Louleli, N. 1 , Azaiez, N. 2 , Lohvansuu, K. 3 , Hämäläinen, J. A. 4 & Leppänen, P. H. 5
1 Department of Psychology, University of Jyväskylä, Finland
2 Department of Psychology, University of Jyväskylä, Finland
3 Department of Psychology, University of Jyväskylä, Finland
4 Department of Psychology, University of Jyväskylä, Finland
5 Department of Psychology, University of Jyväskylä, Finland
Dyslexia could be associated with problems in phonological processing. However, little is known about neurocognitive mechanisms underlying speech perception in dyslexics with and without phonological difficulties. In this study, brain event-related potentials (ERPs) to native speech sounds were investigated in Finnish dyslexic and typical readers. ERPs of 98 children at grades 2-4 (40 typical and 58 dyslexics, including 21 without phonological problems) were measured using the mismatch negativity (MMN) paradigm. The Finnish /y/-vowel was presented as a rare deviant stimulus (18%) embedded among a standard /i/-vowel (82%). Temporal principal component analysis (tPCA) was applied to identify MMN and late discriminative negativity (LDN). Typical readers showed significant MMN and LDN responses for /y/ vs. /i/ vowel difference. However, dyslexics without phonological difficulties did not show significant MMN response. Interestingly, the group with phonological difficulties had greater MMN amplitude compared to the other groups. Neither of the dyslexic groups showed significant LDN. Overall, the results suggest that both dyslexic groups had atypical vowel processing. Atypically large MMN in the dyslexics with phonological difficulties suggests less specific phonemic representations and/or relying less on these representations.