A new study has revealed surprising effects of yawning on the human brain, suggesting that the common action may influence the flow of protective fluid around the brain. Yawning is a natural process that many people experience, often triggered simply by seeing or hearing about it, yet its exact purpose in the body has long remained unclear.
Researchers from the University of New South Wales in Australia discovered that yawning has unusual and unexpected effects on the movement of cerebrospinal fluid, which protects the brain. The findings also provide possible clues as to why humans and many other living beings yawn.
The study involved 22 healthy participants whose head and neck MRI scans were taken while they were yawning, taking deep breaths, trying to suppress yawns, or breathing normally. Since yawning and deep breathing share similar physical mechanisms, researchers initially expected to observe similar results in the scans.
However, the results surprised researchers, as yawning caused the protective brain fluid to move away from the brain, unlike deep breathing. They found that during yawning, the fluid moved in the opposite direction compared to deep breathing, something the researchers said they had not anticipated.
The study also showed that this effect was not the same for everyone and appeared less frequently in men compared to women. Researchers further observed that both yawning and deep breathing increased the outflow of blood from the brain, creating more space for fresh blood circulation. According to the findings, yawning can increase blood flow in the brain by up to one-third, which may help explain why the behavior occurs.
Researchers noted that each person has a unique way of yawning and tends to repeat the same pattern each time. However, they acknowledged that it is still unclear why yawning causes the movement of protective brain fluid or what exact effects it has on brain function. This fluid plays an important role in maintaining the central nervous system by supplying nutrients and removing waste.
Scientists suggested that yawning might play a role in brain cleansing, but emphasized that more research is needed to fully understand its function in the brain and nervous system. The findings of the study were published on the preprint server bioRxiv.
