文字属性・単語属性に基づく書字障害の検討—送り仮名を伴う読みを提示した際に熟語を想起して正答した頭頂葉性純粋失書の一例

Considering writing disorder from the viewpoint of word- and character-level attributes:A case of pure agraphia due to a left parietal lobe hemorrhage who recalled two-kanji compound words in a conjugational word dictation task

　音声言語の理解と表出，仮名の読み書き，漢字の読みは保たれていたが，漢字書字において文字形態想起困難に伴う書字障害を呈した左頭頂葉皮質下出血例に対し，送り仮名を伴う訓読みを音声提示した漢字の書取課題を実施した．約9割は音声提示のみで正答したが，対象漢字を用いた熟語を自ら想起した後に正答したり，検者からの音読みの音声提示により正答する反応を認めた．対象漢字の文字属性や訓読みでの単語属性，症例自身が想起した熟語の単語属性の検討により，反応群間で単語属性や文字属性の違いがあることが示され，対象漢字を用いた熟語を想起して正答した刺激では，対象漢字の音読み比率が高く，音声提示された訓読みよりも親密度が高い熟語を想起していたことで熟語を手がかりに正答に至ったと考えられた．一方，音読みの音声提示により正答した刺激では，他に比べ画数が多く，対象漢字の画数が文字表象の活性度の上昇に繋がらなかったと推測される．

　A patient with a left parietal subcortical hemorrhage exhibited character imagery deficiency with relatively good performance in word production, spoken word comprehension, kana reading and writing, and kanji reading comprehension. To examine the underlying psycholinguistic factors, the patient was asked to perform a kanji dictation task with an auditory presentation of conjugational kun reading. Three types of correct response were observed：(A) correct responses after auditory stimuli ; (B) correct responses after the patient recalled two-kanji compound words herself ; and (C) correct responses after being presented with the on reading from a therapist. We examined and compared the character-level and word-level attributes in (A) with those in (B) and (C). In the results, the on reading ratio of target kanji in (B) was higher than that in (A), and the word familiarity of recalled two-kanji compound words was higher than that of conjugational kun reading words in (B). This suggests that our patient was able to generate the correct answer using the high familiarity kanji compound words that she recalled herself. On the other hand, the number of target kanji strokes in (C) was greater than that in (A). It is presumed that the large number of strokes of the target kanji inhibited the increase in the activity of character representation in this patient. Our analysis revealed various effects of character- and word-level attributes in the patient's writing disorder.