The brains of gay men and women look like those found in straight people of the opposite sex, said a study Monday published in the Proceedings of the U.S. National Academy of Sciences.
A computer image maps a human brain.The brains of gay men and women look like those found in straight people of the opposite sex, said a study Monday published in the Proceedings of the U.S. National Academy of Sciences.(Xinhua/AFP Photo) The Swedish study, comparing the size of the brain's halves in 90 adults, suggested that gay men and straight women had halves of a similar size, while the right side was bigger in lesbian women and straight men.
"The observations cannot be easily attributed to perception or behavior," the researchers from Sweden's Karolinska Institute wrote. "Whether they may relate to processes laid down during the fetal or postnatal development is an open question."
Researchers at the Stockholm Brain Institute in Sweden investigated "two separate parameters, both unlikely to be directly affected by learned patterns and behavior" in 90 men and women -- 50 heterosexual and 40 homosexual -- using magnetic resonance imagery (MRI).
Fifty people who took part in the study were also given positron emission tomography (PET) scans to study the amygdalae, masses of nuclei located deep within the temporal lobes which control arousal, fear and emotional responses, and hormonal secretions.
The results showed that the right-hand brain hemisphere was larger in heterosexual men and homosexual women, while homosexual men's and heterosexual women's brain hemispheres were symmetrical.
Homosexual men showed another brain similarity with heterosexual women in their amygdala connections, which process certain emotions, as did homosexual women and straight men.
"The amygdala has a key role in emotional reactions to external stimuli, including stress," the authors of the study said, hypothesizing that the amygdala of straight men and gay women could be "wired for a greater fight-or-flight response," reportedly more common in men.
The researchers added that the study cannot say whether the differences in brain shape are inherited or due to exposure to hormones such as testosterone in the womb and if they are responsible for sexual orientation.
But this is something they plan to look at in a further study of newborn babies to see if it can help predict future sexual orientation.
Source: Xinhua\agencies
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