A neural code for low-frequency sound localization in mammals

We report a systematic relationship between sound-frequency tuning and sens itivity to interaural time delays for neurons in the midbrain nucleus of th e inferior colliculus; neurons with relatively low best frequencies (BFs) s howed response peaks at long delays, whereas neurons with relatively high B Fs showed response peaks at short delays. The consequence of this relations hip is that the steepest region of the function relating discharge rate to interaural time delay (ITD) fell close to midline for all neurons irrespect ive of BF. These data provide support for a processing of the output of coi ncidence detectors subserving low-frequency sound localization in which the location of a sound source is determined by the activity in two broad, hem ispheric spatial channels, rather than numerous channels tuned to discrete spatial positions.