Objectives: This study examined maturation of mismatch responses (MMRs) to an English vowel contrast (/I/ versus /ε/) in 4- to 7-yr-old children.
Design: Event-related potentials were recorded to a standard [ε] and deviant [I] vowel presented in trains of 10 stimuli at a rate of 1/650 msecs and with an intertrain interval of 1.5 secs. Each train contained two deviant vowels. Averaged responses were calculated for the infrequent (deviant) and the frequent (standard) trials for each child and compared across age groups.
Results: Significantly greater negativity, consistent with the adult mismatch negativity (MMN), was observed to the deviants between 300 and 400 msecs for both younger (4- and 5-yr-old) and older (6- and 7-yr-old) children. This MMN-like negativity shifted earlier in latency by 25 msecs/yr with increasing age. Most of the children younger than 5.5 yrs and some of the older children also showed a positive MMR (p-MMR) peaking between 100 and 300 msecs. The p-MMR diminished in amplitude with increasing age.
Conclusions: Maturation of speech discrimination, as indexed by MMN, occurs more rapidly between 4 and 7 yrs of age for vowels than for tones. A p-MMR preceding the MMN also reflects discrimination in younger children and declines in amplitude with age.
Maturation of electrophysiological mismatch responses (MMRs) to English vowel sounds was examined in 4- to 7-yr-old children. Younger children exhibited both positive and negative MMR, whereas children closer to age 7 showed primarily the negative MMR. This negative response is likely to be comparable with the adult mismatch negativity and shifted earlier in time with increasing age by ∼25 msecs/yr. The positive-MMR response is argued to reflect recovery of refractoriness of neurons in earlier maturing cortical regions than for the source of mismatch negativity.
The Graduate School and University Center, The City University of New York, New York, New York.
This work was supported by NIH HD46193 (to V. S.).
Address for correspondence: Dr. Valerie L. Shafer, The Graduate School and University Center, The City University of New York, 365 Fifth Avenue, Room 7400.14, New York, NY 10016. E-mail: firstname.lastname@example.org.
Received November 10, 2009; accepted April 26, 2010.