Relevance of auditory cortical maturation to early language acquisition

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My lab studies sound processing in children's brains and how this relates to their spoken language development. We know that children of the same age vary in their language skills. By measuring auditory-evoked potentials (AEPs) with electroencephalography, we have learned that children of the same age also vary in their brain responses to sounds, and that the sophistication of these two abilities (auditory processing and language) is somehow related. Prior research has led many in the field to assume that the brain's ability to process sounds causally influences how children learn language. However, research has yet to confirm this assumed direction of influence. Instead, it is possible that more sophisticated sound processing in the brain is a consequence of the child's growing experience with language, and that our prior assumptions have been wrong. In this new research program, I will longitudinally examine directions of influence between auditory and language sophistication during early language acquisition. To do this, my trainees and I will use a metric that we validated and linked to language with my prior NSERC funding. This metric is AEP-age, which is an estimate of the age equivalent of a child's brain response to sound. This metric has an advantage over traditional approaches because it can be acquired with minimal participation, in 5 minutes, in response to a simple tone, and via an analysis approach that does not require identifying individual peaks in the auditory brainwave. This last advantage is key because it can be challenging to compare children across this age range since these peaks can vary in shape, size, direction, and presence across children. Using this metric, we will gather normative AEPs from groups of children aged 12, 18, 24, 30, 36, 48 and 62 months to estimate the AEP-age of individual children's responses. Then we will track changes in both AEP-age and language ability in a group of 18 month olds until they reach 48 months. This will allow us to examine directions of influence between these two processes over a longitudinal period. To enhance this examination, we will not only study children showing typical language development but also late-talkers who catch up, and those with persistent delays. Understanding the direction of influence matters. If auditory sophistication indeed impacts language sophistication, we would be justified in dedicating future research efforts to better understanding the factors that influence auditory maturation in the brain (such as environmental exposures and genetics), the timing of these influences, and whether manipulating them (when possible) could impact language development. If AEP-age shows promise in predicting the trajectory of early language acquisition, future research could examine clinical translation into predicting which children are at risk for later problems in language development even before they begin talking.