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同性恋现象一直是一个让人迷惑不解的问题。最近，瑞典研究人员发现，男同性恋者和女异性恋者的大脑存在某些相似性，女同性恋者和男异性恋者的大脑也具有一些共同点。这或许会有一点启示吧。
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. |
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发表于 2016-7-9 23:49:54