Neurobehavioral studies of the central auditory system

The history of ablation-behavior experimentation into the central system has led to conclusions not obviously derivable from knowledge of neuroanatomy or neurophysiology alone. 1) The ventral, and not the dorsal, acoustic stria is necessary and sufficient for discriminating the physical dimensions of sound. 2) The ventral, and not the dorsal, system is also necessary and sufficient for discriminations of both the azimuth and elevation of a sound source. 3) A functional "acoustic chiasm" is centered in the superior olivary complex, resulting in the neurobehavioral "representation" of each acoustic hemifield only in the contralateral side of the central system (despite the presence of ipsilateral activity). 4) The behavioral usefulness of the ipsilateral activity present above the superior olivary complex, the role of the entire dorsal acoustic system, and the role of the descending system remain unknown. The fact that the only clear structural-behavioral correspondence yet known is that between the superior olives and sound localization seems to suggest that the more fruitful avenues of further inquiry into the roles of the central auditory system might lie in the more biologic (or Darwinian) as opposed to the physical (or Helmholtzian) dimensions of auditory processing.