Evaluating T and you can OT training, we come across your interpretation away from efficiency is frequently selective. Education which administer OT interpret improved amygdala activity as the highlighting concern and you will prevention, whereas T government degree interpret an identical impact while the increased frustration and you will means. In terms of one another hormonal, you want to take into account the chance the effects of exogenous hormone toward male and female brains will likely differ. Considering the deeper OT receptor density on feminine mind, administration from OT may result in high levels of consumption and you may serving outcomes could be nonlinear, due to the fact has been found along with other hormone. It is possible one at the very least some element of T’s sensory consequences can be found through aromatization to oestradiol from inside the presynaptic terminals which in female will get improve sex-typical fear as a result in order to hazard. T sometimes establish very different consequences on the female brain and therefore, as opposed to a man head, hasn’t been prenatally structured from the T. Gene expression on the head is sexually dimorphic and you can subject to sex hormones: a comparable hormones can cause the definition of various genetics inside female and male minds [90,91].
(b) Amygdala–frontal connections
Lower-height affective tendencies so you can strategy otherwise end stimuli found in the limbic system are included in a good ‘reflexive’ behavioural control program cut chiefly by evolutionary forces. From inside the individuals, these tendencies is at the mercy of excellent ‘reflective’ manage. Mental intensity and behavioral impulse are going to be modulated by prefrontal cortex, especially the orbitofrontal (OFC) region, which has lead connections to the fresh new amygdala. In neuroimaging degree, bad correlations can be found anywhere between amygdala and you may OFC passion inside impulsively aggressive anybody . For the knowledge where members are educated to imagine aggressing up against or hurting someone, deactivation of your own OFC is known. Women provides more substantial ventromedial PFC and you will right lateral OFC [95,96]. A meta-analysis away from 88 studies stated greater OFC hobby in women to help you face stimuli portraying negative feelings (, look for and ). This suggests that ladies are more effective for the spontaneously managing emotional responses.
This is supported by studies of hormonal and neurotransmitter serotonin. When you’re progesterone increases functional connections within amygdala and you will PFC , T decreases they, when you find yourself making associations towards notice base unaffected [82,98]. OT, good neuropeptide upregulated by oestrogen, seems to have reverse effects to those regarding T. OT advances amygdala–prefrontal associations while reducing amygdala coupling to your head stalk .
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 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 connections
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 .