Speech Pathology and Audiology, Kent State University, Kent, Ohio.
Department of Communication Sciences and Disorders, University of Iowa, Iowa City, Iowa.
Otol Neurotol. 2020 Aug;41(7):e804-e811. doi: 10.1097/MAO.0000000000002688.
To examine the effect of aging on electrically evoked compound action potential (eCAP) growth functions and their relationship with speech recognition in noise in cochlear implant (CI) users.
Aging typically leads to difficulty understanding speech in background noise. Previous research has explored cognitive and central auditory mechanisms contributing to these age-related changes. However, it is likely that the peripheral auditory system may also play a role. One challenge is separating the effects of aging on cochlear structures from the effects of aging on the auditory nerve in humans. CI users provide a unique way to address this issue, as intracochlear electrical stimulation bypasses surviving hair cells and activates the auditory nerve directly. Studies in animal models suggest that age-related loss of spiral ganglion cells could lead to shallower eCAP growth functions and/or increased eCAP thresholds and potentially negatively impact speech recognition.
Ten younger and 10 older postlingually deafened, adult CI recipients participated in this study. eCAP amplitude-intensity functions were recorded from a mid-array electrode and fit using linear functions. Speech recognition in noise was assessed using the Quick Speech-in-Noise (QuickSIN) test.
Older CI users had significantly shallower eCAP growth functions and higher eCAP thresholds than younger CI users. eCAP growth functions were not correlated with speech recognition in noise.
Results of this study suggest that older adults may have poorer neural survival, resulting in higher eCAP thresholds and shallower eCAP growth functions. These findings expand our understanding of mechanisms underlying age-related changes in the peripheral auditory system.
研究年龄对人工耳蜗植入（CI）使用者电诱发复合动作电位（eCAP）增长函数的影响及其与噪声下言语识别的关系。
年龄增长通常会导致在背景噪声中理解言语的能力下降。先前的研究已经探索了认知和中枢听觉机制对这些与年龄相关变化的贡献。然而，外周听觉系统可能也起作用。一个挑战是将年龄对耳蜗结构的影响与年龄对人类听神经的影响区分开来。CI 用户提供了一种独特的方法来解决这个问题，因为耳蜗内电刺激绕过幸存的毛细胞，直接激活听神经。动物模型研究表明，与年龄相关的螺旋神经节细胞损失可能导致 eCAP 增长函数变浅和/或 eCAP 阈值增加，并可能对言语识别产生负面影响。
本研究纳入了 10 名年轻和 10 名成年后天聋的 CI 使用者。从中数组电极记录 eCAP 幅度-强度函数，并使用线性函数进行拟合。使用快速噪声中言语识别（QuickSIN）测试评估言语识别在噪声中的情况。
与年轻的 CI 用户相比，年龄较大的 CI 用户的 eCAP 增长函数明显变浅，eCAP 阈值更高。eCAP 增长函数与噪声下的言语识别无关。
本研究结果表明，老年人可能存在较差的神经存活，导致较高的 eCAP 阈值和较浅的 eCAP 增长函数。这些发现扩展了我们对与年龄相关的外周听觉系统变化的机制的理解。
