3 ms·

I find that even a quite brief nap (on the order of one to three minutes) is still tremendously refreshing. Is this enough time for this fluid dynamic under stu

I find that even a quite brief nap (on the order of one to three minutes) is still tremendously refreshing. Is this enough time for this fluid dynamic under study to gear up and get some flushing done ? Or would it be some other mechanism.

burning_hamster 2y ago
Some animals get most if not all of their sleep through microsleep [1]. So whatever mechanism "refreshes" the brain, it can work on short time scales. The switch in brain firing dynamics from wake to sleep (NREM) is very fast -- on the order of one to a few seconds. People in team Nedergaard argue that it is the rhythmic neuronal activity during sleep that promotes fluid flow (though to be fair, some argue its arterial pressure). So their answer to your question would be yes, that should be enough time to enhance fluid flow (fluid is flowing all the time, the question debated by scientists is, whether is it being enhanced during sleep). [1] https://www.science.org/doi/10.1126/science.adh0771 https://www.science.org/doi/10.1126/science.adh0771
- HPsquared 2y ago
  I wonder how much of an effect physical brain size has on this. Square-cube law and all that. Bird brains are famously small (though highly efficient).
- elric 2y ago
  I don't think that translates to humans. Sleep disturbances like the micro-arousals triggered by sleep apnea absolutely ruin lives, way before lack od oxygen becomes a problem. Arousals destroy sleep architecture. Humans cannot thrive on microsleep.
theGnuMe 2y ago
I've felt my brain flush, dunno if anyone else has.
- bgroat 2y ago
  For me it feels more like a rinse. My brain feels cloudy/covered in junk. Then I rest and can kind of feel all the crap being hosed away
  - wildpeaks 2y ago
    Same, I can even feel which general areas don't feel rinsed enough when I don't get enough sleep, although I can't be sure if it's the accurate location or merely the position the sensor data gets reported to.
- earslap 2y ago
  Sometimes I hear a 10-20hz pulsing sound (so pretty fast, chirping sound) emanating from around my brainstem / back of neck at the level of my ears and a slight feeling of some liquidy movement inside. I always thought it was connected to CSP movement but maybe it isn't. But if it isn't I can't see what else it can be as it happens when I'm completely stationary.
endoblast 2y ago
Agreed. For me turning over in bed during a lie-in also feels immensely refreshing and I now do it quite consciously. It may be nothing to do with cerebrospinal fluid but I do like to attribute it to the brain's wash cycle.
- elric 2y ago
  I don't think the brain relies on a spin cycle like a washing machine, but maybe it's not so far fetched. Walking and being generally active helps the body "pump" lymph.
  - euroderf 2y ago
    My go-to analogy is a movie theater. Once in a while you have to break out the firehouse and wash down all the accumulated popcorn, gummy bears, dried-up soda pop, and tracked-in dirt. And no, it cannot all be recycled to make new movietime snacks.

burning_hamster 2y ago

Some animals get most if not all of their sleep through microsleep [1]. So whatever mechanism "refreshes" the brain, it can work on short time scales. The switch in brain firing dynamics from wake to sleep (NREM) is very fast -- on the order of one to a few seconds. People in team Nedergaard argue that it is the rhythmic neuronal activity during sleep that promotes fluid flow (though to be fair, some argue its arterial pressure). So their answer to your question would be yes, that should be enough time to enhance fluid flow (fluid is flowing all the time, the question debated by scientists is, whether is it being enhanced during sleep). [1] https://www.science.org/doi/10.1126/science.adh0771 https://www.science.org/doi/10.1126/science.adh0771

HPsquared 2y ago
I wonder how much of an effect physical brain size has on this. Square-cube law and all that. Bird brains are famously small (though highly efficient).
elric 2y ago
I don't think that translates to humans. Sleep disturbances like the micro-arousals triggered by sleep apnea absolutely ruin lives, way before lack od oxygen becomes a problem. Arousals destroy sleep architecture. Humans cannot thrive on microsleep.

theGnuMe 2y ago

I've felt my brain flush, dunno if anyone else has.

bgroat 2y ago
For me it feels more like a rinse. My brain feels cloudy/covered in junk. Then I rest and can kind of feel all the crap being hosed away
- wildpeaks 2y ago
  Same, I can even feel which general areas don't feel rinsed enough when I don't get enough sleep, although I can't be sure if it's the accurate location or merely the position the sensor data gets reported to.
earslap 2y ago
Sometimes I hear a 10-20hz pulsing sound (so pretty fast, chirping sound) emanating from around my brainstem / back of neck at the level of my ears and a slight feeling of some liquidy movement inside. I always thought it was connected to CSP movement but maybe it isn't. But if it isn't I can't see what else it can be as it happens when I'm completely stationary.

endoblast 2y ago

Agreed. For me turning over in bed during a lie-in also feels immensely refreshing and I now do it quite consciously. It may be nothing to do with cerebrospinal fluid but I do like to attribute it to the brain's wash cycle.

elric 2y ago
I don't think the brain relies on a spin cycle like a washing machine, but maybe it's not so far fetched. Walking and being generally active helps the body "pump" lymph.
- euroderf 2y ago
  My go-to analogy is a movie theater. Once in a while you have to break out the firehouse and wash down all the accumulated popcorn, gummy bears, dried-up soda pop, and tracked-in dirt. And no, it cannot all be recycled to make new movietime snacks.