Lateral Asymmetry in the Human Auditory System

描述(由申请人提供)：听觉功能的偏侧化是一种显著的、生物学上重要的现象。左侧颞叶的听觉区域专门用于快速变化的宽带声音的时间处理，而右侧听觉区域用于音调和稳态信号的频谱分析。这些过程的不同大脑区域允许人类听觉系统立即和同时执行准确的频谱分析和精确的时间分析，同时牺牲其中一个。基于受刺激的耳朵，听觉功能也可能以类似的方式不同。本研究的目的是：1)进一步定义决定偏侧性的听觉刺激的声学特征；2)描述听觉功能的偏侧性与听觉皮质激活的偏侧性之间的关系；3)确定单侧感音神经性听力损失受试者大脑皮质的偏侧性如何反映，以及该功能在不同患耳中的变化情况。受试者通常是听力正常的、右撇子、年轻人和单侧听力损失(UHL)的人。将对同等数量的男性和女性进行评估。将对右、左和双耳刺激(正常)或听力(UHL)进行测量。将进行五个听觉实验：在一定频率和音长范围内的频率识别和强度识别、间隙检测阈值、时间调制传递函数和噪声中的语音(句子)阈值。每项任务将使用(A)标准心理物理测量和(B)事件相关电位在具有高密度(通道)脑电记录的古怪范例中执行。对(A)的分析将包括按耳朵的表现。单侧受试者的单耳表现将在左、右耳聋和听力正常受试者中进行比较。电生理记录(B)将在相同电极位置的不同半球之间进行潜伏期和波幅以及表面地形的比较。偶极源分析将被用来确定激活的对称性。这种方法将允许通过受试者的反应模式和生理反应来比较听觉系统不同水平上的偏侧性。我们假设，1)对于听力正常的受试者，单侧刺激可能会增强对侧大脑半球的加工能力；2)单侧听力损失受试者将具有对称的皮质激活，并且在聋人对侧大脑半球的专门功能上显著受损。这些信息可用于改进目前听力损失患者的补救策略，例如通过应用自然发生偏侧的原则，植入人工耳蜗和助听器。公共卫生相关性清楚地了解左耳和右耳如何以单独的方式工作，以便对声音进行同时的频率(左耳)和计时(右耳)分析，这可能会对为听力障碍者提供援助的方法产生重大影响。处理要传递给个人耳朵的声音的设备，如人工耳蜗或助听器，可以利用大脑两侧的自然处理差异的方式进行匹配。该项目将有助于揭示单侧耳聋患者的残疾的真实性质，以及这种残疾与耳聋一侧的关系。

DESCRIPTION (provided by applicant): Lateralization of auditory function is a salient, biologically-important phenomenon. Auditory areas of left temporal lobe are specialized for temporal processing of rapidly changing, broadband sounds and the right auditory areas for spectral analysis of tonal and steady-state signals. Distinct brain areas for these processes allow the human auditory system to perform accurate spectral analysis and precise temporal analysis instantly and simultaneously with sacrificing one to the other. Auditory function may also differ in a similar manner based on the ear stimulated. Objectives of this study are to 1) further define the acoustic characteristics auditory stimuli that dictate laterality 2) characterize the relationship between laterality of auditory function the laterality of activation of the auditory cortex and 3) determine how cortical laterality is reflected in subjects with unilateral sensory hearing loss and how that function varies by affected ear. Subjects will be normally hearing, right handed, young adults and those with unilateral hearing loss (UHL). An equal number of males and females will be evaluated. Measurements will be made for right, left and binaural stimulation (normals) or hearing ear (UHL). Five auditory experiments will be performed: frequency discrimination and intensity discrimination for a range of frequencies and tone durations, gap detection thresholds, temporal modulation transfer functions and speech (sentence) thresholds in noise. Each task will be performed using (A) standard psychophysical measures and (B) event related potentials in an oddball paradigm with high density (64 channel) EEG recordings. Analysis for (A) will include performance by ear. Performance on single ears of unilateral subjects will be compared in left and right deaf and to the normally hearing subjects. Electrophysiologic recordings (B) will be compared across hemispheres at homologous electrode sites for latency and amplitude as well as surface topography. Dipole source analysis will be applied to determine symmetry of activation. This approach will allow for comparison of laterality at a variety of levels of the auditory system, by subject response pattern and by physiologic response. We hypothesize that, 1) for normally hearing subjects, unilateral stimulation may accentuate the processing capacity seen in the opposite hemisphere 2) subjects with unilateral hearing loss will have symmetric cortical activation and be significantly disadvantaged in functions specialized to the hemisphere contralateral to the deafness. This information can be applied to improve current strategies for remediation of persons with hearing loss, such as cochlear implants and hearing aids by applying principles of naturally occurring laterality. PUBLIC HEALTH RELEVANCE A clear understanding of how the left and right ears work in individual fashion to allow for simultaneous frequency (left ear) and timing (right ear) analysis of sound could have a dramatic impact on the approach to providing aid to those with hearing impairment. Devices that process sound to be delivered to individual ears, such as cochlear implants or hearing aids, could be fit in ways that take advantage of the natural processing differences of the two sides of the brain. This project will help to reveal the true nature of the disability imparted to individuals with unilateral deafness and how such disability relates to the side of the deafness.