Abstract
Language acquisition in infants is driven by on-going neural plasticity that is acutely sensitive to environmental acoustic cues. Recent studies showed that attention-based experience with non-linguistic, temporally-modulated auditory stimuli sharpens cortical responses. A previous ERP study from this laboratory showed that interactive auditory experience via behavior-based feedback (AEx), over a 6-week period from 4- to 7-months-of-age, confers a processing advantage, compared to passive auditory exposure (PEx) or maturation alone (Naïve Control, NC). Here, we provide a follow-up investigation of the underlying neural oscillatory patterns in these three groups. In AEx infants, Standard stimuli with invariant frequency (STD) elicited greater Theta-band (4–6 Hz) activity in Right Auditory Cortex (RAC), as compared to NC infants, and Deviant stimuli with rapid frequency change (DEV) elicited larger responses in Left Auditory Cortex (LAC). PEx and NC counterparts showed less-mature bilateral patterns. AEx infants also displayed stronger Gamma (33–37 Hz) activity in the LAC during DEV discrimination, compared to NCs, while NC and PEx groups demonstrated bilateral activity in this band, if at all. This suggests that interactive acoustic experience with non-linguistic stimuli can promote a distinct, robust and precise cortical pattern during rapid auditory processing, perhaps reflecting mechanisms that support fine-tuning of early acoustic mapping.
Highlights
While several peripheral auditory functions appear to be adult-like at birth, developmental changes in the upper brainstem and auditory cortex continue over several years (Kinney et al, 1988; Paus et al, 2001; Deoni et al, 2011)
Residual Variance of the two-dipole model fitting was less than 10% for the STD P1 peak (M4M = 9.5%; MNC = 9.2%; MPEx = 9.7%, MAEx = 9.1%), and slightly higher in the Deviant stimuli with rapid frequency change (DEV) condition (M4M = 11.5%; MNC = 9.8%; MPEx = 13.5%, MAEx = 10.3%)
Maturation of frequency magnitude and phase-coherence over Left and Right auditory cortex was tested with the 2 × 2 × 2 mixed-design ANOVAs for Theta Inter-trial phase locking (ITPL), Theta temporal spectral evolution (TSE) and Gamma TSE
Summary
While several peripheral auditory functions appear to be adult-like at birth, developmental changes in the upper brainstem and auditory cortex continue over several years (Kinney et al, 1988; Paus et al, 2001; Deoni et al, 2011). Recent event-related potential (ERP) research from our lab suggests that early, targeted acoustic experience can enhance and accelerate the maturation of temporal processing in typically-developing infants (Benasich et al, 2014). Infants who experienced interactive, real-time feedback showed enhanced temporal sensitivity, more efficient/faster processing of key acoustic cues and greater generalization to untrained sounds, compared to infants who passively listened to the same sounds. These findings suggest that interactive participation in an acoustic experience may be a powerful catalyst for promoting temporal sensitivity beyond passive listening or maturation alone
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