The authors emphasize that their findings do not discount the additional involvement of higher levels of brain processing in dyslexia, where more complex combinations of information lead to the recognition and interpretation of speech.
At the same time, they argue that the very elementary defect in the brain's processing of sound must be playing an important role in the generation of relatively weak neuronal representations of the sound parts of aural speech. And this elementary neurological deficit, they said, could provide a target for remedial therapies aimed at training the brain to increase the speed and accuracy with which it processes rapidly successive and rapidly changing sounds.
The sound-processing function occurs at a base, or entry, level of sound processing in the brain, and is believed to be a primary step in the brain's representation of normal speech sounds and its creation of speech and language-reception abilities. The process ultimately culminates with a listener learning to recognize the sound parts of words, and to translate these word sounds as written letters.
Previous behavioral studies have suggested that the inability to parse the rapidly successive, changing sounds that make up words, the phonemes of language, may be the primary basis of language-learning impairments in children. Scientists have long argued that children who have difficulty parsing word sounds are destined to have difficulty successfully initiating reading. Other behavioral studies have indicated that most people with dyslexia, characterized by a difficulty with reading, also have impairments in the fidelity of their auditory reception. However, because most dyslexics ultimately develop facile speech reception and production capabilities, the significance of this problem for the origin of reading impairments has been unclear.
The researchers conducted their current study in seven dyslexic adults who we
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Contact: Jennifer O'Brien
jobrien@pubaff.ucsf.edu
415-476-2557
University of California - San Francisco
25-May-1999