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在复杂的听力情况下存在困难(例如，理解 噪音)，尽管在标准听力测试中表现正常或接近正常。这表明在 中枢听觉处理。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， 尤其是那些评估时间加工的研究。在中年成年人中也观察到类似的情况，他们经常 周围听力良好，但在时间加工和言语理解测试中表现出缺陷 噪音。与年龄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。爆炸暴露中听觉障碍的生理来源目前尚不清楚，尽管 衰老和冲击波暴露之间行为特征的相似性表明，类似的机制可能是 受影响。因此，暴露在爆炸中的退伍军人经历的听觉缺陷可能会加剧 随着他们步入中年及以后。这还没有得到系统的调查。本研究将 确定：(A)老化和冲击波暴露之间是否存在时间加工和冲击波暴露的交互作用 语音识别(具体目标1)；(B)是否与年龄和/或爆炸有关的行为差异 表现可以与听觉系统内部或外部的神经解剖变化联系在一起(特定目的 2)；以及(C)老化、冲击波暴露或它们之间的相互作用是否会导致神经元功能表征的变化 听觉皮质中的言语(特定目标3)。由50名暴露于爆炸和50名未暴露的退伍军人组成的小组将 接受测试。青年(18-39岁)和中年(40-60岁)退伍军人的人数将相等 在每个冲击波暴露组内。每个参与者将被评估一系列的时间处理和 众所周知，语音识别测试揭示了中年听众的缺陷。灰质和白质形态 将使用T1和弥散加权磁共振成像(MRI)进行评估。最后，大脑皮层活动 将在一项相互竞争的语音任务中使用功能磁共振进行测量。我们假设衰老和爆炸 暴露会对时间加工和言语测试的成绩产生交互影响， 表现将与中枢听神经结构和功能完整性的变化联系在一起 系统。我们将测试替代方案，例如，听觉表现是否与认知能力或大脑健康有关 在听觉系统之外。我们预计我们的发现将：(A)改善诊断和 对中枢听觉缺陷进行分类；以及(B)推动有重点的康复战略。这项研究将建立 关于候选人之前使用心理物理和神经成像技术检查语音的研究 听力正常和感音神经性听力损失的听者的处理。一个强大的指导团队将 为研究和职业发展做出贡献。Marjorie Leek博士是主要导师，将提供 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，包括高级成像设备、后处理和磁共振物理学。共同-- 导师Bruce Lyeth博士将在实验性创伤性脑损伤(TBI)研究方面提供研究教育。 联合导师Grace Lee博士将提供认知评估方面的培训。约瑟夫·赫尔本博士和克里斯托弗博士 Stecker将分别在扩散加权成像和功能听觉成像方面提供咨询。 培训活动将包括：关于赠款编写、成像方法和TBI的讲习班；与 参与神经心理学、听力学和脑外伤的研究小组和临床医生；以及访问莱斯博士的 实验室。候选人将在接近结束时申请NIH R01和VA RR&D功勋奖资金 获奖期。候选人的短期职业目标是获得与新的临床人群的经验， 学习新的神经成像方法，并建立脑损伤研究的背景。候选人的长期任期 职业目标是成为听觉康复科学领域的一名独立的VA研究员。

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.