Neurophysiological Basis of Speech Perception

描述（由申请人提供）：本项目的长期目标是确定语音感知背后的神经生理过程。语音的一个决定性特征是它们是被分类感知的。也就是说，不同的声刺激倾向于被归为感知类别，从而导致跨类别比类别边界内更好的区分。我们的主要假设是，左半球处理语音的优势程度与它们的分类感知有关，而不是与作为语音的任何特殊地位有关。我们假设左脑半球专门负责声音的分类感知，包括语音和非语音，而右脑半球专门负责声音的连续辨别。功能磁共振成像（fMRI）和事件相关电位（ERP）技术将用于实现五个具体目标：(1)识别语音和类语音的分类和连续感知的大脑区域。我们预测，分类感知将与左侧听觉皮层区域的神经激活有关，该区域在感知声学匹配但连续感知的声音时未被激活。(2)明确声音分类知觉与半球侧化相关模式之间的关系。我们预测，与连续感知声学匹配的声音相比，分类感知将导致更大的神经激活向左偏侧。(3)通过训练，明确大脑在从分类感知到连续感知和从连续感知到分类感知过程中可塑性的神经过程。我们预测，知觉类别的学习和遗忘将导致类别表征的加工和相关的神经基质激活的半球转移。(4)通过比较注意前和主动目标检测条件下古怪辨别的脑激活模式，检验注意对分类知觉的影响。(5)基于fmri约束的偶极子模型，探索涉及分类和连续感知的脑区激活的时间过程。语音感知在人类认知中起着重要的作用。了解言语分类知觉的神经生理基础及其与半球偏侧化的关系，可能为改善阅读障碍、特异性语言障碍和精神分裂症等疾病的治疗提供手段，并为改善单侧影响颞叶的疾病（如中风和颞叶癫痫）的康复方法提供手段。

DESCRIPTION (provided by applicant): The tong-term objective of this project is to identify the neurophysiological processes underlying speech perception. A defining characteristic of speech sounds is that they are perceived categorically. That is, different acoustic stimuli tend to be grouped into perceptual categories, resulting in better discrimination across than within category boundaries. Our main hypothesis is that the degree of left hemispheric dominance for processing of speech sounds is related to their categorical perception rather than to any special status as speech sounds. We hypothesize that the left hemisphere is specialized for categorical perception of sounds, both speech and nonspeech, whereas the right hemisphere is specialized for continuous discrimination of sounds. Functional magnetic resonance imaging (fMRI) and event-related potential (ERP) techniques will be used to achieve five specific aims: (1) Identify brain areas underlying categorical and continuous perception of speech and speech-like sounds. We predict that categorical perception will be associated with neural activation in regions of the left auditory cortex not activated during perception of acoustically matched but continuously-perceived sounds. (2) Define the relation between categorical perception of sounds and associated patterns of hemispheric lateralization. We predict that categorical perception will result in greater leftward lateralization of neural activation than continuous perception of acoustically matched sounds. (3) Define the neural processes underlying plasticity of the brain in shifting from categorical to continuous perception and from continuous to categorical perception, through training. We predict that the learning and unlearning of perceptual categories will induce hemispheric shifts in processing and associated activation of neural substrates for category representations. (4) Test the effects of attention on categorical perception by comparing brain activation patterns during oddball discrimination under pre-attentive and under active target detection conditions. (5) Explore the temporal course of activation of brain areas involved in categorical and continuous perception, based on fMRI-constrained dipole modeling of the neural generators underlying each type of perception. Speech perception plays a fundamental role in human cognition. Understanding the neurophysiological basis of categorical perception of speech and its relation to hemispheric lateralization may suggest means of improving the treatment of disorders such as dyslexia, specific language impairment and schizophrenia, and means of improving rehabilitation methods in diseases affecting the temporal lobe unilaterally, such as stroke and temporal lobe epilepsy.