Matthew Walker

It's low level brain damage.

And sleep is therefore your sanitary salvation to combat that biochemical cascade.

So in other words, a better way of putting it would be sleep is the price that you pay for wakefulness, right?

in some ways.

And I think there was a recent controversial study that came out in 2022 or 2023, and they actually suggested quite the opposite.

They said using their specific imaging methods

they found that the sort of clearance, the amount of cerebrospinal fluid, which is what washes through the brain to cleanse the toxins, the rate of that flow of cerebrospinal fluid was highest during wakefulness and lowest during deep non-REM sleep, the exact opposite of what others have found.

Now, I think the defendants of the glymphatic sleep-dependent hypothesis pushed back and said, well, if you look at their imaging methods, firstly, they're non-standard.

Secondly, they were measuring the cerebrospinal flow in an artificial way because they were actually perfusing solution through the brain rather than naturally letting it flow.

And therefore, the artificial forcing of fluid changed the prototypical result you would get.

And they also argued that the essentially kind of like the sampling rate.

So how quickly are you taking snapshots of the cerebrospinal fluid flow?

Those were different and they were probably missing some of the sleep dependent slow oscillations that seemed to sort of drive that pulsatile flow.

Honestly, I think that paper was still very well done.

And I still think there is... Right now, I would still cleave to the majority of overwhelming evidence, considering it's not just from one group in one species, but across multiple species, multiple groups.

And I think it's...

it's nevertheless a weight of burden that is pushed back.

And my sense right now, I used to think, and cleave to the notion that it was a sleep expressly selective process.

Now, I don't think that that's the case anymore.

I think that the glymphatic system is a dynamic system, but it's always looking for the opportunity to go into cleansing mode.