Lateral Asymmetry in the Human Auditory System

描述（由申请人提供）：听觉功能偏侧化是一个突出的、重要的生物学现象。左颞叶的听觉区专门处理快速变化的、宽频的声音，而右颞叶的听觉区专门处理音调和稳态信号的频谱分析。不同的大脑区域处理这些过程，使人类听觉系统能够立即进行准确的频谱分析和精确的时间分析，同时牺牲一个来换取另一个。听觉功能也可能以类似的方式根据受刺激的耳朵而有所不同。本研究的目的是：(1)进一步定义决定侧边性的听觉刺激的声学特征；(2)表征听觉功能侧边性与听觉皮层激活的侧边性之间的关系；(3)确定单侧感觉性听力损失受试者的皮质侧边性是如何反映的，以及该功能如何随受影响的耳朵而变化。受试者听力正常，右撇子，年轻人和单侧听力损失（UHL）患者。男女人数相等。测量右耳、左耳和双耳刺激（正常）或听力（UHL）。五个听觉实验将进行：频率和音调持续时间范围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。每个任务将使用(A)标准的心理物理测量和(B)在高密度（64通道）脑电图记录的古怪范式中的事件相关电位来执行。(A)的分析将包括按年的性能。将单侧受试者的单耳表现与左右耳聋受试者和正常听力受试者进行比较。电生理记录(B)将在两个半球的同源电极位置进行潜伏期和振幅以及表面形貌的比较。偶极源分析将用于确定激活的对称性。这种方法可以根据受试者的反应模式和生理反应，在听觉系统的不同层次上比较偏侧性。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半球的处理能力；2)单侧听力损失的受试者将具有对称的皮质激活，并且在耳聋对侧半球的功能上明显处于不利地位。这一信息可用于改进现有的听力损失患者的补救策略，如通过应用自然发生的侧耳原理植入人工耳蜗和助听器。清楚地了解左耳和右耳如何以个人方式工作，以便同时对声音进行频率（左耳）和时间（右耳）分析，可能会对向听力受损者提供援助的方法产生重大影响。像人工耳蜗或助听器这样的处理声音的设备，可以利用大脑两侧的自然处理差异来适应。该项目将有助于揭示单侧耳聋患者残疾的真实性质，以及这种残疾与耳聋的关系。

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.