Hsiao Janet Hui-Wen, Shillcock Richard, Lavidor Michal
Department of Computer Science and Engineering, University of California San Diego, San Diego, CA, USA.
Brain Res. 2006 Mar 17;1078(1):159-67. doi: 10.1016/j.brainres.2006.01.072. Epub 2006 Feb 24.
The proposal of human foveal splitting assumes a vertical meridian split in the foveal representation and the consequent contralateral projection of information in the two hemifields to the two hemispheres and has been shown to have important implications for visual word recognition. According to this assumption, in Chinese character recognition, the two halves of a centrally fixated character may be initially projected to and processed in different hemispheres. Here, we describe a repetitive transcranial magnetic stimulation (rTMS) investigation of hemispheric processing in Chinese character recognition, through examining semantic radical combinability effects in a character semantic judgment task. The materials used were a dominant type of Chinese character which consists of a semantic radical on the left and a phonetic radical on the right. Thus, according to the split fovea assumption, the semantic and phonetic radicals are initially projected to and processed in the right hemisphere and the left hemisphere, respectively. We show that rTMS over the left occipital cortex impaired the facilitation of semantic radicals with large combinability, whereas right occipital rTMS did not. This interaction between stimulation site and radical combinability reveals a flexible division of labor between the hemispheres in Chinese character recognition, with each hemisphere responding optimally to the information in the contralateral visual hemifield to which it has direct access. The results are also consistent with the split fovea claim, suggesting functional foveal splitting as a universal processing constraint in reading.
人类中央凹分裂的假说认为，在中央凹表征中存在一条垂直子午线分裂，由此两个半视野中的信息会对侧投射到两个半球，并且这一假说已被证明对视觉单词识别具有重要意义。根据这一假说，在汉字识别过程中，中央固定注视的汉字的两半可能最初会投射到不同半球并在其中进行处理。在此，我们通过在汉字语义判断任务中考察语义部首组合性效应，描述了一项关于汉字识别中半球加工的重复经颅磁刺激（rTMS）研究。所使用的材料是一种占主导地位的汉字类型，其由左侧的语义部首和右侧的语音部首组成。因此，根据中央凹分裂假说，语义部首和语音部首最初分别投射到右半球和左半球并在其中进行处理。我们发现，左侧枕叶皮层的rTMS会损害具有高组合性的语义部首的促进作用，而右侧枕叶的rTMS则不会。刺激部位与部首组合性之间的这种相互作用揭示了汉字识别中半球之间灵活的分工，每个半球对其可直接获取信息的对侧视觉半视野中的信息反应最佳。这些结果也与中央凹分裂的观点一致，表明功能性中央凹分裂是阅读中的一种普遍加工限制。
