Jeff Iliff is a neuroscientist at Oregon Health & Science University, previously doing research into brain cleansing mechanisms at University of Rochester Medical Centre.
We spend roughly a third of our lives asleep, but it is not clear why the body needs it. 2,000 years ago it was proposed by Galen that the brain sent fluids around the body, and these were returned during sleep to rejuvenate the brain. The idea is ludicrous today, but Jeff still suggests brain activity could account for our need of sleep. The brain uses 25% of our energy but takes only 2% of our mass. The first major issue in any body organ is nutrient intake – which is satisfied by the circulatory system and the network of blood vessels surrounding the brain. The second issue is waste disposal, which in most organs is done through the lymphatic system. The lymphatic system transports waste from the cells to bloodstream, however it does not exist in our heads so cannot be used by the brain. So how does the brain dispose of waste? This was where Jeff started tackling the problem.
The brain is surrounded by cerebral spinal fluid (CSF). Waste is dumped into CSF, which is then transported to the blood. To help this, CSF is pumped along the outside of blood vessels – to clean and penetrate deeper into the brain wherever blood vessels are. However, this action only happens while we sleep. As we sleep the brain cells contract, to open up spaces between them and let the CSF flow more easily. Ironically, this idea of fluid rushing through the brain is similar to Galen’s ideas thousands of years ago.
What sorts of wastes need to be cleaned? One is Amyloid Beta – which is made all the time, but an inability to clear them away is thought to be a factor in getting Alzheimers disease. Studies have found that a decrease in sleep is associated with an increase in Amyloid Beta in the brain.
While we sleep, our brain never rests. It is busily cleaning this important machine, and possibly preventing serious issues later. By understanding these housekeeping functions today, we may be able to prevent serious diseases of the mind tomorrow.
Interesting talk and interesting research. I learnt a bit about brain activity, sleep and Alzheimers all at once. He summed up a lot in less than 12 minutes.