Jones, M. 1 , Kuipers, J. 2 & Thierry, G. 1
1 Bangor University
2 University of Stirling
New evidence shows a deficit in binding visual-orthographic information with the corresponding phonological code in developmental dyslexia. Here, we further examined this deficit using event-related brain potentials (ERPs) in dyslexic and typical adult readers performing a letter-matching task. In each trial, a printed letter was presented synchronously with an auditory letter name. Mismatched standard trials were interleaved with matched, infrequent target pairs, to which participants made a button press response. In deviant trials, letter pairs were mismatched but confusable in terms of their visual or phonological features. Typical readers showed early detection of deviants, indicated by larger phonological mismatch negativity (PMN) compared with standards. This was followed by stronger modulation of the P3b for visually confusable deviants and an increased lateralized readiness potential (LRP) for phonological deviants, compared with standards. In contrast, dyslexic readers showed reduced sensitivity to deviancy (PMN). Letter recognition processes were comparable with typical readers (P3b), but a specific impairment emerged for visual-orthographic response selection (LRP). In a follow-up experiment using the same participants and a non-lexical task, we found no reading-group differences. Our findings indicate early insensitivity to over learned, visual-phonological binding in dyslexia, coupled with difficulty selecting the correct orthographic code.