ABSTRACT
Male and female brains differ in terms of structure and reproductive physiology and this is reflected in the distinctive reproductive behaviors and cognitive skills of the two sexes. This is sexual dimorphism. Brain sexual dimorphism occurs in primates, including humans. In humans, lateralization of cognitive functions is seen in which in the great majority of people, the left hemisphere is specialized for language tasks, while the right hemisphere is specialized for nonverbal, visuospatial tasks. Studies of hypothalamic cells in culture show that testosterone promotes neurite outgrowth, but it does so by first being converted by the enzyme aromatase to estradiol. Affected genetic males look like normal women and they behave as females, forming sexual relationships with men, despite their brain having been exposed to high concentrations of estrogens throughout their development. This implies that the rodent model is not applicable in humans. In human male fetuses, the testis secretes testosterone between 12-18 weeks of gestation.
