Functional Organization of Primary Auditory Cortex

描述（由申请人提供）：拟议实验的长期目标是确定听觉皮层感受野转换和复杂声音表征的基本处理原则和策略。我们建议对比和比较两个主要的听觉领域的组织在成年食肉动物（猫卡图斯）和清醒的松鼠猴（Saimiri sciureus）的功能域和层状组织的具体参考。一个主要的前提是，核心区域接收很大程度上独立的输入，并表现出特定的功能差异，可能构成特定任务的处理流。这些问题是如何输入不同的源位置和功能特性;丘脑的输入对皮层感受野（RF）多样性的产生有什么贡献;以及皮层输入水平的功能特性与输出层的功能特性相比如何？拟议工作的主要假设是：（i）与皮质下站相比，初级听觉皮质场中的神经元表达新颖的、涌现的处理特性（“在哪里”的问题）;（ii）这些新兴的功能是由丘脑皮质和皮质的相互作用产生的（“如何”的问题）;（iii）多个刺激维度在每个皮层神经元中表达并且支配非线性相互作用，较少变化的声音表示（“什么”问题）。基于信息论的谱-时间感受野（STRF）估计方法表明听觉前脑中出现了新的刺激处理特性。这些特性与初级视皮层简单细胞和复杂细胞的涌现加工特征有相似之处。我们的目标是描述这些特征，并比较它们在皮层区域和不同物种之间的特性，以推断它们的一般特性及其对人类听觉的潜在贡献。目的1研究听觉丘脑和听觉皮层核心区多特征感受野的参数分布及其非线性。目标2将确定听觉皮层神经元中产生多个特征维度的主要贡献源。目标3将确定神经元处理的多特征非线性模型预测对输入刺激组合和噪声中信号的反应的能力。结合这些研究，将建立初级听皮层信号处理的功能框架。了解这些原则是至关重要的并发皮质上行和下行通路，它们在正常的听觉处理的作用，在知觉学习，以及它们的贡献听觉障碍的系统评估。 周围性听力损失对中枢神经系统的声音处理有许多影响。周围听力障碍的中枢听觉后果的例子是即使患者具有良好的助听器，也会降低患者的言语理解能力，或者即使对于仅患有轻度耳蜗听力损失的患者，也难以理解背景噪声中的言语。我们试图探索听觉皮层处理复杂信号和不同类型背景噪声中的信号的正常功能，以确定导致在噪声中处理信号的通常非常强大的能力的机制。一旦更好地了解正常功能，就可以检查听力损失对这些中枢机制的有害后果，并可能导致开发新的治疗方法来治疗交流障碍。

DESCRIPTION (provided by applicant): The long-term goal of the proposed experiments is to identify the fundamental processing principles and strategies that underlie auditory cortical receptive field transformations and the representations of complex sounds. We propose to contrast and compare the organization of two primary auditory fields in adult carnivores (Felis catus) and the awake squirrel monkey (Saimiri sciureus) with specific reference to functional domains and laminar organization. A main premise is that core areas receive largely independent inputs and exhibit specific functional differences that may constitute task-specific processing streams. The questions are how do the inputs differ in source location and functional properties; what do the thalamic inputs contribute to the generation of cortical receptive field (RF) diversity; and how do the functional characteristics at the cortical input level compare to those in the output layers? The principal hypotheses underlying the proposed work are that (i) neurons in primary auditory cortical fields express novel, emergent processing properties compared to subcortical stations (the "where" question); (ii) these emergent features are generated by thalamocortical and corticocortical interactions (the "how" question); (iii) multiple stimulus dimensions are expressed in each cortical neuron and govern nonlinear interactions that contribute to transformations toward a more robust, less variant sound representation (the "what" question). Information-theory based methods of spectro-temporal receptive field (STRF) estimation suggest the emergence of novel stimulus processing properties in the auditory forebrain. These properties bear some similarities to emergent processing features in simple and complex cells of primary visual cortex. The goal is to characterize these features and compare their properties across cortical fields and across species in order to extrapolate their general properties and their potential contributions to human hearing. Aim 1 will assess the parameter distributions of the multiple-feature receptive fields and their nonlinearities in auditory thalamus and auditory cortical core areas. Aim 2 will determine the main contributing sources to the generation of multiple feature dimensions in auditory cortical neurons. Aim 3 will determine how well a multi-feature, nonlinear model of neuronal processing predicts responses to combinations of input stimuli and to signals in noise. Combined these studies will establish a functional framework of signal processing in primary auditory cortical fields. Understanding these principles is crucial for a systematic evaluation of concurrent cortical ascending and descending pathways, their role in normal auditory processing, in perceptual learning, and their contributions to auditory disorders. PUBLIC HEALTH RELEVANCE: Peripheral hearing loss has many consequences for the processing of sounds by the central nervous system. Examples of central auditory consequences of peripheral hearing disorders are a reduction of speech comprehension for patients even if they that have well-fitted hearing aids, or the difficulty to understand speech in background noise even for patients with only a mild cochlear hearing loss. We attempt to explore the normal function of the auditory cortex for processing complex signals and signals in different types of background noise in order to ascertain the mechanisms that lead to the normally very robust ability to process signals in noise. Once the normal functions are better understood, the detrimental consequences of hearing loss on these central mechanisms can be examined and may lead to the development of new therapeutic approaches to communicative disorders.