The Neurophysiological Dynamics of Lexical and Sub-Lexical Representations

描述(由申请人提供)：这项建议的广泛目标是调查大脑如何根据较低级别的声学-语音和音素信息来构建口语单词的词形和词汇表征。大脑在几百毫秒内从声音感觉输入中解析意义的能力可能来自于多个级别的表征，随着信息在经典语言网络中通过本地和远程皮质回路进行处理，抽象程度增加。这些过程将使用一种综合的、多模式的神经生理学方法进行研究，该方法结合了植入慢性硬膜下电极的癫痫患者的高分辨率侵入性皮质脑电图(ECoG)和提供神经活动的全脑覆盖的无创性脑磁图(MEG)。这些技术是高度互补的，并将提供前所未有的时空分辨率来表征词汇处理，因为它在毫秒级别上跨相邻的神经群体展开。对皮层脑电和脑磁图数据的初步分析将涉及构建一个神经“状态空间”，它代表了电极之间的共同活动。最近开发的方法允许将活动在跨时间的状态空间中可视化为神经轨迹。参与者将听到一系列单词，每个单词由四个不同的说话者说出，神经轨迹将在200-400毫秒后从声学开始到假想的词汇和语义表征进行追踪。假设同一单词的不同实例将开始于状态空间的不同部分(由于说话人之间的声学差异)，并最终会聚到代表与特定词汇项相关的神经活动的区域。这些分析将使用癫痫患者的ECoG数据进行，并将与MEG的健康对照组进行验证。脑磁图将提供有关这些轨迹的额外信息，因为它能够对整个大脑皮层进行采样，并可能检测到未被皮层脑电网格覆盖的区域(例如，对侧半球的区域)的相关活动。最后，由于刺激将根据词汇频率和音向概率等语言特征进行仔细控制，因此将有可能检查大脑中假设的预测机制如何对刺激水平的统计特性进行编码。总的来说，这些方法将阐明词在大脑中的抽象和更高层次的表征过程，并将是从动态、交互过程的角度表征言语感知的神经编码的首批研究之一。了解大脑如何构建包含丰富、可延展和复杂含义的词级表征，对于表征、诊断和治疗损害语言学习和处理的疾病至关重要。它还可能有助于改进人工耳蜗术等辅助技术。在这种情况下解码神经表示的能力 这一水平将促进我们对构成更高认知功能许多方面的基本大脑过程的理解。

DESCRIPTION (provided by applicant): The broad objective of this proposal is to investigate how the brain constructs word-form and lexical representations of spoken words from lower-level acoustic-phonetic and phonemic information. The brain's ability to parse meaning from acoustic sensory inputs within a few hundred milliseconds may arise from multiple levels of representation that increase in abstraction as information is processed through local and long-distance cortical circuits in the classical language network. These processes will be studied using an integrated, multimodal neurophysiological approach that combines high-resolution invasive electrocorticography (ECoG) in epilepsy patients implanted with chronic subdural electrodes, and non-invasive magnetoencephalography (MEG), which provides whole-brain coverage of neural activity. The techniques are highly complementary and will provide unprecedented spatiotemporal resolution to characterize lexical processing as it unfolds on the millisecond level across adjacent neural populations. The primary analysis for ECoG and MEG data will involve constructing a neural "state-space", which represents the common activity across electrodes. Recently-developed methods allow the activity to be visualized in the state-space across time as neural trajectories. Participants will hear a list of words, each spoken by four different speakers, and the neural trajectories will be traced from the acoustic onset to the hypothesized lexical and semantic representations between 200-400ms later. It is hypothesized that different instances of the same word will begin in different parts of the state-space (due to acoustic differences across speakers), and will eventually converge into areas that represent neural activity associated with a particular lexical item. These analyses will be performed with data from ECoG in epilepsy patients, and will also be confirmed with healthy controls in MEG. MEG will provide additional information about these trajectories, since it is able to sample the entire cortex, and may detect relevant activity in areas that are not covered by the ECoG grids (for example, areas in the contralateral hemisphere). Finally, since the stimuli will be carefully controlled for linguistic features such as lexical frequency and phonotactic probability, it will b possible to examine how stimulus-level statistical properties are encoded by hypothesized prediction mechanisms in the brain. In general, these approaches will elucidate the processes of abstraction and higher-level representation for words in the brain, and will be among the first studies to characterize the neural code for speech perception from the perspective of dynamic, interactive processes. Understanding how the brain constructs word-level representations that contain a rich, malleable, and complex meaning is crucial for characterizing, diagnosing, and treating disorders that impair language learning and processing. It may also help improve assistive technologies like cochlear implants. The ability to decode neural representations at this level will further our understanding of fundamental brain processes that underlie many aspects of higher cognitive function.