并非所有的誦讀困難者都是完全一樣的。一項(xiàng)新的研究結(jié)果顯示,，講中文和講英文的誦讀困難癥患者,，其大腦受損的區(qū)域是不同的,。這一發(fā)現(xiàn)為搞清產(chǎn)生誦讀困難的神經(jīng)學(xué)機(jī)制帶來了曙光,，同時(shí)揭示了大腦處理兩種語言的本質(zhì)差別,。
在美國和中國，大約有5%到10%的人患有誦讀困難,。這些人無法將一個(gè)單詞的視覺信號(hào)和聽覺信號(hào)聯(lián)系起來,。在英語中，這種疾病導(dǎo)致了對(duì)組成單詞的字母的曲解或變調(diào),。例如,，誦讀困難者會(huì)將“Dyslexia”讀成“Lysdexia”。而在中文中,，這種疾病會(huì)影響一個(gè)人將文字轉(zhuǎn)化為聲音的能力以及對(duì)文字含義的理解,。對(duì)患有閱讀障礙的中國兒童進(jìn)行的大腦成像研究顯示，與英文的閱讀和書寫相比,，這些功能是由大腦的不同區(qū)域所控制的,。
如今，一個(gè)由中國香港大學(xué)的Li-Hai Tan領(lǐng)導(dǎo)的研究小組發(fā)現(xiàn),，講英語和說中文的人的大腦功能的不同源自于大腦的解剖學(xué)差異,。研究小組使用了一種形態(tài)測量學(xué)分析方法，從而得到了16名患有誦讀困難的北京學(xué)童的精細(xì)三維腦測量結(jié)果,。隨后,，研究人員將這些結(jié)果與16名正常中國人的相關(guān)測量結(jié)果進(jìn)行了對(duì)比。數(shù)據(jù)顯示,，盡管這兩組受試者的灰質(zhì)——與高級(jí)認(rèn)知功能有關(guān)的大腦物質(zhì)——體積并沒有差異，但誦讀困難者左額中回——識(shí)別圖像和形狀以及喚醒記憶的重要大腦區(qū)域——的灰質(zhì)卻明顯少得多,。與之形成對(duì)照的是,，根據(jù)另一個(gè)研究小組在2007年得到的結(jié)果，英語誦讀困難者大腦左頂葉的灰質(zhì)有減少跡象,。這一區(qū)域更多的是參與將字母符號(hào)轉(zhuǎn)化為語音的工作而非對(duì)其形狀的解析,。Tan表示：“這一發(fā)現(xiàn)非常令人吃驚。”他的研究小組在本周的美國《國家科學(xué)院院刊》網(wǎng)絡(luò)版上報(bào)告了這一研究成果,。Tan說：“我們從未想過,，在兩種文化背景下，誦讀困難患兒的大腦結(jié)構(gòu)也出現(xiàn)了差異,。”
美國劍橋市麻省理工學(xué)院(MIT)的神經(jīng)心理學(xué)家Robert Desimone指出,，中文和英文巨大的本質(zhì)差異使得這一發(fā)現(xiàn)具有重要意義。作為中文載體的漢字主要依賴復(fù)雜的圖形表達(dá)全部的含義,，而英文則是一種字母語言,，它更多地憑借規(guī)律而非圖像識(shí)別和記憶,。曾參與英語誦讀困難研究的MIT認(rèn)知心理學(xué)家John Gabrieli強(qiáng)調(diào)，如今,，隨著大腦解剖學(xué)差異的揭示,，科學(xué)家朝著“搞清誦讀困難的發(fā)病機(jī)制又邁出了一步”。
Gabrieli說,，如果你對(duì)于一種語言存在誦讀困難,，那么另一種語言是否也會(huì)讓你感到無所適從呢？這確實(shí)是“一個(gè)很吸引人的問題”,。但Tan對(duì)此表示懷疑,，他說自己的研究小組相信，“不同的基因可能與中文和英文的誦讀困難有關(guān)”,。
生物谷推薦原始出處：
（PNAS）,，doi：10.1073/pnas.0801750105，Wai Ting Siok,，Li Hai Tan
A structural–functional basis for dyslexia in the cortex of Chinese readers
Wai Ting Siok,, Zhendong Niu, Zhen Jin¶, Charles A. Perfetti||, and Li Hai Tan,,
Department of Linguistics and State Key Laboratory of Brain and Cognitive Sciences, University of Hong Kong, Pokfulam Road, Hong Kong; College of Computer Science and Technology, Beijing Institute of Technology, Beijing 100081, China; ¶Beijing 306 Hospital, Beijing 100101, China; and ||Learning Research and Development Center, University of Pittsburgh, Pittsburgh, PA 15260
Communicated by Robert Desimone, Massachusetts Institute of Technology, Cambridge, MA, February 25, 2008 (received for review January 1, 2008)
Abstract
Developmental dyslexia is a neurobiologically based disorder that affects 5–17% of school children and is characterized by a severe impairment in reading skill acquisition. For readers of alphabetic (e.g., English) languages, recent neuroimaging studies have demonstrated that dyslexia is associated with weak reading-related activity in left temporoparietal and occipitotemporal regions, and this activity difference may reflect reductions in gray matter volume in these areas. Here, we find different structural and functional abnormalities in dyslexic readers of Chinese, a nonalphabetic language. Compared with normally developing controls, children with impaired reading in logographic Chinese exhibited reduced gray matter volume in a left middle frontal gyrus region previously shown to be important for Chinese reading and writing. Using functional MRI to study language-related activation of cortical regions in dyslexics, we found reduced activation in this same left middle frontal gyrus region in Chinese dyslexics versus controls, and there was a significant correlation between gray matter volume and activation in the language task in this same area. By contrast, Chinese dyslexics did not show functional or structural (i.e., volumetric gray matter) differences from normal subjects in the more posterior brain systems that have been shown to be abnormal in alphabetic-language dyslexics. The results suggest that the structural and functional basis for dyslexia varies between alphabetic and nonalphabetic languages.
