Sleep Is the Ultimate Brainwasher 210
sciencehabit writes "Every night since humans first evolved, we have made what might be considered a baffling, dangerous mistake. Despite the once-prevalent threat of being eaten by predators, and the loss of valuable time for gathering food, accumulating wealth, or having sex, we go to sleep. Scientists have long speculated and argued about why we devote roughly a third of our lives to sleep, but with little concrete data to support any particular theory. Now, new evidence (abstract, full text paywalled) has refreshed a long-held hypothesis: During sleep, the brain cleans itself."
During sleep, the Cerebrospinal fluid fills channels in the brain, collecting waste products. It uses a lot of energy, leading to the hypothesis that the brain can't clean up waste while also processing sensory input.
Extremely variable sleeping periods (Score:5, Interesting)
I wonder how well this accounts for the extremely variable sleeping periods of various animals? See http://faculty.washington.edu/chudler/chasleep.html [washington.edu] .
Re:Obvious question (Score:5, Interesting)
Many neurological diseases—from Alzheimer's disease to stroke and dementia—are associated with sleep disturbances, Nedergaard notes. The study suggests that lack of sleep could have a causal role, by allowing the byproducts to build up and cause brain damage. "This could open a lot of debate for shift workers, who work during the nighttime,” Nedergaard predicts. "You probably develop damage if you don’t get your sleep."
Beta amyloids are specifically mentioned, those make up the plaques that are found in Alzheimers.
Worth pointing out that the effects of sleep deprivation are well known, this is simply trying to explain HOW those symptoms occur.
Re:Obvious question (Score:5, Interesting)
I went almost a week without sleep and it definitely screws you up. On day 5, I was hallucinating that there were people around me and seeing things out of the corner of my eye. I had a constant fuzzy feeling and had very little energy. It was an interesting experiment and it was not easy to get to sleep. It took me over a month to get back into a proper rhythm.
Evolutionary pressure to not sleep? (Score:3, Interesting)
A higher order species that has brains that can "cleans" itself without requiring sleep would have so much evolutionary advantage that they would rapidly take over the entire planet (sort of like flowering plants). Why hasn't 3+ billion years of evolutionary produced such a species?
Re:Obvious question (Score:5, Interesting)
The second point, you're responding to a new hypothesis put forth by the researcher based on the current findings. The current findings are only that it's cleared out during sleep, not saying that low neural activity is the reason. That part is just speculation. I'd suggest it's probably more complex, that the glial cleaning activity causes abnormal neuronal activity when it's in that mode. Perhaps the reason it happens during sleep is because if it happened while you were awake, you'd hallucinate, act even more irrationally and irregularly etc. Perhaps that's part of the reason that dreams are so bizarre. Pure speculation.
I've seen the defragging happen (Score:4, Interesting)
Dreams are calibration patterns (Score:2, Interesting)
I'm still convinced that dreams are artifacts of calibration routines, and only race conditions allow you to remember them.
Re:Evolutionary pressure to not sleep? (Score:4, Interesting)
There's advantages and disadvantages to every evolutionary option. It's not clear that not sleeping is a very large advantage.
Sure, it means being active for an additional 8 hours a day. But being active also means needing more food. Being active all night in a time before artificial light means more injuries. It also means missing out on the social effects of sleeping - "sleeping together", even without sex, reinforces relationships.
Re:Obvious question (Score:4, Interesting)
Not that I remember. It was rough for the first two days but by day 3 I just didn't feel like sleeping anymore. I watched TV or played games all night until people were alive again and continued on with my day. I was exhausted though both mentally and physically somehow. The day after I finally slept was probably the worst. Still no energy but now coupled with nausea and no appetite. It was like a withdrawal of some sort... not recommended :P
I already kick into REM sleep really fast as it is so when I was not sleeping, I would sort of dream while being awake. It's a crazy experience for sure.
Re: Like so many computer programs... (Score:5, Interesting)
Re:Extremely variable sleeping periods (Score:5, Interesting)
When I was in medical school, I adopted a pattern of going to sleep for 4 hours in the early evening, waking up at midnight and studying for 4 hours then back to sleep for a few hours. This seemed to work well and improved my grades.
Re:Extremely variable sleeping periods (Score:5, Interesting)
Cats must have very clean brains!?
It's hard work running the world and performing the duties of an Egyptian god.
Every cat knows that the human race is merely there to serve them and that's a huge responsibility.
And then there's scripting all those funny cat videos just to keep us humans (their pets) amused.
No wonder cats are tired out most of the time.