Variations in Carrier Pulse Rate and the Perception of Amplitude Modulation in Cochlear Implant Users
Variations in Carrier Pulse Rate and the Perception of Amplitude Modulation in Cochlear Implant Users
复制标题
DOI：
10.1097/aud.0b013e318230fff8
复制
发表时间：
2012-03-01
期刊：
影响因子：
3.7
通讯作者：
Rosen, Stuart
中科院分区：
文献类型：
--
作者：
Green, Tim;Faulkner, Andrew;Rosen, Stuart
目的：近来增强耳蜗植入（CI）系统的尝试的主要焦点是增加脉冲被递送到电极阵列的速率。这些尝试的一个基础是期望更快的刺激速率将导致时间调制信息的增强表示。然而，最近的生理和行为证据表明，情况可能相反。在这里，使用调制检测和调制频率辨别任务来评估刺激速率对幅度调制感知的影响，其中脉冲速率的范围远远高于先前研究中测试的最高速率，并且用于不同的语音相关调制频率。设计：在5名CI用户中，使用单极脉冲串以482、723、1447、2894和5787脉冲每秒（pps）。自适应程序被用来找到在10和100 Hz的调制频率和在25%，50%和75%的电极的动态范围的载波电平的最小可检测的调制深度。对于最高载波电平的相同脉冲速率范围，检查调制频率的辨别力。类似的自适应过程确定相对于10、100和200 Hz的参考调制频率可以检测到的调制频率的最小增加。在这两个任务中，水平漫游实施，以尽量减少可能的响度cue.Results：与以前的证据一致，调制检测阈值更好的载波电平和较低的调制频率。当阈值处的调制深度用调制深度与以dB为单位的载波电平的比率来表示时（即，20 log m），在较低的脉冲频率下性能明显更好。然而，当调制深度相对于动态范围表示时，脉冲频率的影响不再显著，反映了动态范围随脉冲频率增加的事实。随着调制频率的增加，调制频率辨别力明显变差，但脉率没有显著影响。与最近的一些证据相反，没有发现更高的脉冲频率对调制感知有明显的有害影响。然而，即使在非常快的刺激频率下，在宽范围的调制频率和两个不同的任务下进行测试，没有证据表明在幅度调制的感知中更快的刺激速率有益。
Objectives: A major focus of recent attempts to enhance cochlear implant (CI) systems has been to increase the rate at which pulses are delivered to the electrode array. One basis for these attempts has been the expectation that faster stimulation rates would lead to an enhanced representation of temporal modulation information. However, there is recent physiological and behavioral evidence to suggest that the reverse may be the case. Here, the effects of stimulation rate on the perception of amplitude modulation were assessed using both modulation detection and modulation frequency discrimination tasks for a range of pulse rates extending considerably higher than the highest rate tested in previous studies and for different speech-relevant modulation frequencies.Design: Detection of sinusoidal amplitude modulation was assessed in five CI users using monopolar pulse trains presented to a single electrode at rates of 482, 723, 1447, 2894, and 5787 pulses per second (pps). Adaptive procedures were used to find the minimal detectable modulation depth at modulation frequencies of 10 and 100 Hz and at carrier levels of 25%, 50%, and 75% of the electrode's dynamic range. Discrimination of modulation frequency was examined for the same range of pulse rates for the highest carrier level. Similar adaptive procedures determined the minimum increase in modulation frequency that could be detected relative to reference modulation frequencies of 10, 100, and 200 Hz. In both tasks, level roving was implemented to minimize possible loudness cues.Results: Consistent with previous evidence, modulation detection thresholds were better for higher carrier levels and lower modulation frequencies. When modulation depth at threshold was expressed in terms of the ratio of the depth of the modulation and the carrier level in dB (i.e., 20 log m), performance was significantly better at lower pulse rates. However, when modulation depth was expressed relative to dynamic range, the effect of pulse rate was no longer significant, reflecting the fact that dynamic range increases with pulse rate. Modulation frequency discrimination clearly worsened with increasing modulation frequency, but there was no significant effect of pulse rate.Conclusions: In contrast to some recent evidence, no clearly harmful effect of higher pulse rates on modulation perception was found. However, even with very fast stimulation rates, tested over a wide range of modulation frequencies and with two different tasks, there is no evidence of benefit from faster stimulation rates in the perception of amplitude modulation.