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Gay men’s brains respond
differently to a male odor
Posted May 9, 2005
Courtesy Proceedings of the National Academy of Sciences
and World Science staff
The brains of gay men react similarly to those of
women, and differently from those of other men, to the smell of a chemical in male sweat, researchers say.
The chemical has long been suspected as being a possible pheromone, or a substance whose odor induces sexual arousal.
Although pheromones are common among animals, there is no substance generally
agreed upon by scientists to be a human pheromone. However, researchers are studying several chemicals that are considered possible human pheromones.
One is a substance called AND, related to the sexual hormone testosterone. Another is called EST and is similar to estrogen, another sex hormone.
In a past study, Ivanka Savic of the Karolinska Institute, Stockholm, Sweden and colleagues
found that a brain region called the hypothalamus becomes activated when men smell EST and women smell AND, but not vice versa. The
hypothalamus is known to have slightly different characteristics in men and
women, and to influence sexual behavior.
In the new study, the researchers examined whether brain activation patterns induced by EST and AND corresponded with sexual orientation, rather than with biological gender.
The scientists compared brain activity between homosexual men, and heterosexual men and women, in response to smelling EST, AND, and ordinary odors, such as lavender.
The researchers reported that AND activated the hypothalamus in homosexual men and heterosexual women, but not heterosexual men. Conversely, EST activated the hypothalamus in heterosexual men alone.
All three groups responded to common odors similarly, engaging only brain regions that process smell. These findings indicate that the human brain reacts differently to these potential pheromones compared with common odors, the researchers added, suggesting a link between sexual orientation and brain function.
The findings are published in the online early edition of the research journal Proceedings of the National Academy of Sciences this week.
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