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重要现象。左颞叶的听觉区专门用于快速变化的宽带声音的时间处理，而右听觉区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执行精确的频谱分析和精确的时间分析，同时牺牲一个到另一个。听觉功能也可以基于被刺激的耳朵以类似的方式不同。本研究的目的是：1）进一步确定听觉刺激的声学特征，决定偏侧性; 2）表征听觉功能偏侧性与听觉皮层激活偏侧性之间的关系; 3）确定单侧感觉性听力损失受试者的皮层偏侧性如何反映，以及受影响耳朵的功能如何变化。受试者将是听力正常的右利手年轻人和单侧听力损失（UHL）患者。将评价相同数量的雄性和雌性动物。将对右耳、左耳和双耳刺激（正常）或听力耳（UHL）进行测量。将进行五个听觉实验：频率和强度歧视的频率和音调持续时间，间隙检测阈值，时间调制传递函数和语音（句子）阈值在噪声中的范围。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（64通道）EEG记录的古怪范例中执行每个任务。（A）的分析将包括按耳的性能。单侧受试者的单耳性能将在左聋和右聋受试者中与听力正常受试者进行比较。将在同源电极部位比较两个半球的电生理记录（B）的潜伏期和振幅以及表面形貌。偶极源分析将用于确定激活的对称性。这种方法将允许在听觉系统的各种水平上，通过受试者响应模式和生理响应来比较偏侧性。我们假设：1）对于听力正常的受试者，单侧刺激可能会加重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层激活，并且在耳聋对侧半球的功能方面明显处于不利地位。这些信息可以应用于改善目前的听力损失患者的补救策略，例如通过应用自然发生的偏侧性原则进行人工耳蜗植入和助听器。公共卫生相关性清楚地了解左耳和右耳如何以个人方式工作，以允许同时对声音进行频率（左耳）和定时（右耳）分析，这可能会对为听力障碍者提供帮助的方法产生巨大影响。处理声音的设备被传递到个人耳朵，如耳蜗植入或助听器，可以利用大脑两侧的自然处理差异。该项目将有助于揭示单侧耳聋患者残疾的真正性质，以及这种残疾与一侧耳聋的关系。

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.