Contrasting T and you may OT knowledge, we see your translation out of efficiency is often selective. Knowledge and this provide OT understand increased amygdala activity while the showing concern and reduction, while T government degree interpret a comparable feeling while the improved anger and you may means. With respect to one another hormones, we wish to consider the opportunity that effects of exogenous hormones into the female and male brains will in all probability disagree. Considering the greater OT receptor density about feminine attention, government out-of OT can lead to extremely high quantities of use and you can dosage outcomes are nonlinear, just like the has been found with other hormonal. It’s possible you to definitely about particular part of T’s neural consequences exist via aromatization so you can oestradiol when you look at the presynaptic terminals that female can get augment sex-regular fear in reaction to possibilities. T sometimes establish totally different outcomes towards the female mind which, rather than the male notice, has not been prenatally prepared by T. Gene expression from the mind try sexually dimorphic and you may subject to sex hormonal: a comparable hormones can cause the term of different family genes in the male and female thoughts [ninety,91].
(b) Amygdala–front connections
Lower-top affective inclinations to help you means or stop stimuli found in the limbic program are included in good ‘reflexive’ behavioral manage program cut mainly because of the evolutionary forces. Into the individuals, such tendencies is subject to higher level ‘reflective’ handle. Psychological intensity and you can behavioural response should be modulated because of the prefrontal cortex, particularly the orbitofrontal (OFC) area, with direct involvement with the new amygdala. During the neuroimaging knowledge, negative correlations can be found ranging from amygdala and OFC hobby from inside the impulsively competitive anyone . In education in which members was coached to assume aggressing against or hurting someone else, deactivation of your own OFC has been found. Women provides a more impressive ventromedial PFC and you may best lateral OFC [95,96]. A meta-research out-of 88 education stated higher OFC pastime in women to help you facial stimuli portraying bad feeling (, get a hold of in addition to ). This suggests that ladies could be better into the spontaneously managing psychological answers.
It is supported by knowledge out of hormonal plus the neurotransmitter serotonin. While you are progesterone grows useful connectivity between the amygdala and you may PFC , T reduces it, while making connectivity to the brain stem unaffected [82,98]. OT, a neuropeptide upregulated by the oestrogen, seems to have reverse effects to the people away from T. OT enhances amygdala–prefrontal associations when you are cutting amygdala coupling towards mind stem .
Serotonin (5-HT) plays a key role in the functional connectivity between the PFC and the amygdala. There is a dense concentration of 5-HT receptors in the limbic system (including the amygdala) with projections to the prefrontal cortex. Dietary tryptophan depletion (which menn med Panamanian kvinner reduces 5-HT levels) reduces connectivity in the prefrontal–amygdala circuitry specifically when viewing angry faces . Women have higher 5-HT transporter availability and, because this regulates 5-HT neurotransmission, baseline serotonin may be higher in women than men. Studies have reported a higher density of 5-HT1A receptors in women in areas including the amygdala and medial and orbital PFC . Receptor density in these areas is significantly negatively correlated with lifetime aggression. In animal research, 5-HT receptor density is also negatively correlated with T. Although this has not been replicated with humans, men (but not women) with high levels of aggression are characterized by a combination of high T and low 5-HT . Reduced serotonin availability or uptake, associated with high T, may explain men’s diminished prefrontal control over emotion-driven behaviour.
(c) Amygdala–peripheral connectivity
The central amygdala projects downward to the hypothalamus and brain stem to initiate autonomic and hypothalamic–pituitary–adrenal (HPA) responses to threat. Sex differences in self-reported and behavioural measures of fear are not matched by differences in sympathetic nervous system reactivity. When fear is induced through incremental behavioural approach to spiders , inhalation of CO2-enriched air , affective images , scary movie clips or emotional imagery , sex differences in heart rate and blood pressure are not found. In the HPA system, evidence indicates somewhat higher salivary cortisol measures in men after experimental stress induction .
