مدونة ألوان

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هذه المدونة خاصة ب ألوان. نحن شبكة من المثليين والمثليات العرب نعيش في بلاد مختلفة في البلاد العربية والمهجر .

Arab Lesbian Women & Allies Network (ALWAAN) 's Blog

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Alwaan is an online network for Arab lesbians, gay men, bisexual men and women, transgender persons and those who are interested in building bridges with the LGBT Arab community.

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الكثير من الافلام الخاصة بالمثليين والمثليات

Thursday, February 25, 2010

Are Gay Men Born That Way?

Are Gay Men Born That Way?
By Christine Gorman;J. Madeleine Nash/Los Angeles Monday, Sep. 09, 1991 *

Gay men often claim that even as children they knew they were somehow "different" from other boys. Many say that sense even preceded puberty. And yet, though researchers have tried for decades to identify a biological basis for homosexuality -- which seems to be present in all human societies -- they have mostly come up dry. Tantalizing clues have surfaced: gays are more likely to be left-handed, for instance. But in the end, there has been little proof that biology is sexual destiny.

Now new research offers evidence that there may indeed be a physiological basis for sexual orientation. In a study of 41 brains taken from people who died before age 60, Simon LeVay, a biologist at San Diego's Salk Institute for Biological Studies, found that one tiny region in the brain of homosexual men was more like that in women than that in heterosexual men. "Sexuality is an important part of who we are," notes LeVay, who is gay. "And now we have a specific part of the brain to look at and to study."

That specific part is found at the front of the hypothalamus in an area of the brain that is known to help regulate male sexual behavior. Within this site, LeVay looked at four different groupings of cells, technically referred to as the interstitial nuclei of the anterior hypothalamus, or INAH for short. Other researchers had already reported that INAH 2 and 3 were larger in men than in women. LeVay hypothesized that one or both of them might vary with sexual orientation as well.

Routine autopsies provided the tissue LeVay needed. All 19 homosexual men had died of AIDS. So had six of the 16 presumed heterosexual men and one of the six women. Although LeVay hoped to include lesbians in his study, he was unable to obtain brains from women identified as such. After careful examination of the brain samples, he found that the INAH-3 areas of most of the women and homosexual men were about the same size. In straight men this region was on average twice as large -- or about the size of a grain of sand.

In the past, much research on sexual orientation has focused on the role of interpersonal relationships in early childhood. Psychological literature is replete with material suggesting that male homosexuality is triggered by relationships with an overly protective mother or with a distant, even hostile father. "Here is a whole other way of looking at the question," says LeVay. "These children may already be determined to become homosexual or heterosexual. The development plan that is laid out for them may be what causes them to develop certain troubled relationships with their parents."

LeVay's findings are certain to trigger a good deal of controversy. Many technical aspects of the study are subject to question, as the author concedes. He cannot be certain, for instance, that all the heterosexual men in the control group were heterosexual. And since the AIDS virus attacks the brain, the size difference could be an artifact of the disease. It is also possible that the difference actually has nothing to do with sexual orientation or that it is the result rather than the cause of homosexuality.


What the Gay Brain Looks Like

What makes people gay? Biologists may never get a complete answer to that question, but researchers in Sweden have found one more sign that the answer lies in the structure of the brain.

Scientists at the Karolinska Institute studied brain scans of 90 gay and straight men and women, and found that the size of the two symmetrical halves of the brains of gay men more closely resembled those of straight women than they did straight men. In heterosexual women, the two halves of the brain are more or less the same size. In heterosexual men, the right hemisphere is slightly larger. Scans of the brains of gay men in the study, however, showed that their hemispheres were relatively symmetrical, like those of straight women, while the brains of homosexual women were asymmetrical like those of straight men.

The number of nerves connecting the two sides of the brains of gay men were also more like the number in heterosexual women than in straight men.
Just what these brain differences mean is still not clear. Ever since 1991, when Simon LeVay first documented differences in the hypothalamus of gay and straight men, researchers have been struggling to understand what causes these differences to occur. Until now, the brain regions that scientists have come to believe play a role in sexual orientation have been related to either reproduction or sexuality. The Swedish study, however, is the first to find differences in parts of the brain not normally involved in reproduction — the denser network of nerve connections, for example, was found in the amygdala, known as the emotional center of the brain. "The big question has always been, if the brains of gay men are different, or feminized, as earlier research suggests," says Dr. Eric Vilain, professor of human genetics at University of California Los Angeles, "then is it just limited to sexual preference or are there other regions that are gender atypical in gay males? For the first time, in this study it looks like there are regions of the brain not directly involved in sexuality that seem to be feminized in gay males."

Vilain, who studies the genetic factors behind sexuality and sexual orientation, notes that it may turn out that the brains of gay men possess only some 'feminized' structures, while retaining some masculine ones, and this is reflected in how they act on their sexuality. "We know from studies that men, regardless of their sexual orientation, retain masculine characteristics when it comes to their sexual behavior," he says. Both gay and straight men, for example, tend to prefer younger partners, in contrast to women, who gravitate toward older partners. Most men are also more likely than women to engage in casual sex, and to be aroused by visual stimuli. "So I expect that some regions of the brain will remain masculine even in gay men," says Vilain. For something as complex as sexual orientation, it's no surprise that everything from genes to gender to environment may play a role in ultimately determining your perfect partner.

Scans find gays’ feminine side is in the brain

June 15, 2008

Scans find gays’ feminine side is in the brain

Scientists investigating human sexuality have found that the brains of homosexuals have structural and functional differences from those of “straight” people.
Lesbians appear to have a lower proportion of grey matter in their brains than straight women, giving their brains a more “male-like” structure.
The brains of gay men appear to have structural similarities to those of heterosexual women. They also exhibit the same powerful response as straight women to the sex hormones released in male sweat.
The research comes amid growing interest in how variations in brain structure are linked to human behaviour.
It is known, for example, that the greater size of male brains and the higher proportion in females of grey matter – the cells that process signals from the senses – are caused partly by sex hormones released during foetal development. These hormones are also involved in determining sexual orientation.
Scientists have long thought this meant there should be differences in the brains of homosexuals. Brain scanning equipment has only recently become powerful enough to seek them out, however.
In one study, researchers at the Wellcome Trust Centre for Neuroimaging at University College London used magnetic resonance imaging, or MRI, to look at the brains of 80 men and women, including 16 gay men and 15 lesbians.
They found that lesbians had a “male-like” proportion and distribution of grey matter in their brain when compared with heterosexual women.
In a paper published in the Public Library of Science, the researchers said: “In homosexual women the perirhinal cortex grey matter displayed a male-like structural pattern.” The perirhinal area is associated with social and sexual behaviour.
In another study in the Proceedings of the National Academy of Sciences, Ivanka Savic of the Karolinska Institute, Sweden, asked 12 gay men, 12 heterosexual women and 12 heterosexual men to smell hormones found in male sweat while she measured their brain responses.
She found that the anterior hypothalamus, an area linked to sexual behaviour, responded strongly in both heterosexual women and gay men. Straight men showed little response. This implies the brains of gay men have functional similarities to those of straight women.
Savic also measured the brain responses of 12 lesbians who were asked to smell male and female hormones. The lesbians responded much more strongly to female hormones.
The research suggests sexual orientation is largely programmed into people early in life, according to Savic. However, other studies have shown a person’s lifestyle can lead to structural brain changes.
Bookmark and Share هذه المدونة خاصة ب ألوان. نحن شبكة من المثليين والمثليات العرب نعيش في بلاد مختلفة في البلاد العربية والمهجر .


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