The impact of prenatal and postnatal acoustic experience to the discrimination of native versus non-native linguistic rules in the brain: insights from combined electrophysiological and vascular signals in 3-month-olds.

Some scaffolding of later language acquisition begins prenatally. Fetuses perceive slow acoustic features (e.g., stress patterns), while fast aspects relevant for phonetics become fully accessible only after birth. This study investigated how prenatal and postnatal acoustic experience influence 3-month-olds' neural responses to native and non-native linguistic rules. A multi-methodological combination (electroencephalography/EEG and functional near-infrared spectroscopy/fNIRS) assessing temporally and topographically precise neural signals was used, while infants listened to native/non-native pseudowords differing in stress patterns (prenatally accessible) and phonotactics (postnatally accessible). EEG and fNIRS revealed novelty/recognition memory effects for non-native rules (EEG: Nc and positive slow wave/negative slow wave components for phonotactics and stress pattern and fNIRS: larger activations for non-native phonotactic and stress pattern rules). The fNIRS further revealed mature right-hemispheric activations for stress pattern, while a still immature bilateral activation was present for phonotactics. These results suggest a potential impact of prenatal experience for slow prosodic features such as stress pattern and an important postnatal impact for fine-grained phonological features such as phonotactics in 3-month-olds.