ABSTRACT
The first part of this chapter provides an overview of early anatomical and physiological studies and of conceptual models related to sound localization. The remainder is concerned with the processing of interaural time differences (ITDs), a major cue for locating sounds along the azimuth. We first focus on the circuitry and response properties of neurons in the superior olivary complex (SOC), the initial site of ITD processing. The ITD sensitivity of the neurons there is in accord with the basics of the coincidence model for neurons that receive excitatory inputs from both ears, a schema proposed by Jeffress in 1948. One modification to this model is the extension to cells that receive excitatory inputs from one ear and inhibitory inputs from the other ear. Such cells are also found in the SOC and show ITD sensitivity. We then discuss ITD processing in auditory structures above the SOC. Some response properties seen at the SOC are reflected at these higher sites, but several transformations are also evident. For example, ITD tuning appears to be progressively sharpened. This might be akin to narrowing of the receptive field for sound location. Neural circuits that could provide a sharpening mechanism for ITD tuning are described and future directions are discussed.
