An Overview of Central Auditory Processing

A listener’s perception of the world of sound is but an abstraction of physical reality. It is determined initially by the linear acoustic transformation performed by the head, pinnae and external ear canals, followed in turn by the nonlinear mechanoelectric transduction in the bilaterally placed receptor organs of Corti and the ever changing spatio-temporal discharge patterns in ensembles of first-order afferent fibers of the auditory nerve. Within the central auditory system, which faces the acoustic world only indirectly through this filtered and fluctuating afferent input, incoming information encoded in trains of all-or-none action potentials is received, transformed, and then redistributed over parallel pathways to higher centers in the brain. Sound perception involves a number of central auditory mechanisms operating in concert, and these mechanisms form recurrent themes that run through the chapters that follow. They include sensory coding, temporal and spatial transformation, divergent and convergent projection, parallel and serial processing, localization of function and neuronal plasticity. These themes are related to hearing in ways still not fully understood, although all of them have been thought about, discussed, and studied in one form or another for a century or more.