Despite the advantages of listening with two ears, localization and spatial segregation of speech and noise remain difficult for patients who use two cochlear implants (CIs) or a CI in combination with a hearing aid. These difficulties may be due to: 1) poor spectral and/or temporal processing, 2) distorted peripheral patterns, and/or 3) poor binaural integration of peripheral patterns. Auditory training may mitigate these deficits. Our long-term goal is to develop training methods that improve CI patients'binaural perception. It is as yet unclear whether training should target unilateral peripheral processing or bilateral integration of peripheral signals or both. We hypothesize that the difference in unilateral performance across ears (""""""""asymmetry"""""""") must be reduced to maximize the binaural benefit. Unilateral training with the poorer ear alone, followed by bilateral training will provide the best training outcome. For spatial binaural perception (localization and squelch), we further hypothesize that localization requires greater spatial precision than segregation of speech and noise;improving localization will improve spatial segregation. Localization training, followed by spatial segregation training will provide the best outcomes for spatial hearing. In all three Aims, we will use a crossover experimental design to see whether the training sequence affects outcomes. Auditory training has not been extensively studied in bilateral CI or bimodal listeners, and there are few (if any) targeted rehabilitation programs for these patient groups. By addressing these deficits in research and rehabilitation, the proposed research offer novel approaches to increasingly commonplace difficulties for CI patients. The research seeks to identify the best training approach for bilateral CI and bimodal patients, as well as understand how differences in the peripheral input may influence binaural perception as well as the training outcomes. The conceptual framework addresses different factors that may limit performance: auditory resolution, peripheral representation and/or integration of peripheral inputs. Experiments 1 and 2 address whether unilateral psychophysical or speech training is more effective. Experiments 3 and 4 address a fundamental question facing all bilateral CI and bimodal patients: Is it better to train with one ear or two? Experiments 5 and 6 addresses whether spatial training is task-specific (localization vs. spatial segregation). The proposal is o great clinical significance, as the research will guide efficient training methods to maximize CI users'binaural perception. The research is also of great theoretical significance, as it seeks to better understand connections between psychophysical and speech measures, binaural benefits and unilateral performance, as well as localization and spatial segregation in electric hearing. As advances in CI technology seem to be reaching a point of diminishing returns, auditory training may provide the most cost-effective approach to maximize the benefit of cochlear implantation.
The results will yield important fundamental understanding of auditory plasticity in electric hearing and in combined electric and acoustic hearing. The proposed research is clinically relevant in that the findings will provide strong evidence of the benefits of auditory training, undoubtedly leading to affordable, efficient and effective rehabilitation that cochlear implant patients can perform at home, using personal computers.
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