Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal
Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal

mystery of yawning 





mise à jour du
21 juillet 2019
Physiology & Behavior
Manipulating neck temperature alters
contagious yawning in humans
Valentina Ramirez, Colleen P. Ryan,
Omar Tonsi Eldakara, Andrew C. Gallup
Department of Biological Sciences, Nova Southeastern University, United States
Department of Medicine and Surgery, University of Rome Tor Vergata, Italy
Psychology Program, SUNY Polytechnic Institute, United States


 Tous les articles d'Andrew Gallup
The existence of yawning across a diverse array of species has led many researchers to postulate its neurological significance. One hypothesis, which has garnered recent support, posits that yawns function to cool the brain by flushing hyperthermic blood away from the skull while simultaneously introducing a cooler arterial supply. The current study tested this hypothesis by examining how manipulations aimed at modifying carotid artery temperature, which in turn directly alters cranial temperature, influences contagious yawning in humans. Participants held either a warm (46 °C), cold (4 °C) or room temperature (22 °C) pack firmly to their neck, just over their carotid arteries, for a period of five minutes prior to watching a contagious yawning stimulus. Thermographic imaging verified that these manipulations produced predicted changes in temperature at the superomedial orbital area, a region previously used as a noninvasive measure of brain temperature (i.e., the brain temperature tunnel). As predicted by past research, both the urge to yawn and overall yawn frequency significantly diminished in the cooling condition (p < .05). Less than half (48.5%) of the participants in the cooling condition reported the urge to yawn, while this urge was expressed by the vast majority of participants in the warming condition (84.8%). Moreover, there was a threefold difference in the mean number of yawns per participant between the cooling and warming conditions (0.364 compared to 1.121). These findings are consistent with previous research indicating that yawns function as a compensatory brain cooling mechanism.

 L'existence de bâillements repérés dans un large éventail d'espèces a conduit de nombreux chercheurs à postuler une signification neurologique. Une hypothèse, qui a recueilli un soutien récent, postule que les bâillements servent pour refroidir le cerveau en chassant le sang hyperthermique du crâne tout en introduisant simultanément un apport artériel plus froid. La présente étude a testé cette hypothèse en examinant la manière dont les manipulations visant à modifier la température de l'artère carotide, qui à leur tour modifie directement la température crânienne, ont une incidence sur le bâillement contagieux chez l'homme. Les participants ont tenu un sac chaud (46 ° C), froid (4 ° C) ou à la température ambiante (22 ° C) fermement sur leur cou, juste au-dessus de leurs artères carotides, pendant une période de cinq minutes avant de regarder des enregistrements vidéos de bâillements, afin d'en déclencher par contagion.
L'imagerie thermographique a permis de vérifier que ces manipulations produisaient les changements de température prévus au niveau de la région orbitale super-médiale, une région précédemment utilisée comme mesure non invasive de la température cérébrale. Comme prévu par des recherches antérieures, le besoin de bâiller et la fréquence globale de bâillements ont considérablement diminué dans les conditions de refroidissement (p <0, 05). Moins de la moitié (48, 5%) des participants en période de refroidissement ont signalé l'envie de bâiller, à l'inverse de ce qui a été exprimé par la grande majorité des participants en période de réchauffement (84, 8%).
De plus, le nombre moyen de bâillements par participant était trois fois plus important entre les conditions de refroidissement que de réchauffement (0,364 contre 1,121). Ces résultats sont cohérents avec les recherches précédentes indiquant que les bâillements fonctionnent comme un mécanisme accesoire de refroidissement du cerveau.

1. Introduction
Yawning is a complex and reflexive motor action pattern that ap- pears to be evolutionarily conserved across vertebrates. Recent comparative research suggests an important neurophysiological function to this response, as interspecies variability in yawn duration robustly correlates with measures of brain size and neuron density among mammals [22,23]. To date, however, there remains no consensus regarding its adaptive significance [11,25,33].
Human neuroanatomical and physiological investigations support a role of yawning in enhanced intracranial circulation [44] and brain cooling [5,19]. In particular, the brain cooling hypothesis posits that yawns are triggered by rises in cranial temperature, and that both the circulatory and respiratory outcomes of this motor action pattern function to counteract these changes and promote thermal homeostasis [17]. According to this hypothesis, the extended muscular contractions and deep inhalation of ambient air that characterize yawns induce cooling of the brain via convective heat transfer, thermal conduction and evaporative heat loss (reviewed by [14]). These physiological changes associated with yawning could facilitate instances of state change [39] and cortical arousal [2] that follow this behavior.
The first empirical support for the brain cooling hypothesis came from research on human subjects demonstrating an inhibition of contagious yawning by methods of behavioral brain cooling (i.e., nasal breathing and forehead cooling) [17]. Subsequent studies in both humans and non-human animals exhibited predicted changes in brain temperature [40,41], cranial surface temperature [6,24], and oral temperature following yawns [15]. Further comparative studies have revealed the importance of ambient temperature in controlling the expression of this behavior (e.g., [7,20,36]). Moreover, even fever has been shown to influence yawn frequency in a pattern predicted by this hypothesis [16,35]. Nonetheless, the brain cooling hypothesis is not universally accepted (see [8,9,26]), and some researchers have pro- posed that yawning may simply occur conjointly with natural changes in brain temperature rather than functioning in thermoregulation [33]. The current experiment was designed to address this issue by in- directly manipulating brain temperature among human subjects to witness its effect on yawning. Brain temperature in homeotherms is controlled by the temperature of the arterial blood flow to the brain, the rate of arterial blood flow to the brain, and metabolic heat production within the brain [4]. Here, we aimed to temporarily manipulate the first variable by having human subjects hold varying temperature packs directly to the surface of the neck above their carotid arteries prior to viewing a contagious yawning stimulus. Although the temperature of the arterial blood supply is not equivalent to brain temperature (e.g., [31,32]), comparative research has demonstrated that the arterial blood perfusing the brain is the major determinant of cerebral temperature in primates [30]. In addition, the temperature of blood within the carotid arteries has been shown to predict internal brain temperature across diverse species (e.g., [10,34,37]). Based on the brain cooling hypothesis, and past research employing similar procedures to modify cranial temperature in human subjects [17], it was predicted that cooling of the skin just above the carotid arterial blood supply would diminish yawning, while conversely warming of this tissue would in- crease this response. Contagious yawning was used as a proxy for spontaneous yawning since it can be reliably triggered in the laboratory [38] and studies have repeatedly demonstrated that variables altering spontaneous yawns also control yawn contagion (e.g., [7,17,36]).
4. Discussion
The brain cooling hypothesis of yawning has garnered recent empirical support (reviewed [14]), and has shed light on previous un- characterized connections between abnormal or frequent yawning and thermoregulatory dysfunction in humans [18]. To date, the majority of past studies linking yawning with changes in brain/skull temperature have been correlational in nature. That is, yawns have been shown to be preceded by rises in temperature, and followed by decreases in temperature (e.g., [15,40,41]). As a result, some researchers have proposed that yawns may simply coincide with natural changes in brain temperature, and that fluctuations in brain temperature do not actually trigger yawns [33]. This study extended upon this previous work by manipulating the temperature of the neck just above the arterial blood supply to the brain and observing changes in yawn frequency thereafter.
In partial support of the brain cooling hypothesis, results show that manipulations aimed at modifying arterial blood temperature significantly altered contagious yawning among humans. In particular, applying a cold pack (4 °C) to the neck just over both carotids reduced the surface temperature of the BTT and significantly diminished both the urge to yawn and overall yawn frequency in this study. These findings replicate previous research manipulating forehead temperature [17], whereby contagious yawning was markedly lower in the cooling condition. Similar reductions in yawn contagion occur when ambient temperatures fall below a thermal neutral zone [36]. Given that brain temperature is largely influenced by the temperature of arterial blood supply [4], the decreases in temperature produced by the cold condition appeared to inhibit the mechanisms controlling this response. This can be viewed in the same way other cooling mechanisms (e.g., sweating) cease when internal temperatures fall below thermal homeostasis.
No differences emerged between the warm and room temperature conditions, which also mirrors earlier research manipulating forehead temperature [17]. Although the warm temperature condition (46 °C) of the current study produced an increase in temperature at the BTT, associated increases in yawning were not statistically different from the room temperature condition. This particular result is not entirely consistent with the brain cooling hypothesis, which predicts that rises in brain temperature should trigger yawning. However, it has been posited that yawning serves as a compensatory, rather than primary, cooling mechanism, and thus it could be that the elevation in cranial temperature produced by the warm condition (~0.25°C) exceeded the threshold for which yawning would be effective. For example, recordings from free-moving rats show that yawns are preceded by rises in brain temperature of only 0.12°C [41], which is less than half the magnitude produced in this current study. Similar effects have been observed across large deviations in ambient temperature [12]. A range of comparative studies have shown that initial rises in ambient temperature trigger an increase in yawn frequency, but that yawns then decrease in frequency back to baseline levels as temperatures approach or exceed body temperature because counter-current heat exchange is no longer effective [7,13,20,21]. These findings are also consistent with the perspective that yawning operates as an initial and compensatory response to slight deviations in thermal homeostasis. As temperatures continue to elevate, heat dissipation becomes more difficult and more effective regulatory mechanisms are triggered [20]. Future research could specifically test these predictions by comparing yawning across a range of different warm temperature conditions while simultaneously tracking other well-documented thermoregulatory cooling responses. In addition, further studies could examine how temperature manipulations to areas of the body more distant from the skull (e.g., the forearm or abdomen) influence yawn frequency.
The overall findings from this report are consistent with previous research indicating that yawns function as a compensatory brain cooling mechanism. However, it remains unknown whether the temperature manipulations to the neck were sufficient to alter either arterial or brain temperature. Although the reported thermographic recordings revealed predicted changes in temperature at the BTT, intracranial temperatures were not obtained. Nonetheless, this report adds to a growing list of experimental findings demonstrating that the mechanisms controlling yawning, including spontaneous and contagious forms, are sensitive to temperature.
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