Sunday, 20 December 2015

Limits on Neuroplasticity - and the infamous BSTc layer

I found a wonderfully informative site I wasn't aware of, by an author whose talents at conveying complex concepts to a lay audience exceed my own. Even though I'm the one who's supposed to have a Grad Cert in Science Communication from the ANU.

It's Liz - Day by Day, a blog that apparently started as a record of Transition, but has since become an excellent resource on the science of Sex and Gender.

A bit like this blog, though I started it many years before my own atypical and non-volitional transition. (Zoe kicks herself again for not doing it earlier, not having the courage to).

Anyway, from this site, a graphic illustration of one area of the brain where women tend to have one structural pattern (OK, we've not found any exceptions, just degrees) and men another.

As they say, sometimes a picture is worth a thousand words.

Now onto Neuroplasticity - the quality of the brain to change its structure due to environment.

A good article on the limits to it is Equal ≠ The Same: Sex Differences in the Human Brain

"But wait," argue the anti-sex difference authors, "the brain is plastic"-that is, molded by experience. One group of authors uses the word plasticity in the title of their paper three times to make sure we understand its importance.29 (As someone who has studied brain plasticity for more than 35 years, I find the implication that it never occurred to me amusing.) By the plasticity argument-also made explicitly by neuroscientist Lise Eliot in her book Pink Brain Blue Brain-small sex differences in human brains at birth are increased by culture's influence on the brain's plasticity.30 Eliot further argues that we can avoid "troublesome gaps" between the behaviors of adult men and women (a curious contradiction, by the way, of the view that there are no behavioral differences between the sexes) by encouraging boys and girls to learn against their inborn tendencies.

It is critical to understand where the fallacies in this argument lie. First, it is false to conclude that because a particular behavior starts small in children and grows, that behavior has little or no biological basis. One has only to think of handedness, walking, and language to see the point. Second, this argument presupposes that human "cultural" influences are somehow formed independent of the existing biological predispositions of the human brain. But third, and most important, is the key fallacy in the plasticity argument: the implication that the brain is perfectly plastic. It is not. The brain is plastic only within the limits set by biology.

To understand this critical point, consider handedness. It is indeed possible, thanks to the brain's plasticity, to force a child with a slight tendency to use her left hand to become a right-handed adult. But that does not mean that this practice is a good idea, or that the child is capable of becoming as facile with her right hand as she might have become with her left had she been allowed to develop her natural tendencies unimpeded. The idea that we should use the brain's plasticity to work against inborn masculine or feminine predispositions in the brains of children is as ill conceived as the idea that we should encourage left-handed children to use their right hand.

29 Fine, C. et al. Plasticity, plasticity, plasticity. . . and the rigid problem of sex, Trends in Cognitive Sciences November 2013, Vol. 17, No. 11.
30 Eliot, L., Pink Brain, Blue Brain: How Small Differences Grow Into Troublesome Gaps -- And What We Can Do About It, 2009; HMH Publishing.

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