TUESDAY, May 9, 2006 (HealthDay News) -- Lesbians react differently to the powerful sexual chemicals called pheromones than heterosexual women do, a new Swedish study finds.
However, lesbians don't respond to pheromones in exactly the same way as heterosexual men do, said study author Dr. Ivanka Savic, an associate professor of clinical neuroscience at the Stockholm Brain Institute.
"The data suggest that there is a difference between male and female sexuality," said Savic, who, with her colleagues, examined the brains of 12 lesbian women, using positron emission tomography (PET), to evaluate their brains' responses to potential sex pheromones.
The new work builds on previous research by Savic and her colleagues, in which they found the same brain region -- the anterior hypothalamus -- was activated in homosexual men and heterosexual women when exposed to the progesterone derivative 4,16-androstadien-3-one (AND). AND is found in human sweat, and occurs in concentrations 10 times higher in men than in women. But the anterior hypothalamus region in the brains of heterosexual men was activated in response to the female pheromone estra-1,3,5(10),16-tetraen-3-ol (EST), the researchers also found. EST is an estrogen-like substance, found in the urine of pregnant women.
The hypothalamus regulates metabolic process and links the nervous system to the endocrine system by secreting brain hormones. It also responds to odor stimuli, including pheromones.
When Savic's team looked at the brain activity of the 12 lesbian women, it found the lesbians responded to both compounds in a similar way. And they processed them in a way more like heterosexual men than heterosexual women. But the relationship to the opposite sex was not as strong as the researchers found it to be in a previous study between homosexual men and heterosexual women. This lends support to the idea, the researchers said, that AND and EST are pheromones involved in sexual preferences. And it lends credence to the theory that homosexuality is different in men than in women, the researchers said.
The findings appear in the week's issue of the Proceedings of the National Academy of Sciences.
Savic's group also found that in contrast to the heterosexual women they studied, the lesbian women processed the AND pheromone by the olfactory network, not the anterior hypothalamus; when they smelled the EST pheromone, they partly shared activation of the anterior hypothalamus with the heterosexual men studied.
Larger populations need to be studied, Savic said. When asked if her research suggests that programs to change sexuality would not be effective, she said: "We have no proof, but I anticipate in the majority of people these programs will not work."
Others debate the meaning of the new research.
"It certainly suggests biologic processes are at play," said Brian Mustanski, an assistant professor in the department of psychiatry at the University of Illinois at Chicago. "And they certainly could be intersecting with some sort of environmental effects."
The new research suggests that "female sexuality is quite different than male sexuality," he said.
The research suggests that "sexual preference is associated with the brain response," said Warren Throckmorton, an associate professor of psychology and fellow for psychology and public policy at Grove City College in Grove City, Pa. "Lesbian women don't show the same pattern of [brain] activation in response to the pheromones."
While he finds it interesting that different parts of the brain responded differently in the study, "how those differences get there this says nothing about," he added. Whether the women were born that way or learned the behavior, he said, is beyond the scope of this research.
More information
The Council for Responsible Genetics can tell you more about genes and sexual orientation.
