Long Christopher J, Eddington Donald K, Colburn H Steven, Rabinowitz William M
Speech and Hearing Sciences Program, Division of Health Sciences and Technology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
J Acoust Soc Am. 2003 Sep;114(3):1565-74. doi: 10.1121/1.1603765.
Experiments were conducted with a single, bilateral cochlear implant user to examine interaural level and time-delay cues that putatively underlie the design and efficacy of bilateral implant systems. The subject's two implants were of different types but custom equipment allowed presentation of controlled bilateral stimuli, particularly those with specified interaural time difference (ITD) and interaural level difference (ILD) cues. A lateralization task was used to measure the effect of these cues on the perceived location of the sensations elicited. For trains of fixed-amplitude, biphasic current pulses at 100 pps, the subject demonstrated sensitivity to an ITD of 300 micros, providing evidence of access to binaural information. The choice of bilateral electrode pair greatly influenced ITD sensitivity, suggesting that electrode pairings are likely to be an important consideration in the effort to provide binaural advantages. The selection of bilateral electrode pairs showing sensitivity to ITD was partially aided by comparisons of the pitch elicited by individual electrodes in each ear (when stimulated alone with fixed-amplitude current pulses at 813 pps): specifically, interaural electrodes with similar pitches were more likely (but not certain) to show ITD sensitivity. Significant changes in lateral position occurred with specific electrode pairs. With five bilateral electrode pairs of 14 tested, ITDs of 300 and 600 micros moved an auditory image significantly from right to left. With these same pairs, ILD changes of approximately 11% of the dynamic range (in microApp) moved an auditory image from the far left to the far right-significantly farther than the nine pairs not showing significant ITD sensitivity. However, even these nine pairs did show response changes as a function of the interaural (or confounding monaural) level cue. Overall, insofar as the access to bilateral cues demonstrated herein generalizes to other subjects, it provides hope that the normal binaural advantages for speech recognition and sound localization can be made available to bilateral implant users.
对一名双侧人工耳蜗使用者进行了实验，以研究双耳水平和时间延迟线索，这些线索被认为是双侧植入系统设计和功效的基础。受试者的两个植入物类型不同，但定制设备允许呈现受控的双侧刺激，特别是那些具有特定双耳时间差（ITD）和双耳水平差（ILD）线索的刺激。使用了一个定位任务来测量这些线索对所引发感觉的感知位置的影响。对于100次/秒的固定幅度双相电流脉冲序列，受试者表现出对300微秒ITD的敏感性，这为获取双耳信息提供了证据。双侧电极对的选择极大地影响了ITD敏感性，这表明在努力提供双耳优势时，电极配对可能是一个重要的考虑因素。通过比较每只耳朵中单个电极单独受到813次/秒固定幅度电流脉冲刺激时所引发的音高，部分辅助了对显示ITD敏感性的双侧电极对的选择：具体而言，具有相似音高的双耳电极更有可能（但不肯定）显示ITD敏感性。特定电极对会导致侧向位置发生显著变化。在测试的14对双侧电极对中有5对，300和600微秒的ITD使听觉图像从右向左显著移动。对于这些相同的电极对，动态范围约11%（以微安计）的ILD变化使听觉图像从最左边移动到最右边——比另外9对未显示显著ITD敏感性的电极对移动得更远。然而，即使是这9对电极对也确实显示出响应变化是双耳（或混淆的单耳）水平线索的函数。总体而言，就本文所证明的对双侧线索的获取能够推广到其他受试者而言，它为双侧植入使用者能够获得语音识别和声音定位方面正常的双耳优势带来了希望。
