Deviant neural responses of character recognition in Chinese developmental dyslexia - preliminary findings

Abstract

PURPOSE: Event-related potential (ERP) was employed to investigate the underlying deficits in processing Chinese characters by young poor readers (PR). Due to the excellent temporal resolution of ERP, the processing stage(s) at which brain responses of PRs deviate from those of normal readers (CA) would be revealed. METHOD: Sixteen P3-P5 pupils with normal non-verbal intelligence, including six PRs scoring > -1.25 SDs in HKT-SpLD and 10 CAs matched in age, participated in a lexical decision task. Semantic-phonetic compound characters taught by P2 differing in phonological regularity were chosen. Pseudo-characters were random combinations of semantic and phonetic radicals from the real characters. The ERP components of interest were N170 (200-260ms post-onset from PO5, PO3, PO4, PO6) indexing visual/orthographic processing, P200 (200-260ms from FC3, FC1, FC2, FC4) reflecting access to phonology, and N400 (375-500ms from Fz, Cz, Pz) revealing lexico-semantic processing. RESULTS: Above-chance performance (>75%) on accuracy was found in PRs and CAs. The most important findings concerning lexicality were more negative N170 in the left hemisphere only in CAs, and stronger N400 to pseudo-characters by both groups. Regarding regularity, we observed more positive P200 to irregular characters by CAs, and marginally larger N400 to irregular characters in PRs. CONCLUSIONS: CAs demonstrated significant effects of regularity and lexicality in P200 and N400, indicating sensitivity to phonological form and meaningfulness, respectively. PRs differed from CAs in the absence of left-lateralized responses to verbal stimuli and a delayed regularity effect, suggesting inefficient character processing and poor quality of lexical representation.