Role of the central auditory system in hearing: the new direction.

The mammalian central auditory system contains a large number of subcortical auditory nuclei, which were once thought to form a simple relay system, taking signals from the ear to the cortex where all information processing would have occurred. Now it appears that these subcortical nuclei are themselves responsible for the extraction and analysis of the dimensions of sounds. Not only do the nuclei encode dimensions defining the nature of the sound, but also they extract features of sound location. Three major nuclei in the superior olivary complex of mammals extract the horizontal direction of a sound source, and it seems likely that other nuclei in the auditory system encode elevation and distance. This shift in viewpoint away from the attributes of sound to the attributes of sound sources is an important new step in the investigation of the role of the central auditory system in hearing.