Yawning is more than a gesture of boredom: It has a surprising effect on the brain, MRI scans show
Yawning isn't just a reflex of tiredness or boredom: MRI scans by Australian researchers show that it moves cerebrospinal fluid out of the brain and increases blood flow.
Yawning affects the brain PHOTO: archive, the truth
According to researchers at the University of New South Wales, Australia, the findings could provide an important clue to understanding why humans (and many other species) evolved to yawn.
The research team used MRI to scan the head and neck of 22 healthy participants while they were asked to take deep breaths, stop yawning, and breathe normally.
Because yawning and deep breathing share similar mechanisms, the researchers expected the results to be similar across images.
Surprisingly, the images revealed a key difference: unlike deep breaths, yawning sends cerebrospinal fluid (CSF) away from the brain, Science Alert writes.
“Yawning triggers a movement of CSF in the opposite direction to deep breathing,” neuroscientist Adam Martinac told New Scientist's James Woodford.
This phenomenon was not observed in all cases and occurred less often in men, although the researchers caution that this may be due to interference from the MRI scanner.
Analysis also showed yawning increased blood flow leaving the brain, creating more space for fresh blood to be pumped into the brain.
Blood flow did not change direction during yawning. However, in the early stages, carotid artery blood flow to the brain increases by about one-third, providing possible clues to the multiple reasons for this behavior.
Additionally, all participants had unique yawn patterns that repeated almost identically each time. It's a sign that each of us has our own central generator that determines how we yawn.
“This flexibility could explain the variations in yawning patterns between participants, while maintaining a recognizable and individual-specific pattern; and suggests that yawning patterns are not learned but represent an innate aspect of neurological programming,” write the researchers in their paper.
Yawning is often associated with sleepiness or boredom and is meant to help the brain maintain alertness. However, if it occurs frequently, both day and night, it can be a sign of health problems.
Excessive yawning: a health warning sign
Dr Divya Gopal, consultant in internal medicine, explains that frequent and excessive yawning can indicate lack of sleep, boredom or mental exhaustion, heart problems involving the vagus nerve, neurological disorders such as epilepsy.
Iron deficiency or low blood oxygen levels can also be a cause of excessive yawning. Conditions such as sleep apnea or chronic lung disease can reduce oxygen levels and also cause frequent yawning.
