The neurobiology of developmental dyslexia in Chinese : an ERP study : investigating visual-orthographic processing using a repetition detection task

Abstract

Developmental dyslexia is a specific learning disorder which impaired the readers’ ability to decode written words and affects their reading and dictation. There was controversy of the causes of dyslexia in Chinese. It has been suggested that Chinese reader with dyslexic may have a deficit in visual-orthographic processing instead of phonological deficit in alphabetic scripts. Using event-related potential (ERP), the present study aimed to investigate the difference in visual-orthographic processing of characters and objects between normal and dyslexic Chinese readers as they passively viewed characters and line-drawings with different well-formedness, including real, pseudo and non, in a repetition detection task. The first differences emerged at P100 whereby a greater positivity was evoked for objects than characters for readers with dyslexia only. At N170, a greater negativity was evoked for characters than objects in both groups. Result revealed that normal readers develop sensitivity to well-formedness of object, whereby real-objects elicited a greater negativity than nonobjects at N170, but not in dyslexic readers. At N400, dyslexic readers showed a frontal shift of sensitivity, whereby non-characters evoked a greater negativity than real-character, despite the similar effort required in both groups.