A comparison of neural computations underlying stereo vision and sound localization.

Stereo vision and sound localization are behaviors that help organisms to orient in space. Stereo vision provides information about the distance of an object. In sound localization mainly directional signals are analyzed. Two specific cues, binocular disparities underlying stereo vision, and the interaural time difference, suited to represent azimuth in sound localization, have many computational problems in common, although they are generated in two different modalities. The extraction of both cues requires a comparison of signals that arise from two independent sensors, called two-sensor comparison here. This two-sensor comparison is achieved by algorithms similar to summation, half-wave rectification and multiplication. Since the underlying neurons are band-pass filters, the two-sensor comparison results in ambiguities. These are removed in a hierarchical way in several computational steps, involving squaring, inhibition and across-frequency integration.