Fwd: Mindís eye in the deaf

From: Wade T. Smith (wade_smith@harvard.edu)
Date: Mon Jan 21 2002 - 19:35:14 GMT

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    Subject: Fwd: Mindís eye in the deaf
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    Mindís eye in the deaf
    7 January 2002
    by Yang Jiang yjiang@codon.nih.gov

    Finney E. M et al. (2001). Visual stimuli activate auditory cortex in
    the deaf. Nat Neurosci, 4:1171-1173.


    Typically, we see with our eyes, and visual information such as a view
    of our surroundings is sent to the visual cortex in the brain for
    further processing. We hear through our ears, and auditory information
    such as music is projected to the auditory cortex. However, owing to the
    lack of visual input, the visual cortices of blind people do not develop
    normally. Previous studies have revealed that the visual cortex in blind
    peopleís brains can be activated by auditory or tactile stimulation. A
    new study reports a parallel finding Ė visual activation in the auditory
    cortex of early deaf people.

    Using functional brain imaging (fMRI), Finney et al. compared visually
    evoked cortical activation in six profoundly deaf and six healthy
    hearing people. When watching moving dot patterns, the deaf peopleís
    right auditory cortices (Brodmann area 41, 42 and 22) showed
    significantly more responses to the visual stimuli, compared with the
    hearing subjects. As we know, the primary and secondary auditory
    cortices have anatomical connections to secondary visual areas. These
    results demonstrate the possibility that part of the visual information
    is routed to the auditory areas of the brain in deaf people.

    In a second experiment, both groups of subjects were told to ignore the
    moving patterns by focusing their attention to the center fixation. The
    hearing and deaf peopleís cortices responded differently for this
    attention task as well. Even when visual motion was ignored, visual
    activation in the auditory cortex in the deaf was observed. It has been
    reported that auditory cortices of the deaf people could be activated by
    visual images of sign languages. The current study provides evidence
    that the auditory areas respond to non-language visual stimuli as well.
    This demonstration of cross-modal plasticity in the auditory cortex of
    the deaf echoes the complementary findings in the visual cortex of the
    blind and the evidence points to the brainís capability to create the
    mindís eye (or ear) in the underdeveloped cortex of the deaf (or blind).
    Of course, further investigations on humans and animals are necessary
    before we can fully understand how the deprived cortex is used to
    process re-routed sensory information from a different cortical area.

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