Introduction
Qu'est-ce qu'un bâillement
Bâiller : l'étymologie
Quand bâillons-nous ?
Interprétations historiques
Le bâillement dans la magie, l'ethnographie et le folklore
Pourquoi bâillons-nous?
Contagion du bâillement (2004) (2009)
Phylogénèse
Neurophysiologie du bâillement
en anglais, yawning
schéma
Schémas anatomiques, embryologie
Sémiologie et examen clinique
Complications : manoeuvre de Nélaton
Bâillements pathologiques
Bâillements iatrogènes
Enquête en médecine générale
Observations et cas cliniques
Les mystères restant à éclaircir
Bibliographie
Neural basis of drug induced yawning
Visiter des sites sur le sommeil
Visiter des sites médicaux et bibliothèques
Résumé-vulgarisation
Imprimer des textes du site
Les critères éthiques du site
L'actualité du site
Répondre au sondage du site
L'auteur : Dr O. Walusinski
Recherche par thèmes
Recherche par mot du site :

 

 
avec l'aide de
FreeFind

Index du site
La lettre d'information du site
Le bâillement vu par les peintres
Du bâillement en littérature
Télécharger textes du site
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
30 novembre 2017
 Heliyon
2017;3(11)e00437
 
Scholarpedia
Yawning: a cue and a signal
 
Moyaho, A. Flores Urbina, E.
Monjaraz Guzmán, O. Walusinski

Chat-logomini

 
Résumé
Le bâillement est associé à des comportements de nature physique et sociale et un certain nombre de fonctions correspondantes lui ont été attribuées.
 
Le bâillement non-orienté (comportement homéostasique personnel) et le bâillement dirigé (comportement d'affichage vers autrui) englobent toutes les expressions du bâillement, bien qu'il soit souvent difficile de différencier un type de l'autre dans un contexte social.
 
Dans cet article, les auteurs analysent plus complètement les données d'une étude dans laquelle quatre combinaisons d'indices sensoriels ont été présentés à des paires de rats en cage, ces paires étant constitué soient de rats familiers entre eux soient étrangers.
 
Le but de la nouvelle analyse est de démontrer que les bâillements non orientés et ceux dirigés peuvent être identifiés par leurs fonctions distinctives.  Toutes les paires de rats utilisent des signaux olfactifs pour se reconnaître mutuellement comme des compagnons ou des étrangers. Seuls des rats 'étrangers' utilisent des signaux auditifs pour détecter et répondre au bâillement de l'autre.
 
Des vitesses de défécation croissantes (c'est-à-dire un indice de réactivité émotionnelle) inhibent le bâillement chez les rats familiers, de sorte que la fréquence des bâillements est un reflet de l'état physiologique de chacun. Ces résultats suggèrent que le bâillement non-orienté sert de réplique entre rats familiers et que le bâillement dirigé est un signal-avertissement pour les rats 'étrangers'.
 
Les auteurs émettent l'hypothèse que le bâillement 'réplique' pourrait être un acte que les animaux effectuent pour ajuster leur tonus musculaire lors d'un changement d'état afin de s'adapter de façon synchrone. Le bâillement affiché pourrait être un signal indiquant la capacité physiologique des rats à l'approche d'un risque de conflits interindividuels.
 
Introduction
 
Yawning&emdash;a deep inspiration with mouth opening and slow expiration&emdash;is a widespread behaviour amongst all vertebrates. The behavioural repertoire of organisms distantly related to each other such as fish, birds and mammals includes yawning (Walusinski and Deputte, 2004), although most of our understanding about the prominent features of yawning (e.g. contagion) came from studies in humans (for an extensive review, see Provine, 2005). In spite of this ubiquity and the relative ease with which yawning can be identified and yawns counted, the biological significance of yawning is unknown. The growing number of functions linked to yawning reflects the diversity of phenomena to which it has been associated. All of these functions, however, may be grouped as physiological (true or rest yawn) or communicative (e.g. emotion or tension yawn).
 
Most of the physiological hypotheses of yawning's significance are based on a restorative function (i.e. homeostatic mechanism), including the opening of Eustachian tubes (Laskiewicz, 1953), equilibrium of CO2 and/or O2 levels in the blood (Sauer and Sauer, 1967; Provine et al., 1987b), prevention of atelectasis (Cahill, 1978), correction of imbalance in cerebral oxidative metabolism (Lehmann, 1979), proper articulation of the temporomandibular joint (de Vries et al., 1982), evacuation of potentially infectious substances from the tonsils (McKenzie, 1994), brain thermoregulation (Gallup, 2007), stimulation of the carotid body by compression (Matikainen and Elo, 2008), auto-regulation of the locomotor system (Bertolucci, 2011), and more recently, a process of switching the default mode network to the attentional system through the capacity of yawning to increase circulation of cerebrospinal fluid (Walusinski, 2014). However, none of the physiological hypotheses have received sufficient empirical support.
 
Yawning behaviour has also been associated with the presence of physiological disorders. For example, yawning may indicate encephalitis (Wilson, 1940), haemorrhage (Nash, 1942), motion sickness (Graybiel and Knepton, 1976; Matsangas and McCauley, 2014), the beginning of hypoglycaemia, which is a prodromal sign of vaso-vagal reaction (Cronin, 1988), and stress (Kubota et al., 2014). It is still unknown whether there is a cause-effect relationship between yawning and these physiological disorders, or if they are simply coincidental manifestations of a regulatory function.
 
Yawning frequency has also been associated with increased cholinergic and peptidergic activity (Dourish and Cooper, 1990), and decreased dopaminergic activity (Dourish and Cooper, 1990). These associations may contribute to the understanding of the immediate mechanisms involved in yawning behaviour, but they hardly say anything about the biological meaning of yawning.
 
Most communicative hypotheses about yawning come from observational studies performed in non-human primates in whom teeth-bearing during yawning has led to the suggestion that this behaviour reinforces dominant identity rather than signalling a threat (Deputte, 1994). Accordingly, yawning has been compared with intimidating displays that dominant males usually show to subordinate males (Troisi et al., 1990; Walusinski and Deputte, 2004; Zucker et al., 1998). In contrast, Sauer and Sauer (1967) proposed that yawning might induce relaxation of social tension. Yawning has also been described as a displacement activity&emdash;an unexpected display by an animal that appears to be engaged in other activity (Delius, 1967; Troisi, 2002)&emdash;and as an indication of changes in behavioural state (Provine et al., 1987a; Greco et al., 1993). There is also little experimental evidence to support these hypotheses.
 
What makes the identification of yawning with a function even more complicated is the fact that the physiological correlates of yawning, which might be used to support a given hypothesis, may produce contrasting effects. Thus, stimulation or inhibition of yawning has frequently been associated with changes in stress/anxiety, from the mild stress produced by exploration (e.g. a rat placed in a new environment) or vigilance, to the strong stress produced by fear (e.g. response-dependent punishment). For example, a new environment inhibits a rat's yawning, as compared with the increase observed following repetitive exposure to the same observation setup (Moyaho and Valencia, 2010). Low levels of vigilance have been linked to yawning occurrence in young human adults (Provine and Hamernik, 1986). Moreover, a mild shock to the feet in rats failed to suppress the yawning which preceded it (Moyaho and Valencia, 2010). Although these results clearly show a relationship between yawning and stress/anxiety, they do not indicate a consistent pattern; this may be partly due to variables which cannot be quantitatively controlled, making it difficult to determine precise cause-effect relationships. The use of quantitative variables such as defecation rate&emdash;an indication of emotional reaction to external stimuli which reflects the physiological state of the body&emdash;may clarify the relation of yawning with factors that cause stress to an animal, and thus help to recognise yawning functions.
 
Equating physiological and communicative functions of yawning with non-social and social contexts respectively is inaccurate since both forms may occur in a social context. A more precise identification would be with non-directed yawning (i.e. performed without the intention of eliciting a response from another individual) and directed yawning (i.e. performed with the intention of eliciting a response from another individual) respectively (Hall and Devore, 1965; Anderson, 2010). Nonetheless, it is not yet clear how to distinguish them in a social context. If a given animal yawns in front of conspecifics, this might be considered as directed yawning (i.e. display behaviour). Conversely, if an animal yawns without being watched by conspecifics, this could be taken as an instance of non-directed yawning (i.e. self-directed behaviour). Nevertheless, it would be unjustified to assume that other sensory modalities do not also participate in the detection of yawning; therefore, apparently non-directed yawning could indeed be directed. Recently, Moyaho et al. (2015) scored yawning rates in cage mate and stranger rats that were exposed in pairs either to auditory, olfactory or visual cues. The authors found that only stranger rats showed auditory contagious yawning, although cage mate rats showed correlated defecation rates, a possible indication of emotional empathy. These differences between cage mate and stranger rats confirm the participation of sensory cues other than visual cues in yawning, and suggest that the differential effect of the treatments applied to the two groups of rats might help in recognising yawning functions.
 
This study tested the hypothesis that the differences which cage mate and stranger rats showed in terms of yawning reflect two different functions of yawning. For this purpose, the study re-analysed the data obtained by Moyaho et al. (2015) using probabilistic and statistical models.
 
Discussion
 
The purpose of this study was to re-analyse a database from a previous study, which suggested that the differential response of cage mate and stranger rats to a combination of sensory cues could be used to identify the function of yawning. With the re-analysis, directed and non-directed yawning were respectively identified with the response of stranger and cage mate rats to the combination of olfactory and auditory cues. The rats used the olfactory cues to discriminate between cage mate and stranger rats, and the auditory cues to detect and respond to each other's yawning.
 
Yawning frequency could be a reliable indication of a rat's physiological state, as yawning rate and defecation rate (an index of emotional reactivity) showed a consistent negative association in cage mate rats, so that frequent yawning was a genuine indication (i.e. a cue) of a low-arousal state of calm. This interpretation agrees with a steady increase in yawning frequency recorded over several days in HY male rats placed daily in the same observation cages. This increase presumably happened because the rats became acquainted with the test condition (Moyaho and Valencia, 2010), which might have progressively caused less stress. While average yawning rate per test situation decreased with average defecation rate in cage mate rats&emdash;so that the greater the uncertainty about the next cage rat's identity the greater the defecation rate (i.e., NVOC rats)&emdash;the rat of each pair that surpassed the other in yawning frequency was the one that tended to show the lower pre-test defecation rate. Thus, somehow the relative yawning frequency of each pair of cage mate rats reflected a difference acquired before the test situation to which they were exposed.
 
The existence of a negative association between yawning and defecation rate in cage mate rats contrasts with the lack of such an association in stranger rats. Nonetheless, the pairs of stranger rats with olfactory communication yawned more frequently with higher defecation rates, although the relation was moderate. A thorough analysis of this relation revealed the existence of a communicatory effect within each pair of rats, since the yawning of the rats with fewer yawns positively correlated with the defecation rate of the rats with more yawns. Similarly, the yawning of saline-treated rats showed a positive association with the defecation rate of the kanamycin-treated rat. Therefore, stranger rats affected one another's behaviour most likely through yawning.
 
The ways in which cage mate and stranger rats used yawning behaviour in response to olfactory and auditory cues are aligned with the distinction between a cue and a signal (Maynard Smith and Harper, 2003). A cue is a feature of the world, animate or inanimate, that an animal can use as a guide to future action (Hasson, 1994), and a signal is an act or structure that an animal uses to change the behaviour of another animal. The effect that the act produces, fosters its evolution, and the evolution of the receiver's response promotes its effectiveness (Maynard Smith and Harper, 2003). In the case of cage mate rats with olfactory communication, there must have been quick individual recognition based on familiarity and previously established dominance hierarchies, which has been suggested to occur in many animals (Bradbury and Vehrencamp, 1998). Because there was no physical contact between the rats, volatile chemicals likely played a role in mutual recognition, and auditory signals likely played a role in coordinating responses. It is unlikely, however, that the yawning observed in the rats exposed to olfactory communication was a direct response to volatile chemicals, although this could be the case in male bats that yawned during social interactions (Gebhard, 1997; as cited by Voigt-Heucke et al., 2010). In any case, cage mate rats probably recognized each other readily and adjusted their behaviour accordingly; in this context of familiarity, no conflict regarding dominant-subordinate roles should exist between the rats because a dominance hierarchy has already been established. If so, cage mate rats would mostly be irresponsive to each other's behaviour, as evidenced by the finding that they would choose to yawn in association with their own defecation rate. Therefore, this type of yawning can be referred to as a cue which may have evolved into a regulatory act associated with a rat's physiological state.
 
We specifically propose that cue yawning is a motor act used to diminish variation in muscle tone. This function is reasonable as a hypothesis because of the type and large number of muscles involved in yawning (approximately 54 in humans; Walusinski, 2004). These muscles participate in proprioception and interoception by conveying information used to indicate how an individual feels (Craig, 2003; Walusinski, 2006). Moreover, it is known that the main function of proprioceptive reflexes is to adjust the motor output according to the biomechanical state of the body and limbs; thereby a compensating mechanism for the intrinsic variability of such output is achieved (Pearson and Gordon, 2000). Thus if yawning is an involuntary motor act, it would be part of the proprioceptive reflexes involved in decreasing the intrinsic variability of muscle tone&emdash;something like tuning up a musical instrument&emdash;so as to ensure operation efficiency.
 
The hypothesis proposed by Bertolucci (2011)&emdash;that yawning (he did not distinguish between cue yawning and signal yawning) increases the level of tone necessary for activity&emdash;explains the frequency of yawning observed, for example, following awakening, but not the frequency preceding sleep onset, when it is known that most mammals also yawn. The hypothesis that cue yawning reduces the variation in muscle tone accounts for the increase of yawning observed before a change of state, either from resting to activity or from activity to resting. Moreover, if the hypothesis is correct, intra- and inter-individual variation in yawning rates would reflect the magnitude of muscle tone variation in each individual, and thus the number of yawns required to decrease it. Thus, the subjective ratings of feeling associated with yawning can vary from unpleasant to pleasant according to the reduction of muscle tone variation achieved by an individual. As a consequence of a pleasant state following yawning, an individual may show unconcern or indifference (Baenninger and Greco, 1991), and thus the possibility of agonistic behaviour (e.g. dispute, conflict, etc.) decreases.
 
In contrast to cage mate rats, an encounter between stranger rats most likely initiates competitive scent marking so that each rat can determine the other's individual features as well as its ability to defend territory and resources (Hurst and Beynon, 2004). Scent marking and counter-marking are advertising strategies commonly used by rodents to establish control over resources (Hurst and Beynon, 2004); the chemicals released function as a reliable mechanism by which rats can provide information about their strain, sex, individual identity (Brennan and Kendrick, 2006), and current reproductive and health status (Hurst and Beynon, 2004). This creates a context of conflict in which most individuals would attempt to settle any dispute involving territory and resource defence without a fight by using signals to persuade each other to flee (Bradbury and Vehrencamp, 2011).
 
The findings of the present study agree with the existence of conflict&emdash;and concomitant attempts at resolution&emdash;between stranger rats, because those with more yawns and under olfactory (or auditory) communication yawned in response to the yawning of those rats with fewer yawns; the rats with more yawns probably played a dominant role and were more motivated. In fact, previous studies have revealed that a context of frequent male-male encounters might promote yawning (Moyaho et al., 2009). Moreover, the rats with more yawns might also have high levels of steroid hormones. There is a significant positive association between yawning and penile erections (Holmgren et al., 1985; Moyaho et al., 2015) that depends on the action of steroid hormones (Melis et al., 1994; Phoenix and Chambers, 1982), which also facilitate aggressive behaviour. Therefore, the rat with more yawns of a pair might also have more testosterone, and hence better odds of winning an eventual fight. Thus, yawning frequency might be an honest signal of physiological capacity in stranger rats (Moyaho et al., 2015). Nevertheless, for yawning to be an honest signal, it should entail a cost. Although no studies have assessed the costs of yawning, its motor complexity suggests that it could be physiologically exhausting&emdash;a large number of muscles are recruited&emdash;and also a risky act, because whenever an individual yawns it becomes vulnerable to predation, as it exaggeratedly opens its mouth and closes its eyes. In addition to these potential costs, there is evidence that males have low survival rates caused by testosterone-dependent behavioural traits which are necessary to achieve a dominant status (Sinervo et al., 2000).
 
Yawning behaviour could have evolved through the ritualization of a cue resulting from changes in physiological state (Maynard Smith and Harper, 2003). Such a cue might be linked to vomeronasal olfaction, which is involved in intra-specific chemical communication (Bradbury and Vehrencamp, 1998) in many mammals and reptiles. For example, when mammals contact urine or secretions, many of them (e.g. antelopes, felines) raise their heads and retract the upper lip to facilitate perception of odorants. This is a behavioural pattern called flehmen (Bradbury and Vehrencamp, 1998). Indeed, there is a type of yawning in chimpanzees in which the lips are funnelled outwards that resembles flehmen (Vick and Paukner, 2009). Similarly, a pumping mechanism in hamsters facilitates perception of volatile chemicals from the vomeronasal organ (Meredith et al., 1980). Also, the occurrence of mouth gaping in rattlesnakes, which is an analogue behaviour to flehmen or yawning in mammals, increases when snakes are exposed to conspecific skin chemicals (Graves and Duvall, 1983), once again apparently to facilitate vomeronasal olfaction.
 
This type of chemical communication is frequently associated with reproduction in both mammals and reptiles (Meredith and Fernandez-Fewell, 1994). In fact, the vomeronasal organ is larger in males than in females (Halpern, 1987), a size difference that parallels the sexual dimorphism in yawning behaviour, which in several species is more frequent in males than females (Bertrand, 1969; Deputte, 1994; Goy and Resko, 1972; Hadidian, 1980; Hall and Devore, 1965; Redican, 1975). It is unlikely, however, that yawning behaviour is currently used to stimulate vomeronasal olfaction, given that some species which yawn have lost the vomeronasal organ (e.g. fish and birds; Bertmar, 1981), and given the exaggeration of mouth opening. Nonetheless, the ancestral origin of yawning and its broad presence in animals are aligned with the evolution of the vomeronasal organ, including the lachrymal ducts (Bertmar, 1981), the content of which is frequently released with yawning. This coincidence, as well as the association with spontaneous penile erections strongly suggests that yawning behaviour arose from the ritualization of pre-existing cues involved in perceiving stimulating chemosignals in a mating context.
Conclusion
 
To date, there is no convincing explanation for the biological significance of yawning, which remains an elusive issue. The variety of contexts associated with yawning does not necessarily mean yawning has several functions. Instead, current literature suggests that mammals, at least, tend to yawn in two major situations: when an individual most likely directs its yawning to a conspecific, and when an individual does not direct its yawning to any conspecific, because it is either alone or not in the line of sight of the conspecific. In effect, as the analysis of data presented here shows, there seem to be two types of yawning; the one shown by cage mate rats is an act reflecting the physiological state of the body, and therefore might be considered as a cue. We propose that an individual yawns because it needs to adjust muscle tone (i.e. decrease the variation), so that the muscles can appropriately work together when a change of state is needed. The other type of yawning, which stranger rats showed, involves the interaction of at least two individuals in which the yawning of one of them affects or is affected by the other individual's behaviour. Further studies are necessary to clarify the precise direction of the effect; nonetheless, we propose that this type of yawning might function as a signal in male-male conflicts and probably involves the physiological capacity of the contestants. The consistent association of yawning with penile erections and testosterone seems to support this hypothesis.
 
In summary, the findings of this study provide a framework in which earlier categorizations for the function of yawning converge into two expressions: cue yawning, which may function as a regulatory act of the level of muscle tone variation; and signal yawning, which may function as a physiological capacity signal.