[nabs-l] Fwd: Fw: Blind People Hear Better: Truth or Myth?

[Bill]

--- On *Sat, 3/14/09, Tonia Trapp <*:

From: Tonia Trapp <>
Subject: Blind People Hear Better: Truth or Myth?

Date: Saturday, March 14, 2009, 11:59 AM


  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


A 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.