Neocortical Mechanisms of Categorical Speech Perception

理解口语的基本机制尚不清楚。例如，我们不理解人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)。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，如音位对比沿一个连续体被感知时，范畴知觉就会发生，它不是一个渐进的函数，而是一个离散的类别变化。此前的研究表明，在语音处理过程中，大脑的上颞叶皮质也有一定的作用。然而，皮质实际如何表示(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。 直接从大脑皮质表面记录神经活动是一种很有前途的方法，因为它可以提供高的空间和时间分辨率。在这里，我建议利用神经外科手术过程中获得的神经生理记录来研究范畴语音处理的机制。独立的Roo阶段的主要焦点将是阐明在颞叶上回中的音素的紧急不变表征，这是在范畴知觉之下的。高密度电极天线、先进的信号处理和直接的大脑皮层刺激将被用来解开在外侧颞叶皮质中特定声音的局部种群编码以及跨多个感觉和认知区域的全局处理。

The basic mechanisms underlying comprehension of spoken language are unknown. We do not understand, for example, how the human brain extracts the most fundamental linguistic elements (consonants and vowels) 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 phonem ic contrast along a continuum is perceived, not as a gradual function but rather as a discrete category change. Previous research has implicated the superior temporal cortex in the processing Of speech sounds. However, how the cortex actually represents (i.e. encodes) phonemes is undetermined, mainly due to limitations of non-invasive recording techniques. The recording of neural activity di rectly from the cortical surface is a promising approach si nee it can provide both high spatial and temporal resolution. Here, I propose to examine the mechanisms of categorical speech processing by utilizing neurophysiological recordings obtained during ne urosurgical pnacedures. The principal focus of the independent ROO phase wil I be to elucidate the emergent invariant representation of phonemes in the superior tem poral gyrus that underiies categorical perception. High-density electrode anays, advanced signal processing, and direct eiectrocortical stim ulation will be utilized to unravel both local population encoding of speec h sounds in the lateral temporal cortex as well as global processing across multiple sensory and cognitiv e areas.