VISUAL EVENT-RELATED POTENTIALS OF DYSLEXIC-CHILDREN TO RHYMING AND NONRHYMING STIMULI

In a visual event-related potential (ERP) study, children diagnosed as dyslexic in terms of both age and IQ discrepancy criteria were compar ed with two contrast groups: poor for age (SLOW) readers and normal re ading children with Attention Deficit Disorder (ADD). The children vie wed 200 stimulus pairs and judged whether the second stimulus of each pair rhymed with the first. The first stimulus was always a three-lett er word, while half of the second stimuli were pronounceable nonsense words and half were real words. Rhyme probability was 50%. The ERP wav eforms of the dyslexics were significantly different from those of the ADD group in showing less late negativity. The SLOW group's waveforms more closely paralleled those of the ADD group. The major anomalous f eature of the dyslexics' waveform was a pronounced late positive peak (P500), which followed an attenuated N450 peak. Over all groups, the N 450 peak was sensitive to the rhyme manipulation, as has been found in adults (Rugg, 1984a, 1984b). Real words and nonsense words produced s imilar waveforms. Hemispheric effects were found but did not interact with group. Results suggest non-automatic visual cognitive processing of rhyme in dyslexics.