Effects of aging on signal in noise processing

项目总结/摘要 听力损失是一个普遍存在的问题，估计影响到三分之一的人口。这种情况比“重听”更有害，相反，它涉及许多并发症，如认知缺陷和其他精神疾病。目前尚不清楚这是一种因果关系还是一种附带现象。如果是前者，简单的干预措施很可能会改善老年人的心理健康。拟议研究计划的长期目标是确定神经编码原则，使听众能够理解并专注于与其他声音（即背景）混合的特定声音（即你正在听的声音），这在许多听力情况下很常见。虽然这是一个非常困难的计算问题，但听力正常的人可以毫不费力地解决它。不幸的是，这种非凡的能力几乎总是随着年龄的增长而下降，使人们在嘈杂的环境中难以理解语音。为了开发辅助技术或疗法来恢复这一关键功能，我们需要了解大脑如何在复杂的声学场景中处理声音，特别是在老年人中，它是如何失败的。在听觉通路的不同阶段采用的编码策略中与听觉相关的变化被认为涉及与来自更多外围阶段的衰减输入相关的补偿性变化，并且最近对老年动物的研究已经证明了复杂声音的中枢神经表征的定量和定性变化。至关重要的是，这些变化似乎涉及信息如何沿着皮层层级沿着进行转换的变化。因此，对年龄相关性听力损失影响的严格研究必须包括对皮层区域的比较，例如核心与腰带，它们在正常听力的不同处理层次中发挥作用。此外，这些中枢变化不仅影响“自下而上”的声音处理沿着上行听觉通路，但也“自上而下”的注意调制。因此，拟议的研究将对比年轻与老年动物在具有挑战性的听觉环境中处理复杂声音的方式，而这些动物正在执行需要或不需要听觉注意的感知任务。这些研究将是第一个跟踪多个复杂声音如何在灵长类动物衰老模型中的听觉通路中跨层次处理水平编码的变化，同时允许直接比较皮质反应变化和听觉感知缺陷。

PROJECT SUMMARY/ABSTRACT Age-related hearing loss is a ubiquitous problem, estimated to affect up to one third of the population. This condition is much more detrimental than ‘hard of hearing’, rather, it has been implicated in a host of co-morbidities such as cognitive deficits, and other mental illness. It remains unclear if this is a cause and effect situation or an epiphenomenon. If the former, simple interventions may well lead to much better mental health among the elderly. The long-term goal of the proposed research program is to identify the neural coding principles that allow listeners to make sense of, and focus on, particular sounds (i.e. what you are listening to) when they occur mixed with other sounds (i.e. the background), something that is common in many listening situations. Although this is an extremely difficult computational problem, people with normal hearing solve it effortlessly. Unfortunately, this remarkable ability almost always declines with age, leaving individuals struggling to understand speech in noisy environments. In order to develop assistive technologies or therapies to restore this critical function, we need to understand how the brain processes sounds in complex acoustic scenes, and, in particular, exactly how it fails to do so in aged individuals. Age-related shifts in the coding strategy employed at different stages of the auditory pathway are believed to involve compensatory changes related to attenuated input from more peripheral stages, and recent research in older animals has demonstrated quantitative and qualitative changes in central neural representation of complex sounds. Crucially, these changes appear to involve changes in how information is transformed along the cortical hierarchy. For this reason, a rigorous study of the effects of age-related hearing loss must include a comparison of cortical areas, such as core versus belt, that function at different levels of the processing hierarchy in normal hearing. Moreover, these central changes impact not only ‘bottom-up’ sound processing along the ascending auditory pathway, but also ‘top-down’ modulation by attention. The proposed studies will therefore contrast how complex sounds in challenging listening environments are processed in young versus old animals while those animals are performing perceptual tasks that either do or do not require auditory attention. These studies will be the first to track changes in how multiple complex sounds are encoded across hierarchical levels of processing in the auditory pathway in a primate model of aging, while allowing direct comparisons between cortical response changes and auditory perceptual deficits.