An inquisitive group of researchers, with some extra time on their hands, have shed light on a longstanding scientific enigma involving a harmless bodily function.

Yawning could play a role in cleansing and regulating the brain’s temperature, as suggested by findings from an imaging study conducted by the University of New South Wales (UNSW) in collaboration with Neuroscience Research Australia (NeuRA).

“Our study began as an exploration and evolved into something significant,” shared Adam Martinac, one of the researchers involved in the project.

The researchers were initially engaged in an MRI study focused on spinal cord malformations.

“During our scanning sessions, we had some extra time to examine yawning, which led us to a fascinating discovery, ultimately resulting in a comprehensive study,” Martinac explained.

Historically, scientists concentrated primarily on the respiratory aspects of yawning.

“They put people in a room and changed the levels of oxygen in it to see whether it would trigger yawns, and it didn’t seem to. So, then that threw everyone for a loop,” Martinac said.

Fluid movements

Professor Lynn Bilston, who led the research, said that the team’s findings suggest yawning plays a role in cleaning brain fluid, which would most likely happen close to bedtime.

Cerebrospinal fluid (CSF) is a liquid that cushions the brain and spinal cord from injury.

When someone yawns, slightly cooler blood enters the brain, compensating for outflowing blood and CSF, indicating that the yawning mechanism could help prevent the brain from overheating.

Thomas Kalincik is a neurologist and director of Neuroimmunology Center at Royal Melbourne Hospital and University of Melbourne.

He was not involved in the study but said it has interesting findings.

“What I find interesting and novel about the findings that are reported is the difference between the flow of CSF during yawning and deep breathing. That observation is new and unexpected.”

Yawning signatures

Each of the 22 participants, aged 18-72, was found to have distinct yawning motions.

Martinac says he is “tentatively” calling the phenomenon a “yawning signature”.

“It’s almost like a fingerprint, so you could possibly identify someone just based on how they yawn.”

Although human fetuses can also yawn in early development, it’s unknown if adult yawning signatures are distinct due to genetic or social factors.

“You will yawn differently than I yawn. One thing would be to find a way to see why is that repeatable pattern the case and how does that actually link to pulling the CSF out of the head”.

What this may mean

Although the findings of this study could provide an early clue into one of the body’s long-standing mysteries, researchers stressed that the findings were preliminary and questions remain.

“It is exciting, but our study has not determined anything related to human health specifically and improvements,” said Martinac.

“Yawning remains very mysterious, even though it’s a primordial process that has been preserved throughout evolution. We know that crocodiles yawn, so we think dinosaurs also yawned.”

Kalincik said that from these results, “We can tell that yawning is different to just breathing. It will be interesting to better understand the evolutionary reason why we yawn.”

Martinac expressed interest in further researching the mechanics of yawning.

“We think there’s something here worth investigating further. Neurodegenerative diseases are associated with an accumulation of waste and the older you get the more waste there can be.”