PHYSIOLOGICAL AND BEHAVIORAL STUDY OF SOUND LOCALIZATION

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Our sense of hearing is surely one of the most important senses particularly because it allows communication through speech. The auditory system can also determine the location from which sounds arrive. While speech can be understood reasonably well using only one ear, determination of the spatial location of sound requires both ears because the auditory receptors encode the frequencies of sounds, not their locations; central comparisons of neural signals evoked by the acoustic inputs to the two ears are required. The long-term goal is to understand the neural bases of sound localization. One objective of the proposed train is to acquire the methods, techniques, and skills necessary for studying the neural mechanisms for binaural hearing in the cat. The training is designed to build on the applicant's background in behavioral studies of binaural hearing in human observers. The training will encompass two specific aims, both of which investigate two structures though to be important for sound localization. Aim I investigates how the three main sound localization cues are encoded in the lateral superior olive (LSO) of the anesthetized cat using a Virtual Acoustic Space (VAS) technique. The VAS approach affords precise independent manipulation of the cues which is crucial to determining the coding strategies of the LSO. Aim II investigates the effects of echoes on sound localization and on the coding of location in the inferior colliculus (IC). Single units in the IC or an awake cat will be recorded from while the cat is actively participating in a psychophysical sound localization task. The ultimate goal of the training is to develop an integrative approach to understanding hearing which combines traditional behavioral and neurophysiological approaches. Such an integrated approach is required to relate behavioral processes to their neural substrates.