Cochlear-implant high pulse rate and narrow electrode configuration impair transmission of temporal information to the auditory cortex
Cochlear-implant high pulse rate and narrow electrode configuration impair transmission of temporal information to the auditory cortex
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DOI：
10.1152/jn.01114.2007
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发表时间：
2008-07-01
影响因子：
2.5
通讯作者：
Middlebrooks, John C.
中科院分区：
文献类型：
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作者：
Middlebrooks, John C.
在最常用的人工耳蜗系统中，声音的时间特征是通过恒速脉冲串的幅度调制来表示的。几个令人信服的论点预测，语音接收应该通过使用大于或类似于2,000脉冲每秒(PPS)的脉率以及通过使用产生受限电流扩展的耳内电极配置(例如，双极配置而不是单极配置)来优化。这两个预测都没有在语音接收的持续改善中得到证实。麻醉豚鼠听觉皮质中的神经元锁定在正弦调制电脉冲序列的包络线上，这些脉冲串通过人工耳蜗器呈现。本研究使用该动物模型量化了载波脉冲率、电极配置、电流水平和调制器波形对从人工耳蜗体到听觉皮质的时间信息传输的影响。调制敏感度通过对皮质锁相向量强度的信号检测分析来计算。将1倍频程内的载波脉冲率从254增加到4,069 pps会导致灵敏度的系统性降低。对正弦方波调制器波形的比较表明，在高脉冲率下，调制灵敏度的部分(但不是全部)损失是由于在更高脉冲率下的脉间电流阶跃减小的结果。与单极配置相比，使用窄双极配置可显著降低调制灵敏度。这一动物模型的结果解释了高脉搏频率和/或双极电极配置未能在语音接收方面产生预期的改善。
In the most commonly used cochlear prosthesis systems, temporal features of sound are signaled by amplitude modulation of constant-rate pulse trains. Several convincing arguments predict that speech reception should be optimized by use of pulse rates greater than or similar to 2,000 pulses per second (pps) and by use of intracochlear electrode configurations that produce restricted current spread (e. g., bipolar rather than monopolar configurations). Neither of those predictions has been borne out in consistent improvements in speech reception. Neurons in the auditory cortex of anesthetized guinea pigs phase lock to the envelope of sine-modulated electric pulse trains presented through a cochlear implant. The present study used that animal model to quantify the effects of carrier pulse rate, electrode configuration, current level, and modulator wave shape on transmission of temporal information from a cochlear implant to the auditory cortex. Modulation sensitivity was computed using a signal-detection analysis of cortical phase-locking vector strengths. Increasing carrier pulse rate in 1-octave steps from 254 to 4,069 pps resulted in systematic decreases in sensitivity. Comparison of sineversus square-wave modulator waveforms demonstrated that some, but not all, of the loss of modulation sensitivity at high pulse rates was a result of the decreasing size of pulse-to-pulse current steps at the higher rates. Use of a narrow bipolar electrode configuration, compared with the monopolar configuration, produced a marked decrease in modulation sensitivity. Results from this animal model suggest explanations for the failure of high pulse rates and/or bipolar electrode configurations to produce hoped-for improvements in speech reception.