hypothalamus:A portion of the forebrain that lies below the thalamus on each side and plays a major role in controlling the production of sex-hormones and the regulation of fertility and menstrual cycles through its interaction with the pituitary gland. It acts as a control center for certain bodily-functions and plays a vital role in sexual-behavior by means of regulating the pituitary gland (to which it is attached) and many bodily-functions (sexual, metabolism, salt and water balance, growth, etc.). An injury of this portion may cause sexual difficulties. Planned Parenthood refers to is as: ' A small area in the brain that regulates basic animal functions .'
Quote: Charles Panati. Sexy Origins and Intimate Things (1998):
-- (1) ' Where in the Brain Is the Sexual Circuitry Laid Down? Mainly in the hypothalamus, a structure at the base of the brainstem that is a primary center for sex-drive and copulatory behavior. Also in the amygdala (above the ears), an area associated with aggression and violence. And, to a lesser extent, in the cerebral cortex, or "thinking center" of the brain. Men and women apparently do think differently, not just because of social conditioning - which is undeniably important - but also because of brain differences. These neural differences, to some as yet undetermined degree, may be behind many of the Conventional Wisdom traits examined in the previous section. To paraphrase John Grays metaphor: Mens brains are from Mars, womens brains are from Venus . And, it is not impossible that gay brains just might have their own point of developmental origin .'
-- (2) ' Salk Institute researcher Simon LeVay studied forty-one brains and found that part of the hypothalamus was smaller in gay men than in straight men - about only half the size. He also found that a tiny region of the hypothalamus, which is involved in sexual-behaviors, was, in gay men, more like that found in women than in heterosexual men. He looked at four different grouping of cells, technically referred to as the interstitial nuclei of the anterior hypothalamus, or INAH . Others had already reported that INAH 2 and 3 were larger in men than in women. He found that the INAH-3 areas of most of the women and the gay men were about the same size. In straight men, this region was on average twice as large - about the size of a grain of sand. The LeVay study was the second to find a difference between the hypothalamuses of gay and straight men. In 1990, a Dutch team discovered that another group of neurons in the same tiny gland was larger in homosexuals than in straight men. Some scientists believe that this structure governs daily rhythms, not sexual-behavior .' Simon LeVay published his study on the difference in brain structure in homosexual and heterosexual men in Science in 1991; he concluded that these findings ' suggest that sexual-orientation has a biologic substrate '.
See Also: gay gene, hypothalamus, INAH
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