Leuthardt Eric C, Pei Xiao-Mei, Breshears Jonathan, Gaona Charles, Sharma Mohit, Freudenberg Zac, Barbour Dennis, Schalk Gerwin
Department of Biomedical Engineering, Washington University in St. Louis, St. Louis MO, USA.
Front Hum Neurosci. 2012 May 3;6:99. doi: 10.3389/fnhum.2012.00099. eCollection 2012.
Several scientists have proposed different models for cortical processing of speech. Classically, the regions participating in language were thought to be modular with a linear sequence of activations. More recently, modern theoretical models have posited a more hierarchical and distributed interaction of anatomic areas for the various stages of speech processing. Traditional imaging techniques can only define the location or time of cortical activation, which impedes the further evaluation and refinement of these models. In this study, we take advantage of recordings from the surface of the brain [electrocorticography (ECoG)], which can accurately detect the location and timing of cortical activations, to study the time course of ECoG high gamma (HG) modulations during an overt and covert word repetition task for different cortical areas. For overt word production, our results show substantial perisylvian cortical activations early in the perceptual phase of the task that were maintained through word articulation. However, this broad activation is attenuated during the expressive phase of covert word repetition. Across the different repetition tasks, the utilization of the different cortical sites within the perisylvian region varied in the degree of activation dependent on which stimulus was provided (auditory or visual cue) and whether the word was to be spoken or imagined. Taken together, the data support current models of speech that have been previously described with functional imaging. Moreover, this study demonstrates that the broad perisylvian speech network activates early and maintains suprathreshold activation throughout the word repetition task that appears to be modulated by the demands of different conditions.
几位科学家提出了不同的大脑皮层言语处理模型。传统上，参与语言活动的区域被认为是模块化的，具有线性激活序列。最近，现代理论模型提出，在言语处理的各个阶段，解剖区域之间存在更具层级性和分布性的相互作用。传统成像技术只能确定大脑皮层激活的位置或时间，这阻碍了对这些模型的进一步评估和完善。在本研究中，我们利用大脑表面记录[皮层脑电图（ECoG）]，其能够准确检测大脑皮层激活的位置和时间，来研究在不同皮层区域进行公开和隐蔽单词重复任务期间ECoG高伽马（HG）调制的时间进程。对于公开的单词生成，我们的结果显示，在任务的感知阶段早期，大脑外侧裂周围皮层有大量激活，并持续到单词发音阶段。然而，在隐蔽单词重复的表达阶段，这种广泛的激活会减弱。在不同的重复任务中，大脑外侧裂周围区域内不同皮层位点的利用程度因提供的刺激（听觉或视觉线索）以及单词是要说出还是想象而有所不同。总体而言，这些数据支持了先前通过功能成像描述的当前言语模型。此外，本研究表明，广泛的大脑外侧裂周围言语网络在单词重复任务早期就被激活，并在整个任务过程中保持阈上激活，这似乎受到不同条件需求的调节。
