Speech perception deficit in dyslexic adults as measured by mismatch negativity (MMN)

Deficits in phonological processing are known to play a major role in the a etiology of dyslexia, and speech perception is a prerequisite condition for phonological processing. Significant group differences between dyslexics a nd controls have been found in the categorical perception of synthetic spee ch stimuli. In a previous work, we have demonstrated that these group diffe rences are already present at an early pre-attentive stage of signal proces sing in dyslexic children: the late component of the MMN elicited by passiv e speech perception was attenuated in comparison to a control group. In thi s study, 12 dyslexic adults and 13 controls were assessed using a passive o ddball paradigm. Mismatch negativity (MMN) was determined for both tone and speech stimuli. The tone stimuli yielded two MMN components, but no group differences. Three components were found for the speech stimuli. Multivaria te testing for group differences yielded a significant result, and univaria te P values revealed significant differences between dyslexics and controls in two of the three time windows. This suggests that speech perception as measured on an early, pre-attentive level plays a major role in dyslexia no t only in children las shown in our previous study) but also in adults. (C) 2001 Elsevier Science B.V. All rights reserved.