Khaberni - Yawning is no longer just a simple reaction to fatigue or boredom, as a recent scientific study revealed that this involuntary motion plays a complex neurological role associated with fluid regulation inside the brain.
According to research conducted using magnetic resonance imaging, it has been shown that yawning helps in re-coordinating the flow of cerebrospinal fluid and blood within the skull, a process that is completely different from what occurs during normal deep inhalation.
The study involved 22 healthy volunteers, both men and women, who underwent four different respiratory conditions, including normal breathing, yawning, trying to suppress yawning, and forced deep inhalation, all under close monitoring by magnetic resonance imaging.
The results, published on the bioRxiv scientific platform, showed that yawning pushes the cerebrospinal fluid to exit the skull toward the spine, but in a completely opposite manner to what happens during forced deep inhalation.
Biomedical engineer Adam Martiniak of Neuroscience Research Australia said that this result was surprising even to the research team itself.
The scientists also noticed that yawning coordinates the movement of cerebrospinal fluid and venous blood in the same direction outside the brain, unlike deep breathing, where these fluids typically move in opposite directions.
Although the amount of fluid transferred with each yawn is small, not exceeding a few milliliters, the researchers plan to measure it more precisely in subsequent phases, with the hypothesis that the neck, tongue, and throat muscles play a role in pushing these fluids.
The study also revealed that yawning increases blood flow through the carotid artery by more than a third compared to deep breathing, which may allow an extra amount of arterial blood to reach the brain after other fluids have been emptied from the skull.
An interesting observation is that each person has a distinct pattern of tongue movement during yawning, reflecting the individual nature of this evolutionarily rooted neurological behavior.
Martiniak confirms that yawning is one of the behaviors preserved through evolution, as it occurs in most vertebrate animals, from humans to crocodiles, and perhaps even dinosaurs.
However, the ultimate purpose of yawning is still a subject of scientific debate, amid hypotheses linking it to increased oxygen, regulating body temperature, improving brain fluid circulation, and even affecting the stress hormone "cortisol".
