Atypical perceptual narrowing in prematurely born infants is associated with compromised language acquisition at 2 years of age

Background: Early auditory experiences are a prerequisite for speech and language acquisition. In healthy children,
phoneme discrimination abilities improve for native and degrade for unfamiliar, socially irrelevant phoneme
contrasts between 6 and 12 months of age as the brain tunes itself to, and specializes in the native spoken
language. This process is known as perceptual narrowing, and has been found to predict normal native language
acquisition. Prematurely born infants are known to be at an elevated risk for later language problems, but it
remains unclear whether these problems relate to early perceptual narrowing. To address this question, we
investigated early neurophysiological phoneme discrimination abilities and later language skills in prematurely born
infants and in healthy, full-term infants.
Results: Our follow-up study shows for the first time that perceptual narrowing for non-native phoneme contrasts
found in the healthy controls at 12 months was not observed in very prematurely born infants. An electric
mismatch response of the brain indicated that whereas full-term infants gradually lost their ability to discriminate
non-native phonemes from 6 to 12 months of age, prematurely born infants kept on this ability. Language
performance tested at the age of 2 years showed a significant delay in the prematurely born group. Moreover,
those infants who did not become specialized in native phonemes at the age of one year, performed worse in the
communicative language test (MacArthur Communicative Development Inventories) at the age of two years. Thus,
decline in sensitivity to non-native phonemes served as a predictor for further language development.
Conclusion: Our data suggest that detrimental effects of prematurity on language skills are based on the low
degree of specialization to native language early in development. Moreover, delayed or atypical perceptual
narrowing was associated with slower language acquisition. The results hence suggest that language problems
related to prematurity may partially originate already from this early tuning stage of language acquisition.

Citation:
Jansson-Verkasalo, E., Ruusuvirta, T., Huotilainen, M., Alku, P., Kushnerenko, E., Suominen, K., Rytky, S., Luotonen, M., Kaukola, T., Tolonen, U. and Hallman, M. (2010) 'Atypical perceptual narrowing in prematurely born infants is associated with compromised language acquisition at 2 years of age' BMC Neuroscience, 11(1) p. 88.