Effects of aging on signal in noise processing

项目摘要/摘要 与年龄相关的听力损失是一个普遍存在的问题，估计影响多达三分之一的人口。这种情况比重听更有害，相反，它与许多共病有关，如认知障碍和其他精神疾病。目前尚不清楚这是一种因果关系还是一种偶然现象。如果是前者，简单的干预很可能会给老年人带来更好的心理健康。拟议研究计划的长期目标是确定神经编码原则，当特定声音(即你正在听的声音)与其他声音(即背景)混合出现时，允许听者理解并专注于这些声音，这在许多听力情况下是常见的。虽然这是一个极其困难的计算问题，但听力正常的人都毫不费力地解决了。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，导致个人在嘈杂的环境中难以理解语言。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，特别是了解它在老年人身上到底是如何无法做到这一点的。在听觉通路的不同阶段采用的编码策略中与年龄相关的变化被认为涉及与来自更多外围阶段的衰减输入有关的代偿性变化，最近在老年动物身上的研究证明了复杂声音的中枢神经表征的数量和质量的变化。至关重要的是，这些变化似乎涉及到信息在大脑皮层层次结构中转化方式的变化。出于这个原因，对年龄相关性听力损失的影响的严格研究必须包括对皮质区域的比较，例如核心与腰带，这些区域在正常听力的处理层次结构的不同水平上发挥作用。此外，这些中枢变化不仅会影响沿听觉上升通路的声音处理，还会影响注意力的自上而下的调制。因此，拟议的研究将对比年轻动物和老年动物在具有挑战性的听力环境中如何处理复杂的声音，而这些动物正在执行不需要或不需要听觉注意的感知任务。这些研究将是第一次在灵长类衰老模型中跟踪多种复杂声音在听觉通路处理层次和水平上编码方式的变化，同时允许在皮质反应变化和听觉和知觉缺陷之间进行直接比较。

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.