Spitzer Emily R, Hughes Michelle L
Boys Town National Research Hospital, Omaha, NE.
University of North Carolina-Chapel Hill, Chapel Hill, NC.
J Am Acad Audiol. 2017 Oct;28(9):786-798. doi: 10.3766/jaaa.16144.
Contemporary cochlear implants (CIs) use cathodic-leading, symmetrical, biphasic current pulses, despite a growing body of evidence that suggests anodic-leading pulses may be more effective at stimulating the auditory system. However, since much of this research on humans has used pseudomonophasic pulses or biphasic pulses with unusually long interphase gaps, the effects of stimulus polarity are unclear for clinically relevant (i.e., symmetric biphasic) stimuli.
The purpose of this study was to examine the effects of stimulus polarity on basic characteristics of physiological spread-of-excitation (SOE) measures obtained with the electrically evoked compound action potential (ECAP) in CI recipients using clinically relevant stimuli.
Using a within-subjects (repeated measures) design, we examined the differences in mean amplitude, peak electrode location, area under the curve, and spatial separation between SOE curves obtained with anodic- and cathodic-leading symmetrical, biphasic pulses.
Fifteen CI recipients (ages 13-77) participated in this study. All were users of Cochlear Ltd. devices.
SOE functions were obtained using the standard forward-masking artifact reduction method. Probe electrodes were 5-18, and they were stimulated at an 8 (of 10) loudness rating ("loud"). Outcome measures (mean amplitude, peak electrode location, curve area, and spatial separation) for each polarity were compared within subjects.
Anodic-leading current pulses produced ECAPs with larger average amplitudes, greater curve area, and less spatial separation between SOE patterns compared with that for cathodic-leading pulses. There was no effect of polarity on peak electrode location.
These results indicate that for equal current levels, the anodic-leading polarity produces broader excitation patterns compared with cathodic-leading pulses, which reduces the spatial separation between functions. This result is likely due to preferential stimulation of the central axon. Further research is needed to determine whether SOE patterns obtained with anodic-leading pulses better predict pitch discrimination.
当代人工耳蜗（CI）使用阴极领先、对称的双相电流脉冲，尽管越来越多的证据表明阳极领先脉冲可能在刺激听觉系统方面更有效。然而，由于许多针对人类的此类研究使用的是伪单相脉冲或具有异常长相间间隙的双相脉冲，对于临床相关（即对称双相）刺激，刺激极性的影响尚不清楚。
本研究的目的是使用临床相关刺激，研究刺激极性对人工耳蜗植入者通过电诱发复合动作电位（ECAP）获得的生理兴奋扩散（SOE）测量基本特征的影响。
采用受试者内（重复测量）设计，我们研究了阳极领先和阴极领先的对称双相脉冲获得的SOE曲线在平均幅度、峰值电极位置、曲线下面积和空间分离方面的差异。
15名人工耳蜗植入者（年龄13 - 77岁）参与了本研究。他们均使用科利耳有限公司的设备。
使用标准的前向掩蔽伪迹减少方法获得SOE函数。探测电极编号为5 - 18，在10级响度中的第8级（“响亮”）进行刺激。对每个极性的结果测量指标（平均幅度、峰值电极位置、曲线面积和空间分离）在受试者内进行比较。
与阴极领先脉冲相比，阳极领先电流脉冲产生的ECAP平均幅度更大、曲线面积更大，且SOE模式之间的空间分离更小。极性对峰值电极位置没有影响。
这些结果表明，在相同电流水平下，与阴极领先脉冲相比，阳极领先极性产生的兴奋模式更宽，这减少了函数之间的空间分离。这一结果可能是由于对中枢轴突的优先刺激。需要进一步研究以确定阳极领先脉冲获得的SOE模式是否能更好地预测音调辨别能力。
