The stuff （材料 原料 本质）of dreams
It is fairly clear that the sleeping period must have some function（功能）, and because there is so much of it the function would seem to be important. Speculations（猜测） about its natrue（本质） have been going on for thousands of years, and one finding that makes the problem puzzling（困惑） is that it looks as if sleeping is not simply a matter of giving the body a rest. Rest, in terms of muscle relaxation and so on, can be achieved by a brief（简单的） period lying, or even sitting down. The body’s tissues（组织） are self-repairing（自我修补） and self-restoring（自我恢复） to a degree（在一定程度上）, and function（功能） best（最佳） when more or less continuously active（有张有弛地连续活动）. In fact a basic amount of movement occurs（发生） during sleep which is specifically concerned with preventing（防止） muscle inactivity（活动停止）.
If it is not a question of resting the body, then perhaps it is the brain that needs resting? This might be a plausible（似乎合理的） hypothesis
（假说） were it not for two factors（如果不是下面两个方面）. First the electroencephalograph（脑电图仪）shows that while there is a change in the pattern（方式） of activity（活动） during sleep, there is no evidence（迹象） that the total amount of activity is any less（任何减少）. The second factor is more interesting and more fundamental（重要）. Some years ago an American psychiatrist（精神病学家） named William Dement published（发表） experiments dealing with the recording of eye-movements during sleep. He showed that the average individual（平常人）’s sleep cycle is punctuated（不时介入） with peculiar（奇怪） bursts of eye-movements（眼球活动）, some drifting（飘忽） and slow, others jerky（急动的） and rapid（迅速）. People woken during these periods of eye-movements generaly reported that they had been dreaming. When woken at other times they reported no dreams. If one group of people were disturbed from their eye movement sleep for several nights on end（连续）, and another group were disturbed for an equal period of time but when they were not exhibiting eye-movements, the first group began to show some personality（性格） disorders （失常）while the others seemed more or less unaffected（不受影响）. The implications（表明） of all this （这一切）were that it was not the distrubance of sleep that mattered（没有关系）, but the distrubance（打扰） of dreaming.
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