Wednesday, 1 February 2006

Left, Right, Male and Female Brains

Another one from the New Scientist :
Men and women's brains use different strategies to remember highly emotional images, according to a new brain imaging study. The discovery helps explain how women manage to remember emotional events better than men, something psychologists have known for years.

"It's hard evidence that there are differences in the brains of men and women," says Stephen Maren, of the University of Michigan in Ann Arbor, commenting on the research.

He thinks that evolution may explain the differences. Women tend to be caregivers, more empathetic and more verbal: "Those traits are reflected in brain mechanisms."

In the study, Turhan Canli, at the State University of New York at Stony brook, and his colleagues asked 12 women and 12 men to view a selection of images while their brains were being scanned by functional MRI.

Some were neutral pictures of things such as fire hydrants and bookshelves. But others were disturbing - of mutilated bodies and autopsies. Volunteers had to rate each image on a four-point scale for emotional intensity.
Without warning

Three weeks later, without warning, the volunteers were shown all the images again, plus 48 previously unseen images. They were asked to say whether they remembered the images clearly, only vaguely, or not at all.

One hypothesis for why women remember emotional events better than men is that they experience it more deeply - that is, they have the same brain activation but it is stronger. Another theory is that men and women experience and encode emotional memories in completely different ways.

The researchers found that even when both sexes rated an image as "highly emotionally intense", women were better at remembering it three weeks later. They also discovered that men and women really do recruit different parts of their brains during emotional experiences. Women had more activation in their left brains, and men in their right.

More importantly, for women the experiencing and the encoding used many of the same brain regions; in men it did not. "For whatever reason, it seems that integration of emotional experiences and encoding to memory is much tighter in women than in men," says Canli. "But it's unclear what could produce this phenomenon."

Maren also wonders if men and women just find different things arousing. This study used "disgust" to arouse emotions -- but what if they had used rage or aggression or pornography? "Are men worse across the board, or just in this type of arousing images?" he asks.

No bet.

The trouble with all of these studies is that the sample size is so small - double figures.

Such studies are indicative, useful for deciding which lines of research to pursue further, yet follow-ups are rare.

Ideally, an experiment like this should have an order of magnitude more subjects. Also, in an ideal world, once baseline data had been accumulated, people who identify as "transsexual", or with misgendered brains, should also be invited to take part. This might, once and for all, pin down TS as a biological "birth defect", or aklternatively, provide strong evidence that it isn't.

The trouble with doing such research is that there's strong opposition to it. There's a strong Feminist subgroup who holds as an article of Faith that any experiment designed to highlight differences in the way males and females think will be used as yet another tool of Male Oppression. I wish I could say they were totally, rather than almost totally, wrong.

As for Transsexuals, many quite understandably rebel against the notion that they may somehow be "defective". Some just believe in the Glories of Human Diversity, and that any attempt at understanding or ascertaining a biological cause would be used as a tool to discriminate against anyone who feels transgendered, but who doesn't "pass the test". Ultimately, they say that the only way of telling someone's gender is to ask them, and they have a point.

The GLBITQ lobby is also unenthused : for them, Transsexuality is a matter of choice, a choice and a right they defend. Anything that contradicts this thesis is not something they want any part of. And parenthetically, that's why I've had little to do with them. I don't identify as "Queer" or "Transgendered", just a human being with a Female brain and a formerly-male body. A woman who should by her genes have been born with a male mind, but wasn't. In short, a woman.

Me? I say the more we know, the better, and let the cards fall as they may. I personally am convinced from the existing evidence that most, if not all transsexuality is adequately explained by the Dorner Hypothesis, dating back 15 years now.
The Dorner hypothesis proposed that transsexualism is the result of this imprinting in utero. Contrary variation in the testosterone-estrogen ratio causes contrary differentiation of the hypothalamus and related structures in the brain. This results in gender identity and later body-image opposite to gonadal sex. As the sex hormone ratio influences errors of genital dimorphism, transsexualism appears to be a sex error at the level of brain dimorphism. A transsexual's neurological pathways have been laid down opposite to the vector of gonadal differentiation. Once the neuro-endocrine critical period is closed, the pathways reify and it is impossible to change them. Many professionals have noted that transsexuals are notoriously refractory to psycho-therapy. They pursue their cross-gender drives in snow-ball fashion to the point of sex reassignment with a motivation and determination that is hard to explain as other than a biological imperative.

To summarize so far, transsexualism probably is a sex error of the body at the level of brain dimorphism. It is not a matter of choice. It is probably caused by previous stages of neurosexual differentiation; at the level of fetal hormones, testosterone-estrogen ratio is imbalanced due to a defect in fetal gonadal development at the molecular level. This may be determined by the absence or presence of certain genes in the TDF cascade.

Each gene produces an enzyme responsible for correct genetic transcription of instructions for gonadal, hormonal, and neurosexual pathways. When these are disturbed, a small change at the level of the genes can have devastating consequences at the level of the person in society. Correct understanding of this phenomenon will probably be at the molecular genetic level.
That from an article (C) 1991 - before the Dutch experimental results showing differences in BSTc layers bvetween males and females, with MtoF transsexuals having Female patterns. We've had nothing but confirmatory evidence since then, though as I said, the individual sample sizes are far too small for confidence. In aggregate though, there are so many pieces of evidence that the brain is sexually dimorphic, and so many other pieces of evidence that suggest that Intersex is certain to happen in some proportion of neurological development, that I'm convinced.

And yet the most powerful opposition appears to be from religious groups, in an unholy alliance with some psychiatrists who have little understanding of biology, but are fanatic disciples of one or more popular psychiatric cults, such as Freudians or Jungians. I use the word "cult" advisedly : for they have taken some useful core truths, observations and insights, and constructed quite amazingly convoluted intellectual theories from them, backed up with little or no scientific evidence, and not even a lot of anecdote. They aren't to be blamed overmuch though : they're in the same position mainstream medicine was in before the discovery of the germ theory of disease, or even the human circulatory system.

It's ironic that a lot of the opposition to mainstream psychiatry comes from another, far more pernicious and scientifically dubious cult : that of Scientology. So no matter how much superstition is in psychiatry, I prefer the Bad to the Worse.

1 comment:

al fin said...

It is my humble opinion that the reactionaries who oppose followup research to these provocative studies are totally and absolutely wrong. It is far smarter to deal with reality than with fantasy. Current popular concepts of gender being taught on campuses are fantasy. They are creating legions of fantasy indoctrinated zombies who propagate the same delusion ad infinitum.