The long-term objectives of this research are to understand the physiological mechanisms for encoding the dynamic range of acoustic hearing and to restore or compensate for the reduced dynamic range in electrical hearing. This proposal focuses on both psychophysical and speech perception experiments with the goal of better speech perception through the implant.
Specific aims are to optimize electric parameters in individual cochlear implant users and to design better coding strategies and fitting protocols for speech processors. The approach to aim one includes five specific experiments. Experiment 1 examines the optimal encoding of loudness by electric parameters and attempts to partially restore threshold distribution of the auditory nerve in acoustic hearing. Experiment 2 uses noise and high-rate conditioners to restore spontaneous activity and neural independence in the electrically stimulated nerve. Experiment 3 examines various nonlinear amplitude mappings to restore normal loudness growth. Experiment 4 measures excitation patterns of various electrode configurations and attempts to restore normal spread of excitation. Experiment 5 characterizes electrode interactions and evaluates a new electrode configuration to restore two-tone suppression effects. Finally, a parallel set of five experiments on speech perception is planned to address each of these issues.
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