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加工原则和策略。本文拟对成年食肉动物（Felis catus）和清醒松鼠猴（Saimiri sciureus）两种主要听觉场的组织结构进行对比和比较，具体涉及功能域和层流组织。一个主要的前提是，核心区域接受很大程度上独立的输入，并表现出可能构成特定任务处理流的特定功能差异。问题是输入在来源位置和功能属性上是如何不同的；丘脑输入对皮层感受野（RF）多样性的产生有何贡献？皮层输入层的功能特征与输出层的功能特征有何不同？所提出的工作的主要假设是：(i)与皮层下站相比，初级听觉皮层场中的神经元表达新的，紧急的处理特性（“在哪里”的问题）；（ii）这些突现特征是由丘脑皮质和皮质皮质相互作用产生的（“如何”的问题）；（iii）多个刺激维度在每个皮质神经元中表达，并控制非线性相互作用，这些相互作用有助于向更稳健，更少变异的声音表示（“什么”问题）转变。基于信息理论的谱-颞感受野（STRF）估计方法表明，听觉前脑中出现了新的刺激处理特性。这些特性与初级视觉皮层的简单细胞和复杂细胞的紧急处理特征有一些相似之处。目的是表征这些特征，并比较它们在不同皮质区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力的潜在贡献。目的1将评估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。目的2将确定听觉皮层神经元中产生多特征维度的主要贡献来源。目标3将确定神经元处理的多特征非线性模型对输入刺激组合和噪声信号的预测效果。这些研究将建立初级听觉皮层信号处理的功能框架。理解这些原理对于系统地评估并发皮层上升和下降通路、它们在正常听觉加工、知觉学习中的作用以及它们对听觉障碍的贡献至关重要。

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.