29 Comments

Something else that radically minimizes movement is being in the womb for nine months. How would the brain get stimulation when the body is stuck in a sack of warm, salty water for all that time? By dreaming?

I think the real idea with sleep is to allow the brain to "drop" weak connections. Todays events might otherwise have too much influence on long-term memory. Current behaviour versus long-term learnt behaviour might have very different neuronal growth and pruning optimums, so perhaps when awake we operate in mode-A, but there is no mode-B - instead we do the cognitive version of fasting, and allow weak long-term connections built in the present day to fade. A big workaround. Perhaps if you have a traumatic event, you should sleep for a week?

Btw, a nice doco about the first nine months and it's health outcomes - http://www.youtube.com/watc...

Expand full comment

In Dragons of Eden, Carl Sagan posits that sleep may have evolved in our nocturnal mammalian ancestors in part as away for them to stay quiet and out of sight of reptilian predators on the hunt by day.  Not sure how plausible it is, but it's an interesting premise.

Expand full comment

Consider that if the brain is not moving the body in some way, it has no purpose. The sleeping state must as a consequence, atrophy the brain. "Use it or lose it".

Shouldn't short sleepers, then, be smarter than normal or long sleepers?

Expand full comment

Is the apparently common phenomenon of sleep walking some evidence against the hypothesis that human sleep's primary function is to save energy by immobilizing the organism.

Expand full comment

Ioannidis says that the highest impact journals are wrong at a high rate, since they differentially publish the sexiest, most counterintuitive (and more likely false) findings and try to scoop everyone else.

An individual article can advance an idiosyncratic thesis, while wikipedia is more conservative (as a result of the collaborative structure).

Expand full comment

According to neuroscientist Daniel Wolpert, all brains are for movement. http://www.bettermovement.o...Sleep radically minimizes movement. During REM sleep the brain is decoupled from the body so that non-vital movement is impossible. What does 'brains are for movement' and the affect of sleep on movement suggest, when considered together?

Consider that if the brain is not moving the body in some way, it has no purpose. The sleeping state must as a consequence, atrophy the brain. "Use it or lose it".

Why does the hindbrain want to atrophy the 'higher' (more recently evolved) areas of the brain? Is the body (including the spinal column and hindbrain) in some sense at war with the mid/forebrain? Does the hindbrain see the mid/forebrain as a parasite, trying to takeover and control the body? Does the sleep-wake cycle indicate a sort of tug-of-war between the body and brain that oscillates between alternating dominance? Does dreaming indicate a brain that is trying to regain control of its disconnected input-output mechanisms by creating virtual reality scenarios with its otherwise unused processing capacity? Does the mid/forebrain retaliate to this state of helplessness by terrorizing the hindbrain with nightmares?

Some forebrains see our future as distinct from the body. The brain wants to rid itself of the body - eventually. Likewise the body with respect to the brain. That is, it wants to put the brain to sleep, in the same sense that vets put terminally sick animals to sleep.

Expand full comment

Regarding the EMs sleeping, I'd expect that the EM clock time would roughly correspond to number of neuron firings (and to the extent to which the firings are asynchronous), and so the sleep would run considerably faster than productive wakeful state by default and for everyone. Any maintenance which is bottlenecked by chemistry, or which is done slowly for sake of chemical efficiency, can run faster in brain emulator. edit: it may well be that the quick sleepers would take same or even longer time to sleep in even modestly optimized emulator.

Unless we are speaking of some far future brain emulations that emulate chemistry atom by atom, there's no reason to expect them to run at constant speedup factor regardless of what you're doing. Many optimizations of the emulator are possible even with very little understanding of how brain works.

Expand full comment

John Maxwell IV : one cherry picked yet solidly verified fact can falsify a theory, but a thousand cherry picked facts that agree with a theory don't confirm it...

Yes, there is huge variation to the length of sleep. There is also huge variation to the duration of the copulation even though the copulation is absolutely essential for sexually reproducing species.

Drawing the conclusion that sleep is for energy conservation is silly. If sleep initially evolves for maintenance, energy conservation during sleep would evolve; if sleep initially evolves for energy conservation, off-line during-sleep maintenance would evolve. Sleep is evolutionarily very very old.

Ohh, other terrible bit in the article is the very approach of thinking of evolution as having intent - implicit in the question "what is the sleep for?". The animal sleep is consistent with both energy conservation and maintenance taking place; furthermore the conclusion is inescapable that some of said maintenance doesn't evolve to happen during active state (and when it has to, parts of neural network shut down for maintenance). One could be very sceptical of maintenance if we couldn't imagine why a data storage and retrieval system (let alone a half chemical one!) could possibly need to undergo periodic off-line processing. Alas, the real-time, on-line processing poses great difficulty to us in our intelligent design of any systems that have similar functionality.

edit: also, bottlenose dolphins are an example of animal that is comparably brainy to humans, but unable to figure a way to negotiate something with us. Or in simple terms, animal that is not living up to it's brain size.

Expand full comment

Place of publication *does* matter in this case, contra Michael Vassar, 'cause the argument is over whether the data is cherry-picked, and the source could be an indicator of this.  It's not obvious to me that either a Science article or a Wikipedia article would be more likely to have cherry-picked data though.

Expand full comment

Whether sleep (or even human sleep) evolved to conserve energy probably has a different answer than whether individual differences in sleep times evolved for that reason--or the converse.

Expand full comment

It might be possible to compute the transformation of a brain from a tired state to a rested state a lot faster than to actually emulate a brain undergoing sleep. In which case, ems will probably have this transformation computed efficiently and skip the sleep.

Expand full comment

Energy conservation is not automatically useful... you may be consuming less energy, but you are not getting much done either, and you are far less effective at survival. Animals aren't battery powered toys, they have work to do just as much as you do. If you got lost in the woods with bears and other huge predators (or worst of all with feral humans), would you seriously want to sleep more than in comfy bed and with only some economical competition?

Expand full comment

Wikipedia contains a lot of references to peer reviewed research, which you can click and read through (I said, starting point). In this particular case, there's an utterly overwhelming body of facts that square very poorly with the pet theory in question. The article you are speaking of, does nothing of this kind - it is a cherry picked selection. The wikipedia on the other hand is not written by some sleep justification conspiracy. It references peer reviewed research without massive cherry picking. For this reason, wikipedia is generally an excellent starting point, especially on topics as common and non-obscure as sleep.

When we see a huge selection of facts that do not contradict someone's pet theory, and assume some good faith, we assume that author has not found contradictory facts. However I am beginning to get a feeling that nowadays you have to assume less and less good faith.

Expand full comment

I am indeed asserting that place of publication determines whether you should pay attention, if that is what you mean.

Dmitryl said Wikipedia was a good place to start, not that it is the arbiter of fact, and he gave specific arguments against the Science article's conclusions. There are no facts in contention here, to justify the degree of authority you assign to source.

Expand full comment

@ Michael Vassar

I am indeed asserting that place of publication determines whether you should pay attention, if that is what you mean. Disagreement expressed on a website where anybody can publish whatever they please tells you nothing about the accuracy of content of a peer-reviewed journal.

As to other Science articles, I made no assumptions at all. If you would like to cite contradicting information from the same or another trustworthy source, that will be a useful contribution. "Let's ignore this article because maybe there was or will be another reliable one that disagrees with it" is not a valid argument.

Expand full comment

This is interesting and relevant...  http://neuroskeptic.blogspo...

Expand full comment