I do not remember
where this article came from (perhaps FW since I do not have the source) but remembered
it during this latest discussion on the brain and thought to add it to the
menu. It’s fairly long, but
interesting reading for those who are keeping up with the debate over Nature vs
Nurture and research applications.
If anyone would prefer it formatted in a doc, please let me know. The book is now available and
Amazon.com has reviews. Karen
Watters Cole
Survival of the
Busiest
Parts of the Brain That Get Most Use Literally Expand And Rewire on Demand
Adapted from the book “The Mind and the Brain: Neuroplasticity and the Power of
Mental Force.”
Copyright © 2002 by Jeffrey M. Schwartz, M.D., and Sharon Begley. (Oct
2002 ReganBooks, a division of HarperCollins Publishers Inc. Reprinted by
permission). ISBN: 0060393556.
For the conventional wisdom on our gray matter, just open any lavishly
illustrated brain book. There, detailed diagrams map out specialized brain
structures: areas that generate speech and areas that process ‘vision, areas
that sense sound and areas that detect when you touch your left big toe.
The diagrams resemble nothing so much as zoning maps produced by the most rigid
land use board. Every bit of neural real estate is assigned a job, reflecting
the decades-long belief that different parts of the brain are hardwired for
certain functions.
This view of the brain dates back to 1857, when French neurosurgeon Paul Broca
discovered that particular regions are specialized for particular functions,
such as language. His and subsequent discoveries gave rise to the dogma
of the hard-wired adult brain, and it had profound real-world
consequences. It held that if the brain sustained injury through stroke
or trauma to, say, a region responsible for moving the left arm, then other
regions could not step up to the plate and pinch-hit. The function of the
injured region would be lost forever. And it implied that if, by the age
of 12 or so, you had not recruited neurons to the specialized task of playing
the violin, for instance, or learning a second language, then you might as well
give up: your old brain was simply not going to learn new tricks.
But that dogma has been under assault in recent years. Although specific
portions of the brain do, usually, specialize in certain tasks, the brain is
much more adaptable and renewable than previously thought-and that’s true
throughout life.
Animal experiments provided the first hints that the brain is able to change
dramatically after childhood. When lab monkeys practiced - and practiced
- the trick of using a single finger to reach into a tiny dish and grab a
morsel of food, the brain region devoted to fine motor control of that finger
grew like suburban sprawl. And these were grown-up monkeys.
Even the adult brain is “plastic,” able to forge new connections among its
neurons and thus rewire itself. Sensory input can change the brain, and
the brain remodels itself in response to behavioral demands. Regions that
get the most use literally expand. In terms of which neural circuits
endure and enlarge, you can call it survival of the busiest.
In 1993, Alvaro Pascual-Leone, then at the National Institute of Neurological
Disorders and Stroke, led the search for what would become one of the earliest
findings in human neuroplasticity. Does anyone, he wondered, habitually
experience powerful tactile stimulation to a particular portion of their
body? Of course: blind people who read Braille with their fingertips.
Dr. Pascual-Leone recruited 15 proficient Braille readers and wired them up so
he could measure their somatosensory cortex-the part of the brain that
registers and processes the sense of touch. Then he administered weak
electrical shocks to the tip of their right forefingers (the “reading finger”),
recording which parts of the somatosensory cortex registered the
sensation. He did the same thing to the blind people’s left index finger,
and to fingers in non-Braillereaders that don’t get exceptional use.
The result was unmistakable. In the Braille readers, the area of
somatosensory cortex devoted to the reading finger was much larger than the
comparable area for fingers in both blind and sighted people who don’t have
such demands put on them. It was a clear case of sensory input changing the
brain. The cortical region processing that input had expanded, with a
consequent increase in sensitivity. That would explain how Braille readers are
able to make such fine discriminations among patterns of tiny raised dots.
By the spring of 1995, Edward Taub was also exploiting the ability of the brain
to rewire itself. The University of Alabama, Birmingham, scientist was
developing a revolutionary new therapy for stroke patients. The goal was to
enable an intact area of the brain to take over for a region knocked out by
stroke. But Dr. Taub was sure that neuroplasticity went beyond damaged
brains. His goal was to see how normal behaviors changed brain maps.
One evening that spring, he and his wife Mildred Allen, a lyric soprano who had
been a principal artist at New York’s Metropolitan Opera in New York, were
having dinner in Germany with a group of neuroscientists. Casting around for a
study they could collaborate on, Dr. Taub asked the group: Is there any normal
activity that uses one hand way more than the other? The scientists were
flummoxed, but Ms. Allen chimed in, “Oh, that’s easy-playing a string instrument.”
When a right-handed musician plays the violin, four digits of the left hand
continuously finger the strings. (The left thumb grasps the neck of the violin,
undergoing only small shifts of position and pressure.) The right, or
bowing, hand undertakes far fewer individual finger movements. Might this
pattern leave a trace on the cerebral cortex?
To find out, the scientists recruited six violinists, two cellists and one
guitarist, all of whom had played their instrument for seven to 17 years, as well
as six nonmusicians. The volunteers sat still while a pneumatic
stimulator applied light pressure to their fingers to record neuronal activity
in the part of the brain that processes the sense of touch.
There was no difference between the string players and the nonmusicians in how
much of the cortex was devoted to “feeling” the fingers of the right
hand. But there was a huge difference when it came to the left hand: The
amount of brain territory devoted to those fingers had increased
substantially. That increase was greatest in musicians who began to play
before the age of 12.
But to Dr. Taub, the most dramatic finding was that even in people who took up
the violin as adults, regular practice had changed their brains. Their
cortex had rezoned itself so that more neurons were assigned to the fingers of
the left hand. “Even if you take up the violin at 40, you still get brain
reorganization,” he says.
These were the opening shots in what would become a revolution in treatment for
stroke, depression, obsessive-compulsive disorder, Tourette’s syndrome and
other brain diseases. All were based on the discovery that the brain has
the ability to change in response to the input it receives.
At the University of California, San Francisco, researchers led by Michael
Merzenich had shown that sound has the power to reshape the brain in lab
monkeys. Across the country, at Rutgers, University in New Jersey,
neuroscientists Paula Tallal and Steve Miller had begun to suspect that
Specific Language Impairment (a general term that includes dyslexia) might
reflect a problem not with recognizing the appearance of letters and words but,
instead, with processing certain speech sounds-fast ones.
Dyslexics, Dr. Tallal thought, have some brain impairment that prevents them
from hearing staccato sounds like “b, “ p, “ “d” and “g, “ which burst
from the lips and vanish in just a few thousandths of a second. Since
learning to read involves matching written words to the heard language, it’s no
wonder that a failure to hear certain sounds impairs reading ability.
When Dr. Tallal discussed her theory at a science meeting in Santa Fe, you
could almost see-the light bulb go off over Dr. Merzenich’s head. His
experiments on monkeys, he told her, had implications for her ideas about
dyslexia. Dyslexics might become better readers, he said, if their brain
could be rewired to hear staccato phonemes—something that could be done by
harnessing the power of neuroplasticity.
To find out if the brains of young dyslexics could be rewired, and if that
rewiring would help them read better, the Rutgers scientists recruited about a
dozen kids and designed an experiment. One of Dr. Merzenich’s colleagues,
meanwhile, wrote software that slows down staccato phonemes, stretching out the
interval between “b” and “aaah” in “baa,” for example. To everyone else,
the processed speech sounds like someone shouting underwater. But to the
dyslexic children, the scientists hoped, it would, sound like “baa”-a sound
they had never before heard clearly. When Dr. Tallal listened to the
processed speech, she was so concerned that the kids would be bored out of
their minds listening to endless repetitions of words and phonemes, that she
dashed out for a supply of Cheetos. She figured her team would have to bribe
the kids to stick with the program.
And so began Camp Rutgers. For 20 days one summer, 22 kids age five to
nine played CD-ROM games structured to alter the brain. One game asked
the child to “point to rake” when pictures of a lake as well as a rake were
presented, or to click a mouse when a series of the spoken letter “g” was
interrupted by a “k”. To train the brain to hear target sounds, the
computer voice stretched them out, intoning “rrrake” and “ddday” and “bbbay.”
To ease the monotony, the scientists offered the kids snacks and puppets,
frequent breaks and even handstand demonstrations. Steve Miller recalls: “All
we did for hours every day was listen. We couldn’t even talk to the kids;
they got enough normal speech outside the lab. It was so boring that
Paula had to give us pep talks and tell us to stop whining. She would
give us a thumbs-up for a good job-and we’d give her a different finger back.”
After a few months of training, all the children tested at normal or above in
their ability to distinguish sounds. Their language and reading ability
rose two years, something no other dyslexia program had achieved.
Although the research did not include brain scans, it seemed Fast ForWord (as
the software was called) was doing something more dramatic than your
run-of-the-mill educational CD: It was rewiring brains. “You create your
brain from the input you get,” says Paula Tallal.
At first that was only speculation. Critics of Fast ForWord said the
system was being rushed to market before its claims had been proved. The
contention that Fast ForWord reshapes the brain was the target of the most
vituperation. Michael Studdert-Kennedy, past president of the Haskins
Laboratories, a center for the study of speech and language at Yale University,
told the New York Times in 1999 that inducing neuroplasticity was “an absurd
stunt” that would not help anyone learn to read.
Yet a year later, researchers reported compelling evidence to the
contrary. Using brain-scan technology called functional Magnetic
Resonance Imaging (fMRI), John Gabrieli of Stanford University compared the
brains of dyslexics before and after Fast ForWord. He found exactly what
the skeptics said he wouldn’t: In dyslexics whose language comprehension had
been improved, the brain’s left prefrontal region showed more activity after
training. Hearing the drawn-out sounds apparently induced this region,
impaired in dyslexics, to do its job of processing staccato sounds.
As evidence accumulated that changes in the sensory information reaching the
brain can profoundly alter the cortex, an obvious question arose: Can the mind
itself change the brain? Can mere thinking do it? Dr.
Pascual-Leone, now at Harvard University, provided a preliminary answer, with
an experiment that has not received nearly the attention it deserves.
He had one group of volunteers practice a five-finger piano exercise, and a
comparable group merely think about practicing it. This second group
focused on each finger movement in turn, essentially playing the simple piece
in their heads, one note at a time.
Actual physical practice produced changes in each volunteer’s motor cortex, as
expected. But so did mere mental rehearsal. In fact, as big a
change as the physical practice. Like actual movement, imagined movements
change the cortex. Merely thinking about moving produces brain changes
comparable to those triggered by actually moving.
The existence, and importance, of brain plasticity are no longer in
doubt. The brain is dynamic, and the life we lead leaves its mark in the
complex circuitry of the brain -footprints of the experiences we have had, the
thoughts we have thought, the actions we have taken. The brain allocates
neural real estate depending on what we use most: the thumb of a videogame addict,
the index finger of a Braille reader, the analytic ability of a chess player,
the language skills of a linguist.
But the brain also remakes itself based on something much more ephemeral than
what we do: It rewires itself based on what we think. This will be the
next frontier for neuroplasticity, harnessing the transforming power of the
mind to reshape the brain.
Outgoing mail scanned
by NAV 2002
