本研究包括两个实验，采用颜色匹配判断的内隐阅读任务，被试为小学二年级(平均7. 3岁)、四年级(平均9. 3岁)、六年级(平均11. 5岁)和大学生(平均24. 4岁)。实验一采用人脸图形、汉字和物体线条图为材料，探讨汉字与其它刺激间的类别选择性发展。实验二采用符合正字法的真字、伪字和不符合正字法的笔划组合为材料，探讨N170的偏侧化和正字法敏感性发展。
Investigations of functional changes that occur during reading acquisition in cortical regions associated with the perception of visual words are important to understand the nature of reading processing.Previous Event-related Potentials (ERPs) studies of adult readers have demonstrated that letter strings elicited larger N170 component than control stimuli. This relatively specialized ERP component, often shown to be largest over the left occipito-temporal region, is believed to be associated with orthographic processing. However, this claim is confounded by a phonological factor, since pronunciation and orthography is virtually undistinguishable in alphabetic scripts. In contrast, in written Chinese, orthography and phonology can be separately manipulated, while unfortunately only very few studies have been conducted using Chinese characters.
Intuitionly, investigation of N170 changes along with literacy development is vital for understanding of the nature of this reading-related brain activity. While quite a few of studies with alphabetic children have been reported (results are largely inconsistent though), there is essentially no such kind of ERP study conducted in Chinese children. In particular, how it develop in the primary school children.
In the current study, we examined the development of N170 elicited by Chinese characters, in terms of its hemispheric laterality and category/orthography sensitivity,in primary school children as well as adult readers. A context--irrelated color matching task was used, in which participants were required to compare the color of a target stimulus with that of a preceding cue stimulus.
The study includes two experiments. Twenty 20a grade children (10 females, mean age 7.33士0.53 years), twenty 4th grade children (10 females, mean age 9.34士0.54years), twenty 6th grade children (10 females, mean age 11.55士0.36,years) and 13 young adults (7 females, mean age 24.4士0.43 years) participated in the experiments. All subjects were native Chinese. The first experiment was to explore the development of category selectivity of N170 component, by use of Chinese characters, faces, and line-drawings of common bjects. The second experiment used Chinese characters, pseudowords and stroke combinations to detect the development of orthographic sensitivity of this component.
The main foundings and conclusions are as follows:
(1) The N170 sensitive to Chinese characters shifted from bilateral to left-lateralized during development of literacy. Specifically, left lateralization effect did not emerge until the 6th grade children.
(2) The N170 amplitudes evoked by Chinese characters was significantly larger than that by line-drawings of common objects in all four groups, suggesting that the category selectivity of N170 elicited by characters emerges as early as the 20d grade children.
(3) The N170 amplitudes evoked by Chinese characters was significantly larger than that by stroke combinations in the 6`h grade children and adults readers, and this effect was found only on the left hemisphere. These results suggest that orthographic sensitivity effect does not emerge until the 6`h grade children.
(4) The left-lateralized N170 effect of orthographic sensitivity did not differ significantly between the 6th grade children and adult readers, suggesting that orthography in the 6th children has already well developed.
This study, for the first time, charaterized N170 effects associated with reading of Chinese characters in four groups from 2nd grade children to college students,providing important empirical insights into the neural basis of the development of early stages of Chinese character processing.