上下文加工的任务概率效应:事件相关电位时空模式分析

目的利用AX型连续操作测试(AX-CPT)和事件相关电位(ERP)时空模式探讨上下文加工的任务概率效应及其脑机制。方法在AX-CPT任务中,18名大学生仅要求针对反应线索A后的反应探针X按键,而对抑制线索B后的各类探针X或Y均不反应。设立3组互补的AX型/AY型任务概率:0.55/0.15,0.35/0.35,0.15/0.55;保持BX型和BY型任务概率恒定,均为0.15。行为绩效和ERP数据分别采用单因素重复测量方差分析。结果反应线索A概率愈高,AX型反应愈快且BX型虚警愈多。ERP的F值统计参数映像显示概率效应显著脑区和时段分别是:线索A:顶中央区(300~350 ms)与左枕区(450~500 ms);线索B:右前额(350~500 ms)和左前额(750~950 ms)。AX型探针:右额顶(200~250 ms)、左额极、右背前额及双顶区(300~400 ms)和双顶枕区(400~650 ms);AY型探针:额中央区(350~500 ms)-P3效应;BX型探针:右颞区及左枕区(300~350 ms);BY型探针:左颞区(150~250 ms)。结论任务概率不仅影响反应型线索编码和抑制型线索期待,而且分别调节了四种类型探针加工相关的神经集群。

Effects of task probability on context processing: spatiotemporal analysis of event-related potential

Objective To investigate the effects of task probability on context processing using AX-type continuous performance test(AX-CPT) and event-related potential(ERP).Methods We set 3 groups of complementary probabilities(AX/AY: 0.55/0.15,0.35/0.35,and 0.15/0.55) for AX task and AY task and kept the probability 0.15 for both BX and BY tasks.Eighteen subjects were asked to press the button only when the go-probe(X: green "<<<" or ">>>") followed the go-cue(A: blue "ooo") and withdraw response when the go-probe or a nogo-probe(Y: red "<<<" or ">>>") followed the nogo-cue(B: blue "xxx").Results As the task probability increased,the reaction time of AX task was shortened and the rate of false alarm of BX task increased significantly.The probability effects of ERP revealed by statistical parametric mapping occurred in many regions during both cue and probe stages: cue A in the parietal central(300-350 ms) and the left occipital area(450-500 ms);cue B in the right frontal pole(350-500 ms) and the left frontal pole(750-950 ms);AX probe in the right frontoparietal area(200-250 ms),the left frontal pole,the right dorsal prefrontal and bilateral parietal region(300-400 ms),and the bilateral occipital area and parietal region(400-650 ms);AY probe in the frontocentral area(350-500 ms)-the P3 effect;BX probe in the right temporal and the left occipital areas(300-350 ms);BY probe in the left temporal area(150-250 ms).Conclusions The task probability not only influences both the encoding of go-cue and expectancy of nogo-cue but also modulates the neural assemblies of probe processing differentially.