Neural Coding of Sound with Cochlear Damage

Abstract

The cochlea is a delicate and complex structure designed to transduce sound into the electrical activity of neurons. Damage to any of the components of the cochlea can result in hearing impairment. The development, structure, and vulnerability of the cochlea are the subject of the other chapters in this volume. Here, the focus is on the consequences of cochlear malfunction for the representation of sound in the brain. To make the task feasible in the face of the many known physiological causes of hearing impairment, this chapter discusses the well-studied effects of damage to inner (IHCs) or outer hair cells (OHCs) and to spiral ganglion neurons (SGNs). For most cochlear malfunctions, the hair cells and the SGNs are the final common path for the effects of the damage, so that the implications of a particular type of damage can usually be understood in terms of its effects on these cells and the consequent changes in the brain. Most of the chapter focuses on the effects of acoustic trauma (i.e., exposure to a sustained loud sound), with some discussion of the effects of ototoxic substances, because these have most often been used in experimental studies to produce controlled cochlear lesions.