Category: Health and Wellness
>Medical News Today
Tuesday, January 25, 2005
Loss of sight and enhanced hearing: A neural picture
>Stevie Wonder and Ray Charles are often cited as anecdotal evidence
>that blindness confers superior musical ability. In fact, systematic
>studies have shown that blind persons perform nonvisual tasks better
>than those with sight. Neuroimaging studies have suggested that areas
>of the brain normally devoted to vision become active when blind
>persons perform nonvisual tasks, but much remains to be learned about
>the nature and extent of this phenomenon. A new study published in the
>open-access journal PLoS Biology finds a strong correlation between
>superior sound localization skills and increased activity in the brain's
visual center.
>
>The task of localizing sound--which requires integrating information
>available to one ear only (monaural sounds available, for example, when
>one ear is plugged) or information derived from comparing sounds
>binaurally--is particularly suited to investigating the neural
>remapping that seems to follow vision loss. In a previous study, Franco
>Lepore and colleagues showed that people who lost their sight at an
>early age could localize sound, particularly from monaural cues, better
>than those who could see. These findings suggested that areas of the
>brain normally dedicated to processing visual stimuli (the visual
>cortex, located at the back of the brain in the occipital lobe) might play
a role in processing sound in these individuals.
>
>In the new study, the authors hypothesized that if visual cortex
>recruitment bolstered auditory function in some individuals, then
>visual cortex activity would correlate with individual differences in
>performance, and the degree of activity should predict such
>differences. Nineteen people--seven sighted and twelve who lost their
>sight at an early age--were placed in an echo-free chamber and asked to
>indicate where a sound was coming from, using either one (monaural) or both
(binaural) ears.
>
>Only the blind individuals with superior localization skills showed
>increased activity in the visual cortex while performing monaural
>localization tasks. Whether the enhanced auditory performance reported
>here simply reflects increased efficiency of auditory processing or
>indicates "supranormal" powers, Lepore and colleagues argue that their
>results show that the visual cortex is "specifically recruited to
>process subtle monaural cues more effectively." It will be interesting
>to learn whether blind persons can recruit visual centers for other
>auditory tasks or to help them navigate the world without sight.
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