At the moment we are exploring the topic of sleep. Last week we learned that for most people seven to eight hours of sleep are necessary for their brain to function well. The previous week we found out that using the “snooze” button leaves you less instead of more rested. The message is again and again that a good sleep is important. But why do we need sleep?
In a TED Talk Jeff Iliff from Oregon Health and Science University explains what he and his colleagues found: The brain does housecleaning while we are sleeping.
He outlines that all our organs, including the brain, are supplied with nutrients and oxygen via our blood vessels. On the other hand there is the lymphatic system that collects all waste from between the body cells and transports it to the blood vessels so that the body can rid itself from the waste. However, there are no lymphatic vessels in the brain. But there is a less space consuming solution: cerebrospinal fluid (CSF). It surrounds the brain and waste is dumped into it in order for it to be transported into the blood. For this purpose the CSF is pumped inside the brain along the blood vessels – while we sleep. Jeff Iliff says that the brain puts off cleaning away the waste when it is busy while we are awake and then does the housecleaning while we are sleeping.
One of the possible effects of waste not being cleared out is the accumulation of a protein called amyloid beta, one that is associated with Alzheimer’s disease. Jeff Iliff cautions against interpreting the results such that lack of good sleep causes Alzheimer’s. But he points out that good sleep is crucial for keeping our brain clean and thus well-functioning.
This sounds a bit like our brain was resting while we are sleeping. However, this is not the case as a lot of research shows. It does not rest while we are sleeping and it does even not rest when we are actively trying to rest it such as while meditating. So there is always something going on in our brain – including housecleaning at night!