Event-related potential indices of auditory vowel processing in 3-year-old children.
OBJECTIVE
To determine the ERP characteristics and ERP indices of central speech sound encoding and discrimination in young children.


METHODS
Auditory sensory event-related potentials (ERPs) and the ERP index of auditory sensory discrimination (the mismatch negativity, MMN) were elicited by vowel stimuli in 3-year-old children. In an oddball paradigm, the standard stimulus was vowel /a/, one deviant stimulus was vowel /o/ (the across-category change), and the other was nasalized vowel /a/ (within-category change). In addition, the ERP changes occurring during the 14 min uninterrupted recording were examined.


RESULTS
As indexed by the sensory P1, N2, and N4 peaks, the 3-year-old children's transient neural encoding of vowels was comparable to that earlier registered in 1-year-old children but also showed vowel-specific characteristics observed in school-age children. The 3-year-old's MMN was comparable in amplitude to the school-age children's MMN and appeared to be sensitive to the across-category aspects of vowel changes. However, its latency was longer in the 3-year-olds than in school-age children. Among the sensory ERPs, only the N4 peak showed significant diminution during the experiment. The across-category change MMN diminished after 10 min of the recording, however, over the frontal areas only.


CONCLUSIONS
In the 3-year-old children, the sensory processing of vowels exhibited transitional characteristics between those observed in infants and school-age children. The auditory sensory discrimination in the 3-year-olds appeared to be sensitive to the phonemic aspects of stimulus change. The frontally-predominant MMN diminution during the experiment might indicate the greater refractoriness of its frontal-lobe generators. In general, the auditory sensory ERPs show distinct maturational profiles from that of the MMN.
Ceponiene
R
R
Cognitive Brain Research Unit, Department of Psychology and Helsinki Brain Research Unit, University of Helsinki, Helsinki, Finland. rceponiene@crl.ucsd.edu <rceponiene@crl.ucsd.edu>
Lepistö
T
T
Alku
P
P
Aro
H
H
Näätänen
R
R
D000161:Acoustic Stimulation; D000367:Age Factors; D001303:Auditory Cortex / Q000502:physiology*; D002675:Child, Preschool; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000502:physiology; D006801:Humans; D008297:Male; D013067:Speech Perception / Q000502:physiology*