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
http://www.baillement.com

mystery of yawning 

 

 

 

 

 

 

 

 

 

 

 

 

mise à jour du
1 mai 2015
Adaptive Human Behavior and Physiology
march 2015
Temperature-Dependent Variation
in Self-Reported Contagious Yawning
Omar Tonsi Eldakar, Melissa Dauzonne, Yana Prilutzkaya, Daniel Garcia, Carolyn Thadal, Andrew C. Gallup

logo

 Abstract
 
The thermoregulatory theory posits that yawns mnction to cool the brain in part due to counter-current heat exchange with the deep inhalation of ambient air. In support of this theory, previous cross-cultural research on humans has shown that self-reported conta-gious yawning frequency varies between seasons with distinct ambient température ranges. However, it remains possible that différences in yawning across seasons are a resuit of physiological circadian changes across the year rather than variation in ambient température. In an attempt to address this question, hère we discuss the results of a study investigating the variation in the frequency of self-reported contagious yawning within a restricted range of a single season in one géographie location. A total of 142 pedestrians were recraited outdoors during an 18-day period over the summer in an equatorial monsoon climate in southem Florida, USA. Consistent with the thermoregulatory theory of yawning, results showed that self-reported contagious yawning frequency varied predictably across température gradients. This was true after statistically controlling for relative humidity, time of day, time spent outside, testing day, âge of participant, and amount of sleep the night before. Thèse fîndings provide further évidence suggesting a brain cooling function to yawning.
 
A comment on: Eldakar OT, et al. Temperature-dependent variation in self-reported contagious yawning.

Andrew C. Gallup. Yawning and the thermoregulatory hypothesis

Introduction
Yawning is characterized by a large gaping of the mouth with a deep inspiration, a brief acme period with peak muscle contraction, and passive closure of the jaw with a shorter expiration of air (Barbizet 1958). This behavior appears highly conserved, with report-ed observations of yawns having been documented across vertebrate classes (Craemer 1924; Luttenberger 1975; Baenninger 1987; Sauer and Sauer 1967). Overtime numer-ous fonctions of yawning hâve been suggested (Smith 1999), ranging from regulating middle ear pressure (Laskiewicz 1953) to preventing lung atelectasis (Cahill 1978). While many hypothèses hâve been proposed for why we yawn, few hâve been empirically supported (Gallup 2011). For example, it is commonly believed that we yawn to increase oxygen in the blood, yet this respiratory hypothesis was tested and falsified over 25 years ago (Provine et al. 1987). In récent years, the thermoregulatory theory has emerged as the most empirically supported physiological explanation for why we yawn (see Gallup and Eldakar 2013 for a discussion of évidence and critiques). This theory states that the motor action pattern of yawmng functions as a brain cooling mechanism (Gallup and Gallup 2007, 2008). Consistent with this theory, research on both rats (Rattus norvégiens) and humans has demonstrated that yawns are surrounded by predicted fluctuations in brain and skull température, Le., yawning is preceded by rises in température and followed by decreases in température thereafter (humans, Gallup and Gallup 2010; rats, Shoup-Knox et al. 2010). Furthermore, research on birds {Melopsittacus undulatus) has shown that following stress-induced hyperthermia the latency to yawn is negatively correlated with the peak body température (Miller et al. 2010). Literature from diverse fields of medicine, physiology and pharmacology also support the connection between yawning and brain thermorégulation (Gallup and Gallup 2008).
 
According to the thermoregulatory theory, yawning acts to cool brain température through thermoregulatory mechanisms of countercurrent heat exchange, evaporative cooling and enhanced cérébral blood flow (for a discussion, see Gallup and Hack 2011). As a resuit, the ambient air température is critical for yawmng to fonction as a brain cooling mechanism, and therefore yawns should be constrained to a relatively narrow range of température, Le., a thermal window (Gallup and Gallup 2007). The prédictions of this hypothesis are that yawns should (1) increase in frequency with initial rises in ambient température from a thermal neutral zone, as this stimulâtes thermoregulatory cooling mechanisms to control températures within a normal range, (2) decrease as ambient températures approach or exceed body température, since yawns would be counterproductive by introducing deep inhalations of elevated tem-pérature into the body, and likewise (3) diminish when températures fall below a certain point, because thermoregulatory cooling responses are no longer necessary and coun-tercurrent heat exchange may cause déviations in internai température which fall below homeostasis (Massen et al. 2014). Aside from having différent triggers, the motor action patterns of spontaneous and contagious yawns are indistinguishable and there-fore thèse prédictions should apply to both forms. The thermal window hypothesis is already well supported by existing research in comparative psychology and behavioral biology. Observational research on non-human primates has documented that spontaneous yawmng frequency becomes elevated in warm ambient températures (Campos and Fedigan 2009; Deputte 1994). Furthermore, expérimental studies on birds and rats in the laboratory are consistent with the first two prédictions of this model (Gallup et al. 2009, 2010, 2011). For example, in budgerigars spontaneous yawns increase when températures are elevated from 22 to 34C, but then decrease in frequency when températures are held between 34 and 38C. Similar effects have been documented in Sprague Dawley rats using slightly différent température ranges (Gallup et al. 2011).
 
Two récent naturalistic studies on humans have also investigated the relationship between ambient température and yawning frequency by surveying pedestrians while outdoors in the same geographical location during distinct seasonal climate conditions. The ffrst study measured self-reported contagious yawning among pedestrians during the summer and winter months in the arid désert climate of Arizona, USA following exposure to a contagious yawning stimulus (Gallup and Eldakar 2011). The second study used the same methodology but measured the response of summer and winter yawning among pedestrians in the temperate climate of Vienna, Austria (Massen et al. 2014). Overall, the results from thèse studies demonstrated that yawning is signifîcantly less common at température extrêmes. In particular, self-reported contagious yawning was highest in the winter in Arizona and in the summer in Vienna, when ambient températures were near room température (19.4C; 21.9C), but yawning rates declined signifîcantly in the summer months of Arizona, when températures averaged 37C, and in the winter months of Vienna, when températures averaged 1.4C. Furthermore, both studies demonstrated that température was a significant predictor of yawning even when controlling for other variables associated with yawning frequency
 
The aforementioned literature, including naturalistic observations and controlled laboratory experiments, suggests that underlying mechanisms controlling yawning are sensitive to ambient température. Despite accounting for changes in daylight cycles associated with winter and summer months, and statistically controlling for hours of sleep prior to testing, it remains possible that physiological circadian changes across the year contributed to the pattern of self-reported contagious yawning in humans during distinct seasons. Therefore, the current study was designed to investigate whether significant variation in yawning exists within a short timeframe in a single season. Using the same approach as Gallup and Eldakar (2011) and Massen et al. (2014), we recruited pedestrians outside during an 18-day period over the summer in the equatorial monsoon climate of southern Florida, USA (Kottek et al. 2006). Ambient températures during this period ranged from 27.8 to 36.1C. Based on the first two prédictions of the thermal window hypothesis, we expected yawns to be (1) most fréquent during the lower bound of this range, since thèse températures are moderately warm and deviate from a thermal neutral zone, and (2) least fréquent at the highest températures as thèse are drawing near human body température.
 
Discussion
The themioregulatory theory states that the physiological conséquences of yawning fonction in brain cooling. Accordingly, the thermal window hypothesis, an extension of this theory, states that the expression of yawning should be sensitive to ambient température variation. Unlike previous studies to investigate the relationship between ambient température and yawning frequency in humans, which hâve sampled pedes-trians outside during distinct seasonal conditions and daylight cycles, the current study controlled for potential physiological changes that could émerge from changes in daylight cycles throughout the year by restricting data acquisition across a short timeframe. Consistent with the thermal window hypothesis of the themioregulatory theory, results showed that self-reported contagious yawning frequency varied predict-ably across ambient température gradients. That is, there was an increase in self-reported contagious yawning in moderately warm conditions deviating from room température, but as ambient température approached human body température pedes-trians exposed to a contagious yawning stimulus were significantly less likely to report yawning. In addition, the same pattern emerged for the self-reported urge to yawn among pedestrians that did not yawn while being tested.
 
This study demonstrates within season variation in self-reported contagious yawning is largely explained by déviations in ambient température. Thèse findings are présent even after statistically controlling for relative humidity, time of day, time spent outside prior to being surveyed, testing day across the two and half week period, âge of the participant, and hours of sleep the night before. Overall, thèse results support the interprétations of previous naturalistic reports on human yawning, and provide further évidence suggesting that the underlying mechamsms controlling the expression of yawning are involved in thermoregulatory physiology.