睡眠期显然必定具有某种功能，而且由于睡眠占据如此大量的时间，这一功能似乎举足轻重。
It is fairly clear that the sleeping period must have some function, and because there is so much of it the function would seem to be important.
关于睡眠本质的种种推测已延续了数千年之久；而有一个奇特的发现令这一问题愈加扑朔迷离——睡眠似乎并不仅仅是让身体得到休息那么简单。
Speculations about its nature have been going on for literally thousands of years, and one odd finding that makes the problem puzzling is that it looks very much as if sleeping is not simply a matter of giving the body a rest.
就肌肉放松等而言，"休息"其实只需短暂地躺下，或甚至坐下便可实现。
'Rest', in terms of muscle relaxation and so on, can be achieved by a brief period lying, or even sitting down.
身体的组织在一定程度上具有自我修复和自我恢复的能力，且在或多或少持续运作时功能最佳。
The body's tissues are self-repairing and self-restoring to a degree, and function best when more or less continuously active.
事实上，在睡眠过程中会发生一定量的基本运动，其目的专门在于防止肌肉处于不活动状态。
In fact a basic amount of movement occurs during sleep which is specifically concerned with preventing muscle inactivity.
如果说睡眠并非为了让身体休息，那么或许需要休息的是大脑？
If it is not a question of resting the body, then perhaps it is the brain that needs resting?
倘若不是因为两个因素，这或许是一个颇为合理的假说。
This might be a plausible hypothesis were it not for two factors.
首先，脑电图仪（它不过是一种通过将电极贴附于头皮来记录大脑电活动的装置）显示：尽管睡眠期间大脑活动的模式确实发生了变化，但没有证据表明大脑活动的总量有任何减少。
First the electroencephalograph (which is simply a device for recording the electrical activity of the brain by attaching electrodes to the scalp) shows that while there is a change in the pattern of activity during sleep, there is no evidence that the total amount of activity is any less.
第二个因素则更为有趣，也更为根本。
The second factor is more interesting and more fundamental.
数年前，一位名叫威廉·德门特的美国精神病学家发表了涉及睡眠期间眼动记录的实验研究。
Some years ago an American psychiatrist named William Dement published experiments dealing with the recording of eye-movements during sleep.
他的研究表明，普通人的睡眠周期中会不时出现奇特的眼动爆发，有些眼动漂移而缓慢，另一些则急促而快速。
He showed that the average individual's sleep cycle is punctuated with peculiar bursts of eye-movements, some drifting and slow, others jerky and rapid.
在这些眼动时段被唤醒的人们通常都报告说他们一直在做梦。
People woken during these periods of eye-movements generally reported that they had been dreaming.
而在其他时段被唤醒时，他们则报告说没有做梦。
When woken at other times they reported no dreams.
如果一组人连续数个夜晚在快速眼动睡眠期间被打断，而另一组人被打断的时间总量相同，但被打断时并非处于眼动阶段——那么第一组人开始出现一些人格障碍，而另一组人则似乎或多或少地未受影响。
If one group of people were disturbed from their eye-movement sleep for several nights on end, 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 disorders while the others seemed more or less unaffected.
所有这些结果的含义是：起决定作用的并非睡眠被打断本身，而是做梦被打断。
The implications of all this were that it was not the disturbance of sleep that mattered, but the disturbance of dreaming.