Neurophysiological studies of reading fluency: Towards visual and auditory markers of developmental dyslexia

Developmental dyslexia is a neurobiologically based learning disorder that impairs a child’s ability to read and write. To minimize the detrimental effects of dyslexia, it is important to provide optimal intervention at the youngest possible age. Early diagnosis of dyslexia, which is a prerequisite for early intervention, is thus called for. In this light, event-related potentials (ERPs), i.e., electrical brain responses registered at the scalp, are particularly useful in distinguishing poor from normal readers at the initial stage of reading acquisition. In the current PhD project, we therefore use ERPs to investigate early neurophysiological markers of dyslexia in beginning readers of Dutch (second graders). Specifically, we have focused on two lines of research, i.e., visual word recognition and auditory discrimination. Overall, our findings suggest that the N170 print-tuning effect, which indexes the efficacy of visual word recognition, is a valid neurophysiological indicator of dyslexia, one that can be readily elicited by implicit reading tasks and robustly detected at the individual level. On the other hand, the relation between reading ability and the mismatch negativity, which indexes the accuracy of auditory discrimination, is less systematic, and is highly dependent on a series of methodological factors. All in all, the outcome of this thesis contributes to the understanding of the neurobiology of normal and impaired reading acquisition