Figure 1.

Overview of auditory spatial processing. (A) Sample acoustic waveforms are shown for the ipsilateral (i) and contralateral (c) ears following presentation of sound from a source located to one side of the head. The incoming sound is typically delayed and attenuated in the contralateral ear, producing interaural time differences (ITDs) and interaural level differences (ILDs), respectively. These cues are referred to as binaural spatial cues as they depend on comparisons between the two ears. (B) Gain is plotted for an adult ferret ear as a function of sound frequency and azimuth. Because the filtering effects of the head and ears depend on the direction of a sound source, the observed spectra vary with respect to azimuth (and elevation), producing spectral shape cues to sound location. (C) Simplified schematic of the mammalian auditory pathway showing the principal ascending (black) and descending (red) projections between the cochlea, cochlear nuclei (CN), superior olivary complex (SOC), inferior colliculus (IC), superior colliculus (SC), medial geniculate body (MGB), and auditory cortex. For clarity, each of these projections is shown for one side of the brain only. (B) adapted with permission from King et al. (2001).