[Nfbf-l] The mind's eye can learn to see, even in those blind since birth.

[Alan Dicey]

The mind's eye can learn to see, even in those blind since birth.

By Melissa Healy, Los Angeles Times For the Booster Shots Blog.

November 12, 2012.

People blind from birth can be taught to "see" images that are conveyed as
sounds, says a new study that calls into question a longstanding belief
about
the limits of the human brain.

Devices that scan visual images and reinterpret regularities as sounds were
used
to retrain the brains of congenitally blind people in a study published this
week in the journal Neuron. The authors - at the Safra Center for Brain
Science
at Hebrew University in Israel - put people who had been blind since birth
through 70 hours of training with a visual-to-auditory sensory substitution
device.

Initially, the subjects were able to distinguish among faces, houses,
everyday
objects, body shapes and textures. Eventually, they were able to read
letters
and words, identify facial expressions and locate people's positions. In one
video, a blind person is shown a picture of a woman with a ponytail and
identified the hairstyle.

You can see videos of the subjects "seeing" visual images here.

Blind people have long used the capability to use another sensory perception
to
compensate for blindness: Braille and blind walking canes allow people
without
sight to read and navigate. But when the authors of the current study put
subjects in a brain scanner, they gained insight into the process by which
training with a sensory substitution device allowed the mind's eye to "see."

The human brain is a remarkably efficient and adaptable organ: when an
appendage
such as a hand is amputated, or a sensory perception such as sight is lost,
the
specialized regions of the brain in which input from the hand or the eyes is
processed are reassigned to other duties.

But scientists have long believed that the brain's adaptability is limited
by
early conditions: when a person is born blind, the capacity of the brain's
visual cortex to process sight never develops, scientists have believed.
With
that lost opportunity, a window is closed, and even if eyesight were to be
restored, the visual cortex, they believed, would forever remain "blind" to
images.

Not so, the current study finds. When blind subjects listened to the
"soundscapes" that conveyed information about a visual image, they showed
activation in their visual cortex. In fact, when sounds conveyed the shape
of
letters, subjects who had never "seen" a letter showed activation in a patch
of
the left ventral visual cortex that uniquely comes alive when people with
normal
vision read letters and words.

"The adult brain is more flexible than we thought," said co-author Amir
Amedi.
With the right training approaches and technologies, the brains of people
who
have been blind for a long time - even since birth - might be "reawakened"
to
the task of processing visual information, he said. For some, he added, such
training might even restore some lost vision.

In fact, a 2008 study first offered tantalizing evidence that scientists
were
wrong in their long-held belief that a congenitally blind person could never
have normal vision even if eyesight were restored. A young Indian woman
identified only as SRD was born blind of dense congenital cataracts, but her
vision was restored when she was 12 at the Iladevi Eye Clinic in Ahmedabad,
India. Twenty years after she regained her eyesight, a team from the
Massachusetts Institute of Technology discovered this rare instance of a
congenitally blind person whose vision was restored, and tested her
extensively
to see how she saw.

SRD's sight was virtually normal, though the MIT team found that she did not
use
certain cognitive tricks that most sighted people use to make sense of
conflicting visual cues.

Other interesting cases of visual impairment and the cognitive strategies
that
the blind and the sighted use to make sense of their world are discussed by
neurologist Oliver Sacks in his book The Mind's Eye.

Source URL:
http://www.latimes.com/health/boostershots/la-heb-blind-brain-sound-reading-20121109,0,5532598.story

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