Role of the dorsal cochlear nucleus in the sound localization behavior of cats

The role of the dorsal cochlear nucleus (DCN) in directional hearing was ev aluated by measuring sound localization behaviors before and after cats rec eived lesions of the dorsal and intermediate acoustic striac (DAS/IAS). The se lesions are presumed to disrupt spectral processing in the DCN without a ffecting binaural time and level difference cues that exit the cochlear nuc leus via the ventral acoustic stria. Prior to DAS/IAS lesions, cats made ac curate head orientation responses toward sound sources in the frontal sound field. After a unilateral DAS/IAS lesion, subjects showed increased errors in the azimuth and elevation of their responses; in addition, the final or ientation of head movements tended to be more variable. Largest deficits in response elevation were observed in the hemifield that was ipsilateral to the lesion. When a second lesion was placed in the opposite DAS/IAS, increa sed orientation errors were observed throughout the frontal field. Nonethel ess, bilaterally lesioned cats showed normal discrimination of changes in s ound source location when tested with a spatial acuity task. These findings support previous interpretations that the DCN contributes to sound orienta tion behavior, and further suggest that the identification of absolute soun d source locations and the discrimination between spatial locations involve independent auditory processing mechanisms. (C) 2000 Elsevier Science B.V. All rights reserved.