Galvin John J, Oba Sandra I, Başkent Deniz, Chatterjee Monita, Fu Qian-Jie
Department of Head and Neck Surgery, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America; Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; Research School of Behavioral and Cognitive Neurosciences, Graduate School of Medical Sciences, University of Groningen, Groningen, The Netherlands.
Department of Head and Neck Surgery, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America.
PLoS One. 2015 Oct 2;10(10):e0139546. doi: 10.1371/journal.pone.0139546. eCollection 2015.
Previous cochlear implant (CI) studies have shown that single-channel amplitude modulation frequency discrimination (AMFD) can be improved when coherent modulation is delivered to additional channels. It is unclear whether the multi-channel advantage is due to increased loudness, multiple envelope representations, or to component channels with better temporal processing. Measuring envelope interference may shed light on how modulated channels can be combined.
In this study, multi-channel AMFD was measured in CI subjects using a 3-alternative forced-choice, non-adaptive procedure ("which interval is different?"). For the reference stimulus, the reference AM (100 Hz) was delivered to all 3 channels. For the probe stimulus, the target AM (101, 102, 104, 108, 116, 132, 164, 228, or 256 Hz) was delivered to 1 of 3 channels, and the reference AM (100 Hz) delivered to the other 2 channels. The spacing between electrodes was varied to be wide or narrow to test different degrees of channel interaction.
Results showed that CI subjects were highly sensitive to interactions between the reference and target envelopes. However, performance was non-monotonic as a function of target AM frequency. For the wide spacing, there was significantly less envelope interaction when the target AM was delivered to the basal channel. For the narrow spacing, there was no effect of target AM channel. The present data were also compared to a related previous study in which the target AM was delivered to a single channel or to all 3 channels. AMFD was much better with multiple than with single channels whether the target AM was delivered to 1 of 3 or to all 3 channels. For very small differences between the reference and target AM frequencies (2-4 Hz), there was often greater sensitivity when the target AM was delivered to 1 of 3 channels versus all 3 channels, especially for narrowly spaced electrodes.
Besides the increased loudness, the present results also suggest that multiple envelope representations may contribute to the multi-channel advantage observed in previous AMFD studies. The different patterns of results for the wide and narrow spacing suggest a peripheral contribution to multi-channel temporal processing. Because the effect of target AM frequency was non-monotonic in this study, adaptive procedures may not be suitable to measure AMFD thresholds with interfering envelopes. Envelope interactions among multiple channels may be quite complex, depending on the envelope information presented to each channel and the relative independence of the stimulated channels.
先前的人工耳蜗（CI）研究表明，当相干调制传递到额外的通道时，单通道幅度调制频率辨别（AMFD）能力可以得到改善。目前尚不清楚多通道优势是由于响度增加、多个包络表征，还是由于具有更好时间处理能力的组成通道。测量包络干扰可能有助于了解调制通道如何进行组合。
在本研究中，使用三选一强制选择、非自适应程序（“哪个间隔不同？”）对CI受试者进行多通道AMFD测量。对于参考刺激，将参考AM（100 Hz）传递到所有3个通道。对于探测刺激，将目标AM（101、102、104、108、116、132、164、228或256 Hz）传递到3个通道中的1个，将参考AM（100 Hz）传递到其他2个通道。电极之间的间距变化为宽或窄，以测试不同程度的通道相互作用。
结果表明，CI受试者对参考包络和目标包络之间的相互作用高度敏感。然而，作为目标AM频率的函数，表现并非单调变化。对于宽间距，当目标AM传递到基底通道时，包络相互作用明显减少。对于窄间距，目标AM通道没有影响。本研究数据还与之前一项相关研究进行了比较，在该研究中，目标AM传递到单个通道或所有3个通道。无论目标AM是传递到3个通道中的1个还是所有3个通道，多通道时的AMFD都比单通道时好得多。对于参考AM频率和目标AM频率之间非常小的差异（2 - 4 Hz），当目标AM传递到3个通道中的1个而不是所有3个通道时，通常具有更高的灵敏度，尤其是对于窄间距电极。
除了响度增加外，本研究结果还表明，多个包络表征可能有助于解释先前AMFD研究中观察到的多通道优势。宽间距和窄间距结果的不同模式表明，外周因素对多通道时间处理有贡献。由于本研究中目标AM频率的影响并非单调变化，自适应程序可能不适用于测量存在干扰包络时的AMFD阈值。多个通道之间的包络相互作用可能相当复杂，这取决于呈现给每个通道的包络信息以及受刺激通道的相对独立性。
Zotero 插件
