Individuals with developmental dyslexia are reported to have problems in auditory and speech processing. Here we review evidence from the Jyväskylä Longitudinal Study of Dyslexia showing that early processing differences, as measured with brain event-related potentials (ERPs), are related to later language related skills in children at risk for familial dyslexia and control children. Preliminary results for school-aged children also show perceptual differences between the groups.
We earlier found that both obligatory and change detection responses differed between at-risk and control newborns in the right hemisphere. Both responses predicted later language and verbal memory skills at 2.5, 3.5 and 5 years. Group differences were also found for 6-month-olds. Associations for later phonological and language skills language differed between the groups between 2.5 and 5 years.
For school-aged children with and without reading problems, both speech and non-speech stimuli were presented in oddball paradigms and a control experiment. Preliminary results for non-speech complex tones show differences in responses to pitch and rise time changes. In control children, MMN was bilateral for pitch change and left lateralized for rise time change. Poor readers had no MMN response to either of the stimuli.
Our findings indicate that enhanced general responsiveness to speech stimuli and atypical change detection processes predict poorer language related skills. The results suggest differences in the organization of the auditory/speech system sub-serving phonological processing and language functions in at-risk children and poor readers. The results further indicate that ERPs could provide ways to identify children benefiting from early language training.