Department of Communication Sciences and Disorders, The University of Texas Rio Grande Valley, Edinburg, Texas.
Department of Communication Disorders, New Mexico State University, Las Cruces, New Mexico.
J Neurophysiol. 2020 Jun 1;123(6):2437-2448. doi: 10.1152/jn.00136.2020. Epub 2020 May 20.
The descending corticofugal fibers originate from the auditory cortex and exert control on the periphery via the olivocochlear efferents. Medial efferents are thought to enhance the discriminability of transient sounds in background noise. In addition, the observation of deleterious long-term effects of efferent sectioning on the response properties of auditory nerve fibers in neonatal cats supports an efferent-mediated control of normal development. However, the role of the efferent system in human hearing remains unclear. The objective of the present study was to test the hypothesis that the medial efferents are involved in the development of frequency discrimination in noise. The hypothesis was examined with a combined behavioral and physiological approach. Frequency discrimination in noise and efferent inhibition were measured in 5- to 12-yr-old children ( = 127) and young adults ( = 37). Medial efferent strength was noninvasively assayed with a rigorous otoacoustic emission protocol. Results revealed an age-mediated relationship between efferent inhibition and frequency discrimination in noise. Efferent inhibition strongly predicted frequency discrimination in noise for younger children (5-9 yr). However, for older children (>9 yr) and adults, efferent inhibition was not related to frequency discrimination in noise. These findings support the role of efferents in the development of hearing-in-noise in humans; specifically, younger children compared with older children and adults are relatively more dependent on efferent inhibition for extracting relevant cues in noise. Additionally, the present findings caution against postulating an oversimplified relationship between efferent inhibition and measures of auditory perception in humans. Despite several decades of research, the functional role of medial olivocochlear efferents in humans remains controversial and is thought to be insignificant. Here it is shown that medial efferent inhibition strongly predicts frequency discrimination in noise for younger children but not for older children and adults. Young children are relatively more dependent on the efferent system for listening-in-noise. This study highlights the role of the efferent system in hearing-in-noise during childhood development.
下行皮质传出纤维起源于听觉皮层，并通过橄榄耳蜗传出纤维对周围组织进行控制。内侧传出纤维被认为可以增强背景噪声中瞬态声音的可辨别性。此外，观察到传出纤维切断对新生猫听觉神经纤维反应特性的长期有害影响，支持传出纤维介导的正常发育控制。然而，传出系统在人类听力中的作用仍不清楚。本研究的目的是检验内侧传出纤维参与噪声中频率辨别发展的假设。该假设通过行为和生理联合方法进行了检验。在 5 至 12 岁儿童（n=127）和年轻成人（n=37）中测量了噪声中的频率辨别和传出抑制。使用严格的耳声发射方案无创性测定内侧传出纤维的强度。结果显示，传出抑制与噪声中频率辨别之间存在年龄介导的关系。对于年幼的儿童（5-9 岁），传出抑制强烈预测噪声中的频率辨别。然而，对于年龄较大的儿童（>9 岁）和成人，传出抑制与噪声中的频率辨别无关。这些发现支持传出纤维在人类听力发展中的作用；具体而言，与年龄较大的儿童和成人相比，年幼的儿童更依赖传出抑制来提取噪声中的相关线索。此外，本研究结果告诫人们不要简单地假设传出抑制与人类听觉感知测量之间存在关系。尽管已经进行了几十年的研究，但内侧橄榄耳蜗传出纤维的功能作用在人类中仍存在争议，并且被认为不重要。本研究表明，对于年幼的儿童，内侧传出纤维抑制强烈预测噪声中的频率辨别，但对于年龄较大的儿童和成人则不然。年幼的儿童相对更依赖传出系统来进行噪声中的聆听。本研究强调了传出系统在儿童期听力发展中在噪声中聆听的作用。
