Your brain cleans itself while you sleep, and scientists finally saw it happen
Sleep is vital for many reasons, not least because it makes you far more tolerable than you actually are. But there’s a more important long-term health reason why 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 while now, but researchers who have published their findings in two new studies published by the University of Oulu in Finland finally got to see what it looks like while 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 switches to a state where fluids pulsate, swirl and circulate more efficiently, likely helping to clear waste.
They finally saw the brain cleaning itself while we sleep
While 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 in your waking hours shuts down and chaos reigns. Fluid movements become bidirectional, especially in parts linked to sensory processing and cognition. Basically, the brain stops prioritizing specific hotspots and starts washing everything more evenly.
Researchers found that the slow, rhythmic pulses of your brain fluids while you sleep, driven by blood vessel activity, breathing and shifts in electrolytes, tend to occur much more quickly. These pulses remove cerebrospinal fluid and carry ions such as sodium and potassium that appear to generate waves that push fluid through the brain tissue.
It’s not a literal deep clean, like the one you give your sofa once a year in deep horror. It’s closer to spraying your car down with a hose when it’s gotten a little muddy.
Perhaps the biggest breakthrough here is not the observation of cerebrospinal fluids scrubbing down into our thoughts, but the technology that made that observation happen in the first place. To do so before required tracing cerebrospinal 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 non-invasively, in finer detail and in somewhat close to real time.
Researchers believe that the same method can be used for e.g. to monitor or even treat neurodegenerative diseases such as Alzheimer’s, where the brain’s self-cleaning functions may be impaired.
