Interactive Effects of Aging and Blast Exposure on Central Auditory System

许多暴露在爆炸中的退伍军人报告说，在复杂的听力情况下有困难（例如，理解言语 噪声），尽管在标准听力学测试中表现正常或接近正常。这表明， 中央听觉处理事实上，暴露在爆炸中的退伍军人在中枢听觉测试中表现异常， 特别是那些评估时间处理的。在中年人中也观察到类似的模式， 具有良好的周边听力，但在时间处理和言语理解测试中表现出缺陷， 噪声与听觉障碍相关的听觉缺陷与中枢神经系统的功能和解剖学变化有关。 听觉系统爆炸暴露中听觉缺陷的生理起源目前尚不清楚， 老化和爆炸暴露之间行为特征的相似性表明， 影响。因此，爆炸暴露的退伍军人的听觉缺陷可能会加剧 当他们进入中年及以后。这一点尚未得到系统的调查。本研究将 确定：（a）老化和爆炸暴露对时间处理是否存在相互作用， 语音识别（特定目标1）;（B）是否年龄和/或爆炸相关的行为差异 表现可以与听觉系统内或外的神经解剖学变化相联系（特定目标 2）;（c）是否老化，爆炸暴露，或其相互作用导致的功能表征的变化， 听觉皮层中的言语（具体目标3）。50名爆炸暴露和50名未暴露的退伍军人将 得到考验年轻（18-39岁）和中年（40-60岁）退伍军人将以同等数量代表 在每个爆炸暴露组中。每个参与者将被评估一些时间处理， 语言识别测试显示中年人听力有缺陷。灰、白色物质形态 将使用T1和弥散加权磁共振成像（MRI）进行评估。最后，大脑皮层的活动 将通过功能性磁共振成像在竞争性语言任务中进行测量。我们假设老化和爆炸 暴露将对时间处理和言语测试中的表现产生交互作用， 表现将与中枢听觉神经系统的结构和功能完整性的变化联系起来 系统我们将测试替代方案，例如，听觉表现与认知能力或大脑健康有关 在听觉系统之外。我们希望我们的研究结果将：（a）导致诊断的改善， 中枢听觉缺陷的分类;和（B）激励集中的康复策略。这项研究将建立 候选人之前使用心理物理学和神经成像技术检查语言的研究 听力正常和感觉神经性听力损失的听众的处理。一个强大的辅导团队将 有助于研究和职业发展。Marjorie Leek博士是主要的导师， 临床人群行为测试指南（特别是爆炸暴露）和一般监督 职业发展计划。共同导师Barbara Holshouser博士将协调成像活动，并提供 神经成像方面的专家培训，包括高级成像模式、后处理和MR物理学。共- 导师布鲁斯莱思博士将提供实验性创伤性脑损伤（TBI）研究的研究教育。 共同导师Grace Lee博士将提供认知评估培训。Joseph Helpern和Christopher博士 Stecker将分别提供弥散加权成像和功能性听觉成像方面的咨询。 培训活动将包括：关于补助金撰写、成像方法和TBI的讲习班; 参与神经心理学，听力学和TBI的研究小组和临床医生;以及访问Lyeth博士的 实验室候选人将在年底前申请NIH R 01和VA RR&D优异奖资金。 奖励期。候选人的短期职业目标是获得新的临床人群的经验， 学习新的神经影像学模式，并建立TBI研究的背景。候选人的长期 职业目标是成为一个独立的VA调查员在听觉康复科学。

Many blast-exposed Veterans report difficulty in complex listening situations (e.g., understanding speech in noise) despite normal or near-normal performance on standard audiological tests. This suggests a deficit in central auditory processing. Indeed, blast-exposed Veterans perform abnormally on central auditory tests, particularly those assessing temporal processing. A similar pattern is observed in middle age adults who often have good peripheral hearing but show deficits on tests of temporal processing and speech understanding in noise. Age-related auditory deficits have been linked to functional and anatomical changes in the central auditory system. The physiologic origin of auditory deficits in blast-exposure is currently unknown, although the similarity in behavioral profiles between aging and blast exposure suggests similar mechanisms may be affected. It is therefore possible that the auditory deficits experienced by blast-exposed Veterans will intensify as they enter middle age and beyond. This has not been investigated systematically. The present study will determine: (a) whether there is an interaction between aging and blast exposure on temporal processing and speech recognition (Specific Aim 1); (b) whether age- and/or blast-related differences in behavioral performance can be linked to neuroanatomical changes within or outside the auditory system (Specific Aim 2); and (c) whether aging, blast exposure, or their interaction lead to changes in functional representations of speech in the auditory cortex (Specific Aim 3). Groups of 50 blast-exposed and 50 unexposed Veterans will be tested. Young (18-39 years) and middle age (40-60 years) Veterans will be represented in equal numbers within each blast exposure group. Each participant will be assessed on a number of temporal processing and speech recognition tests known to reveal deficits in middle age listeners. Gray and white matter morphology will be assessed using T1- and diffusion-weighted magnetic resonance imaging (MRI). Finally, cortical activity will be measured during a competing speech task using functional MRI. We hypothesize that aging and blast exposure will produce interactive effects on performance in temporal processing and speech tests, and that performance will be linked to changes in the structural and functional integrity of the central auditory nervous system. We will test for alternatives, e.g., that auditory performance is linked to cognitive ability or brain health outside the auditory system. We expect our findings will: (a) lead to improvements in diagnosis and classification of central auditory deficits; and (b) motivate focused rehabilitation strategies. This study will build on the candidate’s previous research using psychophysical and neuroimaging techniques to examine speech processing in listeners with normal hearing and sensorineural hearing loss. A strong mentorship team will contribute to research and career development. Dr. Marjorie Leek is the primary mentor and will provide guidance on behavioral testing in clinical populations (particularly blast exposure) and general oversight of the career development plan. Co-mentor Dr. Barbara Holshouser will coordinate imaging activities and provide expert training in neuroimaging including advanced imaging modalities, post-processing, and MR physics. Co- mentor Dr. Bruce Lyeth will provide research education in experimental traumatic brain injury (TBI) research. Co-mentor Dr. Grace Lee will provide training in cognitive assessment. Drs. Joseph Helpern and Christopher Stecker will provide consultation in diffusion-weighted imaging and functional auditory imaging, respectively. Training activities will include: workshops on grant writing, imaging methods, and TBI; consultation with research groups and clinicians involved in neuropsychology, audiology and TBI; and visits to Dr. Lyeth’s laboratory. The candidate will apply for NIH R01 and VA RR&D Merit Award funding toward the end of the award period. The candidate’s short-term career goals are to gain experience with new clinical populations, learn new neuroimaging modalities, and establish a background in TBI research. The candidate’s long-term career goal is to become an independent VA investigator in auditory rehabilitation science.