UC Irvine

Some of the neurophysiological data for understanding the neural basis of sound localization are reviewed. There are single units at many levels of the auditory pathway that are sensitive to acoustic cues of interaural differences in time of arrival (Δt) and of intensity (ΔI). The unit sensitivities take the form of a gradual change in response probability over a limited portion of the Δt or ΔI continuum. The possibility that the response change supports a receptive field organization of auditory space similar to the neural analysis of the visual and somatosensory dimensions is rejected because of the gross character of the sensitivity. Most auditory units are 'tuned' to between 50 and 180° of auditory space, measures that are more than 10 fold greater than the usual psychoacoustic threshold. It is suggested that information about auditory space is contained in the difference of activity between populations of units sensitive to right sided and to left sided inputs which are segregated into the paired auditory nuclei. The comparators of the relative levels of activity of these paired nuclei are through segmental connections to various kinds of motor mechanisms tending to direct the animal to move in a lateralized manner.