If you were asked to take out the trash, chances are you would do it while you were awake. But if you asked your brain to take out the trash it would wait until you were asleep. That’s because researchers at Northwestern University found deep sleep has the power to clear waste from the brain.
The waste that is removed may include toxic proteins that could potentially lead to neurodegenerative disease, which is yet another confirmation of the importance of getting a good night’s sleep.
Researchers studied the brain activity and behavior of fruit flies, which closely resemble humans in some areas. They reported their findings in the journal Science Advances.
"Waste clearance could be important, in general, for maintaining brain health or for preventing neurogenerative disease," said Dr. Ravi Allada, senior author of the study. "Waste clearance may occur during wake and sleep but is substantially enhanced during deep sleep."
Fruit flies are often used for research on sleep, circadian rhythm and neurodegenerative diseases despite the fact they are very different from humans. The reason is the neurons that govern the flies’ sleep-wake cycles are very similar to that of humans.
During a fruit fly’s deep sleep phase, which is called proboscis extension sleep because their proboscis, or snout, extends and retracts, the pumping action has been observed to clear fluids from the brain.
"This pumping motion moves fluids possibly to the fly version of the kidneys," Allada said. "Our study shows that this facilitates waste clearance and aids in injury recovery."
When the flies had their sleep impaired they were less able to clear a die that was injected for tracking purposes. It also made them more susceptible to traumatic injury.
Allada believes this study sheds more light on the waste removal process in the brain and emphasizes why quality sleep is so important.