Speech Processing Development in Infants: A Longitudinal ERP Study of Native and Nonnative Consonant Discrimination.

Area of Science:

• Developmental neuroscience
• Auditory processing
• Speech perception

Background:

• Perceptual attunement theory predicts infants' neural responses to native speech strengthen while non-native responses diminish within the first year.
• Longitudinal within-subject studies are crucial for testing these developmental predictions.

Purpose of the Study:

• To longitudinally investigate infants' neural responses to native and non-native consonant contrasts.
• To examine the developmental trajectories of auditory event-related potentials (ERPs) and their spatial reorganization.

Main Methods:

• Auditory event-related potentials (ERPs) were recorded from 84 infants at 3, 6, and 12 months.
• An oddball paradigm presented native (/ba/-/da/) and non-native (dental vs. retroflex /ʈa/) consonant contrasts.
• Linear mixed-effects models and center of mass analysis assessed developmental changes and spatial reorganization.

Main Results:

• Most ERP measures showed similar developmental trajectories for native and non-native consonant contrasts, contrary to predictions.
• N1 latency for deviant waveforms was the only measure showing a significant Session × Language interaction.
• Auditory maturation was confirmed by significant main effects of Session on multiple measures, with spatial reorganization observed for P1, N1, and mismatch response (MMR).

Conclusions:

• Neural signatures of perceptual attunement for consonants may be subtler or emerge later than expected.
• Spatial location of neural generators is important for characterizing auditory maturation in infancy.
• Equivalent neural responses to native and non-native contrasts indicate general auditory maturation, not atypical development.