Mind & Body

Microsleep Happens Without You Even Knowing It

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Microsleep is exactly what it sounds like: a tiny sleep, or, to put it more precisely, a several-second episode of unconsciousness. Here's the crazy thing. You don't always notice when it happens.

How Does Microsleep Work?

Usually, you're either awake or asleep — emphasis on usually. The truth is that sleep is more of a spectrum than an all-or-nothing condition. Part of your brain can stay awake while you sleep if, for instance, you're sleeping in unfamiliar surroundings. Likewise, part of your brain can fall asleep while you're awake if you're pulling an all-nighter.

"[W]hen we are sleepy, we make mistakes, our attention wanders and our vigilance goes down," explains Dr. Chiara Cirelli of University of Wisconsin — and that's because our brains are already partially asleep.

When people go beyond sleepy, though, they can lose consciousness for a few seconds in a phenomenon known as "microsleep." This occurs most often in a sleep-deprived brain during monotonous tasks like driving, listening to a lecture, or watching a movie. Sometimes when this happens, you know it, because the movement of your chin falling to your chest jerks you awake. (This can be a godsend if you really have to stay awake — it's likely to get your adrenaline pumping and prevent another bout of microsleep.) Often, though, you don't have the faintest inkling you microslept at all.

Can I Really Nap Without Noticing?

Absolutely. "Sleep has to last beyond a minute or two for your brain to remember it," says Prof. Jim Horne, director of Loughborough University's Sleep Research Centre.

Don't just take his word for it, though. There's proof. For a study published in the January 2014 issue of Human Brain Mapping, researchers had well-rested participants track a randomly moving target on a computer monitor with a joystick for just under an hour. The continuous attention this required led to a whole lot of microsleep: participants experienced 79 microsleep episodes, on average, lasting up to six seconds each. In studies like these, participants usually recall having been wide awake the entire time. That's probably because during microsleep, it's not your whole brain that loses consciousness. It's often just a single region, or even a handful of neurons.

As you might expect, experiencing microsleep during any task comes with a dip in performance. That's why it's especially dangerous to drive or operate heavy machinery when sleep deprived — which people do more than you might guess. A recent survey found that 1 in 25 drivers had fallen asleep at the wheel in the past 30 days. Between 2011 and 2015, there were more than 4,000 car crashes in the U.S. related to drowsy driving. Get your rest!

For a research-backed way to sleep better, check out "The Science of Sleep: What It Is, How It Works, and Why It Matters" by Walter B. Mendelson. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

What Would Happen If You Stopped Sleeping?

Sleep is pretty important to life.

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Key Facts In This Video

  1. People who sleep 6–8 hours per night tend to live longer. 00:23

  2. In some cases, going three days without sleep has resulted in hallucinations. 01:18

  3. Fatal familial insomnia is a rare genetic disease that causes insomnia, dementia, and death. 02:12

Written by Mae Rice April 24, 2018

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