Place-based versus default maps for CI and EAS (Dillon et al., 2022)

Purpose: Cochlear implant (CI) recipients demonstrate variable speech recognition when listening with a CI-alone or electric-acoustic stimulation (EAS) device, which may be due in part to electric frequency-to-place mismatches created by the default mapping procedures. Performance may be improved if the filter frequencies are aligned with the cochlear place frequencies, known as place-based mapping. Performance with default maps versus an experimental place-based map was compared for participants with normal hearing when listening to CI-alone or EAS simulations to observe potential outcomes prior to initiating an investigation with CI recipients.Method: A noise vocoder simulated CI-alone and EAS devices, mapped with default or place-based procedures. The simulations were based on an actual 24-mm electrode array recipient, whose insertion angles for each electrode contact were used to estimate the respective cochlear place frequency. The default maps used the filter frequencies assigned by the clinical software. The filter frequencies for the place-based maps aligned with the cochlear place frequencies for individual contacts in the low- to mid-frequency cochlear region. For the EAS simulations, low-frequency acoustic information was filtered to simulate aided low-frequency audibility. Performance was evaluated for the AzBio sentences presented in a 10-talker masker at +5 dB signal-to-noise ratio (SNR), +10 dB SNR, and asymptote.Results: Performance was better with the place-based maps as compared with the default maps for both CI-alone and EAS simulations. For instance, median performance at +10 dB SNR for the CI-alone simulation was 57% correct for the place-based map and 20% for the default map. For the EAS simulation, those values were 59% and 37% correct. Adding acoustic low-frequency information resulted in a similar benefit for both maps.Conclusions: Reducing frequency-to-place mismatches, such as with the experimental place-based mapping procedure, produces a greater benefit in speech recognition than maximizing bandwidth for CI-alone and EAS simulations. Ongoing work is evaluating the initial and long-term performance benefits in CI-alone and EAS users.Supplemental Material S1. Regression coefficients for the linear mixed model that compared performance between default and place-based maps that would be used clinically. Supplemental Material S2. Regression coefficients for the linear mixed model that assessed the benefit of adding acoustic low-frequency information to default maps with spectrally shifted information and place-based maps. Dillon, M. T., O'Connell, B. P., Canfarotta, M. W., Buss, E., & Hopfinger, J. (2022). Effect of placed-based versus default mapping procedures on masked speech recognition: Simulations of cochlear implant alone and electric-acoustic stimulation. American Journal of Audiology. Advance online publication. https://doi.org/10.1044/2022_AJA-21-00123

研究目的：耳蜗植入术（CI）接受者在使用耳蜗植入术独立或电声刺激（EAS）设备进行听力时，表现出可变的语音识别能力，这可能与默认映射程序产生的部分电频率与空间不匹配有关。若滤波频率与耳蜗空间频率相匹配，即所谓的基于空间映射，则性能可能得到提升。本研究对比了正常听力者在聆听CI独立或EAS模拟时的默认映射与实验性基于空间映射的性能，以观察在开始对CI接受者进行调查研究前的潜在结果。
研究方法：使用噪声声码器模拟CI独立和EAS设备，并使用默认或基于空间的映射程序进行映射。模拟基于实际的24毫米电极阵列接受者，使用每个电极接触的插入角度来估算相应的耳蜗空间频率。默认映射使用了临床软件分配的滤波频率。基于空间的映射的滤波频率与低至中频耳蜗区域中个别接触的耳蜗空间频率相匹配。对于EAS模拟，低频声信息被滤波以模拟辅助的低频可听度。性能评估在+5分贝信噪比（SNR）、+10分贝SNR和渐近线条件下进行的AzBio句子，由10人混合声源掩蔽。
研究结果：与默认映射相比，基于空间的映射在CI独立和EAS模拟中均表现出更好的性能。例如，在+10分贝SNR下，CI独立模拟的中位性能为基于空间映射的57%正确率，而默认映射为20%正确率。对于EAS模拟，这些值分别为59%和37%正确率。添加声学低频信息导致两种映射均获得相似的好处。
研究结论：通过减少频率与空间不匹配，如实验性基于空间映射程序，相较于最大化CI独立和EAS模拟的带宽，能产生更大的语音识别性能提升。正在进行的工作正在评估CI独立和EAS用户初始和长期性能的好处。
补充材料S1：用于比较默认和基于空间映射性能的线性混合模型的回归系数，这些回归系数将用于临床应用。
补充材料S2：用于评估添加声学低频信息到具有光谱偏移信息的默认映射和基于空间映射的好处线性混合模型的回归系数。
Dillon, M. T., O'Connell, B. P., Canfarotta, M. W., Buss, E., & Hopfinger, J. (2022). 基于空间映射与默认映射程序对掩蔽语音识别的影响：耳蜗植入术独立和电声刺激的模拟。美国听觉学杂志。在线预发布。https://doi.org/10.1044/2022_AJA-21-00123