The woman joking with me across the table was born with only
half her brain. Something catastrophic happened while she was in her mother's
womb, though no one knows what for sure. It wasn't a stroke, because stroke
destroys healthy tissue, and Michelle Mack's left hemisphere simply never
developed. Her doctors speculated that her left carotid artery, which supplies
blood to the left hemisphere, may have become blocked while Michelle was still
a fetus, preventing that hemisphere from forming. At birth the doctors gave her
the usual tests and told her mother, Carol, that she was a normal baby. Even
today a neurologist would not likely guess, without a brain scan, that a whole
hemisphere is missing. I find myself wondering how many others have lived out
their lives with half a brain, without themselves or anyone knowing it…
Though she has only a right hemisphere, Michelle is not a
desperate creature barely surviving on life support. She is twenty-nine years
old. Her blue eyes peer through thick glasses. She wears blue jeans, sleeps in
a blue bedroom, and speaks fairly normally. She holds a part-time job, reads,
and enjoys movies and her family. She can do all this because her right
hemisphere took over for her left, and such essential mental functions as
speech and language moved to her right. Her development makes it clear that
neuroplasticity is no minor phenomenon operating at the margins; it has allowed
her to achieve massive brain reorganization…
Michelle has some extraordinary calculating skills—savant
skills—that she employs at lightning speed. She also has special needs and
disabilities. She doesn't like to travel and gets easily lost in unfamiliar
surroundings. She has trouble understanding certain kinds of abstract thought.
But her inner life is alive, and she reads, prays, and loves. She speaks
normally, except when frustrated. She adores Carol Burnett comedies. She
follows the news and basketball and votes in elections. Her life is a
demonstration that the whole is more than the sum of its parts and that half a
brain does not make for half a mind…
Michelle's experience reminds us how ignorant we are about
some of the most basic aspects of human brain functions. What happens when the
functions of both hemispheres must compete for the same space? What, if
anything, must be sacrificed? How much brain is needed for survival? How much
brain is required to develop wit, empathy, personal taste, spiritual longing,
and subtlety? If we can survive and live without half our brain tissue, why is
it there in the first place?...
On the right I can see the gray convolutions of a normal
right hemisphere. On the left, except for a thin, wayward peninsula- of gray
brain tissue—the minuscule amount of left hemisphere that developed—there is
only the deep black that denotes emptiness. Michelle has never looked at the
film.
She calls this emptiness "my cyst," and when she
speaks of "my cyst" or "the cyst," it sounds as though it
has become substantial for her, an eerie character in a science fiction movie.
And indeed, peering at her scan is an eerie experience. When I look at
Michelle, I see her whole face, her eyes and smile, and cannot help but project
that symmetry backward into the brain behind. The scan is a rude awakening…
But because Michelle has no left hemisphere, she has trouble
seeing things coming from her right and is blind in the right visual field. Her
brothers used to steal her french fries from her right side, but she'd catch
them because what she lacks in vision, she has made up for with supercharged
hearing. Her hearing is so acute that she can clearly hear her parents talking
in the kitchen when she is upstairs at the other end of the house. This
hyperdevelopment of hearing, so common in the totally blind, is another sign of
the brain's ability to adjust to a changed situation. But this sensitivity has
a cost.
In traffic, when a horn blares, she puts her hands over her
ears, to avoid sensory overload. At church she escapes the sound of the organ
pipes by slipping out the door. School fire drills frightened her because of
the noise and confusion.
She is also supersensitive to touch. Carol cuts the tags off
Michelle's clothing so she won't feel them. It's as though her brain lacks a
filter to keep out excess sensation, so Carol often "filters" for
her, protecting her. If Michelle has a
second hemisphere, it is her mother…
But at two she still couldn't crawl, so Wally, who knew that
she loved music, would play her favorite record, and when the song was over,
Michelle would cry, "Hmnun, hmmm, hmmm, want it again!" Then Wally
would insist she crawl to the record player before he'd play it again.
Michelle's overall learning pattern was becoming clear—a significant delay in
development; a message from the clinicians to her parents to get used to it;
and then somehow Michelle would pull herself out of it. Carol and Wally became
more hopeful…
Though she can repeat Dr. Grafman's explanation that her
right hemisphere now handles such left-brain activities as speaking, reading,
and math, she sometimes speaks of the cyst as though it has substance, as
though it were a kind of alien being with a personality and will, rather than
an emptiness inside her skull, where a left hemisphere should have been. This
paradox displays two tendencies in her thought. She has a superior memory for
concrete details but difficulty with abstract thought. Being concrete has some
advantages. Michelle is a great speller and can remember the arrangement of letters
on the page, because like many concrete thinkers, she can record events in
memory and keep them as fresh and vivid as the moment when she first perceived
them. But she can find it difficult to understand a story illustrating an
underlying moral, theme, or main point that is not explicitly spelled out,
because that involves abstraction…
I began to suspect Michelle was a savant with some extraordinary
mental abilities when, in our conversations, almost as an aside, she would
unobtrusively, but with uncommon accuracy and confidence, correct her mother
about the date of a particular event…
Because she said that she often could remember days back
into the mid-1980s without using a formula, I tried to push her past her recall
and asked her the day of the week for August 22, 1983.
This time she took half a minute and was clearly
calculating, whispering to herself, instead of remembering.
"August 22, 1983, um, that was a Tuesday"
"That was harder because?"
"Because in my mind I only go back to the fall of 1984.
That's when I remember things well." She explained she had a clear memory
of each day and what happened on it during the period she was in school, and
that she used those days as an anchor.
Grafman's theory provides an explanation of how Michelle's
brain evolved. Michelle's loss of brain tissue occurred before there could have
been any significant commitment of her right hemisphere. Since plasticity is at
its height in the earliest years, what probably saved Michelle from certain
death was that her damage occurred so early. When her brain was still forming,
her right hemisphere had time to adjust in the womb, and Carol was there to
care for her.
It is possible that her right hemisphere, which normally processes
visual-spatial activities, was able to process speech because, being partially
blind and barely able to crawl, Michelle learned to speak before she learned to
see and walk. Speech would have trumped visual-spatial needs in Michelle, just
as visual-spatial needs had trumped arithmetical needs in Paul…
People with right-prefrontal lesions have impaired
foresight. They can watch a movie, but they can't get the main point or see
where the plot is going. They don't plan well, since planning involves ordering
a series of events so that they lead toward a desired outcome, goal, or main
point. Nor do people with right frontal lesions execute their plans well.
Unable to keep to the main point, they are easily distracted. They are often
socially inappropriate because they don't get the main point of social
interactions, which are also a series of events, and they have difficulty
understanding metaphors and similes, which require extracting the main point or
theme from various details. If a poet says, "A marriage is a battle
zone," it is important to know that the poet doesn't mean the marriage
consists of actual explosions and dead bodies; rather, it is a husband and wife
fighting intensely.
All the areas Michelle has difficulty with—getting the main
point, understanding proverbs, metaphors, concepts, and abstract thought—are
right prefrontal activities. Grafman's standardized psychological testing
confirmed that she has difficulty planning, sorting out social situations,
understanding motives (a version of getting the main theme, applied to social
life), and also some problems empathizing with and forecasting the behavior of
others. Her relative absence of
foresight, Grafman thinks, increases her
level of anxiety and makes it harder for her to control her impulses. On the
other hand, she has a savant's ability to remember individual events and the
exact dates they occurred—a left-prefrontal function…
There is a theme to her preferences, tastes, and longings.
The Baby-Sitters Club, Carol Burnett's harmless humor, the toy bear collection,
and everything else I saw in Michelle's blue room were part of that phase of
development called "latency," the relatively calm period that
precedes the storm of puberty, with its erupting instincts. Michelle, it seemed
to me, showed many latency passions, and I found myself wondering whether the absence
of her left lobe had affected her hormonal development even though she was a
fully developed woman. Perhaps these tastes were the result of her protected
upbringing, or perhaps her difficulty understanding the motives of others led
her to a world in which the instincts are quieted and where humor is gentle…
I see the smile—an overflow of inner peace. In Michelle's
heaven are all the things she's striving for—more human contact, vague hints of
increased but safely circumscribed relations between men and women, all that
has given her pleasure. Yet all this occurs in an afterworld where, though she
is more independent, she can find the parents she so loves not too far away.
She has no medical problems, nor does she wish for the other half of her brain.
She's fine there just as she is.
From Norman Doidge, MD, The Brain that Changes Itself .Penguin Books 2007
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