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  3. One fact was clearly demonstrated by the early sleep researchers: one part of the night is not just like another. As scientists

One fact was clearly demonstrated by the early sleep researchers: one part of the night is not just like another. As scientists

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问题       One fact was clearly demonstrated by the early sleep researchers: one part of the night is not just like another. As scientists began to compare the records of volunteers during the 1950s, they observed that human sleep follows a rhythmic schedule. They noted that not only was this schedule much the same in healthy persons of the same age with similar habits but, from night to night, each individual had an EEG record almost as consistent as a signature.
      Sleep and wakefulness, once considered to be the light and dark of consciousness, no longer seem to differ so sharply. To sleep does not mean to drown in an ocean of darkness. Actually, sleep is not a unitary state; it involves many shades or degree of detachment from the surrounding world. While sleep may feel like a blanket of darkness punctuated by dreams—a time when the mind is asleep—nothing could be less true. All night long a person drifts down and up through different levels of consciousness, as if on waves. With laboratory methods, researchers have been able to chart the typical stages of the journey into sleep.
      The journey starts while the subject is still awake but beginning to relax. His brain waves, which have been low, rapid, and irregular, begin to show a new pattern. This new pattern, which is known as alpha rhythm, is an even electrical pulsation of about nine to 12 cycles per second. Most people do not know what the alpha state feels like, but during the last few years researchers have been able to teach subjects how to recognize and control their alpha rhythm.
     When their EEG shows an alpha rhythm, the subjects are notified, either by a sound or by the appearance of a color on a screen. Because the alpha state tends to be pleasant and relaxed, the ability to sustain it can help tense people ease their passage into sleep. A moment of tension, a loud noise, an attempt to solve a problem, however, and the alpha rhythm may vanish.
     As the subject passes through the gates of the unconsciousness, his alpha waves grow smaller, and his eyes roll very slowly. For a moment, he may wake up during this early part of the descent, alerted by a sudden spasm that causes his body to jerk. Like the brain waves, this spasm is a sign of neural changes within. Known as the myoclonic jerk, it is caused by a brief burst of activity in the brain. Although it is related to epileptic seizures, the myoclonic jerk is normal in all human sleep. It is gone in a fraction of a second, after which descent continues. The subject has not felt the peculiar transformation, but now he is said to be truly asleep.
Sleep is described as
选项 A、a gradual parting from the real world.
B、undisturbed by tension or problems.
C、drowning in an ocean of darkness.
D、dependent only upon individual age and health.
答案A
解析 本题考查细节理解。第二段指出“Actually，sleep is not a unitary state；it involves many shades or degree of detachment from the surrounding world．(睡眠不是一个单一的状态，而包含超脱周围现实世界的色彩浓度或程度。)”选项A 的内容正好与原文意思相符。而选项C 的内容与第二段第二句话“To sleep does not mean to drown in an ocean of darkness．”意思相反，应排除；第四段第三句话表明人的睡眠状况与人的精神状况有关，并未提到年龄与健康对睡眠的影响，所以选项D 也应排除；选项B 是讲“睡眠不受紧张与各种问题的影响”，这与原文“A moment of tension，a loud noise，an attempt to solve a problem，however，and the alpha rhythm may vanish．”所表达的意思完全相反，应排除。
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