Neurophysiological evidence of auditory channel anomalies in developmental dysphasia

Developmental dysphasia refers to a group of disorders in children that are characterized by severe retardation of language development, without any known causes. Studies show that children with developmental dysphasia have difficulty in discriminating speech sounds that vary in frequency. The relationship between difficulty with sound distinction and impaired language development is not clear. It is possible that this perceptual difficulty may result either from a language disorder, such as the inability to process speech, or a hearing disorder, such as impaired auditory processing. The role of impaired auditory processing in developmental dysphasia was assessed by measuring auditory evoked responses to tones that varied in frequency. Auditory evoked response is a method of testing the function of the ear with regard to hearing. For example, if the hearing pathway is intact, the brain electrical activity will indicate that the sound stimulus reached the brain. Tests were carried out in normal children and in two groups of children with developmental language disorders. Children with expressive language impairment (difficulties expressing themselves) had auditory evoked responses that were close to that of normal children. However, children with receptive language impairment (difficulties understanding language) had decreased or absent auditory evoked responses. These findings suggest that inability to analyze changes in frequency is associated with impaired receptive language development and may contribute to difficulties in speech perception. (Consumer Summary produced by Reliance Medical Information, Inc.)