Alas, the slides are not available. Here's the abstract:
Homosexuality is a constantly debated issue as to whether it is determined at birth or a choice (nature vs. nurture). The works of the Kinsey Reports and Dr. Evelyn Hooker published in the 1950s resulted in the removal of homosexuality from the DSM4 in 1973. Since then, it has been mentioned as an illness only in the context of being a putative exacerbating factor in anxiety states. Recent studies reveal a clear cut neurobiology to sexual orientation.
Neurobiologist Simon LeVay conducted a study of brain tissue samples from 41 human autopsies performed at several hospitals in New York and California. He found a significant size difference of the interstitial nuclei of the anterior hypothalamus between homosexual and heterosexual men.
In addition, Dr. Ivanka Savic-Berglund and Dr. Per Lindström of the Karolinska Institute, Stockholm, performed fMRI and PET measurements of cerebral blood flow. Using volumetric studies, they found significant cerebral size differences between homosexual and heterosexual subjects; the brains of homosexual men resembled heterosexual women and homosexual women resembled heterosexual men. Extensive controls were performed during testing to exclude analytical variability.
A totally evidence-based medicine presentation will provide current data regarding homosexuality showing differences, or similarities, between the brains of homosexuals and heterosexuals to confirm that sexual orientation is neurobiologic at birth. Scientists and physicians with a keen understanding of the human brain must continue to bring data showing differences- or similarities- between the brains of all sexual orientations- heterosexual, homosexual, bisexual and transgender- to light. Having a good understanding of the natural evolution of sexual orientation is critically important to appropriate and supportive health care and a mature attitude of health care providers in an effort to minimize self blame from parents and to contribute to better patient-care within the lesbian, gay, bisexual, and transgender community.
It's based on evidence and not conjecture.
13 comments:
*sigh* What is the common phrase used in science - correlation does not imply causation? To believe this, I'd have to see data from a multi decadel study following a large cohort and taking measurements every year - do the differences exist at birth, if not when do they appear, are they influenced by people's behaviour, upbringing etc?
- The One Who Comprehends
But correlation can strongly hint at causation. The question is, do the brain changes cause homosexuality or vis versa or do both have a common other cause? It is much easier to come up with causal explanations that the brain differences underly homosexuality than the other way around.
But there is a more serious problem.
If you look at enough features some will show significant differences purely by chance. How many features were looked at and many showed significant differences? Then how many would you expect to show significant differences purely by chance?
Lloyd Flack said... "It is much easier to come up with causal explanations that the brain differences underly homosexuality than the other way around."
Not at all. The causal explanation is well known; connections in the brain which get used a lot get larger.
For example London taxi drivers have characteristic enlargement of certain parts of their brain concerned with spatial reasoning, but I am not aware of anyone suggesting that being a cabbie is innate.
Major - so which parts of the lymbic nucleus are plastic? And given that some of the sexually dimorphic areas of the brain are visibly different in miscarried foetuses, when does a foetus start practicing being gay?
Does the part of the brain that controls heartbeat get larger as time goes by, or are such hindbrain functions "fixed", unlike those in the cerebral cortex?
Sexual orientation is correlated with differences in the lymbic nucleus, not the areas where learning reinforcement occurs. The brain is not so much an organ as a complex of organs, with different degrees of plasticity.
Major - so which parts of the lymbic nucleus are plastic? And given that some of the sexually dimorphic areas of the brain are visibly different in miscarried foetuses, when does a foetus start practicing being gay?
Does the part of the brain that controls heartbeat get larger as time goes by, or are such hindbrain functions "fixed", unlike those in the cerebral cortex?
Sexual orientation is correlated with differences in the lymbic nucleus, not the areas where learning reinforcement occurs. The brain is not so much an organ as a complex of organs, with different degrees of plasticity.
One problem (that I see and that nobody else sees) with "locating homosexuality in the brain" is that before we scientifically locate homosexuality we need a good "scientific" definition of what homosexuality is. Not a social definition but a scientific one and nobody has ever been able to give me a good scientific definition? Is it being sexually attracted to those who appear to be the same sex that you are? In that case you could then be attracted to a member of the opposite sex who does a good job of appearing to be of the same sex as you.
I'm not sure what you are getting at Jade.
No, being biologically homosexual would not give you some superpower of detecting cross dressers.
I can tell you that being (biologically or otherwise) heterosexual I have experienced being attracted to a person of the same sex who appeared to be a person of the opposite sex. The attraction went away once the deception was unmasked.
Major - I'm being rude, and nosey, and feel free not to answer or to tell me impolitely to go to hell, I wouldn't blame you....
But why do you think that is so? Why did the attraction go away? Sorry, on another thread, we're trying to identify what is sexual attraction, and why we feel it.
You're gynephilic, exclusively so, yes? Meaning you're in maybe 30-35% of the population. But what does it mean to be gynephilic, how do you recognise women? Have you thought of that, what is instinctive, what is cultural conditioning?
"I can tell you that being (biologically or otherwise) heterosexual I have experienced being attracted to a person of the same sex who appeared to be a person of the opposite sex. The attraction went away once the deception was unmasked."
I don't disagree with that. I don't think I disagree with anything you said. But it still leaves us with trying to define a scientific definition of homosexuality.
Not trying to speak for "Major" but it's possible that the turnoff is not just prejudice.
People notice what they expect to notice. If, for example, facial hair is a turnoff, then a closely-shaven man with an effeminate face might first appear to be an attractive woman, and the stubble might go unnoticed while the viewer admired the attractive (to them) aspects of the person's appearance. But once the stubble was noticed, it would be difficult to ignore.
I've had experiences like this - once I saw a strikingly handsome woman, and realized after a second that it was a man, and re-cast the cheekbones and chin as masculine... and the face was not attractive to me anymore. On the other hand, I've seen men with effeminate faces who I continued to find just as visually attractive after I knew that they were men.
I wish "Major" hadn't used the word "deception." Perhaps it should be re-read with the phrase "mistake was realized"...
(sorry for the delay replying, I have been dealing with a family emergency)
I don't know how attraction works for me either ;-)
I suspect that humans are ultimately attracted to things they can't see (because of clothes) but establish correlations between what they can see with what they can't. Exceptions to those correlations are particularly jarring.
deception(plural deceptions: 1. An instance of actions and/or schemes fabricated to mislead and/or delude someone into errantly believing a lie or inaccuracy.
The individual concerned was not trans, I stand by the characterization.
Zoe- And given that some of the sexually dimorphic areas of the brain are visibly different in miscarried foetuses, when does a foetus start practicing being gay?
How do you know that the aborted foetuses were gay? Or have we just noted that they are sexually dimorphic not that gay ones are sexually dimorphic the wrong way?
Does the part of the brain that controls heartbeat get larger as time goes by, or are such hindbrain functions "fixed", unlike those in the cerebral cortex?
The cortical structures get larger then there is more information to process. The tracts from the medulla might get larger if you suddenly acquired another heart but not just because you continued using the existing one.
Sexual orientation is correlated with differences in the lymbic nucleus, not the areas where learning reinforcement occurs. The brain is not so much an organ as a complex of organs, with different degrees of plasticity.
The hippocampus (who's function is memorization and spatial reasoning and which is the bit which hypertropies in taxi drivers) is part of the limbic system.
I am not aware any tract in the cortex which has been shown to not be plastic and an awful lot which have be shown to be so.
One thing that makes me suspicious of the idea that this is purely biological is that sexual identification and sexual orientation are separable from each other as well as from anatomical sex (that is all four of cis hetero, cis homo, trans hetero, trans homo).
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