The sensitivity to yawning of others is related to the excitability of the motor cortex. A discovery which helps to understand the syndrome of Tourette.
Two, seven, ten … A good landlord would give away several of his fellows, according to the proverb. This phenomenon has been demonstrated, and is called contagious yawning. It concerns about two thirds of the population.
A University of Nottingham study (United Kingdom) tries to understand the mechanisms governing this phenomenon. Previous studies on the subject had mentioned empathy to explain it. British researchers put forward another explanation. They observed that the excitability of part of the brain, the motor cortex, was linked to sensitivity to contagious yawning.
Unequal before yawning
To do this, the researchers recruited 36 people. First, they stimulated their brain using electrodes directed towards the motor cortex. This zone is associated with anticipation and movement actions. They were then able to measure nerve activity in response to stimuli, and thus classify study participants according to the area’s ability to be excited.
They then released videos of people yawning. They then noticed that those who were most sensitive to contagious yawning were precisely those whose motor cortex was the most “excitable”.
“Some of us have a particularly sensitive motor network, and are very susceptible to contagious yawns, while others are less so”, summarizes Stephen Jackson, professor of cognitive neuroscience at the University of Nottignham, and principal author of the study.
Contradiction spirit
They also extracted another piece of information. Half of the participants could give in to their desire to imitate them, while the other had to resist. And, paradoxically, those who should not yawn were ultimately those who did the most, and who reported wanting the most.
In another experiment, the researchers purposely excited the participants’ motor cortex before performing the contagion test. This was then favored.
Reverse the mechanism
This information makes it possible to better understand the functioning of the reflex, and provides elements of understanding for other more disabling phenomena. By understanding what makes us yawn, and what triggers this overwhelming urge, they could help doctors understand other conditions.
For example, they could find a way to lower this excitability in people with Gilles de La Tourette’s disease, in order to limit the frequency and intensity of their involuntary movements and words.
“By studying contagious yawning, we are trying to better understand the brain mechanisms involved in tics,” adds Professor Jackson. If we could understand how alterations in cortical excitability trigger neuronal disorders, we could potentially reverse them ”.
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