A new imaging study from academics at UNSW Sydney and Neuroscience Research Australia (NeuRA), suggests yawning may help move important fluids out of the brain, prompting further research into links with ageing and neurodegenerative disease.
Although the researchers acknowledge the idea is speculative, they say their work introduces an interesting avenue for understanding the physiological functions of yawning.
Using real-time MRI scans, the team, led by Professor Lynne Bilston, analysed a small-scale group of 22 participants, with results showing that yawning triggered a specific manoeuvre in which cerebrospinal fluid (CSF) and venous blood moved out of the skull together, whereas during deep breathing CSF flowed into the skull.
CSF is a clear liquid that cushions and protects the brain and spinal cord from injury and also helps carry nutrients in and waste products out.
“There has been speculation that yawning can help clear waste from the brain, but so far there has not been solid proof,” Prof Bilston, from UNSW’s School of Biomedical Engineering said.
“Our research suggests that yawning can play a role in cleaning brain fluid, which would most likely happen close to bedtime.”
This finding could be important for further studies into neurodegenerative diseases such as Alzheimer’s, Parkinson’s and dementia — all of which have been potentially linked to the build-up of waste products in and around the brain that can be a result of impaired CSF flows.
“We don’t know how strong the link is related to how CSF is cleared, but in the last 10 years there have already been a lot of investigations into that area, and this can be another element.”
One of the key observations was that CSF flow when people yawned was the opposite of what happened when they simply took a deep breath.
The UNSW research team also say the evidence suggests yawning is a way for the body to regulate the temperature in and around the brain.
The researchers also say they have identified for the first time that people appear to have a unique signature to their individual yawn which can be identified by the complex way their tongue moves during the action.
