Department of Mechatronics, University of Innsbruck, Austria.
MED-EL GmbH, Innsbruck, Austria.
Trends Hear. 2021 Jan-Dec;25:23312165211020645. doi: 10.1177/23312165211020645.
Two-electrode stimuli presented on adjacent mid-array contacts in cochlear-implant users elicit pitch percepts that are not consistent with a summation of the two temporal patterns. This indicates that low-rate temporal rate codes can be applied with considerable independence on adjacent mid-array electrodes. At issue in this study was whether a similar independence of temporal pitch cues can also be observed for more apical sites of stimulation, where temporal cues have been shown to be more reliable than place cues, in contrast to middle and basal sites. In cochlear-implant recipients with single-sided deafness implanted with long lateral-wall electrode arrays, pitch percepts were assessed by matching the pitch of dual-electrode stimuli with pure tones presented to the contralateral normal-hearing ear. The results were supported with an additional pitch-ranking experiment, in a different subject population with bilateral deafness. Unmodulated pulse trains with 100, 200, and 400 pulses per second were presented on three pairs of adjacent electrodes. Pulses were separated by the minimal interchannel delay (1.7 µs) in a short-delay configuration and by half the pulse period in a long-delay configuration. The hypothesis was that subjects would perceive a pitch corresponding to the doubled temporal pattern for the long-delay stimuli due to the summation of excitation patterns from adjacent apical electrodes, if those electrodes were to activate largely overlapping neural populations. However, we found that the mean matched acoustic pitch of the long-delay pulses was not significantly different from that of the short-delay pulses. These findings suggest that also in the apical region in long-array cochlear-implant recipients, temporal cues can be transmitted largely independently on adjacent electrodes.
在接受人工耳蜗植入的患者中，相邻中间电极阵列上的双电极刺激会产生与两个时间模式总和不一致的音高感知，这表明低速率时间率码可以在相邻中间电极上相当独立地应用。本研究的问题是，对于刺激的更顶点部位，是否也可以观察到类似的时间音高线索的独立性，因为与中间和基底部位相比，时间线索在那里比位置线索更可靠。在单侧聋的人工耳蜗植入患者中，使用长侧壁电极阵列进行刺激，通过将双电极刺激的音高与对侧正常听力耳朵呈现的纯音相匹配来评估音高感知。在具有双侧耳聋的不同受试者群体中进行的附加音高排序实验支持了这些结果。以每秒 100、200 和 400 个脉冲的未调制脉冲串在三对相邻电极上呈现。在短延迟配置中，脉冲通过最小的通道间延迟（1.7 µs）分隔，在长延迟配置中通过脉冲周期的一半分隔。假设如果相邻顶点电极激活的神经元群体大部分重叠，那么受试者将感知到与长延迟刺激的时间模式加倍相对应的音高，因为来自相邻顶点电极的兴奋模式会相加。然而，我们发现长延迟脉冲的平均匹配声学音高与短延迟脉冲的音高没有显著差异。这些发现表明，在长阵列人工耳蜗植入接受者的顶点区域，时间线索也可以在相邻电极上大致独立地传输。
