The restorative effect of a good night’s sleep is widely recognized and the popular scientific explanation is that the brain eliminates toxins during sleep.
However, new findings suggest that this theory, which has become dominant in neuroscience, could be false. The study found that fluid clearance and movement in the mice’s brains were actually significantly reduced during sleep and anesthesia.
“It sounded like a Nobel Prize-winning idea,” said Professor Nick Franks, professor of biophysics and anesthesia at Imperial College London and co-leader of the study.
“If you’re sleep deprived, countless things go wrong: you don’t remember things clearly, hand-eye coordination is poor,” he added. “The idea that your brain does this basic housekeeping during sleep just seems logical.”
However, there is only indirect evidence that the brain’s waste disposal system speeds up its activity during sleep, Franks said.
In the latest study, published in the journal Nature Neuroscience, researchers used a fluorescent dye to study mouse brains. This allowed them to see how quickly the dye moved from the fluid-filled cavities, called ventricles, to other regions of the brain and to directly measure the rate of removal of the dye from the brain.
The study showed that clearance of the dye was reduced by about 30% in sleeping mice and 50% in mice under anesthesia, compared to mice kept awake.
“The field has focused so much on the idea of permission as one of the main reasons we sleep, and we were of course very surprised to observe the opposite in our results,” Franks said. “We found that the rate of dye removal from the brain was significantly reduced in animals that were asleep or under anesthesia.”
The researchers predict that the findings will extend to humans, because sleep is a basic need shared by all mammals.
Professor Bill Wisden, acting director of the UK Institute for Dementia Research at Imperial College London and co-lead author, said: “There are many theories about why we sleep, and well that we have shown that the elimination of toxins may not be a key reason. , there is no denying that sleep is important.
The findings are relevant to dementia research because of growing evidence of a link between poor sleep and Alzheimer’s disease risk. It’s not clear whether lack of sleep could cause Alzheimer’s disease or if it is just an early symptom. Some had hypothesized that without enough sleep, the brain might not be able to effectively eliminate toxins, but the latest research raises doubts about the plausibility of this explanation.
“Because this idea has been so influential, it has probably increased people’s anxiety that if they don’t sleep, they are more likely to develop dementia,” Franks said.
Wisden said: “Sleep disturbances are a common symptom experienced by people with dementia. However, we still do not know whether this is a consequence or a determining factor in the progression of the disease. It may well be that good sleep helps reduce the risk of dementia for reasons other than eliminating toxins.
He added: “The other aspect of our study is that we showed that brain cleaning is very effective in the waking state. In general, being awake, active, and exercising can more effectively cleanse the brain of toxins.
News Source : www.theguardian.com
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