Swaab D F, Gooren L J, Hofman M A
Netherlands Institute for Brain Research, Amsterdam.
Horm Res. 1992;38 Suppl 2:51-61. doi: 10.1159/000182597.
Animal experiments have provided evidence for the presence of sex differences from the synaptic level up to behaviour. Although sex differences in the human brain may have been presumed implicitly since the days of Aristotle, research on the presence of functional and structural sex differences of the human brain started only relatively recently. The most conspicuous sex difference in the mammalian brain was described by Gorski et al. [1978] in the preoptic area (POA) of the rat hypothalamus. We found that the volume of a putative homologue of this sexually dimorphic nucleus (SDN) in the adult human hypothalamus was more than twice as large in men as in women and contained about twice as many cells. Recently a similar sex difference and volume has been described for the human bed nucleus of the stria terminalis and 'interstitial nuclei of the hypothalamus' (INAH). Sexual differentiation of the hypothalamus was generally believed to take place between 4 and 7 months of gestation. A life span study on the SDN of more than 100 subjects revealed, however, that only after the age of 2-4 years postnatally sexual differentiation becomes manifest by a decrease in volume and cell number in the female SDN. If sexual differentiation of the brain indeed takes place postnatally, not only chemical and hormonal factors may influence this process but also social factors. A prominent theory on the development of sexual orientation is that it develops as a result of an interaction between the developing brain and sex hormones. According to Dörner's hypothesis, male homosexuals have a female differentiation of the hypothalamus. This hypothesis was not supported by our observations on the SDN. Neither the SDN volume nor the cell number in the hypothalamus of homosexual men differed from that of heterosexual men. However, a difference in SCN cell number was observed in relation to sexual orientation. The volume and cell number of the SCN of homosexual men was twice as large as that of a reference group. During development, the SCN volume and cell counts reach peak values around 13-16 months after birth. At this age the SCN contains about the same number of cells as the SCN of adult male homosexuals, whereas in the reference group the cell numbers subsequently decline to the adult value, which is about 35% of the peak value.(ABSTRACT TRUNCATED AT 400 WORDS)
动物实验已为从突触水平到行为层面存在性别差异提供了证据。尽管自亚里士多德时代起，人们可能就已隐隐推测出人类大脑中存在性别差异，但对人类大脑功能和结构性别差异的研究直到相对较近才开始。哺乳动物大脑中最显著的性别差异由戈尔斯基等人于1978年在大鼠下丘脑的视前区（POA）中描述。我们发现，成年人类下丘脑这个性二态核（SDN）假定同源物的体积，男性比女性大两倍多，且细胞数量也约为女性的两倍。最近，终纹床核和“下丘脑间质核”（INAH）在人类中也被描述有类似的性别差异和体积差异。下丘脑的性别分化一般被认为发生在妊娠4至7个月之间。然而，一项对100多名受试者的SDN寿命研究表明，只有在出生后2至四岁，女性SDN的体积和细胞数量减少，性别分化才会显现出来。如果大脑的性别分化确实发生在出生后，那么不仅化学和激素因素可能影响这一过程，社会因素也可能产生影响。关于性取向发展的一个重要理论是，它是发育中的大脑与性激素相互作用的结果。根据多纳的假设，男同性恋者的下丘脑具有女性化特征。我们对SDN的观察并不支持这一假设。男同性恋者下丘脑的SDN体积和细胞数量与异性恋男性并无差异。然而，在视交叉上核（SCN）细胞数量上观察到了与性取向相关的差异。男同性恋者SCN的体积和细胞数量是一个参照组的两倍。在发育过程中，SCN的体积和细胞数量在出生后约13至16个月达到峰值。在这个年龄，SCN中的细胞数量与成年男同性恋者的SCN中的细胞数量大致相同，而在参照组中，细胞数量随后降至成年值，约为峰值的35%。（摘要截选至400字）
