Sleep is extremely important for both the body and the brain, especially as researchers now have an idea of what happens to the mammalian brain after chronic sleep deprivation--and it's not looking good.

How the Brain Eats Itself

According to a report by ScienceAlert, sleep is more than just a way for the body to replenish energy levels, but it also helps the brain clear itself of toxic byproducts from the day's activities.

This same process also happens with the sleep-deprived, but it gets overboard, and the result is the brain literally eats itself, causing damage that even catching up on sleep may not be able to reverse.

The brain is cleared by two types of glial cells, which are often deemed the "glue" of the nervous system.

The first type is known as microglial cells responsible for the process of phagocytosis--a word that means "to devour" in Greek--and clears out old and worn out brain cells.

Meanwhile, the second is known as astrocytes, and its job is to prune unnecessary synapses in the brain to help it refresh and to reshape its wiring, but due to chronic lack of sleep, the astrocytes increase their activity and begin devouring portions of synapses, much like what microglial cells do.

This process is known as astrocytic phagocytosis.

"We show for the first time that portions of synapses are literally eaten by astrocytes because of sleep loss," Bellesi said in an interview with NewScientist.

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The Research From 2017

Researchers from the Marche Polytechnic University in Italy, headed by neuroscientist Michele Bellesi, conducted the study in 2017 that led to this discovery using four groups of mice with varying degrees of rest.

One group got six to eight hours of sleep, meaning they are well-rested, while another group is periodically woken up.

On the other hand, one group of mice was kept awake for an extra eight hours, making them the sleep-deprived group; the last one was kept awake for five days straight, making them chronically sleep-deprived.

The team then began imaging their brains and compared them, looking for astrocyte activity.

Increased Astrocyte and Microglial Activity

Based on their research, the scientists found astrocytes in 5.7% of the well-rested group's synapses, while the spontaneously awake mice had it in 7.3% of their synapses.

For the sleep-deprived and chronically sleep-deprived group, the astrocytes have significantly increased their activity and began eating parts of the largest synapses, which tend to be the most heavily used ones and the oldest ones.

They could be found in 8.4%, and 13.5% of the synapses of the sleep-deprived and chronically sleep-deprived groups, respectively.

Furthermore, the last group's microglial activity has also increased, which could be worrying as it was linked to various forms of neurodegeneration, including Alzheimer's.

"Only chronic sleep loss activates microglia cells and promotes their phagocytic activity ... suggesting that extended sleep disruption may prime microglia and perhaps predispose the brain to other forms of insult," the researchers wrote.

The paper was published in the Journal of Neuroscience.

For now, scientists are still uncertain whether the same process happens in the human brain.

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Written by: Nhx Tingson

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