アルツハイマー型認知症患者における言語流暢性と意味処理の関連性の検討

The relationship between verbal fluency and semantic processing in patients with Alzheimer Type Dementia

　アルツハイマー型認知症(Alzheimer-type dementia：ATD)の言語流暢性課題(VFT)と意味処理障害との関連性について検討した．対象は，軽度〜中等度のATD患者15名と，対照群として健常高齢者15名であった．方法は，カテゴリ流暢性課題(CFT)と音韻流暢性課題(LFT)，意味処理検査として呼称検査，語の聴覚的理解検査，意味判断検査を作成し実施した．その結果，ATD群は対照群よりCFT，LFTともに想起語数が有意に低下し，CFTとLFTの想起語数に差がない成績パターンを示した．またATD群は，いずれの意味処理検査でも成績が低下し，特にCFTの想起語数との関連を認めた．その一方でCFTの検索初期に想起される語は，対照群と類似し両群とも連想されやすい語から想起する特徴がみられた．以上よりATD患者のVFT成績には，意味処理障害が影響すると考えられた．

　We investigated the relationship between the performance on verbal fluency tasks (VFT) and semantic processing impairment in persons with Alzheimer Type Dementia (ATD). The subjects were 15 patients with mild to moderate ATD and 15 healthy elderly controls. Semantic (category) fluency tasks (CFT), phonemic (letter) fluency tasks (LFT), and semantic processing tests for naming, auditory word comprehension, semantic judgment of words to assess semantic processing were developed and administered. The results show that the ATD group recalled significantly fewer words than the control group in both CFT and LFT, but there was no difference in their scores for CFT and LFT. Also, the ATD group showed a decline in the scores of all semantic processing tasks and the scores were related to the number of words recalled in CFT. In CFT, the ATD group tended to start recall from the words that were similar to those of healthy subjects. From these results, we conclude that semantic processing impairment seems to underlie impaired verbal fluency in ATD patients.