Cortical processing of informational masking

项目总结/摘要 助听器和人工耳蜗最紧迫的问题是它们在嘈杂的环境中功能不佳。 对于大多数用户来说，即使是轻微的听力损失也很难忽略背景声音。 抑制不需要的声音对于社会环境中的沟通至关重要，例如工作场所。无法 在这些情况下理解语言，称为掩蔽，可能导致社会孤立和就业减少。 两种主要类型的掩蔽干扰助听器和人工耳蜗的最佳功能。第一 类型，称为能量掩蔽，通过心理物理学，生理学和建模得到很好的表征。的 第二种类型，称为信息掩蔽，目前仅被定义为一种心理构造， 明白当目标语音和背景声音刺激同一条听神经时，就会发生能量掩蔽 纤维同时即使是一个理想的倾听者，也几乎无法恢复一个被能量掩盖的目标。 相反，即使目标声音和背景声音在时间上不重叠， 频率，以及理想的收听者何时可以恢复目标信息。因此，信息掩蔽保持了 改进助听器和人工耳蜗设计的关键。此外，不同的听众在 抑制信息掩盖的能力然而，助听器和人工耳蜗植入只是为了 减轻能量掩蔽，忽略信息掩蔽的脆弱性。为了改进 助听器和人工耳蜗植入，我们建议制定一个客观的规模脆弱的信息 基于皮层功能的掩蔽。 我们建议在人类和动物模型中研究信息掩蔽的皮质机制 长爪沙鼠（Meriones unguiculatus）是人类听觉处理的有机体。首先，我们将测试 正常听力的人类听众以及沙鼠在信息掩蔽的条件下， 同时从听觉皮层记录。在人类中，我们将记录血液的血流动力学反应， 氧合，使用具有临床相关性的快速和稳健的评估技术。在沙鼠中，我们将测量 神经元的活动。我们将使用这些数据来制定一个客观的指标， 一个人对信息掩盖的脆弱性。第二，我们将研究神经机制， 通过引入背景声音中快速的不可预测的变化来进行信息掩蔽， 对信息掩蔽的脆弱性是由于主要依赖于抑制背景活动（如 与增强对目标的反应相反）在人类和沙鼠中。第三，使用我们的动物模型，我们将测试 听力损失如何影响对信息掩蔽的敏感性。 总的来说，这一建议将在功能上定义信息掩蔽在知觉和皮层 加工水平。预计这些结果将大大促进我们对起源和范围的理解 这种中央听觉处理缺陷在普通的日常生活中与背景声音。

PROJECT SUMMARY / ABSTRACT The most pressing issue with hearing aids and cochlear implants is that they function poorly in noisy environments for most users, where even mild hearing loss can make it difficult to ignore background sound. Suppression of unwanted sound is crucial for communication in social settings, such as the workplace. Inability to understand speech in these situations, called masking, can lead to social isolation and reduced employment. Two principal types of masking interfere with optimal function of hearing aids and cochlear implants. The first type, called energetic masking, is well characterized through psychophysics, physiology and modeling. The second type, called informational masking, is currently only defined as a psychological construct and much less understood. Energetic masking occurs when target speech and background sound excite the same auditory nerve fibers at the same time. Even an ideal listener would be mostly unable to recover an energetically masked target. In contrast, informational masking occurs even when target and background sound do not overlap in time and frequency, and when an ideal listener could restore the target information. Informational masking thus holds a key to improved hearing aid and cochlear implant design. Moreover, individual listeners differ dramatically in their ability to suppress informational masking. However, hearing aids and cochlear implants only intend to mitigate energetic masking, ignoring vulnerability to informational masking. Towards improved fitting of hearing aids and cochlear implants, we propose to develop an objective scale of vulnerability to informational masking based on cortical function. We propose to examine cortical mechanisms of informational masking in humans and in an animal model organism of human auditory processing, the Mongolian gerbil (Meriones unguiculatus). First, we will test normal-hearing human listeners as well as gerbils under conditions of informational masking and simultaneously record from auditory cortex. In humans, we will record the hemodynamic response of blood oxygenation, using a quick and robust assessment technique with clinical relevance. In gerbils, we will measure neuronal activity in auditory cortex from trained animals. We will use this data to develop an objective metric of an individual’s vulnerability to informational masking. Second, we will examine the neuronal mechanisms of informational masking by introducing rapid unpredictable changes in background sound and assessing if high vulnerability to informational masking is due to predominant reliance on suppressing background activity (as opposed to enhanced responses to the target) in humans and gerbils. Third, using our animal model, we will test how hearing loss affects susceptibility to informational masking. Collectively, this proposal will functionally define informational masking at both perceptual and cortical processing levels. The results are expected to significantly advance our understanding of the origins and scope of this central auditory processing deficit in common everyday situations with background sound.