Role of the Auditory Efferent System in Auditory Perceptual Learning

 描述（由申请人提供）：听觉传出系统的内侧橄榄耳蜗（MOC）分支减少了外毛细胞的放大机制，这可能有助于噪声中的信号检测（Guinan，2006）。因为MOC系统被声音反射性地激活（MOC反射，或MOCR），所以其活动可以通过测量耳声发射（OAE）（基于外毛细胞的放大的副产物的低水平声音），然后用呈现给对侧耳的噪声重复OAE测量（例如，柏林等人，1993年）。噪声引起的MOCR激活降低了OAE的振幅（MOCR抑制）。噪声性能中的言语感知与MOCR抑制的幅度相关（例如，Kumar & Vanaja，2004），进一步表明MOCR与噪音中的听力有关。先前的研究通常使用单个言语任务来检查噪声中MOCR抑制与言语感知之间的关系。第一个具体目标 目前的研究是通过在同一组受试者中使用多个语音任务（使用自适应或固定信噪比的单词和句子识别）评估噪声中的语音感知来更清楚地描绘这种关系。由于听觉训练，MOCR抑制和言语感知能力都可以得到改善（de Boer & Thornton，2008; Kumar等人，2010），表明MOCR抑制可能是听觉感知学习的生物标志物。生物标志物可用于识别受听觉训练影响的生理过程，并可预测从训练中获得的益处（de Boer & Thornton）。这些研究只检查了年轻的正常听力参与者，因此对噪声中言语困难人群的普遍性（例如，老年人和听力受损者 成年人不知道。本研究的第二个具体目的是确定MOCR抑制是否可以作为一组听力正常或轻度听力损失的老年人听觉知觉学习的生物标志物。共招募30名年龄在50-89岁之间的受试者。受试者将被随机分配到实验组或对照组。实验组将在10次实验室访视中接受15小时的听觉训练。听觉训练将针对 以自适应方式识别背景噪声中的音素和句子。在训练之前、期间和之后测量噪声中的MOCR抑制和言语感知。对照组（无培训）将完成4次访视，测量噪声中的MOCR抑制和言语感知，以建立重测信度。假设MOCR抑制将与所有言语感知测量显著相关，其中最大的相关性发生在更具挑战性的信噪比条件下。是 还假设实验组中MOCR抑制随时间的变化将与言语感知中观察到的变化显著相关。这项研究的结果将有助于理解噪声中言语感知的生理机制，并客观地评估听觉训练的益处。

 DESCRIPTION (provided by applicant): The medial olivocochlear (MOC) branch of the auditory efferent system reduces the amplification mechanism of the outer hair cells, which may aid in signal detection in noise (Guinan, 2006). Because the MOC system is activated reflexively by sound (MOC reflex, or MOCR), its activity can be assessed by measuring otoacoustic emissions (OAEs), low-level sounds that are byproducts of outer hair cell-based amplification, and then repeating the OAE measurements with noise presented to the contralateral ear (e.g., Berlin et al., 1993). The MOCR activation by the noise reduces the amplitudes of OAEs (MOCR inhibition). Speech perception in noise performance is correlated with the magnitude of MOCR inhibition (e.g., Kumar & Vanaja, 2004), further suggesting that the MOCR is involved with hearing in noise. Previous studies have typically examined the relationship between MOCR inhibition and speech perception in noise using a single speech task. The first specific aim of the current study is to more clearly delineate this relationship by assessing speech perception in noise using multiple speech tasks (word and sentence recognition using either adaptive or fixed signal-to-noise ratios) in the same group of subjects. Both MOCR inhibition and speech perception abilities may be improved as a result of auditory training (de Boer & Thornton, 2008; Kumar et al., 2010), suggesting that MOCR inhibition may be a biomarker for auditory perceptual learning. Biomarkers may be used to identify the physiologic processes impacted by auditory training and may be predictive of the benefit obtained from training (de Boer & Thornton). These studies only examined young normal-hearing participants, so the generalizability to populations with speech-in-noise difficulties (e.g., older and hearing-impaired adults) is not known. The second specific aim of this study is to determine whether MOCR inhibition serves as a biomarker of auditory perceptual learning in a group of older adults with normal hearing or mild hearing loss. A total of 30 subjects ages 50-89 will be recruited. Subjects will be randomly assigned to an experimental or control group. The experimental group will undergo 15 hours of auditory training occurring across 10 lab visits. Auditory training will target the identification of phonemes and sentences in background noise in an adaptive manner. MOCR inhibition and speech perception in noise will be measured before, during, and after training. The control group (no training) will complete 4 visits, where MOCR inhibition and speech perception in noise will be measured to establish test-retest reliability. It is hypothesize that MOCR inhibition will be significantly correlated with all speech perception measures, with the largest correlations occurring for the more challenging signal-to-noise ratio conditions. It is also hypothesized that the change in MOCR inhibition across time in the experimental group will be significantly correlated with the changes seen in speech perception. The results of this study will have implications for understanding the physiologic mechanisms involved in speech-in-noise perception and for objectively assessing the benefit from auditory training.