Appelbaum Lawrence G, Liotti Mario, Perez Ricardo, Fox Sarabeth P, Woldorff Marty G
Center for Cognitive Neuroscience, Duke University Durham, NC, USA.
Front Hum Neurosci. 2009 Nov 30;3:56. doi: 10.3389/neuro.09.056.2009. eCollection 2009.
The decoding of visually presented line segments into letters, and letters into words, is critical to fluent reading abilities. Here we investigate the temporal dynamics of visual orthographic processes, focusing specifically on right hemisphere contributions and interactions between the hemispheres involved in the implicit processing of visually presented words, consonants, false fonts, and symbolic strings. High-density EEG was recorded while participants detected infrequent, simple, perceptual targets (dot strings) embedded amongst a of character strings. Beginning at 130 ms, orthographic and non-orthographic stimuli were distinguished by a sequence of ERP effects over occipital recording sites. These early latency occipital effects were dominated by enhanced right-sided negative-polarity activation for non-orthographic stimuli that peaked at around 180 ms. This right-sided effect was followed by bilateral positive occipital activity for false-fonts, but not symbol strings. Moreover the size of components of this later positive occipital wave was inversely correlated with the right-sided ROcc180 wave, suggesting that subjects who had larger early right-sided activation for non-orthographic stimuli had less need for more extended bilateral (e.g., interhemispheric) processing of those stimuli shortly later. Additional early (130-150 ms) negative-polarity activity over left occipital cortex and longer-latency centrally distributed responses (>300 ms) were present, likely reflecting implicit activation of the previously reported 'visual-word-form' area and N400-related responses, respectively. Collectively, these results provide a close look at some relatively unexplored portions of the temporal flow of information processing in the brain related to the implicit processing of potentially linguistic information and provide valuable information about the interactions between hemispheres supporting visual orthographic processing.
将视觉呈现的线段解码为字母，再将字母解码为单词，对于流畅的阅读能力至关重要。在此，我们研究视觉正字法过程的时间动态，特别关注右半球的贡献以及参与视觉呈现单词、辅音、伪字体和符号串隐式处理的半球之间的相互作用。在参与者检测嵌入在一系列字符串中的罕见、简单的感知目标（点串）时，记录了高密度脑电图。从130毫秒开始，正字法和非正字法刺激通过枕部记录部位上一系列的事件相关电位效应得以区分。这些早期潜伏期枕部效应以非正字法刺激在右侧增强的负极性激活为主，在约180毫秒达到峰值。这种右侧效应之后是伪字体的双侧枕部正性活动，但符号串没有。此外，这种后期枕部正波成分的大小与右侧ROcc180波呈负相关，这表明对于非正字法刺激早期右侧激活较大的受试者，在稍后阶段对这些刺激进行更广泛的双侧（如半球间）处理的需求较小。左侧枕叶皮层还出现了额外的早期（130 - 150毫秒）负极性活动以及潜伏期较长的中央分布反应（>300毫秒），可能分别反映了先前报道的“视觉词形”区域的隐式激活和与N400相关的反应。总体而言，这些结果深入研究了大脑中与潜在语言信息隐式处理相关的信息处理时间流中一些相对未被探索的部分，并提供了有关支持视觉正字法处理的半球间相互作用的有价值信息。
