Can’t focus after a bad night’s sleep? Your dirty brain is to blame
Do you have trouble concentrating? Maybe your brain is washing itself
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We all know that it can be difficult to concentrate when you’re sleep deprived, but why does this happen? This may be because your brain is trying to refresh itself, causing momentary lapses in attention.
During sleep, the brain goes through a flushing cycle, during which cerebrospinal fluid (CSF) is repeatedly flushed into the organ and out at the base of the brain. This process removes metabolic waste that has accumulated throughout the day and would otherwise damage brain cells.
Laura Lewis of the Massachusetts Institute of Technology and her colleagues wondered whether lapses in attention, which frequently occur after a lack of sleep, could result from the brain trying to catch up by wiping out while awake.
To explore this idea, researchers asked 26 people aged 19 to 40 to get a good night’s sleep that left them well-rested, then kept them up all night in a laboratory two weeks later.
In both cases, the team recorded the participants’ brain activity using MRI scans the next morning, while they completed two tasks. During these tests, participants were asked to press a button every time they heard a specific tone or saw a cross on a screen turn into a square. This happened dozens of times in 12 minutes.
As expected, participants didn’t press the button significantly more often when they were sleep deprived than when they were well rested, meaning that lack of sleep made it more difficult to concentrate.
Importantly, when the researchers analyzed the brain scans, they found that participants lost concentration about 2 seconds before CSF was drained from the base of their brains. Additionally, CSF was reintroduced to the brain approximately 1 second after attention was restored.
“If you think of the brain cleaning process as a washing machine, you kind of have to put water in it and then circulate it and then empty it out, and so we’re talking about the part that happens during these attention lapses,” Lewis says.
The findings suggest that when the brain can’t clear itself during sleep, it does so when you’re awake, but this impairs concentration, Lewis says. “If you don’t have these waves [of fluid flowing] at night because you stay up all night, your brain then begins to sneak them in during the day, but they come at a cost in terms of attention.
Exactly why this cleaning process leads to loss of attention remains unclear, but identifying the brain circuits responsible could reveal ways to reduce the cognitive effects of sleep deprivation, Lewis says.
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