Harmful proteins in the brain. The brain uses sleep during the night to eliminate residual toxins accumulated during an intellectually demanding day, say the authors of an American study.
American researchers believe that the "waste disposal system" is one of the fundamental reasons justifying the existence of sleep.
Their study, published in the journal Science, pointed out that brain cells shrink during sleep to enlarge the spaces between neurons and to allow cerebrospinal fluid to clear the brain.
They also suggest that the failure of "washing" certain toxic proteins could play a decisive role in triggering brain diseases.
A major question for sleep researchers is this: "Why do wild animals sleep, given their sleep makes them vulnerable to predator attacks?".
Sleep plays an important role in fixing memories in the brain and in the learning process, but researchers at Rochester University in the United States believe that "household chores" could be one of the main reasons for sleep.
Harmful proteins in the brain
"The brain has only limited energy at its disposal and it seems that it has to choose between two different functional states – awake and conscious or asleep and about to be cleansed," explained doctor Maiken Nedergaard.
"You can think of sleep as organizing a party at home. You can either talk to the guests or clean the house, but you can't do them both at the same time. ”
The study of American researchers is based on the discovery, made in 2012, of the fact that the brain has its own network of "drainage pipes" – known as the "glimfatic system" – that transports the residual material outside the brain.
Scientists, who have been monitoring the brains of mice, have noticed that the glyphimatic system becomes 10 times more active when rodents sleep.
The cells in the brain, probably the glial cells that keep the nerve cells alive, shrink during sleep. This increases the interstitial space, those spaces between the brain tissues, allowing the pumping of a greater amount of fluid to wash the toxins.
Many diseases that lead to brain cell death, such as Alzheimer's and Parkinson's, are characterized by accumulation of damaging proteins in the brain. The authors of the study believe that problems arising in the functioning of the brain cleansing mechanism could lead to such diseases.