自閉症青少年社交障礙與語意處理之交互影響機制

Abstract

目的：根據精神疾病診斷統計手冊第五版(DSM-Ⅴ)，自閉症患者在臨床上兩大核心症狀為社交溝通及社會互動障礙、與重複性刻版行為。自閉症患者在溝通的障礙之一來自於字義的理解策略與一般人不同，然而自閉症青少年患者的社交障礙與語意處理之交互影響機制，卻鮮少研究進行深入的探討。本研究以中文語意判斷作業進行行為實驗與功能性磁振造影(Functional magnetic resonance imaging, fMRI)實驗，探討9-18歲自閉青少年患者，相較於正常發展青少年，其社交障礙與語意處理之交互影響機制。方法：利用自閉症診斷會談問卷（Autism Diagnosis Interview-Revised, ADI-R）中社交障礙的嚴重程度，將自閉症患者區分為輕度社交障礙（mild social deficits group）與重度社交障礙組（severe social deficits group）。在語意判斷作業中，實驗參與者判斷視覺呈現的中文字對是否具有語意關係。結果：腦造影的結果顯示，相較於正常發展組青少年，兩組自閉症青少年在處理語意相關字對時，左腦半球的腦島前區（left anterior insula cortex, BA 13）、額下迴（left inferior frontal gyrus, BA 47）、及顳葉顳中迴（left middle temporal gyrus, BA 21）活化較少。此外，隨著社交反應量表（social responsiveness scale, SRS）中，社交障礙的嚴重程度越高，這些腦區的活化則越少。相反地，相較於正常發展組青少年，重度社交障礙自閉症組在處理語意相關字對時，在視覺區（cuneus, BA 18）有較多的活化。此外，將兩組自閉症青少年合併，發現其視覺區的活化程度與圖畫補充測驗（picture completion）的分數成正相關。結論：自閉症青少年社交障礙與語意處理之交互影響機制，具有下列意涵。一、自閉症青少年社交障礙嚴重程度與左腦半球的腦島前區、額下迴、顳葉顳中迴的活化程度成負相關，推論自閉症青少年隨著社交障礙程度愈高，其在進行語意處理時，愈少仰賴語意資訊且愈難整合所有資訊。二、自閉症青少年其圖畫補充測驗的分數與視覺區活化程度呈正相關，推論自閉症青少年無論社交障礙嚴重程度的多寡，都傾向於仰賴視覺字型的資訊幫助他們進行語意處理。

Introduction：Social-communication is one of the core symptoms in the DSM-5 diagnostic criteria for autism spectrum disorder (ASD). One of the characteristics of communication deficits in ASD is impaired comprehension. However, little is known about the involvement of social deficits on semantic processing in ASD. This study aims to explore the neural substrates of interaction between social ability and semantic processing in youths with ASD as compared to typically developing youths. Methods：Functional magnetic resonance imaging was used to assess 55 youths with ASD (age range: 9-18) and 29 typically developing youths (age mean = 12.48, SD = 2.75). The ASD group was divided into the mild (n = 27, age mean = 13.09, SD = 2.23) and severe (n = 28, age mean = 13.85, SD = 2.65) groups according to their current scores of the reciprocal social interaction on the Autism Diagnostic Interview-Revised. The three groups were matched in age, gender, IQ, and handedness. Participants were asked to judge if two Chinese characters were related in meaning, and the brain activations between groups were compared. Additionally, the magnitudes of brain activations were correlated with the Social Responsiveness Scale (SRS) and the picture completion scores. Results：Compared to typically developing youths, both ASD groups showed reduced activations in left anterior insula cortex (AIC), inferior frontal gyrus (IFG), and middle temporal gyrus (MTG). There were negative correlations between AIC/IFG/MTG activations and SRS scores across groups. In contrast, the severe ASD group showed greater activations in left cuneus relative to the typically developing group. There was a positive correlation between the intensity of cuneus activation and the score of picture completion across mild and severe ASD groups. Conclusion：Our findings imply an association between social deficits and impaired semantic processing in youths with ASD. Reduced activations in the AIC、IFG and MTG associated with the severity of social deficits in youths with ASD highlight their difficulty in integrating social information with meaning and their decreased reliance on semantic information, respectively, as compared to typically developing youths. Our finding of a positive correlation between left cuneus activation and the score of picture completion across ASD groups suggests that regardless of severity of social deficits they tend to rely more on lower-level visual information to process Chinese characters.