Jan 26 2007

The Brain’s Windows

In response to yesterday’s blog, Jim Shaver asked the following question:

“So what effect does childhood development have on the brain’s compartmentalization of function? Are many of the brain’s specialized functions established during early development into an essentially permanent normal or abnormal state? For example, in the very rare cases of so-called “feral” children, who have grown from a very early age with little or no human interaction, they are said to be unable to learn language and other social skills after they have been rescued as teenagers.”

This is an excellent question, and relates to a fascinating aspect of brain development. The brain contains much more information than the genes that code for the brain – so where does all this extra information come from? Primarily from the manner in which the brain develops. Essentially, genes establish the rules of development, but the development process creates emerging complexity that adds information to the final structure.

As an example, the information necessary to describe a bee hive is greater than the information in a bee’s “brain.” A bee brain contains simple rules that, when followed repetitively leads to a complex structure.

The brain does the same thing. It also uses a feedback mechanism called somatotopic mapping. For example, singles from the retina stimulate the visual cortex to map to the visual sensory input. By following simple developmental rules, a complex visual map of the world is created – and because it is based upon sensory feedback it is mapped precisely to the external world.

Part of the developmental programming includes windows of opportunity for development. So, for example, if a newborn were blindfolded for the first couple of years then the visual cortex would be deprived of sensory feedback and it would not be able to develop. Eventually the window of development would close, and the unused portions of the visual cortex would be coopted for other use.

It turns out that all of the compartmentalized portions of the brain that have been specifically investigated have a window of development (at least as far as I am aware). The language portion of the brain retains a plastic structure until about the age of four. During this four year window it maps to the phonemes (language sounds) and grammar to which it is exposed. After the age of four it is then set, like hardened cement. If you learn a language after that, it is more difficult, and you will have to use a much larger portion of your brain (this has been confirmed by fMRI studies).

A colleague of mine who does neurology research for NASA discovered a similar window for the development of our anti-gravity hardwiring. The primitive part of our brains contains motor hardwiring that basically allows us to subconsciously maintain anti-gravity tone and to walk without have to think about it too much. He suspended the hind-legs of rats as they developed and found that after a certain amount of time they could no longer develop their anti-gravity tone and had difficulty walking. The purpose of this research was to investigate the consequence of children growing up in low gravity environments.

This research into windows of neurological development has led to a cottage industry of children’s toys and educational material meant to encourage early development. However, much of this is bunk. First, there seems to be a minimal necessary amount of stimulation for brain functions to develop, but this does not mean that giving extra stimulation will cause the brain to super develop. There are inherent limits of design imposed by our genetics. Also, the evidence clearly shows that you cannot make parts of the brain, like the language centers, develop before they are programmed to develop. So teaching kids to talk at a very young age by intensive programs does not have any long term advantage.

The one application of this information that I think is legitimate is that it is probably helpful to expose children to different languages prior to the age of four. This will enable them to develop the hardwiring so that they can “hear” the different sounds of other languages. So there is probably no benefit to exposing kids to Mozart, but there probably is a language advantage to exposing them to German.

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