Melodic Contour Identification by Cochlear-Implant Listeners With Asymmetric Phantom Pulses Presented to Apical Electrodes.

IF 2.6 2区 医学 Q1 AUDIOLOGY & SPEECH-LANGUAGE PATHOLOGY
Olivier Macherey, Robert P Carlyon
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引用次数: 0

Abstract

Objectives: (a) To compare performance by cochlear-implant listeners on a melodic contour identification task when the fundamental frequency (F0) is encoded explicitly by single-pulse-per-period (SPP) pulse trains presented to an apical channel, by amplitude modulation of high-rate pulse trains presented to several electrodes, and by these two methods combined, (b) to measure melodic contour identification as a function of the range of F0s tested, (c) to determine whether so-called asymmetric phantom stimulation improves melodic contour identification relative to monopolar stimulation, as has been shown previously using pitch-ranking tasks.

Design: Three experiments measured melodic contour identification by cochlear-implant listeners with two different methods of encoding fundamental frequency (F0), both singly and in combination. One method presented SPP pulse trains at the F0 rate to an apical channel in either partial-bipolar or monopolar mode. The second method applied amplitude modulation at F0 to high-rate (~2000 pulses per second) pulse trains on six adjacent electrodes. For this "MOD" stimulation, the channel envelopes were misaligned so as to simulate the effects of the bandpass filters in the commercial signal-processing strategy.

Results: In experiment 1, the SPP stimulation used the asymmetric phantom method: pseudomonophasic pulses were applied in partial-bipolar mode to electrodes 1 and 3, with 25% of current returned via an extra-cochlear electrode, and with the short high-amplitude phase anodic with respect to electrode 1. The MOD stimuli were presented to a set of basal electrodes. Performance for SPP stimulation was better, both when presented alone and when combined with MOD stimulation, relative to MOD stimulation alone. Performance was also better when the range of F0s present in the stimuli spanned a low range (97 to 194 Hz) than when they spanned a medium (161 to 322 Hz) or a high range (242 to 484 Hz). Experiment 2 was similar to experiment 1 except that the MOD stimuli were presented to a set of six apical electrodes. Performance with SPP stimulation alone was again significantly better than with MOD stimulation, but the difference between combined and MOD stimulation was not significant. Experiment 3 compared performance of SPP stimulation applied in asymmetric phantom mode to monopolar stimulation of the most-apical electrode using symmetric biphasic pulses. No differences were found between these two types of stimulation, either presented in isolation or with MOD stimulation of nearby apical electrodes.

Conclusions: The results show that F0 encoding by SPP stimulation was better than with MOD stimulation, that it was robust to possible interference from MOD-stimulated electrodes, but that performance with combined stimulation was not better than with SPP alone. Contrary to previous data from pitch-ranking studies, we found no evidence that asymmetric phantom improved melodic contour identification compared with the monopolar stimulation used in commercial strategies.

耳蜗植入听者顶电极非对称幻像脉冲的旋律轮廓识别。
目的:(a)比较人工耳蜗听者在基频(F0)通过呈现给顶极通道的单脉冲周期(SPP)脉冲序列、呈现给多个电极的高速率脉冲序列的幅度调制以及这两种方法结合进行编码时在旋律轮廓识别任务上的表现;(b)测量旋律轮廓识别作为F0测试范围的函数。(c)确定所谓的非对称幻像刺激是否比单极刺激能改善旋律轮廓识别,正如之前使用音高排序任务所显示的那样。设计:三个实验分别用两种不同的编码基频(F0)的方法,分别测量人工耳蜗听者对旋律轮廓的识别。一种方法是在部分双极模式或单极模式下,以F0速率将SPP脉冲串发送到顶点通道。第二种方法是在6个相邻电极上以F0对高速率(~2000脉冲每秒)脉冲串进行幅度调制。对于这种“MOD”刺激,通道包络被错位,以模拟商业信号处理策略中带通滤波器的效果。结果:在实验1中,SPP刺激采用非对称幻相法:在电极1和3上以部分双极模式施加假单相脉冲,其中25%的电流通过耳蜗外电极返回,并且相对于电极1具有短的高振幅相阳极。MOD刺激被呈现在一组基础电极上。与单独进行MOD增产相比,单独进行SPP增产和联合进行MOD增产的效果都更好。当刺激中的f0范围为低范围(97至194赫兹)时,表现也比它们跨越中范围(161至322赫兹)或高范围(242至484赫兹)时更好。实验2与实验1相似,不同之处在于MOD刺激被呈现在一组6个顶端电极上。单独使用SPP增产的效果也明显优于MOD增产,但联合使用和MOD增产的效果差异不显著。实验3比较了非对称模态SPP刺激与对称双相脉冲单极刺激的性能。这两种类型的刺激之间没有差异,无论是单独出现还是与附近根尖电极的MOD刺激一起出现。结论:SPP刺激对F0的编码效果优于MOD刺激,对MOD刺激电极可能产生的干扰具有较强的鲁棒性,但联合刺激的F0编码效果并不优于SPP单独刺激。与以往音高排序研究的数据相反,我们发现与商业策略中使用的单极刺激相比,没有证据表明不对称幻像能提高旋律轮廓识别。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Ear and Hearing
Ear and Hearing 医学-耳鼻喉科学
CiteScore
5.90
自引率
10.80%
发文量
207
审稿时长
6-12 weeks
期刊介绍: From the basic science of hearing and balance disorders to auditory electrophysiology to amplification and the psychological factors of hearing loss, Ear and Hearing covers all aspects of auditory and vestibular disorders. This multidisciplinary journal consolidates the various factors that contribute to identification, remediation, and audiologic and vestibular rehabilitation. It is the one journal that serves the diverse interest of all members of this professional community -- otologists, audiologists, educators, and to those involved in the design, manufacture, and distribution of amplification systems. The original articles published in the journal focus on assessment, diagnosis, and management of auditory and vestibular disorders.
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