Zoning Out From Poor Sleep? A New Study Says It Can Be a Good Thing

It turns out that when you’re running low on sleep, your brain is actually working overtime. A new MIT study shows that when sleep deprived, the brain periodically releases cerebrospinal fluid (CSF), the same process that normally happens during deep sleep. Researchers found that these waves of fluid are what’s causing lapses in attention.  

Typically, CSF flow during sleep helps get rid of built-up waste from the day. Scientists wanted to know how it might be affected by sleep deprivation, so they recruited 26 volunteers to perform tasks both during the morning after a good night’s sleep and again when sleep deprived.

The tasks tested reaction times while participants stared at an image of a cross on a screen. The first task asked them to press a button each time they noticed the cross change to a square. The second required a response to a beep sound rather than a visual transformation. 

During the task, subjects wore electroencephalogram (EEG) caps to record brain waves while inside a functional magnetic resonance imaging (fMRI) scanner. The setup allowed scientists to measure blood oxygenation in the brain, the flow of CSF to and from the brain, and the participant’s heart rate, breathing rate, and pupil diameter.  

Unsurprisingly, the sleep-deprived volunteers performed worse. They had slower response times, sometimes not registering a change at all.  

But researchers noticed that CSF was flowing out of the brain at the same time as these attention lapses. And when attention recovered, the fluid flowed back in. They hypothesized that it was a sign of the brain working to catch up on cleansing that should have happened overnight.

“One way to think about those events is because your brain is so in need of sleep, it tries its best to enter into a sleep-like state to restore some cognitive functions,” MIT postdoctoral associate and lead author Zinong Yang says, according to a press release. “Your brain’s fluid system is trying to restore function by pushing the brain to iterate between high-attention and high-flow states.”

And it isn’t just the brain experiencing these psychological changes. Scientists found that pupils constricted around 12 seconds ahead of the CSF flow, and dilated again afterwards. Breathing rate and heart rate declined during attention lapses. 

So, it seems there’s a strong connection between our ability to stay alert and the brain’s recovery process. Without enough sleep you’ll likely be slower to complete daily tasks, but it’s comforting to know your brain is really working to catch you up to speed. 

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