Sleep is vitally important for a lot of reasons, not the least of which being that it makes you way more tolerable than you actually are. But there is a more important long-term health reason you should get as many hours of sleep as you can: sleep is your brain’s chance to scrub itself down, take out the trash, and disinfect everything.
We’ve known this for a little while now, but researchers who published their findings in two new studies released by the University of Oulu in Finland finally got to see what it looks like as it’s happening.
Using a newly developed ultrafast MRI technique, the team tracked the movement of water molecules in the brain in real time. They found that during sleep, the brain shifts into a state in which fluids pulse, swirl, and circulate more efficiently, likely helping clear waste.
They Finally Watched the Brain Clean Itself While We Sleep
While you’re awake, blood flow in the brain is tightly directed toward active neurons, a process called functional hyperemia. But once you fall asleep, all the neat, orderly processing you need to function during your waking hours shuts down, and chaos reigns. Fluid movement becomes bidirectional, especially in parts tied to sensory processing and cognition. In essence, the brain stops prioritizing specific hotspots and starts washing everything more evenly.
Researchers found that the slow, rhythmic pulses of your brain fluids as you sleep, driven by blood-vessel activity, breathing, and shifts in electrolytes, tend to occur much faster. These pulses clear cerebrospinal fluid, carrying ions such as sodium and potassium that seem to generate waves that push fluid through the brain tissue.
It’s not a literal deep clean, like the one you give to your couch once a year in abject horror. It’s closer to spraying your car down with a hose after it gets a little muddy.
Maybe the biggest breakthrough here isn’t the observation of brain fluids scrubbing down our thoughts, but the technology that made that observation happen in the first place. To do that before required tracking brain fluid with invasive contrast agents, so movement would show up on a scan. The new approach uses multiple real-time measurements, such as MRI, EEG, and infrared monitoring, to let researchers observe these processes noninvasively, in finer detail, and in something close to real time.
Researchers think the same method can be used to, say, monitor or even treat neurodegenerative diseases, like Alzheimer’s, where the brain’s self-cleaning functions might be impaired.
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