Why Do We Sleep?

[Xei]

There was a documentary on the Beeb last night about sleep, and it was pretty cool to see that Stephen LaBerge and his lucidity research was featured in the last ten minutes or so; it's probably on the net somewhere if you wanna watch it (it was a Horizon program I think). He seems like a pretty cool guy. Anyway, the main thing that hit me during watching it was the following fact; every night, for about 8 hours - a whole third of our day - we go into a state of unconscious paralysis; and we consider it completely normal, even though we have absolutely no idea why it happens. Isn't that utterly bizarre? There is still no accepted hypothesis for the function of sleep at all, which is really quite ironic considering how much we have learnt about the most obscure workings of the the universe, completely detached from human experience. Even more mysterious is how anomalous this is in the context of natural selection. For an entire third of the day, mammals become completely unresponsive. The ability for the organism to find food, reproduce, and defend itself, is effectively decreased by a 1/3. This is a huge disadvantage. The fact that it hasn't been weeded out shows that there is something extremely crucial to the process. But what? The only explanations I've heard so far are extremely weak. For example; 'we need it to form long term links between experiences'. Not particularly; don't we do that to a large extent during waking anyway? This also fails to explain why mental function completely collapses without sleep for a long time, and seems completely inadequate to sacrifice an entire 1/3 of the organism's ability to create offspring. The same applies to an even greater extent to theories such as 'we heal a bit faster' (not remotely worth 1/3, and why exactly do we need to switch off our brains to perform what must be a simple metabolic function?), etcetera. Personally I think the reason could be much more profound, relating to the inner workings of the neural network of the cerebral cortex, which are so far completely unknown. I'm completely open to other ideas though.

[tkdyo]

to me it almost feels like its simply a way for my brain to recoup from all the information being blasted on me and the stress being put on my body. Maybe because we pick up SO much information on a daily basis we need more respite from it?

[drewmandan]

Even more mysterious is how anomalous this is in the context of natural selection. For an entire third of the day, mammals become completely unresponsive. The ability for the organism to find food, reproduce, and defend itself, is effectively decreased by a 1/3. That's not true at all. When sleeping, mammals are responsive, hence why they wake up when threatened. Also, most mammals in the wild don't sleep a full 8 hours, or at least not in a single chunk. And of course, they don't just fall asleep no matter what; the process of falling asleep requires the perception of a perfectly safe surrounding. This is a huge disadvantage. The fact that it hasn't been weeded out shows that there is something extremely crucial to the process. It's clearly an advantage since evolution positively favours it. But what? The only explanations I've heard so far are extremely weak. For example; 'we need it to form long term links between experiences'. Not particularly; don't we do that to a large extent during waking anyway? No. Numerous studies have shown that sleep is necessary for the formation of long term memories. This also fails to explain why mental function completely collapses without sleep for a long time, I don't understand this comment. If the hypothesis is that sleep helps form memory, then that alone would explain mental collapse. and seems completely inadequate to sacrifice an entire 1/3 of the organism's ability to create offspring. Since evolution favours sleep, this 1/3 figure is obviously blatantly wrong. The same applies to an even greater extent to theories such as 'we heal a bit faster' (not remotely worth 1/3, and why exactly do we need to switch off our brains to perform what must be a simple metabolic function?), etcetera. You don't think being immobile for 8 hours might make wounds heal faster? Um...

[Xaqaria]

Constant sensory input would hinder our ability to organize and compartmentalize the sensory input we've already received. Most people have experienced working on a problem, absorbing all of the information about that problem but have been unable to come up with a solution until after a good night's rest. Sleep allows for a period of introspection to reorganize sensory input into a useful combination.

[Man of Steel]

Not to mention the fact that our bodies need a certain amount of rest per day to recuperate from activity, repair muscles torn microscopically in exercising, etc.. Nor does the human body absolutely require a full eight hours of sleep (which is more like seven and a half to nine, anyway, due to 90-minute sleep cycles by and large) every night; biphasic and polyphasic sleep schedules must be taken into account. The latter is not recommended for active people such as athletes or heavy laborers, however, due to the body's need for rest in Delta (I believe) sleep.

[Black_Eagle]

Also, sleep deprivation stunts growth. No sleep=shortness despite genetics.

[drewmandan]

Also, sleep deprivation stunts growth. No sleep=shortness despite genetics. Makes sense. Gravity and all that.

[Black_Eagle]

Makes sense. Gravity and all that. No, it makes sense because of MOS's comment...and this

[Xei]

That's not true at all. When sleeping, mammals are responsive, hence why they wake up when threatened. Also, most mammals in the wild don't sleep a full 8 hours, or at least not in a single chunk. And of course, they don't just fall asleep no matter what; the process of falling asleep requires the perception of a perfectly safe surrounding. Well yes, obviously I realise from personal experience that people wake up if there is a loud noise. I was oversimplifying my point of course but it still stands; and don't talk nonsense, it is perfectly possible to sleep through relatively large disturbances, and there is no such thing as a 'perfectly safe surrounding'. Sleep without function would clearly be a very large disadvantage to an organism. It's clearly an advantage since evolution positively favours it. Yes, that's what I said. No. Numerous studies have shown that sleep is necessary for the formation of long term memories. What do you mean, 'no'? Studies have also shown that sleep is used to form links between memories. If you don't know something please look it up instead of flat out denying it. I'd like to see these studies. Wiki just says 'Some theories consider sleep to be an important factor in establishing well-organized long-term memories', which sounds pretty weak. I don't understand this comment. If the hypothesis is that sleep helps form memory, then that alone would explain mental collapse. We don't need to use links between memories to perform basic tasks like finding food. Why does lack of sleep for about a week cause death? We don't need to use new memories to perform life functions. Constant sensory input would hinder our ability to organize and compartmentalize the sensory input we've already received. Most people have experienced working on a problem, absorbing all of the information about that problem but have been unable to come up with a solution until after a good night's rest. Sleep allows for a period of introspection to reorganize sensory input into a useful combination. Why though? We do we need to be unconscious to do this? And why does lack of sleep have far worse consequences than just an inability to perform more complex cognitive tasks? Not to mention the fact that our bodies need a certain amount of rest per day to recuperate from activity, repair muscles torn microscopically in exercising, etc.. Nor does the human body absolutely require a full eight hours of sleep (which is more like seven and a half to nine, anyway, due to 90-minute sleep cycles by and large) every night; biphasic and polyphasic sleep schedules must be taken into account. The latter is not recommended for active people such as athletes or heavy laborers, however, due to the body's need for rest in Delta (I believe) sleep. Again, I don't see how unconsciousness is required for this. It's a simple metabolic activity of cells, not a complex problem involving the cognitive function of neural network. Why can't it do this during normal resting periods? This alone doesn't really explain any of the features of sleep.

[MrGrEmLiN]

You wanna know why we sleep? Spend more than 24h awake and look at yourself in a mirror! xD If we don't sleep our bodies become tired and I think information starts building up in the brain somehow... Maybe it's necessary for information to go into some kind of storage or something...

[drewmandan]

Well yes, obviously I realise from personal experience that people wake up if there is a loud noise. I was oversimplifying my point of course but it still stands; and don't talk nonsense, it is perfectly possible to sleep through relatively large disturbances, and there is no such thing as a 'perfectly safe surrounding'. Sleep without function would clearly be a very large disadvantage to an organism. Ever see an animal sleep through a loud disturbance? I haven't. Even hibernating bears can be woken up. If you're arguing that sleep = unresponsiveness, then can you give even one example of a mammal species that can't wake up? And I said the perception of being safe. What do you mean, 'no'? Studies have also shown that sleep is used to form links between memories. If you don't know something please look it up instead of flat out denying it. So now you're agreeing with me. I'd like to see these studies. Wiki just says 'Some theories consider sleep to be an important factor in establishing well-organized long-term memories', which sounds pretty weak. First result on google http://www.sciencedaily.com/releases...0629070337.htm We don't need to use links between memories to perform basic tasks like finding food. Why does lack of sleep for about a week cause death? We don't need to use new memories to perform life functions. Who said sleep only affects new memories? The brain is dynamic in structure; it's perfectly plausible that old memories (such as how to breathe) need maintenance. Why though? We do we need to be unconscious to do this? And why does lack of sleep have far worse consequences than just an inability to perform more complex cognitive tasks? Have you ever tried to defrag your hard drive while running a large program? Again, I don't see how unconsciousness is required for this. It's a simple metabolic activity of cells, not a complex problem involving the cognitive function of neural network. Why can't it do this during normal resting periods? This alone doesn't really explain any of the features of sleep. I don' think anyone is claiming that literal sleep is needed for healing. I think it's just the paralysis that's required.

[slash112]

i watched the end of this, i missed the start i was so annoyed, but i think its supposed to be repeated soon, but i dont know when. i started watching at the bit where they were saying about using maths to determine what dreams mean, then it went on to stephen laberge. i dont suppose you know when its repeated xei?

[Xaqaria]

Well yes, obviously I realise from personal experience that people wake up if there is a loud noise. It doesn't take a loud noise, only a dangerous sounding one. People can sleep through loud noises but anything that sounds threatening will wake a person up. A good example is the mother of a friend of mine. He had a tendency to sleep walk. When I would stay over at his house, the dog might bark and she would sleep through it, but just someone creeping as quietly to the bathroom would alert her to wake and check if it was him sleep walking out of the house. We don't need to use links between memories to perform basic tasks like finding food. Why does lack of sleep for about a week cause death? We don't need to use new memories to perform life functions. What makes you think we don't need to use links between memories to perform basic tasks? Consider the example of eating a handful of berries and then puking your guts out 3 hours later. Without those memories being linked through cognitive processes, you will continue to eat poisonous berries. Also, staying awake for a week doesn't cause death. The record is currently 14 days 13 hours, with no lasting physical effects. Why though? We do we need to be unconscious to do this? And why does lack of sleep have far worse consequences than just an inability to perform more complex cognitive tasks? What are the worse consequences? All cognitive tasks are fairly complex, and the entire body is controlled by the brain. When their is a break down in the natural cycle and therefore normal systematic processes of the brain, the entire body suffers. Again, I don't see how unconsciousness is required for this. It's a simple metabolic activity of cells, not a complex problem involving the cognitive function of neural network. Why can't it do this during normal resting periods? This alone doesn't really explain any of the features of sleep. Several reasons. The functions of the brain use valuable resources that could be more efficiently used for faster healing if the brain is partially shut down. It is fairly well known that one burns more calories while awake. Also 'normal resting periods' (which to me means sleep but I guess we are taking it to mean resting while awake) do not typically last long enough to have any real effect on the healing process.

[Alric]

Actually there is a very basic reason to sleep, and its based on food. When you sleep, you use less energy. If you use less energy, you need less food to survive. Just look at diurnal and nocturnal animals. Its very common for an animal to either sleep through the day, or sleep through the night. The reason could range from having poor night vision, because of the temperature difference, or because your food source is more active in one period. An example, you live in the desert as it gets really hot during the day. Why hunt during the day when your body will over heat and you are unlikely to find food? You wouldn't, which is so many desert creatures sleep through the day and hunt only during the night, when its cool and food is easier to find.

[illidan]

I believe sleep is beneficial to humans in many ways, all of which combined provides for an evolutionary advantage. We sleep at night because there are a lot of activities we cannot perform (only with great difficulties) when it is dark (e.g. hunting). Our body can use this time to perform tasks that are more difficult to do when we are active, e.g. healing. I believe there are many other things our body does when we are asleep. There is one little theory I have had for a while now. I believe that humans being a social animal could actually be an evolutionary disadvantage unless it possesses the proper attributes countering the bad effects of being social. Being social usually means spending more time thinking about others rather than yourself. But I think it is important to think about oneself to reflect one's own character and one's own actions. That's why I think every human needs a certain amount of alone-time/solitude and I believe one of the functions of sleep is to ensure that one has enough of it.

[DeathCell]

Without sleep our bodies will deteriorate along with our minds. The day and night cycles aren't their by chance.

[ThreeLetterSyndrom]

Again, I don't see how unconsciousness is required for this. It's a simple metabolic activity of cells, not a complex problem involving the cognitive function of neural network. Why can't it do this during normal resting periods? This alone doesn't really explain any of the features of sleep. Why not? because your consciousness and your unconsciousness can have an effect on every part of the body. I know a guy (he's my boss) who's had cancer. The doctors said he had about 0.1% chance to survive. He'd die in a year, at most, even with meds. It's now 3 years later, and he is walking around free, happy and laughing. And all he did was say: "I don't need your numbers." With solely the power of the mind (and meds, of course ), he conquered this cancer and has stayed clean for 3 years. Cancer is mutation of DNA. The cell still reproduces, but now is malevolent. You can look it up somewhere. Mutation of DNA, destroying of these mutated cells, it's all metabolic process. And you're saying that the mind cannot have an effect on that? You're mad.

[Xei]

You haven't studied biology, have you? How can your consciousness intentionally cause the breakdown of malevolent cells when the body can't even tell which cells are malevolent? Your mind has nothing to do with the immune system.

[ThreeLetterSyndrom]

You haven't studied biology, have you? How can your consciousness intentionally cause the breakdown of malevolent cells when the body can't even tell which cells are malevolent? Your mind has nothing to do with the immune system. Google hysteria.

[Xei]

Mhm. There wasn't anything about any medical effects.

[ThreeLetterSyndrom]

most commonly on an imagined problem with that body part (disease is a common complaint). See also Body dysmorphic disorder and Hypochondriasis. http://en.wikipedia.org/wiki/Hysteria It's the first link on google. It does have physical effects. As for medical effects, see the Placebo effect.

[DuB]

Your mind has nothing to do with the immune system. By now there is an absolute wealth of research showing that the relationship between physical health and mental health is bi-directional. Case in point: the placebo effect. (Although the empirical support reaches far beyond this long-recognized and well-documented phenomenon.) Now, clearly mental interventions are no substitute for drugs and medical procedures, but the assertion that "Your mind has nothing to do with the immune system" is entirely at odds with modern health science.

[YULAW]

Not to mention the body's hormonal response to mental stress alters immune system function in various ways.