Lavidor Michal, Walsh Vincent
Department of Psychology, University of Hull, England.
J Cogn Neurosci. 2003 Apr 1;15(3):354-63. doi: 10.1162/089892903321593081.
The split-fovea theory proposes that visual word recognition is mediated by the splitting of the foveal image, with letters to the left of fixation projected to the right hemisphere (RH) and letters to the right of fixation projected to the left hemisphere (LH). We applied repetitive transcranial magnetic stimulation (rTMS) over the left and right occipital cortex during a lexical decision task to investigate the extent to which word recognition processes could be accounted for according to the split-fovea theory. Unilateral rTMS significantly impaired lexical decision latencies to centrally presented words, supporting the suggestion that foveal representation of words is split between the cerebral hemispheres rather than bilateral. Behaviorally, we showed that words that have many orthographic neighbors sharing the same initial letters ("lead neighbors") facilitated lexical decision more than words with few lead neighbors. This effect did not apply to end neighbors (orthographic neighbors sharing the same final letters). Crucially, rTMS over the RH impaired lead-, but not end-neighborhood facilitation. The results support the split-fovea theory, where the RH has primacy in representing lead neighbors of a written word.
中央凹分裂理论提出，视觉单词识别是由中央凹图像的分裂介导的，注视点左侧的字母投射到右半球（RH），注视点右侧的字母投射到左半球（LH）。我们在词汇判断任务中对左、右枕叶皮质施加重复经颅磁刺激（rTMS），以研究根据中央凹分裂理论，单词识别过程在多大程度上可以得到解释。单侧rTMS显著延长了对中央呈现单词的词汇判断潜伏期，支持了单词的中央凹表征在大脑半球之间分裂而非双侧性的观点。在行为方面，我们发现，有许多共享相同首字母的正字法邻词（“首字母邻词”）的单词比首字母邻词少的单词更能促进词汇判断。这种效应不适用于尾字母邻词（共享相同尾字母的正字法邻词）。至关重要的是，对右半球施加rTMS会损害首字母邻词的促进作用，但不会损害尾字母邻词的促进作用。这些结果支持了中央凹分裂理论，即右半球在表征书面单词的首字母邻词方面具有首要地位。
