The overall goal of this project is to determine how to optimize benefit from a cochlear implant for every patient.
Specific aims are to: 1) evaluate the effect of using speech-processor programming parameters other than default values on speech recognition and usefulness in everyday life; 2) evaluate the relation between intracochlear electrode position and behavioral measures of threshold and dynamic range; 3) evaluate new speech processing strategies; and 4) monitor long-term benefit with cochlear implants. Approximately 65 deaf adults implanted with the Nucleus device will participate in experiments to evaluate these aims. (1) Four speech- processor programming parameters will be evaluated: different electrode pairings within the same program, assignment of frequency bands according to characteristic frequency of neurons near electrodes, selection of electrodes that carry more encoded information, and choice of function (Q- value) for manning sound amplitude onto each electrode's dynamic range. Comparison of performance on audition-only speech tests in quiet and noise will be made between the value presently used and a range of values for each parameter listed above. Responses to a questionnaire will reflect perceived usefulness in everyday life. Prior to data collection, each subject's speech-processor program will be fine-tuned and used for at least three weeks. (2) Multiple regression analysis will be employed to determine whether there is a predictive relation between intracochlear electrode position (measured from 3D reconstructions of CT scans) and behavioral thresholds and dynamic range. This information will be compared with models of electrical field generation, neural recruitment, and predicted thresholds and dynamic ranges. (3) New speech processing strategies, such as A plus MultiPeak and Spectral Maxima Sound Processor, will be compared with the strategy in current use with the same procedures described in (1). 4) Evaluation of long-term benefit will include measures of retest variability to determine if there are significant changes in an individual's performance. Default parameters for programming the Nucleus device are expedient but do not necessarily provide the best hearing. Results from the proposed studies will provide a scientific basis for selecting an individualized set of parameters and speech processing strategy to optimize each patient's benefit. Incorporation of this information into the programming software will make it clinically feasible to significantly improve speech recognition and ease of communication for many patients.
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