汉字字形认知研究的刺激源设计及在fMRI研究中的应用

Design of Simulus for Chinese Character Recognition and Its Application in fMRI Study

目的:评估汉字字形刺激源在汉字认知fMRI研究中的有效性,并对参与汉字处理的脑皮层区域进行定位及初步的量化分析。方法:选择母语为汉语、经利手测试后为右利手且裸眼视力正常(大于等于1．0)的在校大学生10例(男6例,女4例)作为被试。试验任务采用组块设计,将汉字(非字、假字、真字)投射到屏幕上,受试者接受汉字字形图片的视觉刺激,按非字-假字-真字-非字-假字-真字顺序呈现,共6个block。数据处理及统计分析采用国际通用的AFNI软件。结果:左额叶上、中、下回(包括Broca's area)、左中央前回(BA6)、左顶上小叶及顶下小叶(包括缘上回及角回)及双侧枕叶、楔前叶显著激活;左颞叶梭状回(BA37)、右额下回及双侧颞中、上回及扣带回显著激活,左大脑半球的激活体积明显大于右侧大脑半球。结论:本研究设计的汉字字形刺激源结合功能磁共振成像技术可以对汉字处理的相关大脑皮层区域进行定位,为研究人脑加工处理汉字的神经机制提供了一种有效的无创性影像学方法,并应用fMRI技术进一步证实其优势半球为左半球,且需要多种脑区共同参与完成。本试验模式可望成为一种对语言障碍病人进行脑功能检查的有效手段,从而为指导临床治疗和评价预后提供更丰富的信息。

Objective： To investigate the validity of the stimuli about Chinese character forms in the functional localization of cerebral areas that response to Chinese characters recognition; to locate these cerebral areas and make a preliminary quantitative analysis on their properties. Methods： Ten healthy right-handed Chinese University Students （six males and four females ） participated in the study. All participants underwent an ophthalmological examination and no abno.rmality was found in vision. Informed consent was obtained prior to the fMRI experiment. Block design was used in this study. The trial consisted of 6 blocks and each block lasted 32 s. There were 16 characters during every stimulus time, and every character was visually presented for ls. The stimulation words were grouped into three types： true words, pseudo-words, and no-words. During the stimulation time, the subjects were asked to maintain fixate on the center of the screen and identify which type of the three the Chinese characters belong to. The data were analyzed by AFNI to generate brain activation maps. Results： The fMRI experiment indicated that the stimuli of Chinese true word activated left super and middle frontal gyrus, inferior frontal gyrus （Broca＇s area） ,left precentral gyrus（BA6 ）, left superior parietal lobule and inferior parietal lobule, and bilateral occipital gyrus as well as the precuneus, The left fusiform gyrus （BA37）, right inferior frontal gyrus, bilateral superior and inferior temporal gyrus, and bilateral cingulated gyrus were also notably activated. It was showed that the activation volume in left hemisphere of Chinese true-word was larger than that in the right hemisphere. Conclusions： The findings in single character Chinese words processing associated with orthography showed that the experimental stimulus can be used to locate the cerebral areas that response to Chinese characters recognition. The experimental design combining with fMRI is a feasible and non-invasive imaging method for studying language processing in human brain. The dominant hemisphere of processing languages is in the left. This experimental pattern is expected to be an effective method that can be carried on the brain functional examination for language disorder patients, and then provides more information for the clinical treatment and evaluation of prognosis.