Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University of Würzburg, Würzburg, Germany.
Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery and the Comprehensive Hearing Center, University of Würzburg, Würzburg, Germany.
Hear Res. 2021 Dec;412:108375. doi: 10.1016/j.heares.2021.108375. Epub 2021 Oct 22.
Modern cochlear implants employ charge-balanced biphasic and triphasic pulses. However, the effectiveness of electrical pulse shape and polarity is still a matter of debate. For this purpose, a previous study (Bahmer & Baumann, 2013) conducted electrophysiological and psychophysical measurements following triphasic pulse stimulation with constant cathodic second phase and varying anodic first and third phases. Pulse stimulation with constant anodic second phase was not investigated. Therefore, in this study, pulse stimulation with cathodic and anodic second phase was applied for the recording of electrically evoked compound action potentials (ECAPs) as well as for psychophysical thresholds in cochlear implant (CI) recipients. First it was investigated whether the temporal polarity distribution has a different effect on neuronal stimulation when the second phase is cathodic or anodic; second, whether the electrophysiological and psychophysical results show a comparable difference between triphasic stimulation with anodic and cathodic second phases. The results showed that variation of the temporal polarity distribution of the triphasic pulse had a smaller effect on the ECAP response when the second phase was anodic compared to when it was cathodic, whereas for psychophysical detection thresholds this variation had a similar effect for both polarities. While electrophysiological responses and psychophysical detection thresholds showed a high correlation for variations of the triphasic pulse with cathodic second phase, the results for variations of the triphasic pulse with anodic second phase showed only moderate correlation. Furthermore, the difference between triphasic stimulation with cathodic and anodic second phases did not correlate between the electrophysiological and psychophysical results. In summary, after stimulation with different configurations of triphasic pulses used in the present study, the polarity of the second phase has an effect on electrophysiological response at suprathreshold level but not on the psychophysical detection thresholds. Thus, at different stimulation levels a possible substitution of the psychophysical test by an electrophysiological measurement (e.g. neural health measurement of the cochlea) could not be corroborated by the present results.
现代的人工耳蜗采用平衡电荷的双相和三相脉冲。然而，电脉冲形状和极性的有效性仍然是一个有争议的问题。为此，先前的一项研究（Bahmer & Baumann，2013）在三相脉冲刺激下进行了电生理学和心理物理学测量，其中阴极第二相恒定，阳极第一相和第三相变化。没有研究恒定阳极第二相的脉冲刺激。因此，在这项研究中，应用阴极和阳极第二相的脉冲刺激来记录人工耳蜗（CI）接受者的电诱发复合动作电位（ECAP）以及心理物理学阈值。首先研究了当第二相为阴极或阳极时，时间极性分布对神经元刺激的影响是否不同；其次，研究了三相刺激的阳极和阴极第二相之间的电生理学和心理物理学结果是否存在可比差异。结果表明，当第二相为阳极时，三相脉冲的时间极性分布变化对 ECAP 反应的影响较小，而当第二相为阴极时，这种变化对两种极性的心理物理学检测阈值的影响相似。虽然电生理反应和心理物理学检测阈值对阴极第二相三相脉冲变化表现出高度相关性，但阳极第二相三相脉冲变化的结果仅表现出中度相关性。此外，阴极和阳极第二相三相刺激之间的差异在电生理和心理物理学结果之间没有相关性。总之，在用本研究中使用的不同三相脉冲配置进行刺激后，第二相的极性对阈上水平的电生理反应有影响，但对心理物理学检测阈值没有影响。因此，在不同的刺激水平下，通过电生理测量（例如耳蜗的神经健康测量）代替心理物理学测试的可能性不能被本结果证实。
