Cognitive models of reading assume that speech production occurs after visual and phonological processing of written words. This traditional view is at odds with more recent magnetoencephalography studies showing that the left posterior inferior frontal cortex (pIFC) classically associated with spoken production responds to print at 100-150 ms after word-onset, almost simultaneously with posterior brain regions for visual and phonological processing. Yet the theoretical significance of this fast neural response remains open to date. We used transcranial magnetic stimulation (TMS) to investigate how the left pIFC contributes to the early stage of reading. In Experiment 1, 23 adult participants (14 females) performed three different tasks about written words (oral reading, semantic judgment and perceptual judgment) while single-pulse TMS was delivered to the left pIFC, fusiform gyrus or supramarginal gyrus at different time points (50 to 200 ms after word-onset). A robust double dissociation was found between tasks and stimulation sites - oral reading, but not other control tasks, was disrupted only when TMS was delivered to pIFC at 100 ms. This task-specific impact of pIFC stimulation was further corroborated in Experiment 2, which revealed another double dissociation between oral reading and picture naming. These results demonstrate that the left pIFC specifically and causally mediates rapid computation of speech motor codes at the earliest stage of reading and suggest that this fast sublexical neural pathway for pronunciation, although seemingly dormant, is fully functioning in literate adults. Our results further suggest that these left-hemisphere systems for reading overall act faster than known previously.Significance Statement Recent neuroimaging data suggest that left posterior inferior frontal cortex, classically associated with spoken production, responds to print simultaneously with left fusiform and supramarginal gyri, each responsible for visual and phonological processing, contrary to traditional serial cascade models of reading. While the region is now known to mediate different aspects of cognitive processing, the functional significance of this fast neural response remains unclear. Using transcranial magnetic stimulation, we show that early inferior frontal activation plays a specific and causal role in speeded oral reading at 100 ms after word-onset. This fast sublexical neural pathway for pronunciation, although seemingly dormant, is fully functioning in literate adults. We also propose that the left-hemisphere reading systems act differently and faster than known previously.

中文翻译：

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剖析早期下额叶激活在阅读中的因果作用。


阅读的认知模型假设语音产生发生在书面单词的视觉和语音处理之后。这种传统观点与最近的脑磁图研究不一致，该研究表明，经典上与语音产生相关的左后下额叶皮层 （pIFC） 在单词开始后 100-150 毫秒对印刷品做出反应，几乎与用于视觉和语音处理的后脑区域同时。然而，这种快速神经反应的理论意义至今仍有待解决。我们使用经颅磁刺激 （TMS） 来研究左侧 pIFC 如何促进阅读的早期阶段。在实验 1 中，23 名成年参与者 （14 名女性） 执行了关于书面单词的三种不同任务 （口语阅读、语义判断和知觉判断），同时在不同时间点 （单词开始后 50 至 200 毫秒） 将单脉冲 TMS 传递到左侧 pIFC、梭形回或边缘上回。在任务和刺激部位之间发现了强大的双重解离 - 只有当 TMS 在 100 毫秒时被输送到 pIFC 时，口腔阅读而不是其他控制任务才会被破坏。实验 2 进一步证实了 pIFC 刺激的这种任务特异性影响，它揭示了口语阅读和图片命名之间的另一种双重解离。这些结果表明，左侧 pIFC 在阅读的最早阶段特异性和因果地介导了语音运动代码的快速计算，并表明这种用于发音的快速亚词汇神经通路虽然看似休眠，但在识字的成年人中完全发挥作用。我们的结果进一步表明，这些用于阅读整体的左半球系统比以前已知的要快。意义声明 最近的神经影像学数据表明，经典上与口语产生相关的左后下额叶皮层与左梭形和边缘上回同时对印刷做出反应，每个脑回都负责视觉和语音处理，与传统的连续级联阅读模型相反。虽然现在已知该区域介导认知处理的不同方面，但这种快速神经反应的功能意义仍不清楚。使用经颅磁刺激，我们表明早期额下激活在单词开始后 100 毫秒的加速口语阅读中起着特定的因果作用。这种快速的发音亚词汇神经通路虽然看起来处于休眠状态，但在识字的成年人中完全发挥作用。我们还提出左半球阅读系统的行为与以前已知的不同且更快。