Significant similarities exist in the brains of gay men and straight women, and those of lesbians and straight men, according to a 2008 study.

Researchers from the Karolinska Institute in Stockholm, Sweden, performed magnetic resonance imaging (MRI) on 90 subjects — 25 heterosexual men, 25 heterosexual women, 20 homosexual men and 20 homosexual women. Of those original 90 subjects, 50 participated in positron emission tomography (PET), which measures blood flow to the brain.

The MRI results showed a considerable difference between the brains of straight and homosexual subjects. For instance, the straight women and gay men both had more symmetrical halves of their brains, whereas lesbians and straight men had more asymmetrical brains with a larger right hemisphere, according to the study.

Similarities were also found in the connections of the amygdala, the region of the brain responsible for emotional learning. PET scans revealed similar functionality of the amygdala among gay men and straight women, and among gay women and straight men.

“This (study) basically underscores a hypothesis that there are some underlying brain physiology differences between the two groups,” said Dr. Daniel Leonard, a first-year resident in Pediatrics at USF and a member of USF’s Gay, Lesbian, Bisexual and Transgender/Transsexual (GLBT) community.

While the origins of sexual orientation remain a subject of controversy, most researchers in this area feel that differences in sexual orientation can be attributed to many different factors, said Dr. Michael Hoffmann, director of cognitive neurology at USF.

“It is chemical, birth-related, hormone-related, (involves) structural abnormalities and is genetic — all of those have to work together,” Hoffmann said. “This (study) adds to the body of literature we already have. It is an additional piece of evidence that shows that there are structural, chemical and genetic brain differences in people that are gay. It’s important for people to understand.”

Hoffmann said, however, that the meaning behind the differences found in this study is still unknown.

“This may just be what we call an epiphenomenon — in other words, it’s something abnormal, but on its own doesn’t mean much,” he said. “But it may lead you to uncovering other things, to the more important findings.”

Assistant professor of history David Johnson said he uses caution when reading studies of this nature.

“There seems to be some sort of cultural desire in society to find the scientific cause (of homosexuality),” Johnson said. “I think these studies tend to take something like sexual behavior and sexual desire that is very complex, and look for one bodily, genetic or neurological cause.”

He later added that this search for a single origin of homosexuality is what causes some studies to fail.

However, students like Jake Leavitt, a freshman theatre major and a member of the USF People Respecting Individual Diversity and Equality (P.R.I.D.E) Alliance, are still hopeful for the impact the study will have on societal views of the GLBT community.

“I think it’s great — it’s something that I truly believe in,” he said. “I was born gay. It wasn’t something I chose, and it’s not something I can choose not to be.”

Kristen Shalosky, an international business major and president of the P.R.I.D.E Alliance, is optimistic that the study will spread the acceptance already present at USF across the nation.

“I feel like the general impression of GLBT on this campus is very, very accepting, and I think that if this becomes a nationally known study, it will just add to that,” Shalosky said.

The study, which was published in the June 2008 issue of the Proceedings of the National Academy of Sciences, has garnered the attention of many major news outlets, such as National Geographic and the Los Angeles Times, extending the study’s reach from the academic community to the common household.

“My hope is that the study will have a huge impact,” Leavitt said. “I hope that it will change a lot of people’s minds.”