“Curmudge, it seems that we have suddenly changed from
discussing alternative medicine to brain plasticity. Is there a connection?”
“Of course there is, Julie. Techniques that we have already mentioned, like meditation and
tai chi, are designed to relax and refocus the mind. As we quoted a couple of weeks ago, the mind is the software
for the brain. So we are going to
move inside and find out what is really going on inside the brain.”
“In your brain,
Old Guy, nothing other than a big memory leak is going on. Even the smallest parts were cemented
in place by the time you learned that girls were different from boys.”
“Au contraire,
Madame. That’s what was believed
50 years ago, about the time I finished graduate school (good thing I wasn’t
studying physiology). It was
called localization. Here’s how it is described in Doidge’s
book (1): ‘The brain came to be seen as made of parts, each one in a
preassigned location, each performing a single function, so that if one of
those parts was damaged, nothing could be done to replace it.’ ‘Most scientists believed that the
brain areas (devoted to sight, hearing, taste, touch, smell, balance) were so
specialized that one area could never do the work of another.’ “
“I anticipate that you are going to tell me that great
advances have been made in understanding the brain in recent years and that the
localization concept is outmoded.
Please elucidate.”
“Here’s the story: ‘Brain
plasticity, also known as neuroplasticity or cortical remapping, is a term
that refers to the brain's ability to change as a result of experience. These
changes can occur as a result of learning new things or because of damage to
the brain. Up until the 1960’s, experts believed that changes
in the brain were only possible during infancy and childhood, but research has
demonstrated that the brain is capable of altering existing pathways and even
creating new ones.’ “
“Hey, Curmudge,
this neuroplasticity stuff is mindboggling. Don’t stop now.”
“There’s lots more, Julie, such as these
two kinds of plasticity: ‘Functional
Plasticity—refers to the brain's ability to move functions from a damaged
area of the brain to other undamaged areas. Structural Plasticity—refers
to the brain's ability to actually change its physical structure as a result of
learning.’ A two-page overview provides
more detail.“
“Amazing! And neuroscientists learned all of that while you were
teaching analytical chemistry and helping to make soft toilet tissue. One might say that from top to bottom, science
was advancing. So what kind of
experiments did those brainy people perform to demonstrate neuroplasticity?”
“The researchers and their work are
described by Doidge in engaging detail. (1) Merzenich, Taub, and their
coworkers, who did basic studies with animals, followed it up with applications
to human patients. Much of this
was made possible by the invention of microelectrodes ‘so small and sensitive
that they could be inserted inside or beside a single neuron and detect when an
individual neuron fires off its electrical signal to other neurons.’ (Unless otherwise indicated, quoted material
is from Doidge’s book.) A portion
of a monkey’s skull was cut away over an area of the brain’s sensory cortex
believed to respond to the monkey’s hand. Microelectrodes were inserted, tested
by touching, e.g., a fingertip, and a micromap of the part of the brain
responding to each area of the monkey’s hand was created.”
“I’m certain to feel sorry for the
monkeys, Curmudge, but can you tell me what was learned?”
“When two of a monkey’s fingers were sewn
together, over time the separate bran maps for the fingers became joined. Another experiment: In a monkey’s hand, sensation is
conveyed by three nerves, the radial, median, and ulnar. Merzenich cut the median nerve; when he
touched the middle of the monkey’s hand two months later, the area of the brain
map that serves the median nerve showed no activity, as expected. But when he touched the outside of the
monkey’s hand, the median brain map lit up. ‘The brain map for the radian and ulnar nerves had almost
doubled in size and invaded what used to be the median nerve map.’ “
“Voilà,
Old Guy, plasticity! That furry
fellow was a hero. He proved that,
‘When it came to allocating brain-processing power, brain maps are governed by
competition for precious resources and the principle of use it or lose it.’ “
“Here’s a little more ‘monkey business,’
Julie; the researcher is Edward Taub.
He cut the sensory nerves in
one of a monkey’s arms, but not the motor
nerves. Because the monkey had no
feeling in his bad arm and couldn’t determine its location in space, he used
his good arm and hand for eating.
During its period of nonuse, the brain’s motor map for the bad arm began
to atrophy (i.e., use it or lose it).
Taub called this ‘learned nonuse.’ Then he immobilized the monkey’s good arm by putting
it in a sling. In order to
survive, the monkey had to use his ‘bad’ arm for eating. Taub’s finding supported Merzenich’s
conclusion that when an animal is motivated to learn, the brain responds
plastically.”
“I have the feeling, Professor, that these and other
findings have become the basis for alleviating a lot of human beings’ miseries
and weaknesses.”
“And, Julie, we’ll say more
about them in a week or so. See
you then.”
Kaizen Curmudgeon
(1)
Doidge, Norman, MD The Brain That Changes Itself (2007).
Link to posting from blog archives: Communicate—Think—Diagnose—Communicate 6/18/09
http://kaizencurmudgeon.blogspot.com/2009/06/communicate-think-diagnose-communicate.html
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