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Why do we Sleep?

  1. Jul 27, 2011 #1
    One of biology biggest mysteries is why do we sleep. In spite of decades of research. Scientists still haven't figured out the secret of sleep.

    If you are aware of the arguments and research. You would know that anabolism can occur even while being still... so why do living things have to spend one third of their lives sleeping? There are no animals that don't sleep. Even whales that continously swim have to alternatively make their left and right brain sleep at a time. It is also observed that the smaller the animal is the more it sleeps.. this is why rats sleeps 14 hours a day versus human 8 hours and elephants only sleep 3 hours. Maybe there is a clue here somewhere? Why is resting by being still not sufficient? One can't reason the brain is being rested while sleep because it uses even more ATP when sleeping such as during REM sleep. Is it about memory consolidation? But it could just be a secondary to the real purpose of sleep.

    If you have heard of latest cutting edge research about the purpose of sleep. Do share it.
  2. jcsd
  3. Jul 27, 2011 #2


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    I can't tell you, but I confess that I have been sleep-deprived for a couple of months, and that messes you up. I worked for over 10 years in shift-work environments, but you learn to roll with that in some manner. Being sleep-deprived in a normal day-time schedule has bothered me worse than the shift-disruptions.
  4. Jul 27, 2011 #3
    I am also sleep deprived. I only sleep 4 hours a night. I sleep from 11pm and wakes up 3am and can't sleep anymore. But I continue lying down still in bed from 3am to 6am. But I still get fatigue at daytime. So how come staying still is not equal to sleeping for those 3 hours? The body is still and anabolism and ATP hydrolysis should continue to work. Also note the heart continuously pumps 24 hours a day. It doesn't need sleep so we can say some cells don't need sleep. But how come the body as a whole or brain needs sleep? I read a number of books about it but it's still a mystery. Maybe someone can give some insight not shared before.
  5. Jul 27, 2011 #4
    I too would like to know why we sleep.

    Maybe there is a clue here. Perhaps it's to do with memory. Elephants never forget, as I'm sure you know, and they only need three hours sleep. Where as I'm always forgetting things and often sleep past noon.


    I believe the rats you example may also provide a clue. I keep rats and agree they are very intelligent (I know you didn't mention their intelligence, but other people sometimes do). So rats like to sleep allot and as we've just established they're terribly clever. Elephants don't need much sleep, as you say, and aren't so clever as rats*. I, on the other hand, need lots of sleep and...

    Actually, I cant see any correlation. Forget it.

    *They're always getting stuck in the mazes.
  6. Jul 27, 2011 #5
    Rats or dogs who didn't sleep just die after 4 days... they didn't know why. Perhaps finding the reason why can give the secrets why living things need sleep.
  7. Jul 28, 2011 #6


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    Sleeping is a very complex and multifactorial process during which lot's of tasks seem to take place for example; strengthening memories, increased wound healing, huge alterations in hormone release etc. The wiki page on sleep function outlines a lot of current theories quite well. A key thing about sleep is that it hay have evolved for multiple reasons, i.e. lot's of cyclic processes aligned. This could have been driven by the different requirements for survival in the day vs the night.
  8. Jul 28, 2011 #7


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    As far as brain function goes, there's an interesting play between neocortex and hippocampus during sleep (driven partially by sleep motor patterns) starting from the developmental years:


    One idea that has been developed is that memories are first stored episodically in the hippocampus, but later (while sleeping) transferred to the neocortex in a more ordered and generalized fashion:

    Why there are complementary learning systems in the hippocampus and neocortex: Insights from the successes and failures of connectionist models of learning and memory.
    McClelland, James L.; McNaughton, Bruce L.; O'Reilly, Randall C.
    Current issue feed
    Psychological Review, Vol 102(3), Jul 1995, 419-457.

    In not so many words, you incorporate new information into your world model during sleep.
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