The electrophysiological correlates of developmental dyslexia: New insights from lexical decision and reading aloud in adults

Abstract

Many studies have described the electrophysiological specificities of print processing in dyslexic readers, mostly using lexical decision tasks. The aim of the present study was twofold: a) to assess for the first time the electrophysiological correlates of print processing in dyslexic adults in the under-investigated context of reading aloud tasks, acknowledged to be especially relevant to investigate phonological processes relatively to lexical decision; and b) to assess whether the electrophysiological specificities described in dyslexic readers in lexical decision correspond to a different neuronal network engaged in print processing. 21 dyslexic university students and matched controls performed a lexical decision task and a reading aloud task on words and pseudowords under EEG recording. In lexical decision, the pattern of results indicates the engagement of similar brain processes between the groups, but with a sub-efficient visual word form processing in dyslexia. In reading aloud, between group differences revealed completely different distributions of the electric field at scalp between the two groups after the N2 time window, suggesting alternative processing strategies in dyslexic readers. Those specificities seem to be related to their core phonological deficits. Crucially, the present results suggest that the nature of electrophysiological divergences in print processing in dyslexic readers vary according to the task: while lexical decision task appears to be well suited to assess divergences in lexical access, reading aloud tasks should also be used in ERP investigation as it allows a better insight into phonological processes and thus be better suited in the framework of the phonological deficit theory of dyslexia.