Comparisons between detection threshold and loudness perception for individual cochlear implant channels.
Comparisons between detection threshold and loudness perception for individual cochlear implant channels.
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DOI：
10.1097/aud.0000000000000058
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发表时间：
2014-11
期刊：
影响因子：
3.7
通讯作者：
Nye AD
中科院分区：
文献类型：
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作者：
Bierer JA;Nye AD
本研究的目的，在人工耳蜗植入的听众，是研究如何检测单通道电脉冲序列所需的电流水平与响度感知相同的通道。工作假设是，当用聚焦电流模式测量时，具有相对高阈值的通道与听觉神经的接口较差。对于这样的通道，感知阈值和最舒适响度之间的较小动态范围将部分地由与低阈值通道相比对电场扩展的变化的更大灵敏度引起。舒适听力水平的较窄范围可能对言语感知具有重要影响。数据采集自8名植入HiRes 90 k人工耳蜗（Advanced Bionics Corp.）的成人人工耳蜗植入者。部分三极（pTP）电极配置用于刺激，包括一个脑内有源电极、两个携带返回电流分数（σ）的侧翼电极和一个脑外接地。使用可能的最集中的pTP配置（σ ≥ 0.8）获取单通道检测阈值和最舒适的听力水平，以确定每个受试者的三个通道用于进一步测试-具有最高、中值和最低阈值的通道。阈值，等响轮廓（在50%的单极动态范围），和响度增长函数进行了测量，这三个测试通道使用各种部分三极分数。对于所有测试通道，阈值随着电极配置变得更加集中而增加。与中值和低阈值通道相比，高阈值通道的聚焦参数σ的增加率最大。50%等响等值线在测试通道和受试者之间表现出相似的水平增加率。此外，对于所有电极配置，具有最高阈值的测试通道具有最大的动态范围（对于σ ≥ 0.5）和最陡的响度函数增长。连同以前的研究使用集中刺激，结果表明，听觉响应的电刺激在阈值和阈上电流水平是不均匀的电极阵列的个别人工耳蜗植入者。具体而言，对于高阈值通道观察到的响度的陡峭增长以及因此较小的动态范围与退化的电极-神经元界面一致，这可能源于功能听觉神经元的数量较少或神经元与电极之间的相对较大的距离。这些发现可能对临床映射过程中如何设置刺激水平具有潜在影响，特别是对于使用聚焦电场的语音处理策略。
The objective of the present study, performed in cochlear implant listeners, was to examine how the level of current required to detect single-channel electrical pulse trains relates to loudness perception on the same channel. The working hypothesis was that channels with relatively high thresholds, when measured with a focused current pattern, interface poorly to the auditory nerve. For such channels a smaller dynamic range between perceptual threshold and the most comfortable loudness would result, in part, from a greater sensitivity to changes in electrical field spread compared to low-threshold channels. The narrower range of comfortable listening levels may have important implications for speech perception. Data were collected from eight, adult cochlear implant listeners implanted with the HiRes90k cochlear implant (Advanced Bionics Corp.). The partial tripolar (pTP) electrode configuration, consisting of one intracochlear active electrode, two flanking electrodes carrying a fraction (σ) of the return current, and an extracochlear ground, was used for stimulation. Single-channel detection thresholds and most comfortable listening levels were acquired using the most focused pTP configuration possible (σ ≥ 0.8) to identify three channels for further testing – those with the highest, median, and lowest thresholds – for each subject. Threshold, equal-loudness contours (at 50% of the monopolar dynamic range), and loudness growth functions were measured for each of these three test channels using various partial tripolar fractions. For all test channels, thresholds increased as the electrode configuration became more focused. The rate of increase with the focusing parameter σ was greatest for the high-threshold channel compared to the median- and low-threshold channels. The 50% equal-loudness contours exhibited similar rates of increase in level across test channels and subjects. Additionally, test channels with the highest thresholds had the narrowest dynamic ranges (for σ ≥ 0.5) and steepest growth of loudness functions for all electrode configurations. Together with previous studies using focused stimulation, the results suggest that auditory responses to electrical stimuli at both threshold and suprathreshold current levels are not uniform across the electrode array of individual cochlear implant listeners. Specifically, the steeper growth of loudness and thus smaller dynamic ranges observed for high-threshold channels are consistent with a degraded electrode-neuron interface, which could stem from lower numbers of functioning auditory neurons or a relatively large distance between the neurons and electrodes. These findings may have potential implications for how stimulation levels are set during the clinical mapping procedure, particularly for speech-processing strategies that use focused electrical fields.