The Journal of Neuroscience, January 10, 2007, 27(2):315-321; doi:10.1523/JNEUROSCI.1984-06.2007
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Behavioral/Systems/Cognitive
Neural Attunement Processes in Infants during the Acquisition of a Language-Specific Phonemic Contrast
Yasuyo Minagawa-Kawai,1,2,3,4
Koichi Mori,5
Nozomi Naoi,1 and
Shozo Kojima1,2
1Department of Psychology, Keio University, Tokyo 108-8345, Japan, 2Japan Agency of Science and Technology, Saitama 332-0012, Japan, 3Laboratoire de Sciences Cognitives et Psycholinguistique, Ecole Normale Supérieure, Ecole des Hautes Etudes en Sciences Sociales, and Centre National de la Recherche Scientifique, Paris 75005, France, 4Centre for Developmental Language Disorders and Cognitive Neuroscience, University College London, London WC1 NPF, United Kingdom, and 5Department of Rehabilitation for Sensory Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Saitama 359-8555, Japan
Correspondence should be addressed to Yasuyo Minagawa-Kawai, Department of Psychology, Keio University, 2-15-45 Mita, Minato-ku, Tokyo 108-8345, Japan. Email: myasuyo{at}bea.hi-ho.ne.jp
To elucidate the developmental neural attunement process in the language-specific phonemic repertoire, cerebral hemodynamic responses to a Japanese durational vowel contrast were measured in Japanese infants using near-infrared spectroscopy. Because only relative durational information distinguishes this particular vowel contrast, both first and second language learners have difficulties in acquiring this phonemically crucial durational difference. Previous cross-linguistic studies conducted on adults showed that phoneme-specific, left-dominant neural responses were observed only for native Japanese listeners. Using the same stimuli, we show that a larger response to the across-category changes than to the within-category changes occurred transiently in the 6- to 7-month-old group before stabilizing in the groups older than 12 months. However, the left dominance of the phoneme-specific response in the auditory area was observed only in the groups of 13 months and above. Thus, the durational phonemic contrast is most likely processed first by a generic auditory circuit at 67 months as a result of early auditory experience. The neural processing of the contrast is then switched over to a more linguistic circuit after 12 months, this time with a left dominance similar to native adult listeners.
Key words: speech perception; phonemic acquisition; NIRS; cerebral lateralization; auditory area; development
Received May 9, 2006;
revised Nov. 21, 2006;
accepted Nov. 28, 2006.
Correspondence should be addressed to Yasuyo Minagawa-Kawai, Department of Psychology, Keio University, 2-15-45 Mita, Minato-ku, Tokyo 108-8345, Japan. Email: myasuyo{at}bea.hi-ho.ne.jp
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