Shannon R V, Otto S R
House Ear Institute, Los Angeles, California 90057.
Hear Res. 1990 Aug 1;47(1-2):159-68. doi: 10.1016/0378-5955(90)90173-m.
Auditory performance on basic psychophysical tasks was measured in ten deaf patients with electrodes positioned near their cochlear nucleus. The device is called the auditory brainstem implant (ABI). Electrodes were placed during surgery to remove an acoustic neuroma, which results in the removal of the VIII nerve and, thus deafness. In patients who received auditory sensation from electrical stimulation we measured auditory performance on standard psychophysical tasks: thresholds, loudness growth, intensity discrimination, temporal integration, temporal modulation detection, gap detection, and forward masking. Plots of threshold as a function of frequency or biphasic pulse duration were markedly different from those of patients with cochlear implants. The difference in threshold functions is probably partly due to the biophysical difference in the neural elements stimulated. Another possibility is that part of the difference is due to the highly abnormal spatial pattern of activation in the cochlear nucleus from electrical stimulation, which prevents normal spatial integration of activity. The usable range of electrical amplitudes above threshold is comparable with that of cochlear implants, typically 10-15 dB. Little temporal integration occurs over a range of stimulus durations from 2-1000 ms. When compared at equivalent loudness levels, gap detection thresholds are similar to, or a bit longer than, gap thresholds in normal-hearing listeners and cochlear implant patients. Forward masking recovery functions are similar to those of normal listeners and cochlear implant patients. Patients' ability to detect amplitude modulation as a function of modulation frequency is similar to that of cochlear implant patients and normal listeners. Thus, direct electrical stimulation of the brainstem produces temporal resolution that does not significantly differ from that of normal listeners when compared in equivalent amplitude units. This implies that the limiting factors for these tasks are more centrally located, and not directly related to threshold mechanisms. Thus, a properly designed speech processor could preserve the important temporal features of speech for these patients.
对十名聋人患者进行了基本心理物理学任务的听觉表现测量，这些患者的电极放置在靠近耳蜗核的位置。该装置称为听觉脑干植入物（ABI）。电极在手术中放置，以切除听神经瘤，这会导致第八神经被切除，从而导致耳聋。在那些从电刺激中获得听觉感受的患者中，我们测量了他们在标准心理物理学任务上的听觉表现：阈值、响度增长、强度辨别、时间整合、时间调制检测、间隙检测和前掩蔽。阈值作为频率或双相脉冲持续时间的函数的曲线图与接受人工耳蜗植入的患者明显不同。阈值函数的差异可能部分归因于所刺激的神经元件的生物物理差异。另一种可能性是，部分差异是由于电刺激导致耳蜗核中高度异常的激活空间模式，这妨碍了活动的正常空间整合。高于阈值的电振幅可用范围与人工耳蜗相当，通常为10 - 15分贝。在2至1000毫秒的一系列刺激持续时间内几乎没有时间整合。当在等效响度水平进行比较时，间隙检测阈值与听力正常的听众和人工耳蜗植入患者的间隙阈值相似，或稍长一些。前掩蔽恢复函数与正常听众和人工耳蜗植入患者的相似。患者检测幅度调制作为调制频率函数的能力与人工耳蜗植入患者和正常听众相似。因此，当以等效振幅单位进行比较时，对脑干的直接电刺激产生的时间分辨率与正常听众的时间分辨率没有显著差异。这意味着这些任务的限制因素更位于中枢，并且与阈值机制没有直接关系。因此，一个设计合理的言语处理器可以为这些患者保留语音的重要时间特征。
