Effects of Spectral Context on Responses in Auditory Cortex

描述（由申请人提供）：本项目旨在提高我们对哺乳动物听觉系统中环境和交流声音编码机制的理解。从嘈杂的声音信号中提取与行为相关的信息对人工声学处理系统的工程师来说仍然是一个相当大的挑战，而生物听觉系统似乎非常适合这样的任务。了解生物系统中声音的正常编码将使我们能够设计出更实用的人工声音处理器，如助听器或助听设备，以及适当设计听觉神经假体，旨在与故障的人类听觉区域相连接。我们之所以研究普通狨猴（Callithrix jacchus），是因为它们是最会说话的灵长类动物之一，而且它们的听觉皮层结构与人类相当相似。狨猴听觉皮层神经元对诸如发声之类的宽带声音表现出复杂的、通常是非线性的反应。大多数这样的神经元只对相对狭窄的频率范围内的窄带声音做出反应。我们试图通过一系列的实验来证明，至少部分之前观察到的复杂反应是由频率范围广泛的神经元输入引起的。该项目的研究目标将通过以下具体目标来实现：1)测试频谱对比度调节部分是由神经元经典定义的接受野之外的频率介导的假设。这一发现将提供更有力的证据，证明研究者先前描述的这些神经元在宽带背景噪声条件下优先工作。2)验证这样的假设，即自然的、宽带的声音比经过过滤以匹配神经元的经典接受野（特别是对比调谐的神经元）的声音，能引发含有更多信息内容的尖峰。视觉皮层神经元表现出这种特性，这表明神经元具有与自然视觉场景非常匹配的反应特性。如果得到证实，这些假设将意味着生物听觉系统可能在比先前估计的更宽的频率范围内整合声能。因此，为听力损失患者设计的人工系统可能能够利用这些受生物学启发的宽带编码方案，最终提高这些人在现实世界中的沟通能力。该项目旨在通过评估灵长类动物听觉皮层的神经元如何在广泛的频率范围内整合声音能量，从而提高我们对哺乳动物听觉系统中环境和交流声音编码机制的理解。了解生物频率集成可以帮助工程师改进听觉假体设备，以改善自然日常环境（如嘈杂的房间）中的声音编码。

DESCRIPTION (provided by applicant): This project addresses our long-term goal to improve our understanding of the mechanisms underlying environmental and communication sound encoding in the mammalian auditory system. Extracting behaviorally relevant information from noisy acoustic signals remains a considerable challenge for engineers of artificial acoustic processing systems, while biological auditory systems seem exquisitely well-suited to such tasks. Understanding the normal encoding of sounds in biological systems will enable us to design more functional artificial sound processors such as hearing aids or hearing-assist devices, as well as to appropriately design auditory neural prostheses intended to interface with malfunctioning human auditory areas. We study common marmosets (Callithrix jacchus) because they are one of the most vocal primate species and because their auditory cortical structure bears considerable similarity to that of humans. Marmoset auditory cortical neurons have been shown to exhibit complex, often nonlinear, responses to wideband sounds such as vocalizations. Most such neurons respond to narrowband sounds only over a relatively narrow range of frequencies. We seek to establish through a series of experiments that neuronal inputs wide- ranging in frequency are responsible for at least some of the previously observed complex responses. The project's research goals will be pursued through the following specific aims: 1) Test the hypothesis that spectral contrast tuning is mediated, in part, by frequencies outside a neuron's classically defined receptive field. Such a finding would provide stronger evidence that these neurons, previously described by the investigator, operate preferentially in conditions of wideband background noise. 2) Test the hypothesis that natural, wideband sounds elicit spikes with more information content than when these sounds are filtered to match the neurons' classical receptive field, particularly for contrast-tuned neurons. Visual cortex neurons exhibit this property, which reveals that the neurons have response properties well-matched to natural visual scenes. If confirmed, these hypotheses would imply that biological auditory systems may be integrating sound energy over a wider frequency range than has been previously estimated. Consequently, artificial systems designed for individuals with hearing loss may be able to exploit these biologically-inspired, wideband coding schemes to ultimately improve these individuals' ability to communicate in real-world situations. This project addresses our long-term goal to improve our understanding of the mechanisms underlying environmental and communication sound encoding in the mammalian auditory system by evaluating how neurons in primate auditory cortex integrate sound energy over a wide range of frequencies. Understanding biological frequency integration may aid engineers in improving auditory prosthesis devices to improving sound encoding in natural everyday environments such as in a noisy room.