Presentation
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The neural development of auditory temporal modulation processing for phonetic perception in the first year of life
Poster C101 in Poster Session C, Wednesday, October 25, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Monica Hegde1, Laurianne Cabrera1; 1Université Paris Cité-CNRS
Before 10 months of age, infants are not yet attuned to the consonants of their native language, meaning that, compared to adults, they are sensitive to certain non-native phonological contrasts. The nature of the mechanisms shaped by age and exposure to the native language is yet to be discovered. The current project hypothesizes that auditory mechanisms supporting speech perception may play a crucial role in perceptual attunement. This experimental study explores the interaction between auditory and speech perception abilities during early development by using a psychoacoustic approach combined with electrophysiology. We used a psychoacoustic approach suggesting that the auditory system selectively decomposes the spectral and temporal modulations of speech. Such acoustic modulations can be artificially manipulated using vocoders to assess their role in speech perception. To explore the neural underpinnings of the processing of temporal modulations, and particularly of amplitude and frequency modulations (AM/FM), we used electroencephalography (EEG) to measure the cortical auditory evoked potentials (CAEPs) for native and non-native consonants in French-learning 6-month-old (N=21), 10-month-old (N=21) and French adult listeners (N=20). We used vocoders to process three syllables: French-voiced /aba/, French-unvoiced-unaspirated /apa/, and an English-unvoiced-aspirated /apha/. Three vocoder conditions were designed to preserve: i) original FM and AM, ii) original AM only, and iii) the slowest AM (< 8 Hz) only. The results showed that overall, all age groups exhibited different CAEPs between the original sounds and their FM degraded versions, but that degradation of faster AM cues did not further affect CAEPs. Different CAEP amplitudes were also observed between 6 and 10 months of age as a function of the vocoder condition and consonant. Specifically, at 6 months, infants showed sensitivities to FM degradation for the two native sounds. At 10 months, infants showed sensitivities to FM and further fast AM degradation for the non-native consonant. Adults’ data were analyzed separately as a reference group. Their neural responses were also affected differently by acoustic degradation and consonants, and their pattern of responses was qualitatively closer to the one of 10-month-olds, that is, they showed sensitivities to FM and further fast AM degradation for the non-native consonant only. Thus, this study suggests that neural speech-auditory mechanisms evolve during perceptual attunement in the first year of life.
Topic Areas: Language Development/Acquisition, Speech Perception