Forward Masking in Cochlear Implant Users: Electrophysiological and Psychophysical Data Using Pulse Train Maskers
Forward Masking in Cochlear Implant Users: Electrophysiological and Psychophysical Data Using Pulse Train Maskers
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DOI：
10.1007/s10162-016-0613-5
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发表时间：
2017-06-01
影响因子：
2.4
通讯作者：
Macherey, Olivier
中科院分区：
文献类型：
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作者：
Adel, Youssef;Hilkhuysen, Gaston;Macherey, Olivier
使用人工耳蜗 (CI) 对听觉神经纤维进行电刺激显示出长达数百毫秒的心理物理前向掩蔽 (pFM)。相比之下，从前向掩蔽 (eFM) 中恢复电诱发复合动作电位 (eCAP) 的速度更快，时间常数不超过几毫秒。这些差异表明 pFM 的两个主要贡献者：由于听神经的难治特性而导致的快速恢复过程和由更中心结构引起的缓慢恢复过程。在本研究中，我们调查了 eCAP 和心理物理测量之间使用不同的掩蔽器（特别是单脉冲与脉冲串掩蔽器）是否可能是混淆的根源。在实验 1 中，我们使用以下设备测量 eFM：单脉冲掩蔽器、300 毫秒低速率脉冲串掩蔽器（LTM，250 pps）和 300 毫秒高速率脉冲串掩蔽器（HTM，5000） pps）。掩蔽器要么以相同的物理电流（I 断开的垂直条）呈现，要么以与舒适响度相对应的相同感知 (I) 水平呈现。对单脉冲探针的响应测量了 1 至 512 ms 的掩蔽探针间隔。脉冲序列的掩蔽恢复速度比单脉冲掩蔽器慢得多。当以垂直条线水平呈现时，HTM 比 LTM 产生更多且更持久的掩蔽。然而，在 I 水平上比较 LTM 和 HTM 时，结果不一致。在实验2中，使用相同的脉冲序列掩蔽条件测量单脉冲探针的掩蔽检测阈值。与我们的 eFM 研究结果一致，在垂直条线水平上，HTM 的屏蔽阈值高于 LTM 的阈值。然而，当脉冲序列呈现在 I 水平时，却发现了相反的结果。我们的结果证实了 CI 用户的听觉神经水平存在缓慢恢复现象，正如之前在动物研究中所显示的那样。尽管使用相同的掩蔽条件，eFM 和 pFM 结果之间的不一致进一步强调了将电生理学和心理物理测量与相同的刺激范例进行比较的重要性。
Electrical stimulation of auditory nerve fibers using cochlear implants (CI) shows psychophysical forward masking (pFM) up to several hundreds of milliseconds. By contrast, recovery of electrically evoked compound action potentials (eCAPs) from forward masking (eFM) was shown to be more rapid, with time constants no greater than a few milliseconds. These discrepancies suggested two main contributors to pFM: a rapid-recovery process due to refractory properties of the auditory nerve and a slow-recovery process arising from more central structures. In the present study, we investigate whether the use of different maskers between eCAP and psychophysical measures, specifically single-pulse versus pulse train maskers, may have been a source of confound.In experiment 1, we measured eFM using the following: a single-pulse masker, a 300-ms low-rate pulse train masker (LTM, 250 pps), and a 300-ms high-rate pulse train masker (HTM, 5000 pps). The maskers were presented either at same physical current (I broken vertical bar) or at same perceptual (I) level corresponding to comfortable loudness. Responses to a single-pulse probe were measured for masker-probe intervals ranging from 1 to 512 ms. Recovery from masking was much slower for pulse trains than for the single-pulse masker. When presented at I broken vertical bar level, HTM produced more and longer-lasting masking than LTM. However, results were inconsistent when LTM and HTM were compared at I level. In experiment 2, masked detection thresholds of single-pulse probes were measured using the same pulse train masker conditions. In line with our eFM findings, masked thresholds for HTM were higher than those for LTM at I broken vertical bar level. However, the opposite result was found when the pulse trains were presented at I level.Our results confirm the presence of slow-recovery phenomena at the level of the auditory nerve in CI users, as previously shown in animal studies. Inconsistencies between eFM and pFM results, despite using the same masking conditions, further underline the importance of comparing electrophysiological and psychophysical measures with identical stimulation paradigms.