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Comment by raducu | Hacker News Reader

Why can't the brain do the clensing while we are awake?

So why doesn't the brain do this sort of housekeeping all the time? Nedergaard thinks it's because cleaning takes a lot of energy. "It's probably not possible for the brain to both clean itself and at the same time [be] aware of the surroundings and talk and move and so on," she says.

https://www.npr.org/sections/health-shots/2013/10/18/2362118...

If you want more info than that, it's easy to google this question and come up with other articles.

Is it known what mechanism triggers the cleaning process at the cellular level? Is there some molecule/hormone that says "I'm asleep now, go clean up the mess", and does it happen in the entire brain simultaneously or is it done in phases in different parts of the brain?

It seems to be driven by norepinephrine levels,[1] which seems like it it might have some interesting implications.

>Our analysis showed that norepinephrine also is a key regulator of glymphatic activity and that norepinephrine might be responsible for suppression of glymphatic during wakefulness. [1]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4636982/

Not sure, but reminds me of how garbage collectors must sometimes pause application threads.

My oversimplified guess is that cleansing while awake would impair normal function somehow.

I suspect it would feel something like daydreaming or regular dreaming, or experiencing a serious mental disorder.[1][2]

[1]https://www.medicalnewstoday.com/articles/319846#The-seat-of...

[2]https://www.mdlinx.com/article/what-are-lucid-dreams-and-are...

Probably just a one-line change. Can we sneak that in the next release?

Birds that fly long distances sleep with half their brain at a time so they don't fall out of the sky to their doom into the ocean below.

https://www.audubon.org/news/scientists-finally-have-evidenc...

In some old Western movie -- as in The Wild West with cowboys -- there was a Samurai character who claimed to sleep while they marched somewhere.

I have no idea how to look up a citation supporting the idea that this was a real phenomenon, but I did find this article that I kind of skimmed and I don't think it says anything on the topic I want a citation for and additional googling gets me absolutely nothing of value:

https://www.bbc.com/future/article/20160506-the-japanese-art...

Do those birds not have a similar division of labor to us in the brain, where each side of the body is controlled by the opposite side of the brain?

Once, while in the military on a three day exercise with little/no sleep I fell asleep while running in formation (returning from an exercise). I woke up three hours later when the instructors drug us out of our tents.

I won't swear that I was "truly" asleep, but I have no memory of the last three miles of that run, nor of climbing into the fartsack.

Because it didn't evolve to do so?

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