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Oxytocin: Oxytocin is significant for vaginal contraction during child birth as well as ejection of milk during lactation. The magnocellular neurons of the paraventricular and supraoptic nuclei of the hypothalamus project to the posterior pituitary where oxytocin is released into the blood. The parvocellular neurons of the hypothalamic also projects to limbic area (hippocampus, amygdala, striatum, hypothalamus, nucleus accumbens) and the brain stem. This affects maternal and sexual behaviour, pair bonding, as well as social recognition (Donaldson & Young, 2008).
Although both males and females have oxytocin receptors, it is relevant only for females.
Very interesting studies have been conducted in the recent past which shows the significance of oxytocin. For instance, increase in oxytocin level has been reported in study of eye gaze indicating social interest (Guastella, Mitchell, & Dadds, 2008), value of money transferred by the investor indicating interpersonal trust (Campbell, 2010). Faces are crucial for human identity and the right fusiform gyrus is responsible for face recognition. fMRI results confirm association between oxytocin and the activation of fusiform gyrus (Petrovic, Kalisch, Singer, & Dolan, 2008). Together with amygdala and superior temporal sulcus, fusiform gyrus processes facial expressions. Oxytocin receptors are present in the amygdala and hippocampus. Animal research shows that oxytocin is involved in social memory in rats. It regulates prosocial behavior and social cognition in animals.
Oxytocin reduces fear behaviour by reducing amygdala activation, increases parasympathetic functioning, inhibiting corticotropin releasing factor, and decreasing corticosteroid level. fMRI images confirm positive findings in human beings. Oxytocin reduces activation of amygdale and the connection between the amygdale and the upper brainstem in response to fearful visual stimuli, thus affecting autonomic nervous system reactions to threat (Kirsch et al., 2005). Besides reducing fear, oxytocin also helps conserve trust in events of betrayal. “Oxytocin….may serve to inhibit defensive behaviors associated with stress, anxiety or fear, and allows positive social interactions and the development of bonds” (Carter, 1998, p. 782). It facilitates empathy and prepares the person to take other’s viewpoint into account. This has been found in romantic relationships where oxytocin facilitates continuous monitoring of other’s viewpoint. Oxytocin is also referred to as “love hormone” or “liquid trust” as increased level of oxytocin makes the person altruistic, trusting and generous.
The thalamocingulate division of the limbic system activates maternal behaviour. This is specially found in the areas with high receptors for estrogen, progesterone, prolactin, and oxytocin. The orbitofrontal part of the right hemisphere controls attachment. Oxytocin, prolactin and opioids facilitate attachment. Opioid activity and high cortisol facilitates care giving behaviour. Glutamate facilitates separation distress. ACTH and adrenal cortical secretions are high in the depressed phase of separation. Sadness and depression activate the parasympathetic nervous system and HPA axis. Oxytocin, vasopressin, opioids and serotonin affect the hypothalamus and medullary source nuclei of the visceral vagus. Activation of vagus decreases pulse rate, blood pressure, cholesterol, triglycerides, glucose and epinephrine-norepinephrine levels. Thus, one can infer that social bonding will protect against cardiovascular disease.
Oxytocin and opioid systems are considered the physiological basis of sense of security. It makes our attachments essentially pleasurable. Oxytocin provides chemical basis of formation of social preferences. Studying the oxytocin level during pregnancy and first postpartum month, Feldman, Weller, Zagoory-Sharon, and Levine (2007) found positive correlation between oxytocin level and maternal behaviour such as gazing, vocalization, affectionate touch, positive affect, and maternal checking behaviour. Oxytocin released during sexual behaviour reinforces social bonding between the partners. Tend-befriend behaviour has attracted many psychologists. Estrogen augments the effect of oxytocin which, in turn, influences tend-befriend behaviour in females.
Anti-diuretic hormone (ADH)/ Vasopressin: The posterior pituitary secretions influences learning and memory processes. The posterior pituitary secretes vasopressin and oxytocin. These two hormones influence behaviour in opposite ways. Vasopressin facilitates memory processes. It affects consolidation as well as retrieval process. On the other hand, oxytocin facilitates passive avoidance behaviour and extinction of active avoidance reaction.
Increase in certain hormones at puberty increases the risk for psychopathology. Adrenarche and gonadarche are supposed to do this at puberty. For example, adrenarche refers to the maturation of HPA axis. It usually occurs between 6-9 years of and is characterized by rise of adrenal androgens such as dehydroepiandrosterone (DHEA) and its sulfate (DHEAS). Adrenal androgens have been associated with dominance, depression, and antisocial behaviour. On the other hand, gonadarche refers to the maturation of hypothalamic-pituitary-gonadal (HPG) axis. It usually occurs between 9-11 years of age. The HPG axis hormones such as gonadotropins, follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol, progesterone and testosterone rapidly increase during this state. Studies have associated testosterone and estradiol levels to negative affect aggressive behaviour. Pubertal hormones have been linked to psychopathology due to its impact on cortisol secretion. However, the sensitivity of the developing brain decreases with time. Studies have observed higher levels of adrenal androgens during early stages of puberty in females with early growth of pubic hair (before 8 years). Comparatively, this level declined after puberty.