ROLE OF ACOUSTIC STRIAE IN HEARING - DISCRIMINATION OF SOUND-SOURCE ELEVATION

After years of systematic experimentation, we finally uncovered one th ing the dorsal system contributes to hearing which the ventral system may not - the mechanism for orienting to an elevated sound source [Sut herland, D.P., Masterton. R.B., Glendenning, K.K. (1998) Behav. Brain Res. in press]. This paper follows up this one positive result on a hi storical background of uniformly negative results. The focus of this r eport is on the fusiform cells of the dorsal cochlear nucleus whose ax ons course through the dorsal acoustic stria (DAS). Because electrophy siological studies have shown that the cues for sensing the elevation of a sound source would seem to be best analyzed by the dorsal cochlea r nucleus, we tested, behaviorally, normal cats and cats deprived of t heir DAS or intermediate acoustic stria, bilaterally or ipsilaterally (with or without their contralateral ear deafened). for their ability to orient to elevated sources of broad-band noise. For behavioral test ing, we made use of a conventional shock-avoidance procedure. The resu lts lead to the conclusion that DCN and DAS may play no role in learne d elevation discriminations. This result builds on that of another of our papers which suggests that a deficit in reflexive discrimination o f elevation is strictly auditory in nature [Sutherland, D.P., Masterto n. R.B.. Glendenning, K.K. (1998) Behav. Brain Res. in press]. (C) 199 8 Elsevier Science B.V. All rights reserved.