And to clear up the testosteron issue, let me quote some more from that page.
[h=2]Neurochemical differences[/h] [h=3]Hormones[/h]
Steroid hormones have several effects on brain development as well as maintenance of
homeostasis throughout adulthood. One effect they exhibit is on the
hypothalamus, where they increase
synapse formation.
[SUP][17][/SUP]
Estrogen receptors have been found in the
hypothalamus,
pituitary gland,
hippocampus, and
frontal cortex, indicating the estrogen plays a role in brain development.
Gonadal hormone receptors have also been found in the
basal forebrain nuclei.
[SUP][18][/SUP]
[h=4]Estrogen and the female brain[/h]
Estradiol influences cognitive function, specifically by enhancing learning and memory in a dose-sensitive manner. Too much
estrogen can have negative effects by weakening performance of learned tasks as well as hindering performance of memory tasks; this can result in females exhibiting poorer performance of such tasks when compared to males.
[SUP][19][/SUP]
It has been suggested that during development, estrogen can exhibit both feminizing and defeminizing effects on the human brain; high levels of estrogen induce male neural traits to develop while moderate levels induce female traits. In females, defeminizing effects are resisted due to the presence of
α-fetoprotein (AFP), a carrier protein proposed to transport estrogen into brain cells, allowing the female brain to properly develop. The role of AFP is significant at crucial stages of development, however. Prenatally, AFP blocks estrogen. Postnatally, AFP decreases to ineffective levels; therefore, it is probable that estrogen exhibits its effects on female brain development postnatally.
[SUP][20][/SUP]
Ovariectomies, surgeries inducing
menopause, or natural menopause cause fluctuating and decreased
estrogen levels in women. This in turn can “ attenuate the effects” of endogenous opioid peptides.
Opioid peptides are known to play a role in emotion and motivation.
β-endorphin (β-EP), an endogenous
opioid peptide, content has been found to decrease (in varying amounts/brain region),post
ovariectomy, in female rats within the
hypothalamus,
hippocampus, and
pituitary gland. Such a change in β-EP levels could be the cause of mood swings, behavioral disturbances, and hot flashes in post menopausal women.
[SUP][18][/SUP]
[h=4]Testosterone and the male brain[/h]
Testosterone has been found to play a big role during development but may have independent effects on sexually dimorphic brain regions in adulthood. Studies have shown that the medial amygdala of male hamsters exhibits lateralization and sexual dimorphism prior to
puberty. Furthermore, organization of this structure during development is influenced by the presence of
androgens and testosterone. This is evident when comparing medial amygdala volume of men and women, adult male brains have a medial amygdala of greater volume than do adult female brains which is partially due to androgen circulation.
[SUP][9][/SUP]
It also heavily influences male development; a study found that perinatal females introduced to elevated testosterone levels exhibited male behavior patterns. In the absence of testosterone, female behavior is retained.
[SUP][17][/SUP]
Testosterone's influence on the brain is caused by organizational developmental effects. It has been shown to influence proaptotic proteins so that they increase neuronal cell death in certain brain regions. Another way testosterone affects brain development is by aiding in the construction of the "limbic hypothalamic neural networks".
[SUP][17][/SUP]
Similar to how estrogen enhances memory and learning in women, testosterone has been found to enhance memory recall in men. In a study testing a correlation between memory a recall and testosterone levels in men, "fMRI analysis revealed that higher testosterone levels were related to increased brain activation in the
amygdala during encoding of neutral pictures".
[SUP][21][/SUP]
