How neuroscience interprets sexual orientation

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  Last updated November 10, 2017 at 4:54 pm


Could brain structure and development account for differences in sexual orientation?

Brain imaging may hold some clues to the origins of same sex attraction, but findings need to be treated with caution.

As far back as 1991, British-American neuroscientist Simon LeVay published a study looking at the structural differences between gay men and straight men.

Studying three groups (women, men assumed to be heterosexual, and homosexual men) he looked at their post-mortem brain tissues. He found four cell groups from the interstitial nuclei of the anterior hypothalamus (INAH), an area in the brain associated with the regulation of male-typical sexual behaviour. It was found that INAH 3 was more than twice as large in heterosexual men compared to women and homosexual men.

The conclusion he drew from this was that there is hypothalamic structure difference for sexual orientation in men.

Many studies have built on this work, such as in 2008 by the Stockholm Brain Institute that found striking similarities between the brain structures of gay men and straight women on the one hand, and of lesbians and straight men on the other.

Brain imaging showed that in homosexual men and heterosexual women the right and left hemispheres of are the brain almost exactly the same size, whereas lesbians and straight men have asymmetrical brains, with the right hemisphere significantly larger than the left.

Before jumping to conclusions, it’s important to point out that identifying regions is not entirely conclusive. However they at least suggest there is a strong neurological basis in human sexuality. In neuroscience, it’s not enough to identify regions of the brain, functionality of these regions needs further clarification.

Dr Angelo Tedoldi, a neuroscientist, points to some of the difficulties with this sort of study.

“The major problems with studies about sexual preferences and differences in the brain of heterosexual and homosexual people are related to our understanding of sexuality. We do not have extensive information about the brain processes that drive sexuality in either males or females.

“We have an understanding of brain region differences and how some of these differences might be playing a role in sexual behaviour. However, we do not understand the driving forces behind sexual orientation or sexual preferences.”

Science of Sexuality series:

What biology and genetics say about same sex attraction

What role do hormones play in determining sexual attraction?

An evolutionary view of the ‘gay gene

Psychology: Freud has a lot to answer for

About the Author

Kelly Wong
Online producer at Australia's Science Channel. I have a background in immunology, food blogging, volunteering, and social media. I'm passionate about creating communities on social media and getting them excited about science. I enjoy good food and I am on an eternal mission to find the best ice cream. Find me on Twitter @kellyyyllek