The brain of Kim Peek, the real-life 'savant' on
whom Dustin Hoffman's character in the film Rain Man is based, was truly an
unusual one.
Peek was born in with macrocephaly (large cranium), damage to the cerebellum (related
to motor skills), and agenesis of
the corpus callosum, a condition in which the bundle of nerves that
connects the two hemispheres of the brain is missing, secondary connectors such
as the commissure and the hippocampal commissure were also missing.
His brain was studied by NASA scientists in the
hope of explaining his outstanding mental capacities. Peek is called a
"mega-savant" because he was a genius in about 15 different subjects,
from history and literature and geography to numbers, sports, music and dates.
He could speed through a book in about an hour and
remember almost everything he had read, memorizing vast amounts of
information. Peek read by scanning the left page with his left eye, then the right
page with his right eye, a skill neuroscientists believe is related to the lack
of hemisphere connection.
According to an article in The
Times newspaper, he could accurately recall the contents of
at least 12,000 books. He apparently had developed language areas in both
hemispheres. Among his most impressive feats was his ability to provide
traveling directions between any two cities in the world.
Peek did not walk until he was four years old and
had difficulty with other ordinary motor skills, presumably due to his damaged
cerebellum, which normally coordinates motor activities. Despite his phenomenal
memory and arithmetic abilities, his
IQ was only 87.
Agenesis of the corpus callosum is a fairly
rare neurological condition. Individuals without an intact corpus callosum
sometimes experience linguistic and social impairments. It’s generally believed
that the left hemisphere is responsible for linguistic understanding, and the
right hemisphere provides the emotional context and subtlety. The main
linguistic and social problems stem from difficulties understanding non-literal
language, including idioms, proverbs, irony, sarcasm, subtle jokes and
conversational implicatures.
Sometimes a split-brain surgery is performed on
epilepsy patients to prevent the spread of seizures. In these patients,
the right hemisphere, which
controls the left hand and foot, acts independently of the left
hemisphere and the person’s ability to make rational decisions.
This can give rise to a kind of split personality, in which the left hemisphere
gives orders that reflect the person’s rational goals, whereas the right
hemisphere issues conflicting demands that reveal hidden desires. These
fascinating stories are recounted in Michael Gazzaniga and Oliver Sacks’s
numerous books.
Reference:
Huyen Nguyen
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