Department of Otorhinolaryngology, Hannover Medical School and Cluster of Excellence Hearing4all, Hanover, Germany.
Department of Otolaryngology, Massachusetts Eye and Ear, Harvard Medical School, Boston, MA, United States of America.
PLoS One. 2021 Dec 13;16(12):e0261295. doi: 10.1371/journal.pone.0261295. eCollection 2021.
The relationship between electrode-nerve interface (ENI) estimates and inter-subject differences in speech performance with sequential and simultaneous channel stimulation in adult cochlear implant listeners were explored. We investigated the hypothesis that individuals with good ENIs would perform better with simultaneous compared to sequential channel stimulation speech processing strategies than those estimated to have poor ENIs.
Fourteen postlingually deaf implanted cochlear implant users participated in the study. Speech understanding was assessed with a sentence test at signal-to-noise ratios that resulted in 50% performance for each user with the baseline strategy F120 Sequential. Two simultaneous stimulation strategies with either two (Paired) or three sets of virtual channels (Triplet) were tested at the same signal-to-noise ratio. ENI measures were estimated through: (I) voltage spread with electrical field imaging, (II) behavioral detection thresholds with focused stimulation, and (III) slope (IPG slope effect) and 50%-point differences (dB offset effect) of amplitude growth functions from electrically evoked compound action potentials with two interphase gaps.
A significant effect of strategy on speech understanding performance was found, with Triplets showing a trend towards worse speech understanding performance than sequential stimulation. Focused thresholds correlated positively with the difference required to reach most comfortable level (MCL) between Sequential and Triplet strategies, an indirect measure of channel interaction. A significant offset effect (difference in dB between 50%-point for higher eCAP growth function slopes with two IPGs) was observed. No significant correlation was observed between the slopes for the two IPGs tested. None of the measures used in this study correlated with the differences in speech understanding scores between strategies.
The ENI measure based on behavioral focused thresholds could explain some of the difference in MCLs, but none of the ENI measures could explain the decrease in speech understanding with increasing pairs of simultaneously stimulated electrodes in processing strategies.
探索电极-神经界面 (ENI) 估计值与成人人工耳蜗植入者在使用顺序和同时通道刺激时的言语表现的个体间差异之间的关系。我们研究了以下假设：与估计 ENI 较差的个体相比，ENI 较好的个体在使用同时通道刺激言语处理策略时的表现会更好，而不是使用顺序通道刺激言语处理策略。
本研究纳入了 14 名后天性聋的人工耳蜗植入者。使用句子测试评估言语理解能力，每位患者的基线策略为 F120 顺序刺激时的信号噪声比为 50%。在相同的信号噪声比下，测试了两种同时刺激策略，分别是双（配对）或三（三联）组虚拟通道。通过以下三种方法估计 ENI 测量值：(I) 电场成像的电压传播，(II) 聚焦刺激的行为检测阈值，以及 (III) 从两个相间间隔的电诱发复合动作电位获得的幅度增长函数的斜率（IPG 斜率效应）和 50%-点差异（dB 偏移效应）。
发现策略对言语理解性能有显著影响，三联刺激的言语理解性能有趋势比顺序刺激差。聚焦阈值与达到最舒适水平（MCL）的差值呈正相关，这是顺序刺激和三联刺激策略之间通道相互作用的间接衡量标准。观察到显著的偏移效应（两个 IPG 之间较高的 eCAP 增长函数斜率的 50%-点的差异）。测试的两个 IPG 之间的斜率没有观察到显著的相关性。本研究中使用的任何测量方法均与策略之间的言语理解评分差异无关。
基于行为聚焦阈值的 ENI 测量可以解释一些 MCL 差异，但没有任何 ENI 测量可以解释随着处理策略中同时刺激电极对的增加，言语理解能力下降的原因。
