Fitzgerald Matthew B, Prosolovich Ksenia, Tan Chin-Tuan, Glassman E Katelyn, Svirsky Mario A
Department of Otolaryngology - Head and Neck Surgery, Stanford Ear Institute, Stanford University, Palo Alto, CA.
Department of Otolaryngology, New York University School of Medicine, New York, NY.
J Am Acad Audiol. 2017 May;28(5):385-394. doi: 10.3766/jaaa.15077.
Many recipients of bilateral cochlear implants (CIs) may have differences in electrode insertion depth. Previous reports indicate that when a bilateral mismatch is imposed, performance on tests of speech understanding or sound localization becomes worse. If recipients of bilateral CIs cannot adjust to a difference in insertion depth, adjustments to the frequency table may be necessary to maximize bilateral performance.
The purpose of this study was to examine the feasibility of using real-time manipulations of the frequency table to offset any decrements in performance resulting from a bilateral mismatch.
A simulation of a CI was used because it allows for explicit control of the size of a bilateral mismatch. Such control is not available with users of CIs.
A total of 31 normal-hearing young adults participated in this study.
Using a CI simulation, four bilateral mismatch conditions (0, 0.75, 1.5, and 3 mm) were created. In the left ear, the analysis filters and noise bands of the CI simulation were the same. In the right ear, the noise bands were shifted higher in frequency to simulate a bilateral mismatch. Then, listeners selected a frequency table in the right ear that was perceived as maximizing bilateral speech intelligibility. Word-recognition scores were then assessed for each bilateral mismatch condition. Listeners were tested with both a standard frequency table, which preserved a bilateral mismatch, or with their self-selected frequency table.
Consistent with previous reports, bilateral mismatches of 1.5 and 3 mm yielded decrements in word recognition when the standard table was used in both ears. However, when listeners used the self-selected frequency table, performance was the same regardless of the size of the bilateral mismatch.
Self-selection of a frequency table appears to be a feasible method for ameliorating the negative effects of a bilateral mismatch. These data may have implications for recipients of bilateral CIs who cannot adapt to a bilateral mismatch, because they suggest that (1) such individuals may benefit from modification of the frequency table in one ear and (2) self-selection of a "most intelligible" frequency table may be a useful tool for determining how the frequency table should be altered to optimize speech recognition.
许多双侧人工耳蜗植入（CI）接受者的电极插入深度可能存在差异。先前的报告表明，当出现双侧不匹配时，言语理解或声音定位测试的表现会变差。如果双侧CI接受者无法适应插入深度的差异，可能需要调整频率表以最大化双侧表现。
本研究的目的是检验使用频率表的实时操作来抵消双侧不匹配导致的任何性能下降的可行性。
使用人工耳蜗模拟，因为它允许明确控制双侧不匹配的大小。人工耳蜗使用者无法进行这种控制。
共有31名听力正常的年轻人参与了本研究。
使用人工耳蜗模拟创建了四种双侧不匹配情况（0、0.75、1.5和3毫米）。左耳的人工耳蜗模拟分析滤波器和噪声带相同。右耳的噪声带在频率上向上移动以模拟双侧不匹配。然后，听众选择右耳中被认为能最大化双侧言语可懂度的频率表。接着评估每种双侧不匹配情况下的单词识别分数。听众分别使用保留双侧不匹配的标准频率表或他们自己选择的频率表进行测试。
与先前的报告一致，当双耳都使用标准频率表时，1.5毫米和3毫米的双侧不匹配会导致单词识别率下降。然而，当听众使用自己选择的频率表时，无论双侧不匹配的大小如何，表现都是相同的。
频率表的自我选择似乎是减轻双侧不匹配负面影响的一种可行方法。这些数据可能对无法适应双侧不匹配的双侧CI接受者有影响，因为它们表明：（1）这类个体可能会从单耳频率表的修改中受益；（2）“最清晰可懂”频率表的自我选择可能是确定如何改变频率表以优化言语识别的有用工具。
