Chapter 4 - Effects of Nondamaging Sound on the Developing Brain

Abstract

Harmonious auditory development and maturation is often considered a given, except when following preterm birth. The continuous hum and noise in the incubators of the neonatal intensive care unit, even at the relatively low levels of <55dBA, cannot be considered a normal acoustic environment. Periods of time with increased sensitivity for the surrounding acoustics are called critical periods (CP). Abnormal acoustic environments such as low-level continuous noise extend the closure time of the CP, while pulsed noise messes up the tonotopic maps in cortex. The maturation in the human auditory system follows a more protracted time course compared to animals. It can be divided (both structural, electrophysiological and behavioral) in a fast (<2 years) maturation of the discrimination mechanisms and a slow (<20 years) maturation of the perceptual system. Potentially, early exposure to nonnatural acoustic environments may cause the perceptual system to be arrested in suboptimal form. We call that central auditory processing disorder.