Back to list

Detail of contribution

Auteur: Chiara CANTIANI

Co-Auteur(s): Maria Teresa GUASTI, Paolo PEREGO and Maria Luisa LORUSSO

Impaired inflectional morphology in children with dyslexia and SLI: Converging evidence from Event-Related Potentials and behavioral measures

Abstract/Résumé: Based on the widely recognized overlap between Specific Language Impairment (SLI) and Developmental Dyslexia (DD) (e.g., Bishop & Snowling, 2004), the study of inflectional morphology in DD gains theoretical and clinical relevance. Recent studies focusing on children with DD-only revealed impaired inflectional morphology in this population as well, both in production (e.g., Altmann, et al. 2008) and in comprehension (e.g., Robertson & Joanisse, 2010). However, the direct comparison between DD children with (DD+SLI) and without SLI (DD-only) needs to be investigated. Event-related Potentials (ERPs), having the great advantage of providing on-line information about linguistic processing with an excellent temporal resolution, can provide complementary information to classical behavioral tasks. We investigated impaired inflectional morphology in a sample of Italian DD children with and without SLI by means of behavioral and electrophysiological measures. Thirty-two children with DD (16 with DD-only and 16 with DD+SLI) and 16 control children (aged 8-12) were tested with a behavioral linguistic battery requiring the production of nominal and verbal inflections using words and pseudo-words. In addition, sentences containing subject-verb agreement violations were auditorily presented and children were asked to judge the grammaticality of the sentences while ERPs time-locked to the critical morphemes were recorded. The behavioral results show a pervasive disorder involving both production and comprehension in DD+SLI children, and a deficit restricted to the production of pseudo‐words in DD‐only children. Qualitatively different patterns emerge at the electrophysiological level: whereas the control group shows the typical pattern associated to agreement violations (LAN+P600), the DD+SLI group shows only a non-significant Positivity, and the DD-Only group shows a broadly distributed Negativity, interpretable as a N400 component. Based on theoretical models of morphology (e.g., Ullman, 2001), we hypothesize that the strategy reflected in the N400 is related to the retrieval of the inflected forms as stored in the lexicon. This hypothesis, coherent with the behavioral result, highlights the peculiarity of the morphological impairment in DD.