mystery of yawning
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
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29 janvier 2011
Pers Soc Psychol Rev. 2010;14(3):281-295.
Oxytocin and human social behavior
Campbell A.
 
Durham University, Psychology Department, Durham, UK.

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Abstract
 
Despite a general consensus that oxytocin (OT) has prosocial effects, there is no clear agreement on how these effects are achieved. Human research on OT is reviewed under three broad research initiatives: attachment and trust, social memory, and fear reduction. As an organizing perspective for scholars' current knowledge, a tentative model of the causes and effects of alterations in OT level is proposed. The model must remain provisional until conceptual and methodological problems are addressed that arise from a failure to distinguish between traits and states, differing research paradigms used in relation to OT as an independent versus dependent variable, and the possibility that OT effects depend on the initial emotional state of the individual. Social and personality psychologists have important roles to play in developing more rigorous and creative research designs.
 
OT: A Primer and Some Caveats
 
OT is a peptide hormone composed of nine amino acids. It is highly conserved across species in terms of structure and function, although there is interspecies variability in the specific behaviors that it controls. OT has both peripheral and central effects. Peripherally, OT regulates uterine contractions during labor and milk ejection during lactation. It is synthesized in magnocellular neurons of the paraventricular (PVN) and supraoptic (SON) nuclei of the hypothalamus, which project to the posterior pituitary where OT is released into blood circulation. Centrally, OT acts as a neuromodulator: Released from all parts of the neuronal membrane, OT diffuses widely in extracellular fluid, affecting many regions of the brain. It is synthesized in the parvocellular neurons of the hypothalamic PVN, which projects to limbic sites (hippocampus, amygdala, striatum, hypothalamus, nucleus accumbens) and to the brain stem. Central OT effects include maternal and sexual behavior, pair bonding, and social recognition.
 
In some species a small quantity of peripherally administered OT may cross the blood&endash;brain barrier or influence behavior via afferent feedback to the CNS. Studies of plasma OT also vary in their use of basal versus reactive measures.
 
Bear in mind also that although both sexes have OT receptors, OT is of special relevance to females because OT synthesis and OT receptors are upregulated by estrogen. Indeed, McCarthy, McDonald, Brooks, and Goldman (1996) observe that the OT receptor is "one of the most strongly estrogen-regulated systems in the brain. . . . Estrogen-induced increase in OT receptor binding is integral to its behavior-modifying effects".
 
OT's sister nonapeptide arginine vasopressin (AVP), which is very similar in structure, appears to play a more important role in males, although OT has been shown to affect some male behaviors including partner preferences, sexual behavior, and social recognition. Both sexes have receptors for both neuropeptides, and to complicate matters further, the structural similarity of AVP and OT means that they may be capable of binding to each other's receptors.
 
The effects of the same peptide can also vary dramatically in males and females. For example, in men intranasally administered AVP stimulates agonistic facial expressions and decreased perception of friendliness in response to images of same-sex strangers. In women administration of the same peptide results in affiliative facial expressions and increased perception of friendliness. Studies that assay plasma OT as a dependent variable are most often performed on women, although some studies also include men. However, nearly all studies where OT is centrally administered as an independent variable use male participants only because of the small possibility of OT entering the bloodstream where it might cause uterine contractions. Thus, there is a potential confound among participant sex, study design (whether OT is an independent or dependent variable), and OT system (central vs. peripheral).
 
Another note of caution is warranted. Much of our basic knowledge about OT has come from research on rodents, and even here there are important differences between taxa. Extrapolations to humans must be made with caution because there is considerable variation in receptor distribution across mammalian species. In humans, we do not yet know the extent to which "hard-wired" responses, such as maternal behavior, pair bonding, and affiliation, have been superseded by learning and cultural transmission afforded by increased cortical size. There is general consensus that OT has positive effects on human social behavior, but there are at least three implicit proposals about the mediators of these prosocial effects.
 
OT: Attachment and Trust
 
The emotional bond between caregiver and offspring, and between adult partners, lies at the heart of the psychology of relationships. A secure attachment in infancy is important for normal psychological development and provides a base from which the infant explores the world beyond. The infant's internal working model of attachment has implications for the nature and quality of later adult relationships. The continuities and similarities between these two types of relationship have often been noted by developmental and social psychologists. It has been proposed not only that successful adult pair bonding depends on the early child&endash;parent relationship but also that the two share a common psychological mechanism. Although adult relationships incorporate sophisticated cognitive, social, and cultural components, they may share a basic emotional infrastructure with our earliest experience of attachment. Because mother&endash;infant attachment is ubiquitous in mammals, the possibility of a biological basis attracted research interest.
 
Early work on OT focused on its role supporting maternal behaviors toward offspring in rodents. In pregnancy, triggered by rising estrogen levels, OT receptors are upregulated in the uterus and the brain. Vagino-cervical stimulation during parturition activates OT neurons in the hypothalamus, stimulating OT release in many brain areas including the preoptic area, ventral tagmental area, and olfactory bulb. These pathways are responsible for coordinating a range of maternal behaviors including nest building, pup retrieval, licking, crouching, and maternal aggression. In 1979, Pedersen and Prange first demonstrated that intracerebroventricular (icv) infusion of OT can induce maternal responses in estrogen-primed virgin rats. Reciprocally, the onset of maternal behavior can be inhibited by OT antagonists, lesions of OT cells, and antibodies to OT. Recent studies using genetic knockout of OT receptors have confirmed significant deficits in mothering. Even in rodents, the role of OT however is confined to the initiation not the maintenance of maternal behavior (Kendrick, 2000). In humans, there is general consensus that prenatal and postpartum OT both enhances the formation of close bonds with the infant and reduces maternal stress reactivity.