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Yawning: its cycle, its role
Warum gähnen wir ?
 
Fetal yawning assessed by 3D and 4D sonography
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mise à jour du
28 septembre 2017
Curr Biol.
2017;27(17):2713-2717.e2.
A Neural Basis for Contagious Yawning
 
Brown BJ, Kim S, Saunders H, Bachmann C,
Thompson J, Ropar D, Jackson SR, Jackson GM.
The University of Nottingham

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 Tous les articles sur la contagion du bâillement
All articles about contagious yawning
 
 Summary
 
Contagious yawning, in which yawning is triggered involuntarily when we observe another person yawn, is a common form of echophenomena&emdash;the automatic imitation of another's words (echolalia) or actions (echopraxia). The neural basis for echophenomena is unknown; however, it has been proposed that it is linked to disinhibition of the human mirror-neuron system and hyper-excitability of cortical motor areas.
 
The authors investigated the neural basis for contagious yawning using transcranial magnetic stimulation (TMS). Thirty-six adults viewed video clips that showed another individual yawning and, in separate blocks, were instructed to either resist yawning or allow themselves to yawn. Participants were videoed throughout and their yawns or stifled yawns were counted.
 
They used TMS to quantify motor cortical excitability and physiological inhibition for each participant, and these measures were then used to predict the propensity for contagious yawning across participants.
 
They demonstrate that instructions to resist yawning increase the urge to yawn and alter how yawns are expressed (i.e., full versus stifled yawns) but do not alter the individual propensity for contagious yawning. By contrast, TMS measures of cortical excitability and physiological inhibition were significant predictors of contagious yawning and accounted for approximately 50% of the variability in contagious yawning. These data demonstrate that individual variability in the propensity for contagious yawning is determined by cortical excitability and physiological inhibition in the primary motor cortex.
 
 
Résumé
Le bâillement « contagieux », celui qui est déclenché involontairement quand nous observons une autre personne bâiller, est une forme de comportement en écho comme il en existe d'autres tels la répétition involontaire des paroles d'autrui (échalolie) ou des actions (échopraxie). La base neurale des comportements en écho est mal connue ; cependant, il a été proposé qu'ils soient liés à la désinhibition du système ses neurones miroirs et à l'excitabilité des zones motrices corticales.
 
Les auteurs ont étudié la base neuronale du bâillement « contagieux » en utilisant la stimulation magnétique transcrânienne (TMS). Les mesures ont cherché à quantifier l'excitabilité motrice corticale d'une part et l'inhibition physiologique d'autre part.
 
Trente-six adultes ont regardé des clips vidéo montrant un bâillement. Ils ont reçu comme consigne de résister au besoin de bâiller ou au contraire de se laisser aller.
 
La TMS a été utilisée pour quantifier l'excitabilité corticale motrice et l'inhibition physiologique pour chaque participant. Les mesures ont ensuite été utilisées pour prédire la propension à la contagion de chacun des participants.
 
Les auteurs démontrent ainsi que les instructions pour résister au bâillement augmentent l'envie de bâiller et modifient la façon dont les bâillements sont extériorisés (c.-à-d. bâillements francs ou étouffés), mais ne modifient pas la propension individuelle à la contagion du bâillement.
 
En revanche, les mesures du TMS de l'excitabilité corticale et de l'inhibition physiologique sont des prédicteurs significatifs de contagion du bâillement et représentaient environ 50% de la variabilité à la susceptibilité à la contagion. Ces données démontrent que la sensibilité individuelle à la contagion du bâillement est déterminée par le seuil à l'excitabilité corticale et une inhibition physiologique dans le cortex moteur primaire.
 
Discussion
 
We investigated the neural basis for contagious yawning, an example of echophenomena, using non-invasive brain stimulation (TMS) techniques. Contagious yawning can be triggered by seeing another individual yawn, but the propensity for contagious yawning, although stable over time, is known to vary across individuals. Here we provide evidence that the propensity for contagious yawning may be triggered automatically and is strongly linked to the cortical excitability of the primary motor cortex. Specifically, TMS was used to quantify baseline cortical excitability and physiological inhibition within the primary motor cortex and to predict behavioral measures of contagious yawning, and we tested the hypothesis that the propensity for contagious yawning was linked to the balance of cortical excitability and physiological inhibition within the primary motor cortex.
 
The key findings from the study can be summarized as follows. First, the instruction to resist yawning proved to be only partially successful. Although it led to a significant decrease in the number of full yawns observed, there was a significant increase in the number of stifled yawns recorded. Furthermore, when the numbers of full and stifled yawns were combined into a single measure, the difference between the resist and allow conditions was not statistically significant. Nonetheless, urge-to-yawn estimates increased significantly when participants were instructed to resist yawning. This is consistent with the proposal that urges for action are chiefly associated with actions that cannot be realized immediately and must be held in check. Together, these findings demonstrate that the instruction to resist yawning significantly increases the urge to yawn and alters how the yawn may be expressed (i.e., stifled yawns rather than full yawns), but it does not alter the individual's propensity for yawning.
 
Second, the propensity for contagious yawning was shown to be strongly predicted by individual variability in TMS measures of cortical motor excitability and physiological inhibition recorded from the hand area of the primary motor cortex.
 
We suggest that these findings may be particularly important in understanding further the association between motor excitability and the occurrence of echophenomena, observed in a wide range of clinical conditions, e.g., epilepsy, dementia, autism, and Tourette syndrome, that have been linked to increased cortical excitability and/or decreased physiological inhibition.

Interview by Lindsay Brooke
The University of Nottingham
 
 
Stephen Jackson, Professor of Cognitive Neuroscience, in the School of Psychology, led the multidisciplinary study. He said: "We suggest that these findings may be particularly important in understanding further the association between motor excitability and the occurrence of echophenomena in a wide range of clinical conditions that have been linked to increased cortical excitability and/or decreased physiological inhibition such as epilepsy, dementia, autism, and Tourette syndrome."
 
Echophenomena isn't just a human trait
 
Contagious yawning is triggered involuntarily when we observe another person yawn &emdash; it is a common form of echophenomena &emdash; the automatic imitation of another's words (echolalia) or actions (echopraxia). And it's not just humans who have a propensity for contagious yawning &emdash; chimpanzees and dogs do it too.
 
Echophenomena can also be seen in a wide range of clinical conditions linked to increased cortical excitability and/or decreased physiological inhibition such as epilespsy, dementia, autism and Tourette syndrome.
 
The neural basis for contagious yawning
 
The neural basis for echophenomena is unknown. To test the link between motor excitability and the neural basis for contagious yawning the Nottingham research team used transcranial magnetic stimulation (TMS). They recruited 36 adults to help with their study. These volunteers viewed video clips showing someone else yawning and were instructed to either resist yawning or to allow themselves to yawn.
 
The participants were videoed throughout, and their yawns and stifled yawns were counted. In addition, the intensity of each participant's perceived urge to yawn was continuously recorded.
 
Using electrical stimulation they were also able to increase the urge to yawn.
 
Georgina Jackson, Professor of Cognitive Neuropsychology in the Institute of Mental Health, said: "This research has shown that the 'urge' is increased by trying to stop yourself. Using electrical stimulation we were able to increase excitability and in doing so increase the propensity for contagious yawning. In Tourettes if we could reduce the excitability we might reduce the ticks and that's what we are working on."
 
The search for personalised treatments
 
TMS was used to quantify motor cortical excitability and physiological inhibition for each participant and predict the propensity for contagious yawning across all the volunteers.
 
The TMS measures proved to be significant predictors of contagious yawning and demonstrated that each individuals's propensity for contagious yawning is determined by cortical excitability and physiological inhibiton of the primary motor cortext.
 
The research has been funded by ESRC doctoral training award to Beverley Brown and is part of Nottingham's new Biomedical Research Centre (BRC) leading research into mental health technology with the aim of using brain imaging techniques to understand how neuro modulation works.
 
Professor Stephen Jackson said: "If we can understand how alterations in cortical excitability give rise to neural disorders we can potentially reverse them. We are looking for potential non-drug, personalised treatments, using TMS that might be affective in modulating inbalances in the brain networks."
 
This latest research follows the publication of their study 'On the functional anatomy of the urge-for-action' which looked at several common neuropsychiatric disorders associated with bodily sensations that are perceived as an urge for action.