分裂病の認知・行動と事象関連電位のP300成分（Ⅱ）—反応行動の遅さの成因

Cognitive and Behavioral Deficits and P300 Components of Event-Related Potentials in Schizophrenia (Ⅱ): Mechanisms of slow response-behaviors

　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「三音弁別課題」遂行時の事象関連電位のP300成分の振幅・潜時と反応時間を測定し，両者の関連の特徴をまとめ2部に分けて報告した。本稿はその第II部である。第I部の報告に加え，本稿では適応型相関フィルタを用いて解析して得た次の特徴を報告した。（1）分裂病患者群では目標音に正しく反応した場合でもP300成分の振幅が低いことが多く，またP300潜時のバラツキも大きかった。このことから刺激評価機能の機能的不安定性が示唆された。（2）患者群では反応すべき目標音が増加しても目標音に対するP300潜時は変化せず，不利な課題遂行方略を採用していることが再確認された。（3）患者群ではP300潜時と反応時間の相関が低く，刺激評価過程と反応組織化過程の結合がゆるいと考えられた。（4）患者群では反応すべき目標音が増加すると反応時間の延長が明らかで反応組織化の遅さが認められた。

　This paper is a continuation of our previous article which focused on schizophrenic deficits in cognition and behavior in terms of the relation-ship between P300s and reaction times during threetone discrimination tasks. Further information reported here is based on the analysis of P300 data using an adaptive correlating filter. (1) Schizophrenics produced lower amplitudes of P300s as compared to normals, though they detected the targets correctly. Schizophrenics also displayed greater variation in P300 latencies. These results suggested an instability of the stimulus-evaluating function in schizophrenics. (2) An increase in the number of target types did not affect P300 latencies in schizophrenics, as opposed to normals, confirming our previous speculation that schizophrenics employed disadvantageous task-performing strategies. (3) The correlation coefficients between P300 latencies and reaction times were lower in schizophrenics. which suggested a loose coupling between the stimulus-evaluating process and response-organizing process. (4) An increase in the number of target types markedly delayed schizophrenic reaction times, implying a slowness in the response-organizing process.