Mismatch negativity to speech stimuli in 8-month-old infants and adults

The mismatch negativity (MMN) was measured in 15 normal awake 8-month-old infants and 10 adults to the speech consonants /da/ and /ta/. ERPs were analyzed at 11 electrodes (Fz, Cz, Pz, C3, C4, T3, T4, T5, T6, P3, P4). Four-hundred trials were presented: the /da/ standards with 80% probability and the /ta/ deviants with 20% probability. The ISI was 600 ms. An MMN was observed for both adults and infants but with different scalp distributions. A clear infant MMN was observed only at C3 and T3 electrodes, whereas the adult MMN was present at Fz, Cz, C3, C4 and Pz. A repeated-measures ANOVA on the normalized summed area between 200 and 250 ms revealed an age (adult vs. infant) x electrode interaction. Paired t-tests indicated that adults and infants showed significant differences at the C3, Cz, T3, Pz and T6 electrodes. The adult MMN was largest at Cz and C3 whereas the infant MMN was largest at T3. These data are discussed in terms of possible maturational changes in the MMN.