Development of medial efferent mechanisms in children.

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PROJECT SUMMARY/ ABSTRACT (parent R01) Efferent feedback—a hallmark of peripheral sound coding—plays a critical role in auditory development and plasticity and offers a potential mechanism for minimizing noise-induced cochlear synaptopathy and supra-threshold perceptual deficits. However, our knowledge of how efferent mechanisms develop in humans is extremely limited. The overarching goal of this research is to understand the development of medial efferent mechanisms in humans and their involvement in auditory development. The objective of the proposed project is to systematically investigate the development of the temporal features of efferent effects. Our central hypothesis is that children exhibit developmental changes in efferent effects as a result of developmental plasticity in the brainstem. Our rationale is that detailed knowledge of how efferents work and develop will lead to a better understanding of the role of efferents in auditory development and perceptual deficits. The proposed project has two specific aims: 1) To determine the development of the efferent sensitivity to temporal fluctuations; and 2) To determine the developmental changes in the temporal dynamics of efferent effects. The proposed work is conceptually innovative because it will provide information on the poorly-understood developmental aspects of efferent effects in the children. The approach involves a compelling mix of sweep-tone OAE measurements with advanced signal processing (time-frequency analysis) techniques. The proposed research will provide significant new knowledge regarding how efferents develop in humans, and has implications for (1) for understanding the involvement of efferents in supra-threshold hearing, (2) forming theories of auditory development, (3) developing OAE-based tests of efferent function for predicting susceptibility to noise-induced hearing loss, (4) constructing accurate auditory models, and (5) designing improved hearing device algorithms. The principal investigator is experienced in conducting this kind of research in the current environment. Overall, the proposed project will make a sustained impact on our understanding of the human efferent system and its development, and on the field of pediatric audiology.