Sleep Helps to Clean the Brain

Sleep ‘cleans’ the brain of toxins

Brain in a head

The brain uses sleep to wash away the waste toxins built up during a hard day’s thinking, researchers have shown.

The US team believe the “waste removal system” is one of the fundamental reasons for sleep.

Their study, in the journal Science , showed brain cells shrink during sleep to open up the gaps between neurons and allow fluid to wash the brain clean.

They also suggest that failing to clear away some toxic proteins may play a role in brain disorders.

One big question for sleep researchers is why do animals sleep at all when it leaves them vulnerable to predators?

It has been shown to have a big role in the fixing of memories in the brain and learning, but a team at the University of Rochester Medical Centre believe that “housework” may be one of the primary reasons for sleep.

“The brain only has limited energy at its disposal and it appears that it must choose between two different functional states – awake and aware or asleep and cleaning up,” said researcher Dr Maiken Nedergaard.

“You can think of it like having a house party. You can either entertain the guests or clean up the house, but you can’t really do both at the same time.”


Their findings build on last year’s discovery of the brain’s own network of plumbing pipes – known as the glymphatic system – which carry waste material out of the brain.

Scientists, who imaged the brains of mice, showed that the glymphatic system became 10-times more active when the mice were asleep.

Cells in the brain, probably the glial cells which keep nerve cells alive, shrink during sleep. This increases the size of the interstitial space, the gaps between brain tissue, allowing more fluid to be pumped in and wash the toxins away.

Dr Nedergaard said this was a “vital” function for staying alive, but did not appear to be possible while the mind was awake.

She told the BBC: “This is purely speculation, but it looks like the brain is losing a lot of energy when pumping water across the brain and that is probably incompatible with processing information.”

She added that the true significance of the findings would be known only after human studies, but doing similar experiments in an MRI machine would be relatively easy.


Commenting on the research Dr Neil Stanley, an independent sleep expert, said: “This is a very interesting study that shows sleep is essential downtime to do some housekeeping to flush out neurotoxins.

“There is good data on memory and learning, the psychological reason for sleep. But this is the actual physical and chemical reason for sleep, something is happening which is important.”

Dr Raphaelle Winsky-Sommerer, a lecturer in sleep at Surrey University, said: “It’s not surprising, our whole physiology is changing during sleep.

“The novelty is the role of the interstitial space, but I think it’s an added piece of the puzzle not the whole mechanism.

“The significance is that, yet again, it shows sleep may contribute to the restoration of brain cell function and may have protective effects.”

Many conditions which lead to the loss of brain cells such as Alzheimer’s or Parkinson’s disease are characterised by the build-up of damaged proteins in the brain.

The researchers suggest that problems with the brain’s cleaning mechanism may contribute to such diseases, but caution more research is needed.

The charity Alzheimer’s Research UK said more research would be needed to see whether damage to the brain’s waste clearance system could lead to diseases like dementia, but the findings offered a “potential new avenue for investigation”.

Read More Here…


Key Terms…
  • wash away ↔ lavar
  • built up ↔ acumulados
  • waste removal system ↔ sistema de remoção de resíduos
  • shrink ↔ encolher
  • open up the gaps ↔ abrir as brechas
  • wash ↔ (wash something clean) lavar algo
  • failing to clear ↔ a falta de lavar
  • may play a role ↔ pode desempenhar um papel
  • brain disorders ↔ distúrbios cerebrais
  • at all ↔ em primeiro lugar, por qualquer que seja a razão
  • It has been shown ↔ Já foi demonstrado (present perfect)
  • big role ↔ grande papel
  • housework ↔ trabalhos domésticos (qq trabalho de cuidar de coisas)
  • at its disposal ↔ à sua disposição
  • aware ↔ consciente
  • Plumbing ↔ Canalização
  • pipes ↔ tubos, canos
  • imaged ↔ criaram imagens
  • brain tissue ↔ tecido cerebral
  • allowing ↔ permitindo
  • pumped in ↔ bombeado para dentro
  • downtime ↔ inatividade, paralisação
  • housekeeping ↔ (same as ‘housework’)
  • flush out ↔ expulsar (lavar, enxaguar)
  • chemical reason ↔ razão química
  • novelty ↔ novidade
  • the whole mechanism ↔ todo o mecanismo
  • the loss ↔ a perda
  • damaged proteins ↔ proteínas danificadas
  • caution ↔ advertam que
  • charity ↔ caridade


wash away lavar
to clean something by scrubbing and flushing away the dirt
Fresh water will wash the seawater away. Let’s wash away these muddy footprints.
built up acumulados
bulid up: To accumulate or collect
sediment building up on the ocean floor.
waste removal system sistema de remoção de resíduos
The word ‘waste’ is used in many contexts, below are samples of just a few…
▪ We need to find ways to reduce/avoid unnecessary waste.
▪ These old computers are still useful. It seems like such a waste to throw them away.
A pressa é inimiga da perfeição ↔Haste makes waste.
▪ disposal of industrial waste
▪ It’s a shame to see all that food go to waste.
governo esbanjador ↔wasteful government
Não perca tempo ↔Don’t waste time.
A pressa é inimiga da perfeição ↔Haste makes waste.
É tempo perdido ↔It’s a waste of time.
nunca se deve desperdiçar uma crise ↔“A Crisis Is a Terrible Thing to Waste”
Love is never wasted. ↔Amar nunca é um desperdício.
We mustn’t waste our energy resources. ↔Não devemos gastar nossos recursos energéticos.
at all em primeiro lugar, por qualquer que seja a razão
In any way: unable to walk at all.
To any extent; whatever: not at all sorry.
He’s had no food at all.
I haven’t been at all well recently.
Is there any uncertainty at all about the way she died?
flush out expulsar (lavar, enxaguar)
They had to flush out the sewer pipe to make it drain properly.
Drinking lots of water helps to flush out the toxins.


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