Word: sleepings
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Without a good theory of what sleep is for, scientists for many years concentrated on describing what it is--and treating conditions that interfere with it, such as anxiety, restless-leg syndrome and sleep apnea (see box). They've learned that most mammals, with the possible exception of dolphins and whales, cycle between two distinct phases of sleep, one of which is characterized by rapid eye movement--the famous REM sleep. The other is called, straightforwardly enough, non-REM sleep. Humans generally take about 90 minutes to complete a full cycle of REM and non-REM sleep. As dawn approaches...
...look at the EEGs of people in REM sleep, you see a pattern that shows lots of brain activity--and if you wake them up during it, they will tell you that they have just been dreaming. Any dreams in non-REM sleep usually consist of no more than a simple image or two. But despite all the mythology that surrounds dream imagery, scientists who have searched for the hidden purpose in dreams haven't had much luck. The consensus among sleep researchers today is that dreams are nothing more than random recycling of bits and pieces of the previous...
EEGs taken during non-REM sleep reveal four distinct stages as we progress from light to very deep sleep. Stages 3 and 4 of non-REM sleep are characterized by distinctive low-frequency electrical waves; researchers call that slow-wave sleep. Intriguingly, humans spend much more time in slow-wave sleep during the first three hours of the night than they do in the hours just before waking. Children are champion slow-wave sleepers, which is why they sleep so soundly when being carried from the car to bed. Adults, on the other hand, get less and less slow-wave...
...years sleep researchers focused most of their attention on REM sleep because, frankly, it seemed more interesting--all those dreams and everything. But they kept running into blank walls. Early work that tried to link REM sleep to learning foundered when scientists discovered that their test subjects could remember long lists of new words or facts whether or not they got any REM sleep. Indeed, an Israeli man with a piece of shrapnel in his brain became famous in sleep circles for not getting any REM sleep at all. Despite that, he went to law school and seems to have...
...things happened in the mid-1990s, however, that revived research into the fundamental purposes of sleep. A 1994 study by scientists at the Weizmann Institute in Rehovot, Israel, suggested that researchers had been looking at the wrong kind of memory processing. And the technology for peering inside a sleeping brain got a whole lot better...