失語症における名詞と動詞の呼称能力の乖離

Verb-noun double dissociation in aphasic naming difficulties

　近年，名詞と動詞の呼称能力に差を示す失語症例が報告されているが，検査語の語彙特性を統制し，厳密に両呼称能力を比較検討した研究は少なく，症例も左大脳半球前方病変例が多い．本研究では名詞と動詞の語彙特性(親密度，動詞の概念構造：項)を統制した呼称検査を作成し，左大脳半球後方病変の失語症例について動詞と名詞の呼称能力の差を検討した．その結果，①名詞より動詞の呼称成績が有意に低い者が3名，その逆の傾向を示す者が2名存在した．②主病変部位は，動詞不良群は左下頭頂小葉，名詞不良群は左側頭葉であった．③語の親密度が呼称正答率および誤反応に及ぼす影響は両群で異なった．結果から，左大脳半球後方病変の失語患者において名詞と動詞の呼称に二重乖離現象を認める症例が存在し，各群の語彙処理における障害特徴および病変部位は異なることが示された．

　Several studies have shown that the retrieval of nouns and verbs can be damaged selectively in aphasics.　Only a few studies have considered lexical-semantic variables.　We administered a confrontation naming task for nouns and verbs to seven aphasic patients with left posterior lesions.　The lexical variables of familiarity and verb argument structure were controlled in constructing the task.　Three patients were significantly more impaired with verbs, while two patients were more impaired with nouns.　The patients with selective verb impairment had lesions in the left inferior parietal lobule, and those with selective noun impairment had lesions in the left temporal lobe.　The results confirmed the existence of double dissociation for noun/verb naming in aphasic patients with left posterior lesions.　We offer an interpretation of the results in light of current cognitive neuropsychological models of lexical processing.