The “plasticity” of the human brain

For Christmas last year, Teresa tried to buy me the latest book by Stephen Pinker, evolutionary psychologist and linguist.  She found that someone had bought all the copies of every title by Pinker from the local Barnes & Noble. Either that person was a real fan, or someone trying to suppress Pinker’s work. So she got me another book for Christmas, “The Brain that Changes Itself” by Norman Doidge, M.D., and he presents some results that are fascinating and relevant for everyday life.

We are all aware that the brain uses different areas for different functions. Vision is processed in the upper back of the head. Your right brain controls your left side and vice versa. It turns out that parts of the body that are close together physically are managed in the brain by regions close to each other. Fine motor control is handled by the lower back of the brain. It’s called “localization”. But the implications of localization have been grossly exaggerated.

First of all, although it is true that different areas in the brain are physically “mapped” for different functions, the brain is capable of some amazing adjustments. People with massive injuries or extensive birth defects of the brain are able to function because other regions of the brain take over with varying degrees of functionality. This is one kind of “plasticity”. Another kind of plasticity is when a part of the body is lost or becomes non-functional, The part of the brain that is no longer needed for that function is taken over by other functions. (They find this out by using Functional Magneto Resonance Imaging (fMRI) to see what part of the brain is active during various activities.) For example, in a blind person, scans show the occipital lobe in the rear of the brain, which normally processes vision, is active listening instead. With more brain processing power available, the auditory capabilities of a blind person can be enhanced.

(Trivia item not related to plasticity:  fMRI scans show that cocaine and sex activate the same regions of the brain.)

As an individual develops, plasticity is enhanced for particular functions on a schedule that is fairly consistent from one person to another. These critical stages for brain wiring occur up to the late teens, typically. However, even for mature adults, the brain does not lose all its plasticity. For example, studies show that the “neuromodulator”  oxytoxin is higher in new parents and people in love. The chemical increases the ability of old brain connections to be “unlearned” and new ones to form.  Thus we have “bonding”.  The very process of learning increases neuroplasticity. While intellectual activity such as reading and crossword puzzles is beneficial in general, the process of learning takes plasticity to a new level. This is true not not only for the activity being learned but for the brain in general, because of various chemical processes going on during learning activities.

So now I am more glad than ever that I continue to learn new songs in our chorus, and that I took up the guitar last.year.

By the way, the brain is rewired through repetition, not surprisingly, but what is surprising is that it is a more physical rewiring than was previously known.  For an acrophobic person, the perception of height is “wired” to fear.  If that same perception is repetitively associated with more pleasant feelings, the brain will actually develop connections to a different part of the brain.

Studies on the effects of television viewing by children show that they tend to have a variety of mental problems, including reduced attention span. Spoken language and written language are processed in different parts of the brain, and professors report that they have had to “dumb down” their courses over successive years. I don’t think we are at all surprised.

It’s a fascinating book that presents some astonishing information about the the human brain and how it works and changes itself.

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