数の統語処理に障害をきたした1例 [in Japanese] A case of impaired syntactic processing of numerals [in Japanese]
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左被殻出血により軽度失語症および数の桁処理に顕著な障害を呈した症例を経験し, その障害特徴および発現機序について数処理過程におけるコード変換機能の観点から検討した。本例では, アラビア数字形式と, 数の日本語形式とのコード変換課題において, 桁がずれる誤りが頻繁にみられ, 個々の数字の処理との間に乖離を示したことから, 数の統語処理的側面が障害を受けた例と思われた。数の両形式間の変換処理には, 双方向ともに桁という空間的表象への定位が必要であり, 本症例の数の統語処理障害には, 内的な空間的表象の操作機能の低下が関係していると考えられた。
We report a case who frequently misplaced digits in reading or writing tasks involving numerals, and discuss his numeral processing. The case was a 58-year-old, left-handed male who suffered from right hemiplegia, mild Broca aphasia and visual-spatial perception disabilities after a left putaminal hemorrhage. Numerals have two codes : one the Arabic code using Arabic numerals, and the other a verbal code which corresponds to reading out aloud. Most numeral processing tasks entail transcoding between the two codes. The patient's basic knowledge of numerals was intact, but he commonly erred in transcoding tasks : for example, he read aloud “ three hundred forty ” for “ 34 ”, and wrote “ 2105 ” when hearing “ two hundred fifteen ”. However, there was rarely any paralexia or paragraphia for digits, which confirms the dissociation of his two processing systems. In recent research on cognitive mechanisms of numeral processing, a distinction between lexical and syntactic processing has been proposed. On the basis of that, the patient's performance suggests that his syntactic processing of numerals is impaired. We think that, in both directions, transcoding between the two codes requires orientation to the spatial representation of the decimal system, and in this case we suggest the possibility that his deficits in operations involving internal spatial representation affect his syntactic processing.
- Higher Brain Function Research
Higher Brain Function Research 24(1), 11-20, 2004-03-31
Japan Society for Higher Brain Dysfunction