Development of infants’ neural speech processing and its relation to later language skills: an MEG study

Abstract

The 'sensitive period' for phonetic learning (~6-12 months) is one of the earliest milestones in language acquisition where infants start to become specialized in processing speech sounds in their native language. In the last decade, advancements in neuroimaging technologies for infants are starting to shed light on the underlying neural mechanisms supporting this important learning period. The current study reports on the largest longitudinal dataset to date with the aim to replicate and extend on two important questions: 1) what are the developmental changes during the 'sensitive period' for native and nonnative speech processing? 2) how does native and nonnative speech processing in infants predict later language outcomes? Fifty-four infants were recruited at 7 months of age and their neural processing of speech was measured using Magnetoencephalography (MEG). Specifically, the neural sensitivity to a native and a nonnative speech contrast was indexed by the mismatch response (MMR). They repeated the measurement again at 11 months of age and their language development was further tracked from 12 months to 30 months of age using the MacArthur-Bates Communicative Development Inventory (CDI). Using an a prior Region-of-Interest (ROI) approach, we observed significant increases for the Native MMR in the left inferior frontal region (IF) and superior temporal region (ST) from 7 to 11 months, but not for the Nonnative MMR. Complementary whole brain comparison revealed more widespread developmental changes for both contrasts. However, only individual differences in the left IF and ST for the Nonnative MMR at 11 months of age were significant predictors of individual vocabulary growth up to 30 months of age. An exploratory machine-learning based analysis further revealed that whole brain MMR for both Native and Nonnative contrasts can robustly predict later outcomes, but with very different underlying spatial-temporal patterns. The current study extends our current knowledge and suggests that native and nonnative speech processing may follow different developmental trajectories and utilize different mechanisms that are relevant for later language skills.

Development of executive function‐relevant skills is related to both neural structure and function in infants

“…The Native MMR averaged across the whole brain at 7 and 11 months is shown in Figure 4a. Detailed information regarding the development of MMRs for both Native and Nonnative contrasts can be found in Zhao and Kuhl (2022), and additional results regarding correlation with the Nonnative MMR can be found in Supplemental Information (Figure S4). Here our main question is whether there are significant correlations between Native MMR and the behavioral task performance at either age.…”

“…To examine this question, we employed a machine‐learning based method that utilized the whole‐brain spatial‐temporal pattern of the MMR to predict each individual's mCAL value within each age. The machine‐learning analyses were performed using the open source scikit‐learn package (Pedregosa et al., 2011) in conjunction with the MNE‐Python software, and were used in previous studies (Zhao et al., 2021; Zhao & Kuhl, 2022; Zhao, 2022). Specifically, for each time sample, we used a support‐vector regression (SVR) where the model uses MMR values from all 114 labels, which takes the spatial pattern of the MMR into consideration, to predict individual mCAL value (Drucker et al., 1996).…”

The impact of a community‐based music program during infancy on the quality of parent–child language interactions

“…Previous research has established that CTs are important for a child's long‐term language development and academic achievement, and that parent–child CTs during daily routines and interactions can be enhanced via parent‐coaching language interventions (Donnelly & Kidd, 2021; Ferjan Ramírez et al, 2020; Leech & Rowe, 2021). Emerging literature has also documented links between music experiences and child language outcomes (Franco et al, 2021; Zhao & Kuhl, 2021), though the evidence base is limited concerning the relation between an enriched music environment for infants and toddlers, and changes in specific language behaviors. Additionally, some research has demonstrated a positive association between music and caregiver‐child interactions that are supportive of an optimal language development environment (Nicholson et al, 2008; Teggelove et al, 2019), The present study utilized a secondary analysis to examine the impact of a music enrichment program on child's language environment, specifically CTs.…”

“…Neural networks for language acquisition are present before birth and their circuitry is influenced by language input long before an individual speaks their first words (Benasich et al, 2014). In fact, peak growth in synapses responsible for language occurs by 6 months and is influenced by a child's language environment (Zhao & Kuhl, 2021). Thus, high‐quality contingent parent–child language interactions are important during infancy.…”