Another question possibly answered in this study below:Blind People Hear Better: Truth or Myth?Do the auditory skills of the visually impaired compensate for their
loss of sight?
By Rich Maloof for MSN Health & Fitness.Source Link: Source URL:
health.msn.com/health-topics/articlepage.aspx?cp-documentid=100234436A popular perception holds that blind people have a highly developed sense of
hearing. As the thinking goes, our five senses work in concert with one another
such that the loss of one is compensated by increased sensitivity in the
remaining four.
Generally speaking, the idea springs from one part assumption, one part
anecdotal evidence, and perhaps one small part guilt: We like to think those
who lack a sense that so richly informs our lives are able to make up the
difference.
We further embrace the notion that some blind people can parlay a tragic
handicap into a distinct advantage. After all, blind musicians like Stevie
Wonder and vocal legend Andrea Bocelli exhibit exceptional musical skill and
have what fellow musicians would call "a great ear."
Until recently, there had been little scientific evidence that blind people
really do benefit from sensory compensation. At the Montreal Neurological
Institute of Canada's McGill University, graduate students working under the
tutelage of Robert Zatorre, Ph.D., a neuroscientist and experimental
psychologist, put popular perceptions to the test. Their results confirmed
expectations - and also yielded some exciting surprises.
Testing 1-2-3.The study began simply enough, with groups of blind and sighted subjects alike
tested on pitch perception (how high or low a note is) and position perception
(where in space a sound is located). In line with expectations, blind subjects
scored better than their sighted counterparts.
However, an unforeseen observation arose: The people who had been blind since
birth were the ones who scored best. In fact, the scores correlated directly to
the point in life at which each subject lost his or her eyesight. Those born
blind had the best performance, followed by subjects who became blind at age
four or five. Among those blinded at 10 years old or later, there was little to
no difference at all compared to the sighted group.
"What this tells us is that there is plasticity in the brain," says Dr. Zatorre.
"That is, when we're young we can actually change around the way neurons work,
and reorganize brain function to suit our survival needs. But as we get older,
the brain becomes more or less fixed in terms of sensory perception."
In a second test, subjects had one ear plugged and were then asked to locate
where sounds were coming from in a room with hidden speakers. Knowing that the
brain compares input from both ears to locate sound, the researchers didn't
expect anyone to score highly. Yet, half of the blind people scored with
impressive accuracy.
These results are probably the best evidence of one sense being compensated by
another. Zatorre believes that the blind people who scored well were gleaning
highly specific location information from the sound as it was bouncing off of
their outer ears. While the cartilage in everyone's outer ear has a unique
topography of bumps, grooves, and dents, these subjects were using the ear's
features to far greater effect. The sound was there for all to hear, but these
subjects had become extremely sensitive to the information it provided.
A startling discovery.The biggest surprise came when the researchers used a PET scan (positron
emission tomography), which can indicate brain activity as someone performs
various tasks. Zatorre's team, led by then-doctoral student Frédéric Gougoux,
knew every subject would show activity in the auditory cortex since that's where
the brain processes sound. But for some subjects, the PET revealed activity in
the visual cortex, where the brain processes sight. The people with visual
activity, it turned out, were the same ones who had shown that particular
ability to locate sound with one ear blocked.
"We learned that the part of the brain that normally handles vision does not
just die or atrophy without input," says Zatorre. "It somehow adds functionality
to process subtle auditory information."
No guarantees.The startling PET-scan results are a testament to the incredible adaptive
abilities of the brain. It can practically be rewired in our earliest years,
and areas of the brain previously understood to have discrete functions can
sometimes be recruited to help accommodate a loss.
Is it reasonable to say that some blind musicians benefit from better hearing?
Arguably, heightened pitch perception and spatial location skills would improve
a musician's ability to play in tune and perform with other instrumentalists,
so they'd have a good head start. But don't romanticize it. Blindness is no
guarantee of increased auditory perception, let alone musical ability, and by
far the vast majority of musical geniuses are lucky enough to have all of their
senses intact.
