Objective: To investigate the working mechanism of the conflict processing system for dual-attribute conflict under different attentive conditions. Methods : Event-related potentials ( ERPs ) were recorded in 15 subjects while they were performing a dual-attribute matching task. Visual stimulus spots were sequentially presented in pair, which were of four categories: ①C - P - , color same, position same; ② C - P+ , color same,position different; ③C + P - , color different, position same; ④C + P + . color different, position differenL Participants were instructed to discriminate whether the attributes of the first stimulus ( S1) were the same as those of the second one ( S2) in pair in two different sessions according to different attention instructions: attending to color ( Ac) and attending to position ( Ap) . Four conditions, match , task-irrelevant conflict. task-relevant conflict, conjunction conflicts were included. Results : In the time window of 201 ～ 350 ms after the onset of S2 , an ERP component N270 . was elicited in all the conflict conditions with the amplitude enhanced in the taskrelevant mismatch. The amplitude of N270 in the conjunction mismatch condition was lower than that of the taskrelevant mismatch condition in Ac or Ap session. The N270 amplitude of the task-relevant condition was equal to that of the summation of the task-irrelevant and the conjunction conditions. Conclusion: The decrement of N270 may reflect an active suppression for the processing of the irrelevant conflict under top-down inhibitory modulation.%目的:采用事件相关电位的方法,研究包含颜色和位置两种物理特征的视觉冲突信息进入大脑后,人脑冲突处理系统的工作机制以及注意系统对该系统的影响.方法:15名健康志愿者参与试验.视觉刺激为同时具有颜色和位置两种特征的圆点图片.先后呈现的两张图片(S1和S2)组成一个刺激对.3种颜色(红、黄、兰)和3种位置(屏幕中央点、水平轴上左右各距中央点100mm的两点)随机组成4种类型的刺激对,即,①S1和S2的颜色、位置均相同;②S1和S2的颜色相同,位置不同;③S1和S2的颜色不同,位置相同;④S1和S2的颜色、位置均不同.实验分为两部分,①受试者只需注意颜色特征,即判断S1和S2的颜色是否相同,并做出相应的按键反应,不管位置如何.②受试者只需注意位置特征,即判断S1和S2的位置是否相同,并做出相应的按键反应,不管颜色如何.将刺激对类型与两个任务结合起来,归纳为4种状态:匹配状态、注意无关冲突状态、注意相关冲突状态和双冲突状态.结果:注意单一特征时注意无关冲突状态、注意相关冲突状态和双冲突状态均可引出N270,注意相关冲突状态的N270波幅最高,双冲突状态引出的N270波幅高于注意无关冲突状态,且注意相关冲突状态的N270波幅等于双冲突状态和注意无关冲突状态的N270波幅之和.结论:注意单一特征时双冲突状态的N270波幅减低可能反映了注意对冲突处理系统自上而下的抑制性调节.
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