Struggling to concentrate? Maybe your brain is being washed
Jenny Evans/Getty Images
We all know that it can be difficult to concentrate when you are sleep deprived, but why does this happen? It could be because your brain is trying to refresh itself, causing momentary lapses in attention.
During sleep, the brain performs a flushing cycle, in which cerebrospinal fluid (CSF) is repeatedly flushed into the organ and out again at the base of the brain. This process removes metabolic waste that has built up during the day – and that would otherwise damage brain cells.
Laura Lewis of the Massachusetts Institute of Technology and her colleagues wondered whether attention lapses, which often occur after sleep deprivation, might be due to the brain trying to catch up with the flushing when it is awake.
To explore this idea, the researchers asked 26 people aged between 19 and 40 to get a good night’s sleep that made them feel well-rested, then kept them awake 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 performed two tasks. During these tests, participants had to press a button whenever they heard a certain tone or saw a cross on a screen turn into a square. This happened dozens of times over the course of 12 minutes.
As expected, participants failed to press the button significantly more often when they were sleep-deprived compared to when they were well-rested, meaning that lack of sleep made it harder to focus.
Crucially, when the researchers analyzed the brain scans, they found that the participants lost focus about 2 seconds before the CSF was flushed out of the base of their brain. Furthermore, CSF was withdrawn into the brain approximately 1 second after attention was regained.
“If you think of the brain cleansing process as a washing machine, you have to put the water in and then slosh it around and then drain it out, and then we’re talking about the sloshing part that occurs during these inattentions,” Lewis says.
The results suggest that when the brain can’t clean itself during sleep, it does when you’re awake, but that impairs concentration, says Lewis. “If you don’t have these waves [of fluid flowing] at night, because you’re kept awake all night, your brain kind of starts to sneak them in during the day, but they come with this cost of attention.”
Exactly why this cleansing process leads to a loss of attention remains unclear, but pinpointing the brain circuits responsible may reveal ways to reduce the cognitive effects of sleep deprivation, Lewis says.
Subjects: