Human auditory system maturation: A neurophysiological comparison between normal-hearing children and children who use a cochlear implant

Abstract

Auditory-evoked responses provide detailed, objective measures of maturational change in the central auditory system from the level of the brainstem to the cortex. Auditory-evoked responses can reflect activity originating from three pathways: the lemniscal and nonlemniscal pathways as well as from a modality nonspecific pathway originating in the reticular activating system (RAS) and its associated thalamic nuclei. Maturational time courses for these pathways were derived from evoked response data recorded from 156 normal-hearing subjects ranging from 5–20 years of age. Analyses of these data indicate that each pathway may have a unique developmental sequence. For normal-hearing children, the lemniscal pathway appears to follow a longer developmental time course than either the nonlemniscal or RAS pathways. For children with implants, the developmental sequences for these pathways are differentially affected depending on onset and duration of deafness. Specifically, maturation of the lemniscal pathway is delayed by an amount that approximates the period of deafness, whereas maturation of the RAS pathway may be related to the age at onset of deafness.