Psychophysical assessment of spatial spread of excitation in electrical hearing with single and dual electrode contact maskers
Psychophysical assessment of spatial spread of excitation in electrical hearing with single and dual electrode contact maskers
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DOI：
10.1097/01.aud.0000246683.29611.1b
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发表时间：
2006-12-01
期刊：
影响因子：
3.7
通讯作者：
Briaire, Jeroen J.
中科院分区：
文献类型：
--
作者：
Dingemanse, J. Gertjan;Frijns, Johan H. M.;Briaire, Jeroen J.
目的：从心理生理角度评价双接触掩蔽器对电听力刺激空间传播的影响，探讨在何种条件下刺激电极接触附近的纤维不受邻近电极接触的刺激。设计：本研究采用双接触掩蔽器的心理物理前向掩蔽范式，以避免非现场听音，即电模拟离频听音。掩蔽刺激(300毫秒)不同时呈现在两个电极接触上，一个在探头接触的顶侧和另一个在探头接触的底侧，随后是20毫秒的探头刺激。在多个掩蔽-探头距离处比较未掩蔽的探头阈值和掩蔽的探头阈值，为了与现有方法进行比较，采用了标准的选择性测量(单接触掩蔽)和前向掩蔽恢复的方法。所有的实验都是在6名参与者中进行的，这些参与者使用的是带有HiFocus I电极阵列的Clarion CII器件。结果：双接触掩蔽的掩蔽量明显大于单接触掩蔽，并且掩蔽图案的宽度比单接触掩蔽平均宽1.1min，从而产生了较宽的激发区域，掩蔽-探针重叠的距离大于3 mm。双接触掩蔽和单接触掩蔽的掩蔽宽度高度相关，掩蔽曲线的生长高度非线性。他们显示，大多数受试者在动态范围的中间或更高处开始的斜坡高度很高。在6名受试者中，有4名在掩蔽幅度约为400-500 mA的范围内没有发现探测阈值。最大可测量的掩蔽探测阈值与非掩蔽探测阈值的比率为1.7至2.6(不包括S4)。掩蔽函数的恢复遵循指数衰减规律。恢复过程的时间常数tau在21.6ms~114.9 ms之间。结论：使用双接触掩蔽可以避免异地监听，从而导致对刺激模式宽度的估计比单接触掩蔽更大，(2)可以估计在哪个刺激水平下，相邻电极接触的兴奋模式完全重叠，(3)只有当探头刺激幅度与邻近接触的幅度相比足够高时，才能刺激电极接触附近的神经纤维。
Objective: To evaluate psychophysically the spatial spread of excitation in electrical hearing with a new dual contact masker and to investigate under which conditions it is possible to stimulate fibers in the immediate neighborhood of an electrode contact, which were not excited by neighboring electrode contacts.Design: In this study a psychophysical forward masking paradigm with a dual contact masker was used to avoid off-site listening, the electrical analogue of off-frequency listening. The masker stimulus (300 msec) is presented nonsimultaneously on two electrode contacts, one on the apical side and another on the basal side of the probe contact, followed by a probe stimulus of 20 msec.Unmasked probe thresholds were compared with masked ones at a number of masker-probe distances, whereas growth of masking curves were measured for a fixed masker contact pair.Standard selectivity measurements (single contact masking) and the recovery of forward masking with one masker contact were included for comparison with existing methods.All experiments were carried out with six participants who use the Clarion CII device with a HiFocus I electrode array.Results: For dual contact masking the amount of masking was significantly greater than for single contact masking and the width of the masking patterns was on average 1.1 min broader than for single contact masking, resulting in a broad region of excitation, with masker-probe overlap for distances greater than 3 mm. Masking widths for dual and single contact masking were highly correlated.Growth of masking curves were highly nonlinear. They showed a strong elevation of the slope that starts for most subjects around the middle of the dynamic range or above. For 4 out of 6 subjects, no probe threshold was found above a masker amplitude of about 400-500 mu A. The ratio of the maximum measurable masked probe thresholds and unmasked probe threshold ranged from 1.7 to 2.6 (S4 excluded).Recovery of masking functions follow an exponential decay. Time constants tau for the recovery process ranged from 21.6 msec to 114.9 msec.Conclusions: With a dual contact masker (1) off-site listening can be avoided, leading to larger estimates of the width of excitation patterns than in single contact masking, (2) it can be estimated for which stimulation level there is complete overlap of excitation patterns of adjacent electrode contacts, (3) it can be shown that stimulation of nerve fibers in the immediate neighborhood of an electrode contact which were not excited by neighboring electrode contacts is only possible if the probe stimulation amplitude is sufficiently high in comparison with amplitudes on neighboring contacts.