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Damaged Ears at the Cocktail Party - Investigating How Cochlear Damage Impairs the Neural Representation of Speech in Background Noise

鸡尾酒会上受损的耳朵 - 调查耳蜗损伤如何损害背景噪音中语音的神经表征

基本信息

批准号：
MR/L022311/1
负责人：
Roland Schaette
金额：
$ 52.56万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=MR%2FL022311%2F1
关键词：
Damaged Ears Cocktail Party Investigating

项目摘要

The ability to understand speech is one of the most important functions of the human auditory system, but this ability is considerably degraded in people with hearing deficits. Estimates from the World Health Organization indicate that 360 million people worldwide exhibit some type of hearing loss. Hearing aids have provided some benefit for patients affected with hearing loss, nevertheless, this benefit has been, to a large extent, restricted to making sounds more audible via amplification with little, if any, benefit to increase the performance to separate speech from background noise. Recent data suggest that a range of hearing problems, including speech-in-noise deficits, may arise as a result of the loss of auditory nerve fibres (ANFs), i.e., the bundle of fibres that carry information from the inner ear to the brain. This represents a type of peripheral damage that can arise even in supposedly normal-hearing subjects (i.e. those with no evidence of reduced sensitivity in the audiogram). Moreover, it is likely that phenomena, such as adaptive coding, a process in which neurons adapt their rate of discharge of action potentials (a measure of responsiveness) to better represent the most commonly occurring sound intensities in the acoustic environment thus allowing the average background intensity to be averaged out, also contribute towards the processing of signals in the presence of a noisy background. We hypothesize that A) the loss of ANFs, in particular, those involved in the processing high-intensity sounds, is involved in a decrease ability to understand speech-in-noise due to a degraded representation of the acoustic signal and B) that hearing loss will decrease the adaptive coding capability of the auditory system, which may be critical for the discrimination of speech from background noise.To test these hypotheses, we will investigate mechanisms used by the auditory system to process speech signals embedded in noise. For this purpose, we will use an animal model and manipulate its auditory system at the level of the periphery. Through the administration of drugs, the use of earplugs or by exposure to high intensity noise, we can induce different types of hearing loss by targeting different populations of cells in a highly controlled manner that can be assessed using standard methods. Then, to investigate the effects of these manipulations we will use sophisticated in vivo electrophysiological techniques to record the activity of individual neurons in the inferior colliculus (IC) of the midbrain, a major relay nucleus on along the ascending auditory pathway. This technique allows us to record from neurons "extracellularly", i.e., the activity of neurons in the close vicinity of the recording electrode. We will characterize the responses of auditory neurons to different types of stimuli, including pure tones, speech tokens and broadband noise. Subsequently, we will use identical acoustic stimuli and intracellular recording techniques to record the activity elicited from within individual neurons. This technique has the benefit of allowing us to record supra-threshold (action potentials) and sub-threshold events from individual neurons. The latter reflect inputs from many other neurons and can either increase (excitatory) or decrease (inhibitory) the likelihood of more action potentials been fired by a neuron. The analysis of these electrophysiological measurements will allow us to understand a) how well snippets of speech can be discriminated based on the responses of neurons in the midbrain, b) the capability of neurons to exhibit adaptive coding and how this relates to speech discriminability, and c) the effect hearing loss on these measures. This will help us to uncover the peripheral and central factors that contribute to speech-in-noise performance. The results we obtain from this research will be important for the development new strategies to improve the performance of hearing aids and cochlear implants.

理解语音的能力是人类听觉系统最重要的功能之一，但这种能力在听力缺陷的人中大大降低。世界卫生组织估计，全世界有3.6亿人表现出某种类型的听力损失。助听器为听力损失患者提供了一些益处，然而，这种益处在很大程度上仅限于通过放大使声音更清晰，几乎没有（如果有的话）提高将语音与背景噪声分离的性能的益处。最近的数据表明，一系列听力问题，包括噪音中的言语缺陷，可能是由于听觉神经纤维（ANF）的损失，即，将信息从内耳传递到大脑的纤维束。这代表了一种即使在假定听力正常的受试者（即听力图中没有证据表明灵敏度降低的受试者）中也可能出现的外周损伤。此外，可能的是，诸如自适应编码的现象也有助于在存在噪声背景的情况下处理信号，其中自适应编码是神经元调整其动作电位的放电速率（响应性的量度）以更好地表示声学环境中最常见的声音强度从而允许平均背景强度的过程。我们假设A）ANF的损失，特别是那些参与处理高强度声音的ANF的损失，涉及由于声学信号的退化表示而导致的理解噪声中的语音的能力降低，以及B）听力损失将降低听觉系统的自适应编码能力，这可能是区分语音与背景噪声的关键。我们将研究听觉系统用来处理嵌入噪声中的语音信号的机制。为此，我们将使用动物模型，并在外周水平上操纵其听觉系统。通过给药、使用耳塞或暴露于高强度噪声，我们可以通过以高度受控的方式靶向不同的细胞群来诱导不同类型的听力损失，这种方式可以使用标准方法进行评估。然后，为了研究这些操作的效果，我们将使用复杂的在体电生理技术来记录单个神经元的活动在下丘（IC）的中脑，一个主要的中继核沿着上行听觉通路。这项技术允许我们从神经元“细胞外”记录，即，记录电极附近神经元的活动。我们将描述听觉神经元对不同类型刺激的反应，包括纯音，语音标记和宽带噪声。随后，我们将使用相同的声刺激和细胞内记录技术来记录从单个神经元内引起的活动。这种技术的好处是允许我们记录来自单个神经元的阈上（动作电位）和阈下事件。后者反映了来自许多其他神经元的输入，并且可以增加（兴奋）或减少（抑制）神经元激发更多动作电位的可能性。对这些电生理测量的分析将使我们能够理解：a）基于中脑神经元的反应，语音片段可以被区分得有多好; B）神经元表现出自适应编码的能力，以及这与语音可辨别性的关系;以及c）听力损失对这些测量的影响。这将有助于我们发现有助于噪声中语音性能的外围和核心因素。我们从这项研究中获得的结果将是重要的发展新的策略，以提高助听器和人工耳蜗植入的性能。