According to DF Swaab (2008: "Sexual orientation and its basis in brain structure and function", PNAS 105 (30): 10273-10274. DOI: 10.1073 / pnas.0805542105. PMC 2,492,513th PMID 18,653,758th"...) neurobiological research on sexual orientation man only gain momentum, and have already shown that people have a number of differences in the brain, not only in terms of gender, but also in relation to sexual orientation ... ". Svab was first announced that sexual orientation in men and biological "clock" located in the hypothalamus, in his suprachiazmatic nucleus.
In Journal of Eng. Proc Natl Acad Sci USA (2008) Ivanka Savic and Per Lindstrom, after conducting brain research of 25 heterosexual men and women and 20 lesbians and gay men, by the application of magnetic resonance volumetry of cerebral and cerebellar hemispheres, showed that the relationship between brain hemispheres, and the form amigdale connectivity, atypical in sexually different gay homosexual persons.
Laura Allen and Simon LeVay showed that two of the four anterior hypothalamic nuclei (INAH 2 and 3) are significantly higher in men than in women on the basis which it is hypothesized that dimorphism of these nuclei might accord to sexual orientation. Le Vayi hypothesized that (INAH 2 and 3) are higher in individuals sexually oriented toward women (heterosexual men and homosexual women) and lower in individuals sexually oriented toward men (heterosexual women and homosexual men).
In humans and in animals, there is a drive homosexual patients of both sexes. Biological specificity is homosexual men, but also is present between the number of animals, in particular mammals. Thus, it is likely that homosexual activity a man can be considered as a biological variant of humans sexuality.
In 1990, the Krauts and Hoffman reported that the suprachiasmatic nucleus (SCN) in heterosexual men significantly higher than in women and that in gay significantly lower than in heterosexual men. In the same year, the Krauts and his colleagues investigated the correlation of brain development with his sexual orientation, treating the brain of male rats pre-and postnatally aromatase blocker ATD, and this presentation was produced enlarge SCN, which resulted in bisexual behavior in adult male rats.
Although the study of brain structures observed morphological - dimorphic difference in the persons of different sexual orientation ... maybe they are just a reflection of the observation but no real difference. That is why the researchers homosexuality posed an intriguing question whether perhaps certain sexually dimorphic features in the brain are different sample of individuals of the same sex but different sexual orientation? But whether the observed sex-atypical characteristics result of processes that occur during fetal (prenatal) or neonatal development, as is the case with gender identity and sexual orientation, it is still an open question.
Also, results Simon LeVay research and his discovery of the nucleus differ in size between heterosexual and homosexual men suggest that sexual orientation in humans requires further research on the biological level.
Identifying, on which essentially based the largest number of forwards studies it is not the same as finding the cause. Of course, anatomy is not the etiology, but may offer a starting point for further research in the quest for the ultimate origins of sexual orientation.
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