Interactive Effects of Aging and Blast Exposure on Central Auditory System

许多经历过爆炸的退伍军人报告说，他们在复杂的听力环境中遇到困难（例如，理解 尽管在标准听力测试中表现正常或接近正常，但噪音）。这表明存在赤字 中枢听觉处理。事实上，遭受爆炸袭击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人。在中年人中也观察到类似的模式，他们经常 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。目前尚不清楚爆炸暴露中听觉缺陷的生理起源，尽管 衰老和爆炸暴露之间行为特征的相似性表明相似的机制可能是 受影响。因此，经历过爆炸的退伍军人所经历的听觉缺陷可能会加剧 当他们进入中年及以后。这尚未得到系统的研究。本研究将 确定：(a) 老化和爆炸暴露在时间处理上是否存在相互作用； 语音识别（具体目标 1）； (b) 行为上的差异是否与年龄和/或急变相关 表现可能与听觉系统内外的神经解剖学变化有关（具体目标 2）； (c) 老化、爆炸暴露或它们的相互作用是否会导致功能表征的变化 听觉皮层的言语（具体目标 3）。 50 名经历过爆炸的退伍军人和 50 名未经历过爆炸的退伍军人组成的小组将 被测试。年轻（18-39岁）和中年（40-60岁）退伍军人的比例将相同 在每个爆炸暴露组内。每个参与者都将接受一系列时间处理和评估 众所周知，语音识别测试可以揭示中年听众的缺陷。灰质和白质形态 将使用 T1 和扩散加权磁共振成像 (MRI) 进行评估。最后，皮质活动 将在竞争性言语任务期间使用功能性 MRI 进行测量。我们假设老化和爆炸 暴露会对时间处理和言语测试的表现产生交互影响，并且 表现将与中枢听觉神经的结构和功能完整性的变化相关 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相关 听觉系统之外。我们期望我们的发现将：（a）改善诊断和 中枢听觉缺陷的分类； (b) 激发有针对性的康复战略。这项研究将建立 候选人之前使用心理物理学和神经影像技术检查言语的研究 听力正常和感音神经性听力损失的听众的处理。强大的导师团队将 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（特别是爆炸暴露）的指导和一般监督 职业发展计划。联合导师 Barbara Holshouser 博士将协调成像活动并提供 神经影像方面的专家培训，包括高级成像模式、后处理和 MR 物理。共同 导师 Bruce Lyeth 博士将提供实验性脑外伤 (TBI) 研究方面的研究教育。 共同导师 Grace Lee 博士将提供认知评估培训。博士。约瑟夫·赫尔伯恩和克里斯托弗 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：关于拨款写作、成像方法和 TBI 的研讨会；咨询 涉及神经心理学、听力学和 TBI 的研究小组和临床医生；并拜访 Lyeth 博士的诊所 实验室。候选人将在该项目结束时申请 NIH R01 和 VA RR&D 优异奖资助 颁奖期。候选人的短期职业目标是获得新临床人群的经验， 学习新的神经影像学模式，并建立 TBI 研究背景。候选人的长期 职业目标是成为听觉康复科学领域的独立 VA 研究者。

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.