Neocortical Mechanisms of Categorical Speech Perception

描述（由申请人提供）：口语理解的基本机制尚不清楚。例如，大脑如何从复杂多变的声音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？对分类知觉过程中语音的皮层表征的研究可能会揭示这个基本问题。当一个变量的变化，如音位对比沿着一个连续体被感知时，就会发生范畴感知，而不是作为一个渐进的函数，而是作为一个离散的范畴变化（例如，从“pa”到“ba”）。以往的研究表明，颞上皮层和运动皮层参与了音素的加工。然而，由于非侵入性记录技术的限制，这些区域实际上如何表示（即代码）音素尚不确定。皮质电图（ECoG）是一种将电极直接应用于大脑表面以记录皮层活动的方法，由于它可以提供高空间和时间分辨率，因此是一种很有前途的方法。在这项研究中，我建议通过在神经外科手术过程中利用人类新皮层的直接高密度ECoG记录来检查分类语音处理的机制。所指导的K99阶段的主要重点将是阐明在分类知觉基础上的颞上回中音素的涌现表征。为了实现这一目标，将获得高密度脑电图训练、先进的信号处理和信号源重建方法以及直接皮层电刺激。这些方法将在独立的R00阶段应用于研究运动皮层在语音感知中的作用-具体而言，1)确定其在音素感知和产生过程中的功能组织，2)确定其与听觉语音皮层的功能连接，以及3)确定其在分类语音感知中的本质和因果作用。

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.