Weakened Cochlear Nonlinearity During Human Aging and Perceptual Correlates.
Weakened Cochlear Nonlinearity During Human Aging and Perceptual Correlates.
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DOI：
10.1097/aud.0000000000001014
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发表时间：
2021
期刊：
影响因子：
3.7
通讯作者：
Guardia YC
中科院分区：
文献类型：
--
作者：
Abdala C;Ortmann AJ;Guardia YC
随着人类年龄的增长，压缩非线性--一个健康耳蜗功能的标志--会发生变化。失真产物的非线性失真分量耳声发射(DPOAE)提供了一种非侵入性的耳蜗非线性度测量方法。早先发表的研究表明，减弱的非线性从中年开始；目前的工作使用先进的DPOAE数据收集和分析方法以及包括响度尺度测试在内的多种非线性度量方法，将这项研究扩展到生命的第八个十年。20名年轻人、25名中年人和32名老年人记录到2f1-f2DPOAE，频率范围为f2=0.78~9.4 kHz，基音(f2/f1=1.22)以0.5倍频程/秒的速度向上扫频。分析中只包括听力阈值为≤20dBHL的频率，并在可能的情况下，对耳朵进行听力匹配，以消除听力阈值作为观察到的年龄效应的一个因素。对分离的DPOAE失真分量生成输入/输出函数以探测耳蜗声压非线性，并对DPOAE进行同侧抑制以探测双音抑制。为了研究弱化非线性对响度知觉的知觉影响，相同的受试者进行了绝对响度测量。评估了年龄对DPOAE和响度尺度变量的影响，并对关键的OAE和知觉指标进行了相关性分析。年龄×频率方差分析显示，与年轻人相比，两组老年人的DPOAE I/O功能的压缩膝关节都出现在更高的刺激水平，这表明随着年龄的增长，线性范围扩大；而且，与年轻人相比，老年人的压缩斜率(超过膝点处的生长)更陡峭。这些结果在高频下最为显著。以年龄和听阈为因素的单因素方差分析证实，观察到的年龄效应与听阈值无关。此外，在听力测量数据匹配的较小亚组受试者中，同样的趋势持续存在，进一步排除了听力阈值作为影响因素。与青壮年相比，中老年人DPOAE同侧抑制在4 kHz附近的生长较浅，抑制阈值较高。绝对响度量表的结果显示，老年人的响度增长更快，在固定的感觉水平(DBSL)下，老年人组的音调比年轻人组的音调更大，这表明响度增长和知觉异常。DPOAE I/O功能的压缩膝部与响度尺度的关键指标之间的几个相关性非常显著，可解释高达三分之一的方差。结果表明，老化的耳蜗体在中年时开始表现出较弱的非线性，并逐渐减弱至衰老。在衰老过程中，非线性减弱的知觉影响表现为异常的响度判断；也就是说，在老年人的耳朵中，被认为在年轻人的耳朵中舒适或中等的音调在老年人中被认为是响亮的。这种减弱的非线性的生物物理起源尚不清楚。它被假设为反映了与衰老有关的外毛细胞及其立体纤毛的损害或丧失。需要更多的工作来更好地定义老年人线性化耳蜗反应的知觉影响，并考虑这种缺陷可能如何影响助听器和其他干预策略的安装。
As humans age, compressive nonlinearity –a hallmark of healthy cochlear function– changes. The nonlinear distortion-component of the distortion product otoacoustic emission (DPOAE) provides a noninvasive gauge of cochlear nonlinearity. Earlier published work has suggested that weakened nonlinearity begins in middle-age; the current work extends this investigation into the 8th decade of life using advanced DPOAE data collection and analysis methods as well as multiple metrics of nonlinearity including a test of loudness scaling. The 2f1-f2 DPOAE was recorded in 20 young-adults, 25 middle-aged adults and 32 older-adults from f2 = 0.78 to 9.4 kHz with primary tones (f2/f1 = 1.22) swept upward at a rate of 0.5 octave/sec. Only frequencies with audiometric thresholds ≤20 dB HL were included in the analysis and to the extent possible, ears were audiometrically matched to eliminate hearing threshold as a contributing factor to the observed age effects. Input/Output functions were generated for the separated distortion-component of the DPOAE to probe compressive nonlinearity of the cochlea, and ipsilateral suppression of the DPOAE was conducted to probe two-tone suppression. To investigate the perceptual effects of weakening nonlinearity on loudness perception, the same subjects performed categorical loudness scaling. Age effects on both DPOAE and loudness scaling variables were assessed, and correlations were conducted between key OAE and perceptual metrics. Age × Frequency ANOVAs revealed that the compression knee of the DPOAE I/O function occurred at higher stimulus levels in both groups of older adults compared to young adults, suggesting an expanded linear range with aging; also, the compressive slope (growth beyond the knee point) was steeper in older- compared to young adults. These results were most notable at high-frequencies. ANOVAs including age and auditory threshold as factors confirmed that the age effect observed was independent of threshold. Additionally, in smaller subsets of subjects with audiometrically matched data, these same trends persisted, further rulilng out hearing threshold as an influential factor. The growth of DPOAE ipsilateral suppression was shallower near 4 kHz in middle-aged and older adults compared to young-adults and elevated suppression thresholds were observed. Results of categorical loudness scaling showed steeper growth of loudness for older adults and, at fixed sensation levels (dB SL), the older-adult group rated tones as louder than did their young-adult counterparts, suggesting abnormal loudness growth and perception. Several correlations between the compression knee of the DPOAE I/O function and key metrics of loudness scaling were significant and accounted for up to one-third of the variance. Results indicate that the aging cochlea begins to show weakened nonlinearity in middle age and it progressively weakens further into senescence. The perceptual impact of weakened nonlinearity during aging is manifest as abnormal loudness judgements; that is, in older-adult ears, a tone considered comfortable or medium in young-adult ears can be considered loud in older adults. The biophysical origin of this weakened nonlinearity is not known. It is hypothesized to reflect aging-related damage to, or loss of, outer hair cells and their stereocilia. More work is warranted to better define the perceptual impact of a linearized cochlear response in older adults and to consider how this deficit might impact the fitting of hearing aids and other intervention strategies.