How is dysfluent reading reflected in the ERP?

The present study focused on early ERP differences between dyslexic and fluent readers which may reflect a deficit in letter string processing. We compared the ERPs of dyslexic and fluent readers (20 German-speaking boys in each group, age 13-14 years) in response to words and consonant strings. Due to the regularity of German orthography, our dyslexic readers suffered mainly from impaired fluency and not from errors. In a word task each trial presented short, highly frequent words and the occurrence of a pseudoword among the eight items of a trial had to be reported. In a corresponding string task each trial presented consonant strings and the occurrence of a word among the strings had to be reported. The blocked presentation allowed expectations about the nature of the stimuli and their timing. Dyslexic readers exhibited a reduced CNV in anticipation of words and strings, which in the case of words was followed by a compensatory enhanced N220. This pattern was limited to left posterior sites and may reflect a sluggish response of brain regions involved in visual letter string processing.