Researchers have found one big reason sleeping is so important to your brain

Ever have a poor night's sleep and wake up the next day feeling foggy and slower than normal?

That's because when you lose out on sleep, you're not giving your brain the opportunity to clean up after a long day of work.

Researchers found that while you sleep, the brain flushes out dangerous proteins that it makes during the day.

Jeff Iliff, a neuroscientist at Oregon Health & Science University, explained during a Ted Talk that while brains are unusually active during sleep, they're actually going through a beneficial process that makes you smarter, perkier, and healthier during your waking hours.

Inside the skull, the brain sits in a clear fluid that acts as a buffer or cushion, but that's not all it does. During sleep, it flows between the brain cells and acts as the waste removal system of the brain. While the rest of the body's organs have fluid from the blood flowing through them to remove waste, the brain relies on this fluid.

In the GIF below, you can see the liquid - called cerebrospinal fluid - barely moves through the mouse's brain while it's awake. But as soon as the mouse falls asleep, the fluid suddenly rushes into spaces that open up between the cells.

"We discovered when the brain goes to sleep, the brain cells themselves seem to shrink, opening up spaces in between them, allowing fluid to rush through and allowing waste to be cleared out," Iliff said.

When the mouse falls asleep, brain cells called glial cells create channels around the neurons and allow the cerebrospinal fluid to flood in and wash way toxic proteins that build up throughout the day. The fluid than washes the toxins to the liver to be excreted.

We spend roughly a third of our lives asleep, but sleep is a remarkably productive time for our bodies. Sleep helps us form strong memories, allows our muscles, bones, and organs to repair themselves, and helps strengthen the immune system.But this discovery is the first to really show the mechanisms behind sleep's rejuvenating effects on the brain, Iliff said.

"While our body is still and our mind is off walking in dreams somewhere, the elegant machinery of the brain is quietly hard at work cleaning and maintaining this unimaginably complex machine," Iliff says in the talk.

"In your house, if you stop cleaning your kitchen for a month, your home will become completely unlivable very quickly. But in the brain, the consequences of falling behind may be much greater than the embarrassment of dirty countertops. When it comes to cleaning the brain, it is the very health and function of the mind and the body that's at stake."

Watch the full TED talk below.