Timing cues such as interaural time differences (ITDs) and temporal pitch are pivotal for sound localization and source segregation, but their perception is degraded in cochlear-implant (CI) listeners as compared to normal-hearing listeners. In multi-electrode stimulation, intra-aural channel interactions between electrodes are assumed to be an important factor limiting access to those cues. The monaural asynchrony of stimulation timing across electrodes is assumed to mediate the amount of these interactions. This study investigated the effect of the monaural temporal electrode asynchrony (mTEA) between two electrodes, applied similarly in both ears, on ITD-based left/right discrimination sensitivity in five CI listeners, using pulse trains with 100 pulses per second and per electrode. Forward-masked spatial tuning curves were measured at both ears to find electrode separations evoking controlled degrees of across-electrode masking. For electrode separations smaller than 3 mm, results showed an effect of mTEA. Patterns were u/v-shaped, consistent with an explanation in terms of the effective pulse rate that appears to be subject to the well-known rate limitation in electric hearing. For separations larger than 7 mm, no mTEA effects were observed. A comparison to monaural rate-pitch discrimination in a separate set of listeners and in a matched setup showed no systematic differences between percepts. Overall, an important role of the mTEA in both binaural and monaural dual-electrode stimulation is consistent with a monaural pulse-rate limitation whose effect is mediated by channel interactions. Future CI stimulation strategies aiming at improved timing-cue encoding should minimize the stimulation delay between nearby electrodes that need to be stimulated successively.

中文翻译：

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双侧和单侧人工耳蜗刺激中单耳颞电极异步性和通道相互作用的影响


耳间时间差 (ITD) 和时间音调等时间线索对于声音定位和声源分离至关重要，但与正常听力的听众相比，人工耳蜗 (CI) 听众的感知能力会下降。在多电极刺激中，电极之间的耳内通道相互作用被认为是限制获取这些线索的重要因素。假设电极间刺激时序的单耳异步性调节了这些相互作用的量。本研究使用每个电极每秒 100 个脉冲的脉冲序列，研究了两个电极之间的单耳颞电极异步 (mTEA)（类似地应用于双耳）对 5 位 CI 听众基于 ITD 的左/右辨别灵敏度的影响。在双耳处测量前向掩蔽空间调谐曲线，以找到引起跨电极掩蔽受控程度的电极间距。对于小于 3 mm 的电极间距，结果显示了 mTEA 的效果。模式呈 u/v 形，与有效脉冲率的解释一致，有效脉冲率似乎受到电听力中众所周知的速率限制。对于大于 7 mm 的间距，没有观察到 mTEA 效应。与一组单独的听众和匹配设置中的单声道速率-音高辨别力的比较表明，感知之间没有系统性差异。总体而言，mTEA 在双耳和单耳双电极刺激中的重要作用与单耳脉冲速率限制一致，其影响是由通道相互作用介导的。未来的 CI 刺激策略旨在改进定时提示编码，应最大限度地减少需要连续刺激的附近电极之间的刺激延迟。