Purpose: The aim of the present study is to characterize the maturational changes during the first 6 months of life in the neural encoding of two speech sound features relevant for early language acquisition: the stimulus fundamental frequency (fo), related to stimulus pitch, and the vowel formant composition, particularly F1. The frequency-following response (FFR) was used as a snapshot into the neural encoding of these two stimulus attributes.
Method: FFRs to a consonant-vowel stimulus /da/ were retrieved from electroencephalographic recordings in a sample of 80 healthy infants (45 at birth and 35 at the age of 1 month). Thirty-two infants (16 recorded at birth and 16 recorded at 1 month) returned for a second recording at 6 months of age.
Results: Stimulus fo and F1 encoding showed improvements from birth to 6 months of age. Most remarkably, a significant improvement in the F1 neural encoding was observed during the first month of life.
Conclusion: Our results highlight the rapid and sustained maturation of the basic neural machinery necessary for the phoneme discrimination ability during the first 6 months of age.