The present work uses behaviorally trained cats to study the cochlear implant. The cochlear implant is a device designed to restore hearing to the totally deaf by passing minute electrical currents through the inner ear. We have found A) a 60 - 70% decrease in threshold over a period of 3-4 months following implantation, B) that repetition rate of a rectangular stimulus does not affect loudness and C) pulse width affects loudness below 0.4 msec. but has no effect on loudness above 0.4 msec. We plan to A) obtain frequency discrimination thresholds in both damaged and undamaged ears, B) determine whether or not the cat can discriminate between identical electrical stimuli delivered through various channels of stimulation, C) determine how various cochlear pathologies affect impedance, and threshold.