It was probably not long after humans first questioned the meaning of life that someone turned to the significance of sleep. Why do we need it? Why do we spend so much of our life doing it? And what is this strange alternative reality we experience while we sleep?These big questions still loom large, but researchers have been focusing on more practical matters. We now know how an intricate interaction of neurotransmitters in different parts of the brain switches us from being fully alert to unconscious, and back again (page S2). But the brain does not shut down -studies of its electrical activity are revealing how sleep boosts learning, providing tantalizing clues to the formation of memory (S4).
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