Neocortical Mechanisms of Categorical Speech Perception

描述(申请人提供)：口语理解的基本机制尚不清楚。例如，大脑如何从复杂和高度可变的声学信号中提取最基本的语言元素-辅音和元音，或组成它们的独特特征？对语音在绝对知觉过程中的皮层表征的研究很可能有助于揭示这一基本问题。当一个变量的变化，如音位沿连续体的对比，不是一个渐进的函数，而是一个离散的类别变化(例如，从“pa”到“ba”)，范畴知觉就会发生。先前的研究已经表明，在音素的处理过程中，上颞叶皮质和运动皮质也有一定的作用。然而，这些区域如何实际表示(即编码)音素尚不确定，这主要是由于非侵入性记录技术的限制。脑电地形图(ECoG)是一种将电极直接应用于大脑表面以记录皮质活动的方法，因为它可以提供高的空间和时间分辨率，是一种很有前途的方法。在这项研究中，我建议在神经外科手术过程中，利用来自人类新皮质的直接高密度ECoG记录来检验分类语音处理的机制。指导的K99阶段的主要焦点将是阐明作为范畴知觉基础的颞上回中音素的出现表征。为了实现这一目标，将获得高密度脑电、先进的信号处理和信号源重建方法以及直接大脑皮质刺激方面的培训。然后，这些方法将被应用于独立的R00阶段，以研究运动皮质在言语知觉中的作用--具体地说，1)确定其在音素知觉和产生过程中的功能组织，2)确定其与听觉语音皮质的功能连接，以及3)确定其在范畴言语知觉中的基本和因果作用。 公共卫生相关性：这项研究的目的是揭示理解口语的基本机制。理解语言在大脑中的编码方式对于开发新的语言障碍(如失语症、阅读障碍、自闭症等)的诊断和康复策略具有重要意义。在所有这些情况下，对音素的异常感知是语言障碍的核心组成部分。

DESCRIPTION (provided by applicant): The basic mechanisms underlying comprehension of spoken language are unknown. For example, how does the brain extract the most fundamental linguistic elements-consonants and vowels, or the distinctive features which compose them-from a complex and highly variable acoustic signal? An investigation of the cortical representation of speech sounds during categorical perception can likely shed light on this fundamental question. Categorical perception occurs when a change in a variable such as phonemic contrast along a continuum is perceived, not as a gradual function but rather as a discrete category change (for instance, from "pa" to "ba"). Previous research has implicated the superior temporal cortex and also motor cortex in the processing of phonemes. However, how those areas actually represent (i.e. code) phonemes is undetermined, mainly due to limitations of non-invasive recording techniques. Electrocorticography (ECoG), the direct application of electrodes to the brain surface for recording cortical activity, is a promising approach since it can provide high spatial and temporal resolution. In this study, I propose to examine the mechanisms of categorical speech processing by utilizing direct high-density ECoG recordings from the human neocortex during neurosurgical procedures. The principal focus of the mentored K99 phase will be to elucidate the emergent representation of phonemes in the superior temporal gyrus that underlies categorical perception. Training in high-density ECoG, advanced signal processing and source reconstruction methods, and direct electrocortical stimulation will be acquired to achieve this aim. These approaches will then be applied during the independent R00 phase to investigate the role of the motor cortex in speech perception- specifically, 1) to determine its functional organization during phoneme perception and production, 2) to determine its functional connectivity with auditory speech cortices, and 3) to determine its essential and causal role in categorical speech perception. PUBLIC HEALTH RELEVANCE: The aim of this research is to reveal the fundamental mechanisms that underlie comprehension of spoken language. An understanding of how speech is coded in the brain has significant implications for the development of new diagnostic and rehabilitative strategies for language disorders (e.g. aphasia, dyslexia, autism, et alia). Abnormal perception of phonemes is a central component to language disability in all of these conditions.