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Abstract:
Japanese adults usually have difficulty perceiving the
difference between English /l/ and /r/ sounds which do not occur in
Japanese. However, this ability has shown to be improved by
extensive identification training. To investigate the neural
mechanism associated with the acquisition of foreign speech
perception, magnetic cortical responses were recorded from native
speakers of Japanese before and after the training. Subjects were
16 right-handed adults (4 females, aged 21-28). Stimuli were the
male speech sounds /la/ and /ra/ (150 ms), and were presented
binaurally in each trial (/la/ 15%, /ra/ 85%; Inter-trial interval,
600 ms). Identification tests were administered before and after
the training. The accuracy improved from pretest [55 - 68 % (mean
61 %)] to post-test [57 - 96 % (mean 78 %)] significantly. We found
two changes in Mismatch fields (MMF) by training. First, in five
subjects, MMF to /la/ was observed only after the training. Second,
in three subjects, latency of MMF after the training was shorter
than that before the training. These changes were not observed for
subjects whose improvement in identification accuracy was less than
10 points, suggesting that the changes may be associated with the
acquisition of foreign speech sounds.
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