Saturday, January 3, 2015

How Our Brain "Trims the Fat"

In the book “The Mind’s Past” by Michael S. Gazzaniga, in chapter 2 the author is discussing how the much of the brain’s growth is dependant on interaction with the environment and simple mandate from the genome.  Near the end of the chapter the author talks about how neurobiology has deepened this curiosity with the discovery of “a tremendous overproduction  of cells during cortical development”.  

Cortical development is another way of saying the development of the cortex, a part of the brain (the dark purple outline in the picture) with many purposes one of which language will be the focus of this article.  The interesting thing is that after all the cells involved with the development of neurons have been produced (neurogenesis), “as many as 50 percent [of these cells] die off”.  Why would our bodies allow for the production of so many cells only to allow half of them die off.  Doesn't it seem like a waste of energy?  Isn't the waste of anything spell death and possible extinction in the game of natural selection?  And lastly, why would the body allow so much waste to occur with the brain, undoubtedly the most valuable organ in the human body?  I will not answer any of these questions specifically, I apologize.  I will however hypothesize as to why the production of so many cells in general.

Needless to say it is a mystery to which would reward the next nobel prize to the whomever can provide a verifiable answer and many neurobiologists have made their attempts.  For some reason the author feels that 3 ideas of one scientist named James Voyvodic merit their mention in the book I referenced above but I don’t share his sentiment.  I will include reference below so you can check them out on your own time because I reserve the space in this article for my own idea as to why our body conducts its own cellular holocaust during its cortical development.

My idea is steeped in the linguistic capacities of the cerebral cortex.  One of the criticisms of many attempts neurobiologists have made to explain this phenomenon (including our best friend James Voyvodic) is that their answers do not apply to other developmental systems where this overproduction of cells also occurs.  I admit my idea also succumbs to the same criticism but I must start somewhere.  My idea starts with the fact that every single human is born with the same vocal capabilities - to make incoherent sounds human adults have a hard time understanding so often describe with words like giggle, cry, babble, etc.  Regardless to where in the world a baby is born, amongst all the diverse types of language and culture every single new-born is limited to giggling, crying, babbling, and etc.  At this point if a baby’s linguistic capability were likened to a genome, every single baby in the world would be genetic twins.  The body waits for the brain to start interacting with it’s environment before it decides how neuronal framework related to language should be formed.  Unlike other organs that develop to a much greater degree within the womb, certain parts of the brain are not as aware of what kind of environment awaits it once it leaves the womb.  

I shall make a comparison using lungs as an example.  The body knows with 100% certainty that regardless to where in the world it is born, the need for oxygen is universal; therefore a baby enters the world with organs ready to properly use oxygen.  The cortex of the brain is not as certain.  It doesn’t know whether it will be born in England, Russia, the jungle, or even if there will be a need for language at all.  It accommodates to this by producing twice as many cells that are necessary to produce a functional neuro-linguistic system after it leaves the womb.  Then, as the brain interacts with its environment, it figures out the types of sounds it needs to produce, eventually shapes these sounds into crisp words, and it slowly locks down onto a certain combination of neurons that produce a language fit for its environment by eradicating cells that would not be used in their production.

In this respect our environment doesn't actually affect the growth of our brains, it determines in what way our body “trims the fat”.


Gazzaniga, Michael S. (1998) The Mind’s Past, pp. 54-56. University of California Press. ISBN: 0-520-21320-3  

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