1 Department of Hearing and Speech Sciences, University of Maryland, College Park, MD, USA.
2 Department of Speech and Hearing Sciences, University of Washington, Seattle, WA, USA.
Trends Hear. 2018 Jan-Dec;22:2331216518813811. doi: 10.1177/2331216518813811.
Speech understanding abilities are highly variable among cochlear implant (CI) listeners. Poor electrode-neuron interfaces (ENIs) caused by sparse neural survival or distant electrode placement may lead to increased channel interaction and reduced speech perception. Currently, it is not possible to directly measure neural survival in CI listeners; therefore, obtaining information about electrode position is an alternative approach to assessing ENIs. This information can be estimated with computerized tomography (CT) imaging; however, postoperative CT imaging is not often available. A reliable method to assess channel interaction, such as the psychophysical tuning curve (PTC), offers an alternative way to identify poor ENIs. This study aimed to determine (a) the within-subject relationship between CT-estimated electrode distance and PTC bandwidths, and (b) whether using focused stimulation on channels with suspected poor ENI improves vowel identification and sentence recognition. In 13 CI listeners, CT estimates of electrode-to-modiolus distance and PTCs bandwidths were measured for all available electrodes. Two test programs were created, wherein a subset of electrodes used focused stimulation based on (a) broad PTC bandwidth (Tuning) and (b) far electrode-to-modiolus distance (Distance). Two control programs were also created: (a) Those channels not focused in the Distance program (Inverse-Control), and (b) an all-channel monopolar program (Monopolar-Control). Across subjects, scores on the Distance and Tuning programs were significantly higher than the Inverse-Control program, and similar to the Monopolar-Control program. Subjective ratings were similar for all programs. These findings suggest that focusing channels suspected to have a high degree of channel interaction result in quite different outcomes, acutely.
人工耳蜗（CI）使用者的言语理解能力差异很大。稀疏的神经元存活或电极放置较远导致的电极-神经元界面（ENI）不良可能会导致更多的通道相互作用，从而降低言语感知能力。目前，无法直接测量 CI 使用者的神经元存活情况；因此，获得有关电极位置的信息是评估 ENI 的一种替代方法。可以使用计算机断层扫描（CT）成像来估计这些信息；但是，术后 CT 成像通常不可用。可靠的方法评估通道相互作用，如心理物理调谐曲线（PTC），为识别不良 ENI 提供了另一种方法。本研究旨在确定：（a）CT 估计的电极距离与 PTC 带宽之间的个体内关系，以及（b）使用疑似不良 ENI 的通道进行聚焦刺激是否可以改善元音识别和句子识别。在 13 位 CI 使用者中，对所有可用电极进行了 CT 估计的电极-蜗轴距离和 PTC 带宽测量。创建了两个测试程序，其中基于（a）宽 PTC 带宽（调谐）和（b）远电极-蜗轴距离（距离）对一部分电极使用聚焦刺激。还创建了两个对照程序：（a）Distance 程序中未聚焦的通道（Inverse-Control），以及（b）所有通道的单极程序（Monopolar-Control）。在所有受试者中，Distance 和 Tuning 程序的得分明显高于 Inverse-Control 程序，与 Monopolar-Control 程序相似。所有程序的主观评分均相似。这些发现表明，聚焦被怀疑具有高度通道相互作用的通道会导致截然不同的结果，尤其是在急性情况下。
