A π-Limit for Coding ITDs: Implications for Binaural Models

Abstract

Interaural time difference (ITD) is an important sound localization cue, arising from the different travel time of a soundfrom its source to the left and right ears for sources located to either side of the head. Neural extraction of ITDs occursin the superior olivary complex (SOC). SOC neurons receive binaural input and are thought to perform a process of cross-correlationbetween the spike trains arriving from left and right ear. Since the acoustic signals are bandpass filtered by the cochlea,the ITD tuning curves of SOC neurons to noise stimuli exhibit shapes similar to cross-correlation functions of bandpass noise(Yin and Chan 1990). They are generally sinusoidal in shape and their amplitude is symmetrically damped either side of theirtuning maximum (Fig. 1A).