脉冲速率对人工耳蜗使用者单通道和多通道包络处理及辅音识别的影响

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中文摘要

人工耳蜗（CI）通过电脉冲串刺激听觉神经元，其幅度由从不同频带提取的包络进行调制，从而传递必要的言语线索。本研究探讨了刺激脉冲速率如何影响十名语后聋CI使用者的包络处理和言语感知。研究使用多通道和单通道策略处理的声学刺激来检查幅度调制（AM）检测和辅音识别，多通道刺激的脉冲速率范围为125至2000脉冲/秒（pps），单通道刺激为125至4000 pps。单通道条件通过单个电极编码整体宽带言语包络，用于分离电极内时间调制编码。对于AM检测，调制频率为25 Hz，以确保在所有测试的载波速率下具有足够的调制采样；即使在125 pps下，25 Hz调制也由每个调制周期五个脉冲表示。结果：结果显示，在125 pps下AM检测和辅音识别均显著下降，提示低速率下言语识别较差可能部分归因于时间调制处理的限制，而不仅仅是可表示包络频率范围的受限。辅音识别表现在临床相关脉冲速率（250-2000 pps）范围内保持稳定，尽管观察到显著的听者特异性和特征特异性效应。值得注意的是，虽然在该小队列中AM检测与辅音识别无显著相关性，但两项任务中单通道与多通道表现之间均存在显著相关性。结论：这些发现支持电极内时间编码在CI言语感知中的重要作用，并强调了脉冲速率效应个体差异的临床相关性。

英文摘要

Cochlear implants (CIs) stimulate auditory neurons with electric pulse trains whose amplitudes are modulated using envelopes extracted from different frequency bands, conveying essential speech cues. This study investigated how the rate of stimulation pulses affects envelope processing and speech perception in ten post-lingually deaf CI users. Amplitude modulation (AM) detection and consonant identification were examined using acoustic stimuli processed by multi-channel and single-channel strategies, with pulse rates ranging from 125 to 2000 pulses per second (pps) for multi-channel stimulation and from 125 to 4000pps for single-channel stimulation. The single-channel conditions encoded the overall broad-band speech envelope by a single electrode and were used to isolate within-electrode temporal modulation coding. For AM detection, the modulation frequency was 25 Hz ensuring sufficient modulation sampling across all carrier rates tested. Even at 125pps, the 25-Hz modulation was represented by five pulses per modulation cycle. Results revealed a significant decline in both AM detection and consonant identification at 125pps, suggesting that poorer speech recognition at low rates may be partly attributable to limitations in temporal modulation processing rather than solely to a restricted range of representable envelope frequencies. Consonant recognition performance remained stable across clinically relevant pulse rates (250-2000pps), though significant listener- and feature-specific effects were observed. Notably, while AM detection and consonant recognition were not significantly correlated within this small cohort, significant correlations were found between single-channel and multi-channel performance in both tasks. These findings support an important role for within-electrode temporal coding in CI speech perception and highlight the clinical relevance of individual variability in pulse rate effects.