past two decades concerns memory. Experimental evidence now indicates that sleep consolidates newly learned information, transferring it from short-term storage in the hippocampus to long-term storage in the cortex. In one widely cited 2013 study, medical students who slept for seven hours after learning anatomy outperformed sleep-deprived peers on tests administered a week later, despite identical waking study time.

More recently, researchers identified the glymphatic system — a network of channels surrounding brain blood vessels — which becomes markedly more active during deep NREM sleep. This system flushes out metabolic waste, including beta-amyloid proteins associated with Alzheimer's disease. Chronic sleep restriction may therefore contribute to the long-term accumulation of such proteins, offering a plausible mechanism behind the observed link between poor sleep in midlife and later cognitive decline.

Modern societies, however, sleep significantly less than those of a century ago. Average adult sleep in industrialised countries has fallen from around nine hours in 1900 to under seven today, a trend attributed to electric lighting, shift work and, most recently, the widespread use of screens before bedtime.

1. Before the 1950s, most researchers considered sleep to be an active process.
2. NREM and REM are equally associated with vivid dreaming.
3. A 2013 study found that sleep after learning improved students' later test performance.
4. The glymphatic system was discovered in the twentieth century.

1. According to the passage, a typical adult sleep cycle lasts approximately:

- A. 45 minutes - B. 90 minutes - C. 2 hours - D. 4 hours

1. The writer mentions beta-amyloid proteins to illustrate:

- A. a cause of poor sleep - B. a possible link between sleep loss and dementia - C. a treatment for Alzheimer's disease - D. a function of REM sleep

1. The passage suggests that the decline in average sleep since 1900 is mainly due to:

- A. diet changes - B. longer working hours only - C. technology and lifestyle factors - D. population ageing

Complete the summary using NO MORE THAN TWO WORDS from the passage.

During NREM sleep, the body cools and the brain's electrical activity slows, while the body releases (8) ______ and strengthens the immune system. REM sleep is marked by temporary paralysis of (9) ______ despite active brain patterns. Recent research has shown that sleep also clears waste products through the (10) ______ system.

1. FALSE Supporting sentence: "sleep was regarded as a passive state — essentially a temporary switching-off of the brain". "Passive" directly contradicts "active". Explicit reversal.

2. FALSE Supporting sentence: "Most vivid dreaming occurs during this phase [REM]". Only REM is linked to vivid dreaming, not both.

3. TRUE Supporting sentence: "medical students who slept for seven hours after learning anatomy outperformed sleep-deprived peers on tests administered a week later". Direct paraphrase.

4. NOT GIVEN Supporting sentence: "More recently, researchers identified the glymphatic system". "Recently" suggests the twenty-first century, but no exact date is given. Don't assume — choose NOT GIVEN.

5. B — 90 minutes Supporting sentence: "each lasting approximately 90 minutes". Direct statement.

6. B — a possible link between sleep loss and dementia Supporting sentence: "Chronic sleep restriction may therefore contribute to the long-term accumulation of such proteins, offering a plausible mechanism behind the observed link between poor sleep in midlife and later cognitive decline". "Cognitive decline" = dementia. Option C is a trap (passage does not claim treatment).

7. C — technology and lifestyle factors Supporting sentence: "a trend attributed to electric lighting, shift work and, most recently, the widespread use of screens before bedtime". These are all technology/lifestyle. Option B is a trap (shift work is mentioned, but not "only").

8. growth-hormone (or growth hormone) Supporting sentence: "this stage is associated with physical restoration, growth-hormone release and immune regulation". One or two words matches the passage.

9. skeletal muscles Supporting sentence: "skeletal muscles are temporarily paralysed". Two words, exact match.

10. glymphatic Supporting sentence: "the glymphatic system ... This system flushes out metabolic waste". Single word, directly from passage.