从响度水平和反映电极-神经接口的因素预测双侧人工耳蜗使用者的双耳时间差敏感性

文献信息

中文摘要

本研究评估了双侧人工耳蜗使用者的双耳时间差（ITD）阈值如何与和行為响度感知相关的单耳及双耳因素，以及与电极触点与目标神经元之间接口（电极-神经接口，ENI）相关的客观指标相关联。
方法： 对11名双侧人工耳蜗使用者，在阵列上五个位置测量了编号匹配的双耳电极对的ITD阈值。在这些相同电极上，记录了用于刺激的最舒适电流级（C级）、电诱发复合动作电位（ECAP）以及基于计算机断层扫描的电极相对于蜗轴的位置。单耳预测因素包括刺激水平（以C级量化）、蜗轴距离（与神经激活宽度相关）以及听神经纤维对电刺激反应的效能[ECAP幅度增长函数（AGF）斜率]。双耳预测因素包括C级和蜗轴距离的双耳不对称程度。假设更好的ITD敏感性与更高的C级和更大的蜗轴距离（由于响度增加和神经激活更广泛）、更陡的ECAP AGF斜率（由于更多且健康的神经元）以及更小的双耳不对称（由于更大比例的双耳兴奋神经元）相关。
结果： 这些假设通过混合效应模型中的后向消除法进行检验，并使用自举法进行偏倚和稳定性分析。部分证实了假设：在ENI较好（主要由ECAP AGF斜率定义）的耳中，较高的C级和较大的蜗轴距离与更好的ITD阈值显著相关。
结论： 这些结果突出了单耳处理在双耳表现中的作用。

英文摘要

This study evaluated how interaural-time-difference (ITD) thresholds for bilateral cochlear-implant listeners were related to monaural and binaural factors associated with behavioral loudness perception and objective measures associated with the interface between electrode contacts and target neurons (the electrode-to-neural interface, ENI). For 11 bilateral cochlear-implant listeners, ITD thresholds for number-matched interaural electrode pairs were measured at five places along the array. On these same electrodes, the most comfortable current level used for stimulation (C-level), electrically evoked compound action potentials (ECAPs), and electrode positions relative to the modiolus based on computed-tomography scans were recorded. Monaural predictors included stimulation level (quantified by C-levels), modiolar distance (related to the width of neural activation), and efficacy of auditory nerve fiber responses to electrical stimulation [ECAP amplitude growth function (AGF) slopes]. Binaural predictors included the degree of interaural asymmetry in both C-levels and modiolar distances. It was hypothesized that better ITD sensitivity would be related to higher C-levels and larger modiolar distances (because of increased loudness and broader neural activation), steeper ECAP AGF slopes (because of more numerous and healthy neurons), and smaller interaural asymmetry (because of a larger proportion of binaurally excited neurons). The hypotheses were tested via backwards elimination in mixed-effects models with bias and stability analyses performed using bootstrapping. Partially confirming the hypotheses, higher C-levels and greater modiolar distance for electrodes in the ear with better ENI (as defined primarily by the ECAP AGF slope) were significantly associated with better ITD thresholds. These results highlight the role of monaural processing in binaural performance.