A distinct low-level mechanism for interaural timing analysis in human hearing.

The detection of phase or timing differences, and amplitude differences between the two ears are cues for the spatial analysis of sound by humans. Previous physiological and anatomical studies of animals suggest that phase and amplitude differences between the ears may depend on different pathways, though human psychophysical studies suggest that interaural phase and amplitude differences between the two ears may be coded in the same way. Here we describe detailed psychophysical analysis of a subject with multiple sclerosis affecting the brain stem. He has a complete deficit in the detection of phase between the ears with preserved detection of interaural amplitude. The results prove that a distinct mechanism exists in humans for interaural phase detection.