Rosazza Cristina, Cai Qing, Minati Ludovico, Paulignan Yves, Nazir Tatjana A
Institut des Sciences Cognitives, 67, Boulevard Pinel, 69675 Bron Cedex, France.
Brain Res. 2009 May 26;1272:32-44. doi: 10.1016/j.brainres.2009.03.033. Epub 2009 Mar 28.
Visual expertise underlying reading is attributed to processes involving the left ventral visual pathway. However, converging evidence suggests that the dorsal visual pathway is also involved in early levels of visual word processing, especially when words are presented in unfamiliar visual formats. In the present study, event-related potentials (ERPs) were used to investigate the time course of the early engagement of the ventral and dorsal pathways during processing of orthographic stimuli (high and low frequency words, pseudowords and consonant strings) by manipulating visual format (familiar horizontal vs. unfamiliar vertical format). While early ERP components (P1 and N1) already distinguished between formats, the effect of stimulus type emerged at the latency of the N2 component (225-275 ms). The N2 scalp topography and sLORETA source localisation for this differentiation showed an occipito-temporal negativity for the horizontal format and a negativity that extended towards the dorsal regions for the vertical format. In a later time window (350-425 ms) ERPs elicited by vertically displayed stimuli distinguished words from pseudowords in the ventral area, as confirmed by source localisation. The sustained contribution of occipito-temporal processes for vertical stimuli suggests that the ventral pathway is essential for lexical access. Parietal regions appear to be involved when a serial mechanism of visual attention is required to shift attention from one letter to another. The two pathways cooperate during visual word recognition and processing in these pathways should not be considered as alternative but as complementary elements of reading.
阅读所依赖的视觉专长归因于涉及左腹侧视觉通路的过程。然而，越来越多的证据表明，背侧视觉通路也参与视觉单词处理的早期阶段，尤其是当单词以不熟悉的视觉形式呈现时。在本研究中，通过操纵视觉形式（熟悉的水平形式与不熟悉的垂直形式），使用事件相关电位（ERP）来研究在处理正字法刺激（高频和低频单词、假词和辅音串）期间腹侧和背侧通路早期参与的时间进程。虽然早期ERP成分（P1和N1）已经能够区分不同的形式，但刺激类型的影响在N2成分（225 - 275毫秒）的潜伏期出现。这种区分的N2头皮地形图和sLORETA源定位显示，水平形式在枕颞区有负电位变化，垂直形式的负电位变化则向背侧区域扩展。在稍后的时间窗口（350 - 425毫秒），垂直显示刺激引发的ERP在腹侧区域能够区分单词和假词，源定位也证实了这一点。枕颞区对垂直刺激的持续作用表明腹侧通路对于词汇通达至关重要。当需要一种视觉注意串行机制将注意力从一个字母转移到另一个字母时顶叶区域似乎会参与其中。在视觉单词识别过程中这两条通路相互协作，并且在这些通路中的处理过程不应被视为相互替代，而应被看作是阅读的互补要素。
