Electrophysiological evidence of a sound localizing binaural subsystem in the human auditory brainstem

The binaural interaction components of auditory brainstem evoked potentials reflect electrical changes which are specific to binaural stimuli. Analysis of these components indicated that different click lateralizations result in spatially distinct distributions of activity in the pons, but not at more peripheral levels. The effects of ipsilateral and binaural masking on evoked activity indicated distinct binaurally- and monaurally-activated neural subsets in the human brainstem. These results on the effects of noise and the distinct distributions of pontine activity to different lateralizations provide the first electrophysiological evidence that the auditory system in the humans pons includes a subset which is specific to binaurally presented sounds and which is anatomically distributed according to the lateralization of the sound. These results suggest auditory spatial mapping, similar to other sensory systems. In contrast to other systems, in which mapping is according to receptor distribution in the periphery, auditory spatial mapping is achieved computationally at central levels of the pathway.