Mishra Srikanta K, Lutman Mark E
Institute of Sound and Vibration Research, University of Southampton, Southampton, United Kingdom ; Department of Communication Sciences and Disorders, Butler University, Indianapolis, Indiana, United States of America.
Institute of Sound and Vibration Research, University of Southampton, Southampton, United Kingdom.
PLoS One. 2014 Jan 20;9(1):e85756. doi: 10.1371/journal.pone.0085756. eCollection 2014.
One of the putative functions of the medial olivocochlear (MOC) system is to enhance signal detection in noise. The objective of this study was to elucidate the role of the MOC system in speech perception in noise. In normal-hearing human listeners, we examined (1) the association between magnitude of MOC inhibition and speech-in-noise performance, and (2) the association between MOC inhibition and the amount of contralateral acoustic stimulation (CAS)-induced shift in speech-in-noise acuity. MOC reflex measurements in this study considered critical measurement issues overlooked in past work by: recording relatively low-level, linear click-evoked otoacoustic emissions (CEOAEs), adopting 6 dB signal-to-noise ratio (SNR) criteria, and computing normalized CEOAE differences. We found normalized index to be a stable measure of MOC inhibition (mean = 17.21%). MOC inhibition was not related to speech-in-noise performance measured without CAS. However, CAS in a speech-in-noise task caused an SNRSP enhancement (mean = 2.45 dB), and this improvement in speech-in-noise acuity was directly related to their MOC reflex assayed by CEOAEs. Individuals do not necessarily use the available MOC-unmasking characteristic while listening to speech in noise, or do not utilize unmasking to the extent that can be shown by artificial MOC activation. It may be the case that the MOC is not actually used under natural listening conditions and the higher auditory centers recruit MOC-mediated mechanisms only in specific listening conditions-those conditions remain to be investigated.
内侧橄榄耳蜗（MOC）系统的一个假定功能是增强噪声中的信号检测。本研究的目的是阐明MOC系统在噪声中言语感知中的作用。在听力正常的人类受试者中，我们研究了：（1）MOC抑制强度与噪声中言语表现之间的关联，以及（2）MOC抑制与对侧声刺激（CAS）引起的噪声中言语敏锐度变化量之间的关联。本研究中的MOC反射测量考虑了以往研究中被忽视的关键测量问题：记录相对低水平的、线性短声诱发耳声发射（CEOAEs），采用6 dB的信噪比（SNR）标准，并计算归一化的CEOAEs差值。我们发现归一化指数是MOC抑制的一个稳定指标（平均值 = 17.21%）。在没有CAS的情况下，MOC抑制与噪声中言语表现无关。然而，在噪声中言语任务中的CAS导致了SNRSP增强（平均值 = 2.45 dB），并且这种噪声中言语敏锐度的提高与通过CEOAEs测定的MOC反射直接相关。个体在噪声中听言语时不一定会利用现有的MOC解掩蔽特性，或者没有利用到人工激活MOC所能显示的程度。可能的情况是，在自然聆听条件下MOC实际上并未被使用，只有在特定的聆听条件下高级听觉中枢才会调用MOC介导的机制——这些条件仍有待研究。
