Department of Otorhinolaryngology and Head and Neck Surgery, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands.
Otol Neurotol. 2013 Apr;34(3):579-87. doi: 10.1097/MAO.0b013e318280db5a.
Interactions between cochlear responses to combined electrical and acoustic stimulation (EAS) depend on electrically evoked hair cell activity (i.e., electrophonics).
Although relevant for EAS strategies in cochlear implant users with residual low-frequency hearing, cochlear responses to EAS are not well characterized. Previously, we have shown that acoustically evoked compound action potentials (CAPs) can be suppressed by electrical stimulation. In the present study, we characterized the role of electrophonics in CAP suppression in guinea pigs, under conditions representative of clinically applied EAS.
Electrophonics depend on the frequency spectrum of the electric pulse train, which is mainly determined by pulse width and, to a lesser extent, by pulse rate. We measured suppression of tone-evoked CAPs by electric pulse trains, while varying the pulse width (80 - 400 μs, n = 5) and the pulse rate (500 - 4000 pps, n = 5). The role of outer hair cells (OHCs) in electrophonics was tested in animals with varying degrees of OHC loss (n = 24).
Suppression of acoustically evoked CAPs varied with pulse width, indicating that electrophonics were involved. Short pulse widths resulted in minimal CAP suppression at low acoustic frequencies. Pulse rate did not significantly affect CAP suppression. OHC loss had no significant effect on electrophonic activity.
Electrophonic activity was present in cochleae with extensive basal hair cell loss, indicating that electrophonics can occur in EAS users. Our results show that short pulse widths are optimal for use in EAS stimulation strategies, on the assumption that minimal suppression is best.
联合电声刺激（EAS）的耳蜗反应之间的相互作用取决于电诱发毛细胞活动（即电声）。
尽管对于残留低频听力的人工耳蜗使用者的 EAS 策略相关，但 EAS 的耳蜗反应尚未得到很好的描述。先前，我们已经表明，电刺激可以抑制声诱发复合动作电位（CAP）。在本研究中，我们在代表临床应用 EAS 的条件下，研究了电声在豚鼠 CAP 抑制中的作用。
电声取决于电脉冲串的频谱，该频谱主要由脉冲宽度决定，在较小程度上由脉冲率决定。我们测量了电脉冲串对音调诱发 CAP 的抑制作用，同时改变了脉冲宽度（80-400 μs，n=5）和脉冲率（500-4000 pps，n=5）。在外毛细胞（OHC）损失程度不同的动物中测试了 OHC 在电声中的作用（n=24）。
声诱发 CAP 的抑制随脉冲宽度而变化，表明电声参与其中。短脉冲宽度在低频时导致最小的 CAP 抑制。脉冲率对 CAP 抑制没有显著影响。OHC 损失对电声活动没有显著影响。
即使在基底毛细胞大量丧失的情况下，电声活动也存在于耳蜗中，这表明电声可以在 EAS 用户中发生。我们的研究结果表明，在 EAS 刺激策略中，使用短脉冲宽度是最佳的，因为假设最小的抑制是最好的。
