Magazine article Science News

Brain Feature Linked to Sexual Orientation

Magazine article Science News

Brain Feature Linked to Sexual Orientation

Article excerpt

A comparison of 41 autopsied brains has revealed a distinct difference between homosexual and heterosexual men in the brain region that controls sexual behavior. The finding supports a theory that biological factors underlie sexual orientation, although it remains unclear whether the anatomical variation represents a cause or result of homosexuality, says neurobiologist Simon LeVay, who describes the study in the Aug. 30 SCIENCE.

LeVay, of the Salk Institute for Biological Studies in San Diego, found that a particular cluster of cells in the forefront of the hypothalamus was, on average, less than half as large in the brains of homosexual men as in their heterosexual counterparts. Although scientists have yet to identify the precise function of the clump, called the interstitial nuclei of the anterior hypothalamus 3 (INAH 3), the hypothalamus is known as the seat of the emotions and sexual drives.

LeVay obtained brain tissue from autopsies performed at seven hospitals in New York and California. His study included 19 homosexual men, 16 men presumed heterosexual, and six women presumed heterosexual. All of the homosexual men died of AIDS, as did six of the heterosexual men and one of the heterosexual women.

As a group, the heterosexual men had larger INAH 3 regions than either the homosexual men or the heterosexual women, LeVay reports. The size difference remained statistically significant whether or not the subjects died of AIDS, ruling out the possibility that it resulted from the disease, he says.

"This proves that you can study sexual orientation at the biological level," LeVay asserts. …

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