Brain responses to speech sounds in infants and children with and without familial risk for dyslexia

Abstract

Dyslexia, a specific reading disability, runs in families. Therefore, the risk for a child to become dyslexic increases multifold if reading difficulties occur in the family. One risk factor for dyslexia is a deficit in speech perception. Using EEG, speech sound discrimination was found to be more demanding than non- speech discrimination in typical readers in Study I. In Study II, in children with dyslexia in 3rd grade, enhanced brain responses were observed and found to be associated with better performance in reading accuracy, spelling accuracy and phonemic length discrimination tasks. The brain responses of the most accurate readers in the dyslexia group originated from a more posterior site of the right auditory cortex, suggesting the employment of compensatory brainprocessing for changes in phonemic length. In Study III, the brain responses of six-month- old infants at risk for dyslexia were found to predict their reading speed in adolescence at 14 years. The prediction was mediated via preschoolage rapid naming speed, which suggests that the same cognitive processes are needed in both fluent reading and naming. Possibly those common processes are related to automatization of the retrieval process from a mental lexicon via phonological representations. Atypical brain activation to speech in infancy seems to implicate a deficient development of phonological representations in at-risk infants that later hinders lexical access. These results indicate that even if a child is born with an increased risk for dyslexia, the risk is not insurmountable. Overall it seems that accurate speech perception, well-developed speech sound representations and automatized access to them are necessary for the development of fluent reading. This information is important in developing remediation for children at increased risk for dyslexia.