分裂病の認知・行動と事象関連電位のP300成分（Ⅰ）—課題遂行方略の特徴と組織制御系の機能の問題点

Cognitive and Behavioral Deficits and P300 Components of Event-Related Potentials in Schizophrenia (Ⅰ): Possible problems in taskperforming strategies and organizing-system functioning

　抄録　認知・行動の基本的機構における分裂病の問題点を整理する目的で「検査室場面での課題遂行」の特徴をまとめ2部に分けて報告した。具体的には，「三音弁別課題」遂行時の事象関連電位のP300成分の振幅・潜時と反応時間を，DSM-Ⅲの基準に合致する9名の軽症分裂病男性患者（平均28.2歳）と9名の男性正常対照者（平均28.6歳）について測定した。第Ⅰ部（本稿）では次の特徴を報告した。（1）正常群では高頻度非目標音によっても潜時約400ミリ秒のP300成分がCz優位に出現したが患者群では出現しなかった。これは患者群では課題無関連刺激を文字どおり無視するという不利な方略を採用するためで冗長性利用に問題があると考えられた。（2）患者群では目標音に対する無反応が有意に多かった。無反応時にはP300は出現しないことから，患者群における無反応の増加は反応組織化の失敗ではなく刺激評価の失敗によるものと考えられた。

　Delineation of schizophrenic deficits in the basic mechanisms of cognition and behavior was attempted on the basis of our experimental data, referring to a specially devised model of human cognition and behavior. All results are reported in two serial papers, with the present one being the first. Specifically, P300 components of ERPs along with reaction times were recorded in 9 DSM-Ⅲ schizophrenic male patients with mild symptomatology (mean age, 28.2 years) and 9 male normal controls (mean age, 28.2 years) and 9 male normal controls (mean age, 28.6 years) during threetone discrimination tasks. Analyses of the relationships between amplitudes and latencies of P300s and performance data suggested the following features of cognition and behavior in schizophrenics: (1) Clear P300 components with latencies of approximately 400 msec were elicited predominantly in the Cz region by the frequent non-targets in normals, while these components were not clearly identified in schizophrenics. On the basis of this result, it was suggested that schizophrenics completely ignored task irrelevant stimuli rather than utilizing such redundant information in their taskperforming strategies. (2) Omission errors of targets were significantly greater in schizophrenics. In the case of omission-error trials, P300s were not elicited, suggesting that the increase of omission errors in schizophrenics were due to failures in the stimulus-evaluating process, not in the response-organizing process.