NEUROBEHAVIORAL STUDIES OF THE CENTRAL AUDITORY-SYSTEM

The history of ablation-behavior experimentation into the central audi tory system has led to conclusions not obviously derivable from knowle dge of neuroanatomy or neurophysiology alone. 1) The ventral, and not the dorsal, acoustic stria is necessary and sufficient for discriminat ing the physical dimensions of sound. 2) The ventral, and not the dors al, system is also necessary and sufficient for discriminations of bot h the azimuth and elevation of a sound source. 3) A functional ''acous tic chiasm'' is centered in the superior olivary complex, resulting in the neurobehavioral ''representation'' of each acoustic hemifield onl y in the contralateral side of the central system (despite the presenc e of ipsilateral activity). 4) The behavioral usefulness of the ipsila teral activity present above the superior olivary complex, the role of the entire dorsal acoustic system, and the role of the descending sys tem remain unknown. The fact that the only clear structural-behavioral correspondence yet known is that between the superior olives and soun d localization seems to suggest that the more fruitful avenues of furt her inquiry into the roles of the central auditory system might lie in the more biologic (or Darwinian) as opposed to the physical (or Helmh oltzian) dimensions of auditory processing.