A Good Night’s Sleep Really Does ‘Clear the Mind’

sleepWhy do we sleep?  It is a question that has long puzzled scientists and philosophers alike.  While the ancient Greeks saw sleep as a doorway to the divine, scientists and biologists see it as an invitation to be devoured by nocturnal predators.  A new study – appearing today in the journal Science – may provide the answer: when we sleep our brain ‘takes out the trash.’

The findings are one in a series of discoveries that have revolutionized our understanding of how the brain deals with the by-products of cellular activity.  The body’s normal waste removal process – called the lymphatic system – does not extend to our brains.  This is because the brain essentially maintains its own closed “ecosystem.”  However, as any student of biology knows waste removal is a critical biological function.  In the brain, the unchecked accumulation of proteins such as beta-amyloid can lead to Alzheimer’s disease. 

Last year, URMC researchers – led by Maiken Nedergaard, M.D., D.M.Sc. – revealed that the brain has its own waste removal system consisting of a plumbing system that piggybacks on the brain’s blood circulation system and uses cerebral spinal fluid to wash away waste.  The studies were conducted in mice, whose brains are remarkably similar to humans.

The study out today shows that this system is 10-times more active during sleep and more effective at removing beta-amyloid.  This finding has led researchers to speculate that the brain essentially has two functional states – awake and processing information about our surroundings and asleep and cleaning away the material that neurons generate during their normal activity.   

Another startling finding was that the brain’s cells “shrink” during sleep – by as much as 60 percent – which allows the cerebral spinal fluid to more easily flow between the cells and flush away waste. 

You can read more about the Science paper here.

Mark Michaud | 10/17/2013 | 5 comments


Thomas Gates
Is there a particular predominant brainwave pattern, such as Delta, occurring during times that this "flushing" process is at its most effective state? Or what are the specific brainwave patterns present when this process is initiated?
7/28/2014 12:16:40 PM
Joserph A. Salmon, Jr.
I have been researching the NIH Brain Initiative. Is there an affordable encyclopedia of Brain Initiative Science that I can buy to master? Where can I visit to further research the Brain Initiative?
10/29/2013 12:48:24 PM
Peter Handley
Very interesting - many of my family worked for the Ford motor company who famously carried out research into which shift pattern produced the most 'obedient, compliant, and productive' employees (the answer being alternating two weeks of nights followed by two weeks of days) and implemented it worldwide even though it was also known to cause the most stress/disruption to sleep pattern! My father in law recently passed away from dementia and was constantly complaining of being unable to sleep soundly or for more than a few hours at a time. My own father is showing early signs. Has anyone researched if car workers as a group have higher than normal incidence of dementia/parkinsons?
10/22/2013 12:21:05 PM
Dr Y Bradley
This gives rise to the questions whether taking sleep products/meds (which admittedly make the actual sleep DIFFERENT) might slow down or inhibit the removal of proteins like beta-amyloid. Next, alcohol before sleep alters the sleep, so is alcohol a confounding factor in the good works of the brain during sleep?
10/21/2013 5:36:19 PM
Teresa Demarcos
One thing that strikes me while reading this is the potential impact to be explored here for a possible connection with fibromyalgia. Though there's been little exploration of whether or not it may be caused by build up of waste in the brain, it has been long accepted that fibromyalgia patients have great difficulty sleeping. If these problems in the sleep cycle of fibromyalgia patients are preventing waste from being removed in the brain it stands to reason that not only would they be at increased risk of developing diseases like alzheimers but it may also provide insight into the cognitive difficulties and possibly even pain experienced by fibromyalgia sufferers. The majority of patients see a decrease in pain and increase in cognitive function if/when sleep can be improved. Perhaps fibromyalgia as a sleep disorder should be further explored.
10/18/2013 11:28:26 AM
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