Department of Neurology, Christian-Albrechts-University Kiel, 24105 Kiel, Germany.
Proc Natl Acad Sci U S A. 2010 Sep 21;107(38):16494-9. doi: 10.1073/pnas.1008121107. Epub 2010 Aug 31.
Recent functional imaging studies demonstrated that both the left and right supramarginal gyri (SMG) are activated when healthy right-handed subjects make phonological word decisions. However, lesion studies typically report difficulties with phonological processing after left rather than right hemisphere damage. Here, we used a unique dual-site transcranial magnetic stimulation (TMS) approach to test whether the SMG in the right hemisphere contributes to modality-independent (i.e., auditory and visual) phonological decisions. To test task-specificity, we compared the effect of real or sham TMS during phonological, semantic, and perceptual decisions. To test laterality and anatomical specificity, we compared the effect of TMS over the left, right, or bilateral SMG and angular gyri. The accuracy and reaction times of phonological decisions were selectively disrupted relative to semantic and perceptual decisions when real TMS was applied over the left, right, or bilateral SMG. These effects were not observed for TMS over the angular gyri. A follow-up experiment indicated that the threshold-intensity for inducing a disruptive effect on phonological decisions was identical for unilateral TMS over the right or left SMG. Taken together, these findings provide converging evidence that the right SMG contributes to accurate and efficient phonological decisions in the healthy brain, with no evidence that the left and right SMG can compensate for one another during TMS. Our findings motivate detailed studies of phonological processing in patients with acute or long-term damage of the right SMG.
最近的功能成像研究表明，当健康的右利手受试者进行语音单词决策时，左、右缘上回（SMG）都被激活。然而，病变研究通常报告左半球损伤后而不是右半球损伤后出现语音处理困难。在这里，我们使用独特的双部位经颅磁刺激（TMS）方法来测试右半球的 SMG 是否有助于模态独立（即听觉和视觉）语音决策。为了测试任务特异性，我们比较了在语音、语义和感知决策过程中真实或假 TMS 的影响。为了测试侧化和解剖特异性，我们比较了 TMS 在左侧、右侧或双侧 SMG 和角回上的效果。当真实 TMS 施加于左侧、右侧或双侧 SMG 时，语音决策的准确性和反应时间相对于语义和感知决策选择性地受到干扰。当 TMS 施加于角回时，未观察到这些影响。后续实验表明，在单侧 TMS 对右侧或左侧 SMG 进行语音决策时，引起干扰效应的阈强度是相同的。综上所述，这些发现提供了一致的证据，表明右 SMG 有助于健康大脑中准确有效的语音决策，并且没有证据表明左和右 SMG 在 TMS 期间可以相互补偿。我们的发现促使对急性或长期右 SMG 损伤患者的语音处理进行详细研究。
