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The effects of age on temporal coding in the auditory system

年龄对听觉系统时间编码的影响

基本信息

批准号：
BB/M007243/1
负责人：
Chris Plack
金额：
$ 36.32万
依托单位：
Lancaster University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=BB%2FM007243%2F1
关键词：
effects age temporal coding auditory

项目摘要

Hearing ability deteriorates with age, leading to communication difficulties and a reduced quality of life. Some of these changes are apparent in the audiogram, the standard clinical measure of hearing sensitivity, which describes the sensitivity of the ear to pure tones at different frequencies. However, in addition to the changes that can be detected using standard clinical techniques, it is becoming increasing clear from animal and human studies that a deterioration in auditory function may occur before, or independently from, a significant decline in sensitivity to low-level sounds as measured by the audiogram. Listeners with clinically normal hearing may experience an age-related decline in their ability to understand speech in noisy environments, an ability that is vital for real-world communication. It has been suggested that this may be due, in part, to a deficit in the ability of nerve fibres to represent the rapid fluctuations in sounds in terms of their synchronised patterns of activation. An age-related deficit in this "temporal coding" has been demonstrated recently in humans using techniques that record the electrical activity of nerve fibres in the auditory brain by attaching electrodes to the scalp. Temporal coding may be important for speech identification per se, but it is thought to be particularly important for segregating speech from interfering sounds. In particular, we rely on fine-grained timing information to separate sounds on the basis of their spatial locations (for example, several people talking at a noisy party).The neural bases for the age-related decline in temporal coding are unclear, but there are two potential candidates. First, animal studies and post-mortem examinations of human ears suggest that there is a progressive loss in auditory nerve fibres with age, particularly those fibres that represent information at medium-to-high levels. Hence, this loss can occur without a reduced sensitivity to quiet sounds. Second, it is possible that the deficit in temporal coding may be due to a loss of synchrony between nerve fibres. This may occur because age is associated with a patchy degeneration of the fatty sheaths that surround nerve fibres and increase the speed of transmission of nerve impulses.The proposed research will use a combination of state-of-the-art electrophysiological and listening-test techniques to provide a comprehensive understanding of the neural bases and perceptual consequences of the age-related decline in temporal coding in humans. Our focus will be on listeners with clinically normal hearing, so that we can study these effects in isolation from the effects of dysfunction of the hair cells and other structures in the inner ear that are associated with clinical loss. By testing a large cohort of volunteers across the age range with measures of nerve-fibre function and listening ability with laboratory and "real world" sounds, we will be able to make connections and inferences that are not possible with less ambitious studies. In particular, we will determine whether the age-related temporal coding deficits are due to a loss in nerve fibres, a reduction in nerve fibre transmission speed, or both. We will also be able to determine how the deficit in temporal coding is related to real-world hearing ability on tasks such as speech detection in noise, and musical pitch perception. The results will provide the basis for a diagnostic test that can identify the neural dysfunction. Early diagnosis of damage, before any deficit is apparent in the audiogram, will allow clinicians to provide personalised healthcare advice, for example, to avoid any situations that will compound the problems, such as exposure to recreational noise. The research will also pave the way for future interventions that may correct for the deficits, for example hearing aids with directional microphones to facilitate speech reception, and drug and stem cell therapies to restore neural function.

听力随着年龄的增长而下降，导致沟通困难和生活质量下降。其中一些变化在听力图中很明显，听力图是听力灵敏度的标准临床测量，它描述了耳朵对不同频率的纯音的灵敏度。然而，除了使用标准临床技术可以检测到的变化之外，动物和人类研究越来越清楚地表明，听觉功能的恶化可能发生在听力图测量的对低水平声音的敏感性显著下降之前，或独立于此。临床听力正常的听众可能会经历与年龄相关的在嘈杂环境中理解语音的能力下降，这种能力对现实世界的交流至关重要。有人认为，这可能部分是由于神经纤维在同步激活模式方面表现声音快速波动的能力不足。最近，通过将电极贴在头皮上记录听觉大脑中神经纤维的电活动，在人类身上证明了这种“时间编码”中与年龄有关的缺陷。时间编码对于语音识别本身可能是重要的，但是它被认为对于将语音与干扰声音分离特别重要。特别是，我们依赖于细粒度的时间信息，根据声音的空间位置（例如，几个人在嘈杂的聚会上交谈）来分离声音。时间编码与年龄相关的下降的神经基础尚不清楚，但有两个潜在的候选者。首先，动物研究和对人耳的死后检查表明，随着年龄的增长，听觉神经纤维逐渐丧失，特别是那些代表中高水平信息的纤维。因此，这种损失可能会发生，而不会降低对安静声音的敏感性。其次，时间编码的缺陷可能是由于神经纤维之间失去同步性造成的。这可能是因为年龄与神经纤维周围的脂肪鞘的片状变性有关，并增加了神经冲动的传输速度。拟议的研究将使用最先进的电生理学和电生理测试技术的组合，以全面了解与年龄相关的人类时间编码下降的神经基础和感知后果。我们的重点将放在临床听力正常的听众身上，这样我们就可以研究这些影响，而不受与临床损失相关的内耳毛细胞和其他结构功能障碍的影响。通过测试一大批年龄范围内的志愿者，用实验室和“真实的世界”的声音测量神经纤维功能和听力，我们将能够做出不太雄心勃勃的研究所不可能的联系和推断。特别是，我们将确定与年龄相关的时间编码缺陷是否是由于神经纤维的损失，神经纤维传输速度的降低，或两者兼而有之。我们还将能够确定时间编码的缺陷如何与现实世界的听觉能力有关，例如噪声中的语音检测和音乐音高感知。这些结果将为可以识别神经功能障碍的诊断测试提供基础。在听力图中出现任何缺陷之前，早期诊断损伤将使临床医生能够提供个性化的医疗建议，例如，避免任何会使问题复杂化的情况，例如暴露于娱乐性噪音。该研究还将为未来可能纠正缺陷的干预措施铺平道路，例如带有定向麦克风的助听器，以促进语音接收，以及恢复神经功能的药物和干细胞疗法。