In the October issue of the Report on Progress, titled “Why is Sleep So Important?,” Giulio Tononi, M.D., Ph.D., and Chiara Cirelli, M.D., Ph.D., discuss the effects sleep has on the human brain.
The sleeping brain is almost as active as during wake: neurons fire at comparable rates as in wake, and metabolism is only slightly reduced. Moreover, we all know that every night while we lie asleep, blind, dumb, and almost paralyzed, we are in for a remarkable treat: hours upon hours of free slide shows and movies – a virtual reality made up by your brain that is so powerful it rivals the one in “The Matrix.” This is easy to show: have somebody wake you up at random times during the night, whether in REM (REM stands for rapid eye movements) or in non-REM (NREM) sleep and ask what was going through your mind. More often than not, you will find that you were experiencing something: at times mere snapshots and still scenes, at times full-fledged, vivid dreams, especially toward the morning. It is not surprising, then, that unless you wake up immediately, you don’t remember anything at all. To the point that, although everybody dreams, many people are convinced they never do. But then, if during sleep the brain does not actually rest, why does it disconnect from the environment, turn on its internal activity, broadcast movies on its private network, but form no new memories?
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