Oxytocin
Nasally administered oxytocin has been reported to reduce fear, possibly by inhibiting the amygdala (which is thought to be responsible for fear responses). Indeed, studies in rodents have shown oxytocin can efficiently inhibit fear responses by activating an inhibitory circuit within the amygdala. Some researchers have argued oxytocin has a general enhancing effect on all social emotions, since intranasal administration of oxytocin also increases envy and "Schadenfreude". Individuals who receive an intranasal dose of oxytocin identify facial expressions of disgust more quickly than individuals who do not receive oxytocin. Facial expressions of disgust are evolutionarily linked to the idea of contagion. Thus, oxytocin increases the salience of cues that imply contamination, which leads to a faster response because these cues are especially relevant for survival. In another study, after administration of oxytocin, individuals displayed an enhanced ability to recognize expressions of fear compared to the individuals who received the placebo. Oxytocin modulates fear responses by enhancing the maintenance of social memories. Rats that are genetically modified to have a surplus of oxytocin receptors display a greater fear response to a previously conditioned stressor. Oxytocin enhances the aversive social memory, leading the rat to display a greater fear response when the aversive stimulus is encountered again.
Social cue
Oxytocin has been named "the social hormone". Research done on rats provide strong evidence that social contact enhances oxytocin levels in the brain which then sets the stage for social bonds. In recent years it has been found that inhaling oxytocin through the nasal passage increases trust toward strangers and increases a person's ability to perceive social cues. Activation of face-induced amygdala was found to be increased by oxytocin in women. There have been findings that oxytocin increases occurrence of attention shifts to the eye region of a face which suggests that it alters the readiness of the brain to socially meaningful stimuli. Dopamine neuron from the ventral tegmental area codes the salience of social as well as nonsocial stimuli. Bartz and his colleagues found that the effects of oxytocin is person-dependent, meaning that every individual will be affected differently, especially those who have trouble in social situations. Research done by Groppe and colleagues supports that motivational salience of social cues is enhanced by oxytocin. Oxytocin has been found to increase cues that are socially relevant.