There are odors that drive a person's sexual response, and scientists have found that homosexual men differ from heterosexual men in the way they respond to such smells. Their brain activity more closely resembles the responses observed in women, new research has shown.
"This is another piece of evidence that the brains of gay and straight people are organized differently," said Simon LeVay, a biologist who almost 15 years ago identified a structural difference in the brains of homosexual and heterosexual men.
The new work, by Ivanka Savic and her colleagues at the Karolinska Institute in Stockholm, grew out of an earlier finding that brain scans of men and women differed dramatically from each other in response to chemical smells that mimic male and female hormones.
In their latest study, in the Proceedings of the National Academy of Sciences, the researchers put gay men into a brain-scanning machine and saw that the region of the anterior hypothalamus became activated when the men were given male sex hormones to smell. By contrast, heterosexual men showed more brain activity in this region when smelling odors associated with female hormones.
The smells used in the Swedish study were made by reconstructing chemicals in male perspiration and female urine that mimic derivatives of testosterone and estrogen.
In the current study, the brains of the homosexual men showed similar responses to that of heterosexual women when sniffing testosterone. The brains were no different from heterosexual men and women when responding to a nonsexual smell, lavender.