Hearing Systems Group, Department of Health Technology, 5205Technical University of Denmark, Kgs. Lyngby, Denmark.
Brain and Sound Lab, Department of Biomedicine, 27209Basel University, Basel, Switzerland.
Trends Hear. 2021 Jan-Dec;25:23312165211061116. doi: 10.1177/23312165211061116.
The electric stimulation provided by current cochlear implants (CI) is not power efficient. One underlying problem is the poor efficiency by which information from electric pulses is transformed into auditory nerve responses. A novel stimulation paradigm using ramped pulse shapes has recently been proposed to remedy this inefficiency. The primary motivation is a better biophysical fit to spiral ganglion neurons with ramped pulses compared to the rectangular pulses used in most contemporary CIs. Here, we tested the hypotheses that ramped pulses provide more efficient stimulation compared to rectangular pulses and that a rising ramp is more efficient than a declining ramp. Rectangular, rising ramped and declining ramped pulse shapes were compared in terms of charge efficiency and discriminability, and threshold variability in seven CI listeners. The tasks included single-channel threshold detection, loudness-balancing, discrimination of pulse shapes, and threshold measurement across the electrode array. Results showed that reduced charge, but increased peak current amplitudes, was required at threshold and most comfortable levels with ramped pulses relative to rectangular pulses. Furthermore, only one subject could reliably discriminate between equally-loud ramped and rectangular pulses, suggesting variations in neural activation patterns between pulse shapes in that participant. No significant difference was found between rising and declining ramped pulses across all tests. In summary, the present findings show some benefits of charge efficiency with ramped pulses relative to rectangular pulses, that the direction of a ramped slope is of less importance, and that most participants could not perceive a difference between pulse shapes.
目前的耳蜗植入物（CI）提供的电刺激效率不高。一个潜在的问题是，电脉冲转化为听神经反应的效率很低。最近提出了一种新的刺激模式，使用斜坡脉冲形状来弥补这种效率低下的问题。这种新的刺激模式的主要动机是与大多数现代 CI 中使用的矩形脉冲相比，斜坡脉冲与螺旋神经节神经元具有更好的生物物理拟合。在这里，我们测试了以下假设：与矩形脉冲相比，斜坡脉冲提供更有效的刺激；与下降斜坡相比，上升斜坡更有效。在七位 CI 聆听者中，比较了矩形、上升斜坡和下降斜坡脉冲形状在电荷效率和可分辨性以及阈值变异性方面的差异。任务包括单通道阈值检测、响度平衡、脉冲形状的辨别以及电极阵列的阈值测量。结果表明，与矩形脉冲相比，斜坡脉冲在阈值和最舒适水平下需要减少电荷，但需要增加峰值电流幅度。此外，只有一名受试者能够可靠地区分等响度的斜坡和矩形脉冲，这表明在该参与者中，不同脉冲形状的神经激活模式存在差异。在所有测试中，都没有发现上升斜坡和下降斜坡之间的显著差异。总之，目前的研究结果表明，与矩形脉冲相比，斜坡脉冲在电荷效率方面具有一些优势，斜坡斜率的方向不太重要，而且大多数参与者无法感知脉冲形状之间的差异。
