Kim SungHee, Frisina D Robert, Frisina Robert D
Otolaryngology Division, Department of Surgery, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
Audiol Neurootol. 2002 Nov-Dec;7(6):348-57. doi: 10.1159/000066159.
The auditory efferent system presumably plays a role in enhancing signals in noise and, in particular, speech perception in background noise. This study measured the age-related changes of the medial olivocochlear (MOC) system by comparing distortion product otoacoustic emissions (DPOAEs) with and without contralateral white noise stimulation. Otoacoustic emissions were typically reduced in level (magnitude) when white noise was presented to the contralateral ear. This contralateral suppression (CS) is attributed to activation of the MOC system, which has an inhibitory effect on the outer hair cell (OHC) system. By studying CS on cochlear output in human listeners of different ages, it is possible to describe aging effects on the MOC system. Human subjects were young adult, middle aged and old (n = 10/group). All subjects had normal hearing and middle-ear function based upon standard audiometric criteria. The present study recorded 2f(1)-f(2) DPOAE-grams in response to moderate primary tones (L1 = 75, L2 = 65 dB SPL), from 1 to 6.3 kHz. The principal findings were that DPOAE levels were smaller in the old compared to the young group and that CS declined with age for the middle-aged and old groups. In addition, CS in the 1- to 2-kHz range was greater than in the 4- to 6-kHz range for all ages, but especially for the old group. These findings suggest that a functional decline of the MOC system with age precedes OHC degeneration. Moreover, the MOC system maintains better function in the 1- to 2-kHz range than in the 4- to 6-kHz range as a function of age.
听觉传出系统可能在增强噪声中的信号，特别是在背景噪声中的语音感知方面发挥作用。本研究通过比较有和没有对侧白噪声刺激时的畸变产物耳声发射（DPOAE），测量了内侧橄榄耳蜗（MOC）系统与年龄相关的变化。当向对侧耳呈现白噪声时，耳声发射的水平（幅度）通常会降低。这种对侧抑制（CS）归因于MOC系统的激活，该系统对外毛细胞（OHC）系统具有抑制作用。通过研究不同年龄的人类受试者耳蜗输出的CS，可以描述衰老对MOC系统的影响。人类受试者分为年轻成年人、中年人和老年人（每组n = 10）。根据标准听力测定标准，所有受试者听力和中耳功能均正常。本研究记录了在1至6.3 kHz范围内，对中等强度的初级音调（L1 = 75，L2 = 65 dB SPL）做出反应的2f(1)-f(2) DPOAE图。主要发现是，与年轻组相比，老年组的DPOAE水平较小，并且中年组和老年组的CS随年龄下降。此外，在所有年龄段中，尤其是老年组，1至2 kHz范围内的CS大于4至6 kHz范围内的CS。这些发现表明，MOC系统随年龄的功能衰退先于OHC退化。此外，作为年龄的函数，MOC系统在1至2 kHz范围内的功能比在4至6 kHz范围内保持得更好。
