Jenni Lacey, marketing assistant as the Society Biology, shares new research which could offer a molecular basis for why we need sleep.
I’m someone who confidently claims to need no more than 7 hours sleep and, when necessary, happily survive on 6 hours. I’m reassured that my claims are justified by a range of sources: The National Sleep Foundation in the America and the Mental Health Foundation – the bottom line seems to be that the amount you need varies for everyone. This is fortunate as my current commute requires a pre-6am wakeup call and an hour plus train journey, however this temptingly offers adequate time for napping…. So on the occasions when I do find myself dozing off what is my brain trying to tell me?
We have all heard that sleep is needed for learning, memory consolidation, and brain and body repair – which all contribute to good mental and physical health. However, the fundamental biological purpose of sleep remains elusive. A study published in Science last month (Xie et al, 2013) has got experts excited at the prospect of uncovering, for the first time, a molecular basis for why we sleep. The study hypothesises that the restorative nature of sleep is a result of the brain cleaning out toxic metabolic byproducts while we slumber.
The team built on previous work that had revealed important networks of fluid filled channels that transported “waste-laden cerebrospinal fluid (CSF)” away from the brain. As this is an energy intensive process the researchers thought the brain may not be able to process sensory information (abundantly necessary when we’re awake) and remove waste at the same time.
Their recent study used two-photon imaging to compare the movement of CSF through the brain of mice during wakeful and sleep states. They found that large volumes of CSF was transported into brain during sleep and also that the channels carrying the CSF expanded by 60% at this time. They went on to demonstrate the removal of toxic byproducts (β amyloids), via the CSF, occurred twice as quickly during sleep.
This revealing evidence supports the theory that sleep is necessary for the brain to carry out regular cleaning and prevents build-up of harmful neurotoxic waste. The question does still remain as to whether the presence of waste products actively encourages sleep? And does this brainwashing occur in all species?
But, for the time-being, I’m confident that when I catch a few extra minutes sleep on the train my brain is carrying out some necessary maintenance that will improve my health and wellbeing throughout the day.
Further reading:
- Xie et al Sleep Drives Metabolite Clearance from the Adult Brain, Science 18 October 2013: 373-377.
- Underwood E. Sleep: The Brain’s Housekeeper? Science News and Analysis 18 October 2013