A major task across infancy is the creation and tuning of the acoustic maps that allow efficient native language processing. This process crucially depends on ongoing neural plasticity and keen sensitivity to environmental cues. Development of sensory mapping has been widely studied in animal models, demonstrating that cortical representations of the sensory environment are continuously modified by experience. One critical period for optimizing human language mapping is early in the first year; however, the neural processes involved and the influence of passive compared with active experience are as yet incompletely understood. Here we demonstrate that, while both active and passive acoustic experience from 4 to 7 months of age, using temporally modulated nonspeech stimuli, impacts acoustic mapping, active experience confers a significant advantage. Using event-related potentials (ERPs), we show that active experience increases perceptual vigilance/attention to environmental acoustic stimuli (e.g., larger and faster P2 peaks) when compared with passive experience or maturation alone. Faster latencies are also seen for the change discrimination peak (N2*) that has been shown to be a robust infant predictor of later language through age 4 years. Sharpening is evident for both trained and untrained stimuli over and above that seen for maturation alone. Effects were also seen on ERP morphology for the active experience group with development of more complex waveforms more often seen in typically developing 12-to 24-month-old children. The promise of selectively "fine-tuning" acoustic mapping as it emerges has far-reaching implications for the amelioration and/or prevention of developmental language disorders.

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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 (4-6Hz) 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 (33-37Hz) 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.

The aim of the study was to examine the profiles of children with a family history (FH+) of language-learning impairments (LLI) and a control group of children with no reported family history of LLI (FH-) and identify which language constructs (receptive or expressive) and which ages (2 or 3 years) are related to expressive and receptive language abilities, phonological awareness, and reading abilities at ages 5 and 7 years. Participants included 99 children (40 FH+ and 59 FH-) who received a standardized neuropsychological battery at 2, 3, 5, and 7 years of age. As a group, the FH+ children had significantly lower scores on all language measures at 2 and 3 years, on selected language and phonological awareness measures at 5 years, and on phonological awareness and nonword reading at 7 years. Language comprehension at 3 years was the best predictor of later language and early reading for both groups. These results support past work suggesting that children with a positive family history of LLI are at greater risk for future language and reading problems through their preschool and early school-age years. Furthermore, language comprehension in the early years is a strong predictor of future language-learning status.

Speech-in-noise electrophysiology can be easily recorded across infancy and provides unique insights into developmental differences that tests conducted in quiet may miss.