we’re increasingly realizing that sleep is one of the most essential things we need

to be functioning, healthy human beings.

And new research looks into how sleep helps us maintain clean brains, but what does that mean?

And why is it that important?

Well to understand this latest news, we have to go back to 2013, when a study of mouse brains

found that while those furry, little rodents slept, neurotoxic waste products got swept away.

Some kind of cleaning crew comes in overnight and gets rid of built up stuff like beta amyloid,

that sticky peptide that can aggregate into plaques and disrupt brain function.

Amyloid plaques are highly associated with the occurrence of diseases like Alzheimer’s,

and the ‘amyloid hypothesis’ suggests that amyloid plaques could be the primary

cause of that devastating disease.

So it’s real nice that your brain can get rid of it while you sleep.

That 2013 study saw an interesting relationship.

While the mice slept, their glymphatic systems opened up.

This let in a big wash of cerebrospinal fluid, or CSF, which seemed to clear these waste

products away.

And just so you know, CSF is a watery, clear substance that surrounds your brain and spinal

cord and acts kinda like a little cushion to protect your brain, and provide it with nutrients.

A team at Boston University took this 2013 finding and wanted to know exactly how.

In this new study they published in Science, the researchers delved into what about sleep

was so special.

Why did a sleep state in particular allow for these changes in the brain?

The team got human participants to fall asleep inside an fMRI machine, which is seems like

quite a feat in itself, and which let the team measure both the blood oxygen levels in the participants’

brains and show the flux of cerebrospinal fluid.

They also measured the electrical currents in subjects’ brains using an EEG cap.

The results gave the team a pretty clear answer, one that came in waves.

We’ve been finding out more over the past several years about the phases our brains

go through while we sleep, and how those phases are essential to information processing and

memory formation.

And it turns out, it’s not just during rapid-eye-movement or REM sleep that our brains are consolidating

information and committing it to our long-term memory, but they’re doing it during nonREM too.

And in humans, these two states of sleep—REM and nonREM—alternate throughout the night.

Non-REM sleep is divided into 3 stages, and that third stage is our deepest state of sleep,

called slow wave sleep.

During slow wave sleep, electrical activity slows down and syncs up.

So our neurons start to fire in sync with one another at quite a slow frequency that

neuroscientists call delta waves.

And while slow wave sleep has been shown to be essential to memory formation, this latest

study is the first to demonstrate exactly how those slow waves keep our brains clean

and healthy.

From all of their many measurements, the Boston team saw that during slow wave sleep, the

brain was actually being washed by waves of cerebrospinal fluid,

like a free nighttime spa for your brain.

See, when neurons start to fire in sync they’re all electrically active at the same time,

and that means there’s empty time in between activity.

When those neurons aren’t firing, they need less oxygen, so less blood is flowing to the

brain.

But cerebrospinal fluid comes in and fills in that extra space!

So this pattern in CSF flow is intrinsically linked to neuron firing.

The neurons light up, the neurons go dark, the CSF comes in, the CSF goes out.

It’s all very relaxing.

This study not only found a direct relationship between electrical activity in the brain and

this CSF cleansing mechanism, but also confirmed that an increase in CSF is linked to increased

clearing of neurotoxic waste products like beta amyloid.

This indicates that sleep—and slow wave sleep in particular—is essential to clearing

out all the gunk in your brain.

Your brain garbage, if you will.

And the thing is—we still don’t understand a whole lot about neurodegenerative diseases

like Alzheimer’s.

We know that we see these build-ups of amyloid plaques, we know that a protein called tau

causes damage to neurons, but so far, our forays into developing treatments that target

those variables haven’t been very fruitful.

So improved understanding, like this new study provides of how the brain clears out toxic

buildup naturally, could help us combat neurodegenerative diseases

in novel and innovative ways.

Plus, it’s just huge inspiration to get better sleep, and more of it.

I’m gonna get right on that.

If you want to learn more about Alzheimer’s, check out this video here from our series

Sick, and make sure you subscribe to Seeker for all your neuroscience updates.

If you have another brain question in mind that you want us to cover, let us know down

in the comments below and as always, thanks for watching.

I’ll see you next time.