Link between smell & sexuality cited

Lesbians react to the smell of certain bodily odours in ways similar to heterosexual men and different from heterosexual women, new research suggests. Building on their previous studies that showed significant differences in the ways heterosexual and homosexual men’s brains process odours, the researchers may be narrowing the search for the elusive human pheromone.
The existence of phero-mones, the sex-specific chemicals that send messages by smell to other members of the species, is well known in animals, but their existence among humans is in dispute. The authors do not claim that they have discovered human pheromones or even that odours are a major factor in human sexual choices. But they have found suggestive differences in physiological responses to odour.
The study appeared online on May 8 in the Proceedings of the National Academy of Sciences. The substances involved are a progesterone derivative produced in male sweat and an estrogenlike steroid that has been detected in female urine. The two smells are processed in the brain differently from ordinary odours.
In the experiment, 12 lesbians smelled the two substances while researchers observed blood flow in their brains with PET scans. The scents activated parts of the brain that ordinarily process odours, but the estrogenlike compound also activated a part of the hypothalamus, as it does in heterosexual men.
Animal studies suggest that the hypothalamus is important in sexual behaviour. So, when that part of the brain lights up under the stimulus of an odour, a sexual response, rather than simply an olfactory one, is implied. In previous research, Dr Ivanka Savic and her colleagues established that brain responses to these odours were reciprocal in heterosexual men and women.
Despite the similarities, lesbians do not respond to these two odours in exactly the same way as heterosexual men, so the analogy with gay men and heterosexual women is imperfect. “This observation could favour the view that male and female homosexuality are different,” said Dr Savic, an associate professor of neurology at the Karolinska Institute in Stockholm.
By Nicholas Bakalar