Project V is concerned with the behavioral analysis of the biophysical mechanisms underlying cochlear implant function. Behaviorally trained cats will be deafened unilaterally and implanted with an experimental 11- electrode point-source array. Auditory function under conditions of intracochlear electrical stimulation will be assessed using standard psychophysical paradigms to ascertain absolute threshold, loudness growth, dynamic range, and difference limens for frequency and intensity. Once trained, behavioral performance of a given animal on a given task will be determined for multiple electrical field coupling configurations. Following stabilization of an animal's behavioral performance, electrophysiological recordings of single-cell activity will be obtained in acute experiments, using the same stimuli and testing paradigms that had been employed behaviorally. Animals will then be sacrificed, and their cochleas will be processed histologically to determine the number and spatial positions of surviving spiral ganglion cells. The behavioral, physiological and anatomic data will then be merged and analyzed in the context of neural-behavioral models designed to account for perceptual performance on the basis of patterns of neural activity and tailored to reflect the anatomic condition of the spiral ganglion in the tested animal.
