Tuesday, October 30, 2012

Too much information

I was just reading a quite well-written book about baby brain development: Brain Rules for Baby by John Medina. I like the book for the most part, but this little bit annoyed me:

In the chapter where he talks about relationship between the parents, the author discusses how having frequent fights between the parents is bad for the baby's brain development. In passing, he mentions that epinephrine and cortisol are secreted as a part of the 'fight-or-flight' reflex.

And that's it. He sort of just mentions them and then says that if the brain is 'cooked' in the appropriate set of hormones, it grows up healthy, but if not, then it grows up not as well developed.

I really hate when people do that: mention some facts of physiology or anatomy without explaining their relevance. It smacks of a cheap parlor trick. It's almost as if they were doing that to impress the audience with their knowledge of biology or somehow use the biological 'illustration' to give greater credence to their (often non-biological) argument.

I once saw a textbook of Psychology that had a picture of the map of Vienna at the beginning of the chapter on sexual behavior. The caption under the picture said something like the following: 'Many psychology textbooks have pictures of reproductive organs in the chapters on sexual behavior. The authors of this textbook are not sure what the relevance of those pictures is. That is why we included the map of Vienna — while equally irrelevant, it may be more entertaining.' When I read this caption, I thought it made an excellent point.

I have recently given a talk on the role of DNA methylation in late brain development. I had a slide in which I showed a figure from a study that showed that blocking DNA methylation affected long-term potentiation; I also wrote on the slide that 'a number of genes were upregulated'. My advisor asked me if I was planning to discuss or list those genes. I answered 'no'; I didn't think it was relevant, and the authors of that study had only provided a table of genes without discussing them much themselves. My advisor said: 'In that case, don't mention them at all.'

Again, I thought this was an excellent advice. If you're not going to explain how something fits into the puzzle, don't have it lying around, just for decoration. People have limited attention, and, more importantly, everything thing you say must make a point.

So... how could the author have made a better point with the mentioning of cortisol, etc.? Well, as it turns out, the function of cortisol is to draw glucose from most cells of the body towards muscle cells. Basically, when you see a lion and need to run away from it, your body needs quickly to raise energy 'currency' to supply your muscle cells. Release of cortisol does exactly that. And it makes sense to do that in a short term. As Robert Sapolski (an expert on the biology of stress) once put, 'Run away from the lion first; ovulate later.'

Imagine, however, if this process goes on for days or weeks or months! Your cells being constantly depleted of their energy resources. That will create energy crisis in most tissues of your body (except the muscles) and the long-term effects will be disastrous: the lining of your stomach will develop ulcers, your reproductive system will lose ability to perform well, and your brain cells will suffer damage (first, ability to make plastic changes in connectivity is diminished; next, dendritic complexity is reduced; finally, even cell loss -- the irreversible change -- can take place).

Now, if you think about the developing baby brain undergoing energy crisis, it makes sense that exposure to stress can be detrimental to brain development.

I am sure a writer as talented as John Medina could put the above into fewer words. Then, his mentioning of cortisol and epinephrine would be relevant to the discussion of the baby brain.

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