中英雙語孩童構詞處理上神經機制的發展變化

Abstract

本縱貫研究旨在探討長期雙語經驗對於孩童構詞處理上的影響。由於大腦較常使用腹側迴路處理中文詞彙，並且使用背側迴路來處理英文詞彙，中英雙語孩童便可能因為語言轉移和互動歷程的影響，發展出獨特的神經運作模式。再者，孩童於7歲時開始使用顳葉和額葉來處理語言，9歲時能夠更精確地使用這些腦區，故縱貫研究提供進一步檢視跨語言轉移及互動歷程，理解對於雙語孩童腦部發展的影響。本研究招募6-7歲孩童受試者，41位中英雙語孩童和27位中文單語孩童，來進行構詞判斷作業，並且同時使用功能性近紅外光譜來測量腦部活化。進行構詞判斷作業時，孩童受試者聽見三個連續播放的詞彙，需要選擇和目標詞彙擁有相同構詞結構的字詞。接著雙語組孩童接受兩年的雙語教育，單語組孩童則少量接觸英文。兩年後，兩組孩童於8-9歲時，再次進行構詞判斷作業。腦造影的結果顯示，相較於處理英文詞彙，雙語孩童使用更多左腦背側額下回和左腦頂下小葉來處理中文詞彙。此外，和單語組孩童相比，雙語組孩童使用更多左腦背側額下回和左腦顳上回來處理中文詞彙。整體而言，研究發現雙語孩童使用更多背側迴路來處理中文詞彙，呈現中英語言轉移和互動歷程的影響，故長期中英雙語經驗將使得孩童發展出獨特的神經運作模式來進行閱讀和處理語言。

This longitudinal research aims to investigate the long-term influence of bilingualism on children’s morphological processing. Since the brain utilizes the ventral pathway to process Chinese words and the dorsal pathway to process English words, bilingual children may develop unique neural patterns for language transfer and interaction effects. Moreover, children begin to learn reading with a specialization in the temporal and frontal lobes at the age of 7 and utilize more specific brain regions by the age of 9. Thus, it is crucial to conduct longitudinal research to discover the transfer and interaction effects across languages in bilinguals’ brains. We recruited 6-7 years old children, 41 Chinese-English bilinguals and 27 Chinese monolinguals, to conduct a morphological judgment task, using fNIRS (functional near-infrared spectroscopy). The subjects heard three words and decided which word shared the same compound root or derivational affix as the first word. After 2 years of bilingual education for bilinguals, both groups conducted the task again at 8-9 years old. The neuroimaging results showed that bilingual children developed the left dorsal inferior frontal gyrus and the left inferior parietal lobule to process Chinese compared to English. Furthermore, the bilingual group recruited more of the left dorsal inferior frontal gyrus and the left superior temporal gyrus when processing Chinese than monolinguals. Overall, the findings revealed the English-to-Chinese transfer effects and interactive language effects, as the dorsal pathway was more activated in the process of Chinese in bilingual children. Young bilinguals may develop distinctive neural patterns for reading due to the long-term effect of bilingualism.