Thursday, March 30, 2006

The developing brain: some big surprises

This is quite surprising. The human brain changes extensively between birth and adolescence (that we knew), but what's interesting is that it the pattern of changes is highly variable. Not everyone's brain follows the same developmental path.
Science & Technology at Scientific Smart Kids Found to Undergo Delayed Brain Development

... Rapoport and her colleagues at NIMH and McGill University followed 307 children of varying ages as they grew up, scanning them with an MRI machine periodically. They then compared such measures as brain volume with the results of a standard IQ test. Contrary to popular perception, the brightest kids did not necessarily have the largest brains.

They did, however, exhibit a distinctive pattern of brain development. Whereas an average child's cortex thickness peaked around age eight, the smartest children experienced thickening of the cortex until early adolescence. In all of the subjects, the cortex waned during adolescence, perhaps due to the pruning of neurons as the brain becomes more efficient, the researchers speculate.

Complicating the picture, however, relatively intelligent children--smarter than average but not the smartest--followed roughly the same development pattern as their more typical peers. And in the smartest kids the cortex shrank more than most during adolescence, in some cases dropping them below their relatively intelligent peers.

Although such intelligence seems to be genetic, the child-rearing environment may play an even more critical role, the researchers stress. Studies in rats have shown that their cortex thickness depends on richness of experience. [jf: I think this is misleading. The experimental rats they refer to had very limited environments, any reasonably decent human environment may be more than rich enough to make genetics the rate limiting step.]
It will be very interesting to see the results of similar studies performed in autistic children, particularly if we study not only pre-adolescents but also changes extending into the 20s. I have long wondered what the true natural history of so-called "high functioning autism" really is ...

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