中文成人語意處理的腦區間的交互影響

Interaction Between Brain Regions During Semantic Processing in Chinese Adults

本研究利用功能性磁振造影 (fMRI) 及動態因果推論模型 (DCM)，探討中文語意處理的神經機制，並計算不同腦區之間的動態連結。中文成人需要判斷以視覺呈現的中文字對在意義上是否相關。本實驗採用兩種刺激字對，分別是語意相關組與語意無關組。在行為表現上，語意相關組的反應時間顯著地快於無關組。在功能性磁振造影結果，針對語意相關組與對照組的差異得到較大的活化區，分別位於左腦下額葉 (IFG, BA 45, 47)，左腦中顳葉(MTG, BA 21) 及左腦梭狀回 (FG, BA 37)；而針對語意相關組與無關組的差異，得到較大的活化區在左腦下頂葉 (IPL, BA 39, 40)。在動態因果推論模型推論出的有效性連結，發現從左腦下額葉到左腦中顳葉的顯著調節效果(modulatory effects)，推論為左下額葉負責從上到下提取語意表徵的歷程。同時，從左腦中顳葉到左腦下額葉的顯著調節效果，推論左腦中顳葉負責提供語意記憶中相關的表徵聯結，協助左下額葉進行提取。最後，從左腦梭狀回到左腦中顳葉的顯著調節效果，推論左梭狀回將字形訊息藉由從下到上的歷程，傳送至左腦中顳葉處理語意表徵訊息。本研究的結果顯示成人進行中文語意處理的腦區間的動態交互作用。

Using functional magnetic resonance imaging (fMRI) and dynamic causal modeling (DCM) methods, we investigated the neural correlates of meaning processing in different brain regions and calculated the inter-connection among these regions during semantic judgments to visual Chinese characters. Twentyfive healthy Chinese adults were asked to indicate if character pairs were related in meaning. Experimental stimuli were character pairs that included semanticallyrelated and semantically-unrelated pairs. The behavioral results showed that reaction times were significantly faster for the related condition than the unrelated condition. fMRI analyses showed greater activation in left inferior frontal gyrus (IFG, BA 45, 47), left posterior middle temporal gyrus (MTG, BA 21) and left fusiform gyrus (FG, BA 37) for the related versus baseline condition, and in left inferior parietal lobule (IPL, BA 39, 40) for the related versus unrelated condition. Effective connectivity from DCM analyses showed modulatory effects from left inferior frontal gyrus to left posterior middle temporal gyrus, suggesting top-down influences of the frontal cortex on retrieval of semantic representations. Effective connectivity analyses also showed modulatory effects from left posterior middle temporal gyrus to left inferior frontal gyrus, suggesting the role of MTG on providing relevant associations in verbal semantic memory for IFG to perform retrieval. We also found significant modulatory effects from left fusiform gyrus to left posterior middle temporal gyrus, suggesting bottom-up orthographic influences on semantic representations. These findings suggest dynamic interaction between brain regions during semantic processing to written characters in Chinese adults.