Abstract：
Contemporary cochlear implants (CIs) use cathodic-leading symmetric biphasic (C-BP) pulses for electrical stimulation. It remains unclear whether asymmetric pulses emphasizing the anodic or cathodic phase may improve spectral and temporal coding with CIs. This study tested place- and temporal-pitch sensitivity with C-BP, anodic-centered triphasic (A-TP), and cathodic-centered triphasic (C-TP) pulse trains on apical, middle, and basal electrodes in 10 implanted ears. Virtual channel ranking (VCR) thresholds (for place-pitch sensitivity) were measured at both a low and a high pulse rate of 99 (Experiment 1) and 1000 (Experiment 2) pulses per second (pps), and amplitude modulation frequency ranking (AMFR) thresholds (for temporal-pitch sensitivity) were measured at a 1000-pps pulse rate in Experiment 3. All stimuli were presented in monopolar mode. Results of all experiments showed that detection thresholds, most comfortable levels (MCLs), VCR thresholds, and AMFR thresholds were higher on more basal electrodes. C-BP pulses had longer active phase duration and thus lower detection thresholds and MCLs than A-TP and C-TP pulses. Compared to C-TP pulses, A-TP pulses had lower detection thresholds at the 99-pps but not the 1000-pps pulse rate, and had lower MCLs at both pulse rates. A-TP pulses led to lower VCR thresholds than C-BP pulses, and in turn than C-TP pulses, at the 1000-pps pulse rate. However, pulse shape did not affect VCR thresholds at the 99-pps pulse rate (possibly due to the fixed temporal pitch) or AMFR thresholds at the 1000-pps pulse rate (where the overall high performance may have reduced the changes with different pulse shapes). Notably, stronger polarity effect on VCR thresholds (or more improvement in VCR with A-TP than with C-TP pulses) at the 1000-pps pulse rate was associated with stronger polarity effect on detection thresholds at the 99-pps pulse rate (consistent with more degeneration of auditory nerve peripheral processes). The results suggest that A-TP pulses may improve place-pitch sensitivity or spectral coding for CI users, especially in situations with peripheral process degeneration.
摘要：
当代的耳蜗植入物（CI）使用阴极前导对称双相（C-BP）脉冲进行电刺激。尚不清楚强调阳极或阴极阶段的非对称脉冲是否可以改善CI的频谱和时间编码。本研究用C-BP测试了位置和时间间距灵敏度，阳极中心三相（A-TP），和根尖上的阴极中心三相（C-TP）脉冲序列，中间,和10只植入耳朵的基础电极。虚拟通道排序（VCR）阈值（用于位置间距灵敏度）在99（实验1）和1000（实验2）脉冲每秒（pps）的低脉冲速率和高脉冲速率下测量，在实验3中以1000-pps的脉冲速率测量幅度调制频率等级（AMFR）阈值（用于时间音调灵敏度）。所有刺激均以单极模式呈现。所有实验的结果表明，检测阈值，最舒适的水平(MCL)，VCR阈值,在更多的基础电极上，AMFR阈值较高。与A-TP和C-TP脉冲相比，C-BP脉冲的活动阶段持续时间更长，因此检测阈值和MCL更低。与C-TP脉冲相比，A-TP脉冲在99-pps但在1000-pps脉冲速率下具有较低的检测阈值，并且在两个脉搏率下都有较低的MCL。A-TP脉冲导致比C-BP脉冲更低的VCR阈值，反过来比C-TP脉冲，以1000pps的脉搏率。然而,脉冲形状不影响在99-pps脉冲速率下的VCR阈值(可能是由于固定的时间间距)或在1000-pps脉冲速率下的AMFR阈值(其中整体高性能可以减少不同脉冲形状的变化)。值得注意的是,在1000-pps脉搏率时,极性对VCR阈值的影响更强(或在使用A-TP脉搏时比使用C-TP脉搏时VCR的改善更多)与在99-pps脉搏率时对检测阈值的极性影响更强(与听神经外周过程的退化程度一致).结果表明，A-TP脉冲可以提高CI用户的位置间距灵敏度或频谱编码，尤其是在有外周过程退化的情况下。
