Cochlear Efferent Feedback and Hearing-in-Noise Perception in Autism

描述（由申请人提供）：在背景噪声中过滤相关听觉信息的困难是自闭症谱系障碍（ASD）的关键特征之一，这种过滤困难会显著损害一个人的社交能力。家长和老师经常报告说，自闭症儿童在嘈杂的环境中特别难以注意和理解言语。这些观察结果得到了使用标准化问卷测量感觉功能的研究的支持。虽然患有ASD的人难以过滤背景噪声中的语音信息，但过滤能力可能存在变化，并且这种变化中的一些可能与以下各项的处理有关：i）听觉目标（语音或非语音信号），ii）听觉背景噪声（掩蔽物类型），以及iii）听觉系统在空间上将目标与掩蔽物分离的能力（从掩蔽的空间释放）。过滤相关听觉信息的能力的生理基础被认为是由于中枢神经系统通过下行听觉通路（橄榄耳蜗传出系统）对耳蜗活动的调节。内侧橄榄耳蜗（MOC）传出系统介导耳蜗外毛细胞（OHC）的主动微机械收缩特性，然后调节内毛细胞传入放电率。此外，可以在人类受试者中评估OHC的收缩活动，因为它们的收缩产生声信号（耳声发射; OAE），其可以记录在外耳道中，使得可以直接测量耳蜗外周处的听觉过滤过程。先前已经表明，患有ASD的青少年和儿童使用瞬态耳声发射（TrOAE）降低了MOC传出反馈强度。在目标1中，我们将调查高功能自闭症青少年和典型发展控制中的掩蔽能力的听觉过滤和空间释放，使用语音和音乐音调作为目标，以及语音形状和合成的牙牙学语噪声作为掩蔽物。我们将使用心理物理学和自适应跟踪来测量不同条件下的目标阈值，以评估ASD是否与语音特定听力任务的受损表现相关。在目标2中，我们将使用两种不同的基于耳声发射的测试来测量耳蜗MOC传出反馈强度：失真产物耳声发射（DPOAE）和瞬时耳声发射（TrOAE），并采用双耳宽带刺激以最大限度地激活MOC传出反馈。我们将测试的假设，MOC传出反馈强度和R/L耳对称性受损的ASD。从这些研究中获得的信息将使我们能够确定传出反馈强度的非侵入性测量是否可以作为这种疾病中听觉过滤能力的生理指标。 公共卫生相关性：这项研究将推进我们对自闭症患者如何在背景噪音存在下听到语音的理解。这种过滤相关听觉信息的能力对于言语感知和更广泛的语言社会使用至关重要。使用微型扬声器-麦克风耳塞，我们还将测量内耳感觉细胞产生的声信号（耳声发射），因为这些发射在背景噪音存在下受到抑制。我们将确定自闭症患者是否减少了噪声引起的对这些发射的抑制，以及这种自闭症特异性发射差异是否与该人群的听觉过滤能力有关。

DESCRIPTION (provided by applicant): Difficulty in filtering relevant auditory information in background noise is one of the key features of autism spectrum disorders (ASD) and such filtering difficulties can significantly impair a person's social communication abilities. Parents and teachers often report that children with autism have particular difficulty attending to and understanding speech in noisy environments. These observations are supported by studies using standardized questionnaires to measure sensory functioning. While people with ASD have difficulties filtering speech information in background noise, there may be variability in filtering abilities, and some of this variability maybe be related to processing of: i) the auditory target (speech or non-speech signals), ii) auditory background noise (masker type), and iii) the ability of the auditory system to spatially separate the target from the masker (spatial release from masking). The physiological basis for the ability to filter relevant auditory information is believed to be due to regulation of cochlear activity by the CNS via descending auditory pathways-the olivocochlear efferent system. The medial olivocochlear (MOC) efferent system mediates active micromechanical contractile properties of cochlear outer hair cells (OHCs) which then modulate inner hair cell afferent firing rates. Moreover, the contractile activity of the OHCs can be evaluated in human subjects, because their contractions generate acoustic signals (otoacoustic emissions; OAEs), which can be recorded in the external ear canal, making it possible to directly measure auditory filtering processes at the cochlear periphery. It has previously been shown that adolescents and children with ASD have reduced MOC efferent feedback strengths using transient OAEs (TrOAEs). In Aim 1, we will investigate auditory filtering and spatial release from masking ability in adolescents with high functioning autism and typically developing controls, using both speech and musical tones as targets, and both speech-shaped and synthesized babble noise as maskers. We will use psychophysics and adaptive tracking to measure target thresholds in the different conditions to evaluate whether ASD is associated with impaired performance on speech-specific listening tasks. In Aim 2, we will measure cochlear MOC efferent feedback strength using two different otoacoustic emission-based tests: distortion-product OAEs (DPOAEs) and transient OAEs (TrOAEs) with binaural broadband stimulation to maximally activate MOC efferent feedback. We will test the hypothesis that MOC efferent feedback strength and R/L ear symmetry is impaired in ASD. Information gained from these studies will allow us to determine if a non-invasive measure of efferent feedback strength can serve as a physiological indicator of auditory filtering capabilities in this disorder. PUBLIC HEALTH RELEVANCE: This research will advance our understanding of how individuals with autism can hear speech sounds in the presence of background noise. This ability to filter relevant auditory information is critical for speech perception and the social use of language more generally. Using miniature speaker-microphone earplugs, we will also measure acoustic signals (otoacoustic emissions) generated by sensory cells in the inner ear as these emissions are suppressed in the presence of background noise. We will determine if individuals with autism have reduced noise-induced suppression of these emissions, and if such autism-specific differences in emissions are related to auditory filtering capabilities in this population.