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Abstract:
While some behavioral studies have documented delayed
language acquisition in blind children, other studies have revealed
better speech discrimination abilities for blind than sighted
adults. Although several brain imaging studies have provided
evidence for cortical reorganization of sensory processing
following visual deprivation, little is known about the cerebral
representation of language functions in blind humans. Previous
research on the effects of auditory deprivation on
language-relevant aspects of cerebral organization raise several
hypotheses concerning blind individuals. Event-related potentials
were recorded while 11 congenitally blind and 11 sighted adults
matched in age, gender, handedness and education listened to
sentences in order to decide whether or not they were meaningful.
Incongruent sentence-final words elicited an N400 effect in both
groups. The N400 effect had a left-lateralized fronto-central scalp
distribution in the sighted but a symmetric and posteriorly
extended topography in the blind. Furthermore, the N400 effect
began earlier in the blind than in the sighted. In addition, the
difference between closed and open class medial words was more
pronounced in the blind than in the sighted. These results suggest
that blind people may process speech faster than sighted people and
furthermore that some language systems may be less
focal/specialized following early visual deprivation.
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