Event-Related Brain Potentials and Frequency-Following Response to Syllables in Newborns and Adults

Auditory event-related brain potentials such as the mismatch negativity (MMN) and the frequency-following response (FFR) allow exploring speech sound encoding along the auditory pathway. Here, we collected event-related brain potential (ERP) and FFR neural responses to syllables in healthy full-term newborns (N = 17, mean age = 3 days) and adults (N = 21, mean age = 22.7). Participants were passively exposed to alternating blocks of syllables presented at either fast or slow stimulation rates while we recorded electroencephalography (EEG). Specifically, blocks containing the synthetic /oa/ syllable alternated with "oddball" blocks containing three natural syllables differing in place of articulation (one standard /da/ and two deviants /ba/ and /ga/). At the FFR level, we found that 3-day-old newborns (i) exhibit an already functional encoding of vowel pitch, (ii) show an immature encoding of vowel formant structure, replicating previous observations. At the ERP level, the two deviants elicited clear MMN in the two groups, although with different topographies, suggesting an immature sensitivity to place of articulation in newborns. These results confirm the role of experience-dependent developmental factors that may differentially shape FFR and ERPs of speech sound features. Furthermore, this study highlights the feasibility of assessing the hierarchy of neural speech sound encoding in a short experimental session.