閱讀障礙兒童大腦形態學的發現

Brain Morphology in Dyslexic Children

孟令夫(Ling-Fu Meng) ； 洪儷瑜(Li-Yu Hung)

《中華民國復健醫學會雜誌》 28卷3期 (2000/09) Pp. 125-137

摘要

本文關心兒童階段閱讀障礙與大腦形態學的關連性，藉由分析電腦斷層與核磁共振影像的發現以瞭解閱讀障礙學童的大腦形態學與普通學童的差異。從僅有少數文獻的研究結果顯示出閱讀障礙學童的大腦有以下五種特質，分別為(1)閱讀障礙學童的胼胝體膝部較小，(2)有閱讀障礙家族史的學童胼胝體傾向較厚較大，(3)閱讀障礙學童的大腦側化傾向與普通兒童有不一致的現象，(4)閱讀障礙學童後方區域左側SSTL、左顳葉表面積、或左腦總體積傾向較小，(5)右腦島寬度、左腦島寬度、右額葉寬度、左額葉寬度、右顳平面寬度、左顳平面寬度等六種形態學指標可用於區辨閱讀障礙學童與其他學童，當加入年齡與智力時將使區辨更為準確。
研究者推論胼胝體膝部較小反映出閱讀障礙學童的腦傷可能性；胼胝體較厚可能與左右兩大腦溝通互動的問題有關連；左右大腦比一般學童較為對稱導致側化行為不明顯；左腦部分區域面積或顳葉體積較小則是產生閱讀問題的相關因素。以上形態學的發現對於瞭解生物學基礎與閱讀障礙的相關性有很大的幫助，同時也補強神經行為理論與閱讀障礙關連性的證據。

關鍵字

學習障礙 ； 閱讀障礙 ； 大腦結構學 ； 神經影像學

並列摘要

This article concerns the correlation between children with dyslexia and brain morphology. Computed tomography (CT) and magnetic resonance imaging (MRI) studies suggest that five major differences exist between dyslexic and typical children. Primarily, the genu of the corpus callosum is significant smaller in dyslexic children. Secondly, the corpus callosum in dyslexic children with family history is larger and thicker. Thirdly, dyslexics demonstrate more deviations from normal patterns of left and right hemisphere asymmetry. Fourthly, posterior superior surface of temporal lobe, planum temporal surface area and brain volume in left brain are smaller in dyslexics. Finally, six brain regions account for at least 60% percentage of the variance while discriminating dyslexia and other groups.
The smaller genu of the corpus callosum reflects that brain damage might exist in dyslexia children. The thicker corpus callosum might imply the limited interaction between left and right hemis-phere. Symmetrical morphology between left and right hemisphere might result in poor lateralized behavior. Smaller areas or volumes in some regions of left brain in dyslexics might correlate to lang-uage limitations. The findings from CT and MRI studies are helpful to tell the relation between dyslexia and brain morphology. It also enhances neurobehavioral theories while addressing behavioral corre-lates of dyslexia and neurological basis.

並列關鍵字

learning disabilities ； reading disabilities ； brain architecture ； neuroimaging studies