【作者】 徐琳；

【导师】 许百华；

【作者基本信息】 浙江大学 ， 应用心理学， 2008， 博士

【摘要】 认知控制是指在面对干扰或冲突时,通过促进与任务相关的信息的加工及促进与任务相关的行为,来灵活适应当前需求的能力。它是完成认知活动所必需的高级认知功能,它对注意、抑制、工作记忆、语言加工及评价等认知过程有很大的影响。近年来,采用脑神经科学的手段对认知控制进行研究,探讨大脑如何对分心刺激所带来的冲突进行监控,并作出相应的认知调节以减少冲突的发生已经成为认知研究的一个热点。Stroop任务是认知控制研究的一种常用范式,而在认知控制的脑神经科学研究中计数Stroop任务是一种较为理想的Stroop任务范式。以往Stroop任务的认知控制研究均采用单个分心刺激作为干扰。然而,在认知加工时,人们往往面临多个分心刺激的干扰,在这种条件下的认知控制是否与呈现单个分心刺激时的认知控制具有相同的功能特点与神经机制?这个问题还有待商榷。本研究采用ERP技术系统地考察了在呈现多个分心刺激的计数Stroop任务中认知控制的功能特点及其神经机制。研究总共包含三组实验,每组实验各包含了两个小实验,分别采用两种不同的研究范式探讨了在计数Stroop任务中,呈现多个数字或汉字分心刺激时认知控制的功能特点及其脑神经机制,同时重点考察了在这些条件下认知控制的评价与执行两种成分的时间进程及脑区分布。本研究的主要结果如下:(1) Stroop效应是一种非常稳定的现象,并可以有效地反映认知控制的变化。认知控制对冲突的调节作用受到分心刺激的个数和类型、刺激材料、冲突背景、刺激类型等多种因素的影响。(2)改变刺激类型的比例以及改变前后两个相邻试次的刺激类型这两种研究范式都能有效反映认知控制对冲突的监控作用。与改变前后两个相邻试次的刺激类型相比,在改变刺激类型的比例这种研究范式下认知控制能够更有效地对冲突进行调节,在不一致试次比例较高的情况下,认知控制能够有效地减小冲突。(3)当呈现多个分心刺激时,改变刺激类型的比例与改变前后试次刺激类型这两种研究范式都能够有效区分认知控制的评价和执行两种成分,但这两种研究范式所区分出的成分涉及不同的神经机制。改变刺激类型的比例所区分出的执行成分包含了情节控制与感觉控制两种子成分,而在改变前后试次刺激类型时则包含了执行控制中情境控制与感觉控制两种子成分。(4)在计数Stroop任务中,汉字干扰比数字干扰耗费更多的认知资源,并对计数过程产生了较大的影响,从而使得执行控制过程无法得到足够的认知资源,减弱了认知控制。(5)在呈现多个分心刺激的计数Stroop任务中,在400-500ms时间窗口出现了N450和P450。N450主要分布在中线区,P450主要分布在额外侧区,反映了认知监控的过程;在600-800ms时间窗口出现SP波,主要分布在左颞顶区,与意义的复核有关。(6)在计数Stroop任务中,呈现多个分心刺激与呈现单个分心刺激的条件相比,两种条件下认知控制的两种成分的时间进程及其头皮分布存在相同与不同之处。呈现多个分心刺激条件下的认知监控的神经机制与呈现单个分心刺激条件下认知监控的神经机制相同,即出现了中线区的N450和额外侧区的P450。而与呈现单个分心刺激条件不同的是,在呈现多个分心刺激条件下认知控制的冲突解决是一个连续变化的过程,它由执行成分的情节控制、情境控制、感觉控制三个子成分在不同的时间段共同完成。其中在300-390ms,情节控制对知觉评价过程进行调节,减少知觉冲突,其头皮分布主要在颞顶区域;从400ms开始情境控制对冲突监控进行调节,加强对冲突的监控,该过程可一直延续到600-800ms,其头皮分布较为广泛,主要分布在中线区;在600-800ms感觉控制对反应冲突进行调节,最终完成运动反应,其头皮分布主要在中线区。更多还原

【Abstract】 Cognitive control refers to the ability to flexibly adapt behavior to current demands by promoting task-relevant information in the face of interference or competition. This ability is central to most higher cognitive functions, including attention, inhibition, working memory, language process and evaluation, etc. Recent years have seen an explosion of research on cognitive control by using neuroscience technique. Many of these researches have examined the functions of cognitive control in monitoring and resolving conflict in the presence of distractor stimuli.On the other hand, Stroop task has been widely used in the researches of cognitive control, while counting Stroop task is an ideal paradigm used in the neuroscience researches on cognitive control. Previous studies only used single distractor stimulus in the Stroop task. However, people usually face multiple distractor stimuli during the cognitive process. It is still an open question whether the functional characteristics and neural mechanism of cognitive control in the context of multiple distractor stimuli would be the same as that in single distractor stimulus.This study aimed to systematically explore the functional characteristics and neural mechanism of cognitive control in counting Stroop task with multiple distractor stimuli by using ERP technique. Three groups of experiments were designed in this study, and each of them consisted of two sub-experiments, which used a different research paradigm. In these experiments, the functional characteristics and neural mechanism of cognitive control in counting Stroop task with multiple distractor stimuli were explored by using digits or Chinese characters as distractor stimuli. For the two distinct components of cognitive control, i.e. the evaluative and executive components, the time course and distribution of them were detailedly analyzed and discussed.The main conclusions of this study are summarized as follows:(1) Stroop effect is a robust phenomenon, which could sensitively reflect adaptive changes in cognitive control. The regulation of cognitive control was influenced by many factors, such as the number and type of distractors, material of stimuli, context of conflict, stimulus type, etc.(2) Cognitive monitoring function could be observed in the two experimental paradigms of cognitive control. Compared to the condition in which the previous and current trials were manipulated, cognitive control could adjust the conflict much more effectively when the proportion of congruent and incongruent trials was varied between blocks of trials. When incongruent trials appeared frequently, the conflict could be dramatically reduced by cognitive control.(3) In the condition of multiple distractor stimuli, the evaluative and executive components could be separated in both of experimental paradigms. However, the sub-components separated in the two kinds of experimental paradigms were associated with the different neural mechanisms. When the proportion of congruent and incongruent trials was varied between blocks of trials, the executive components consisted of episodic control and sensory control components. However, when the previous and current trials were manipulated, the executive components consisted of contextual control and sensory control.(4) Chinese character distractors consumed more cognitive resources than digit distractors in counting Stroop task, and they had more significant influences on counting process. As a result, when Chinese character distractors were presented, cognitive control was impaired by cognitive resource limitation during cognitive executive process.(5) In counting Stroop task with multiple distractor stimuli, N450 and P450, which could be used to reflect conflict detection, had been found in the 400-500 ms time window. N450 distributed mainly on fronto-central region and P450 distributed mainly on lateral fronto-polar region. SP wave, which was considered to be associated with additional meaning analysis, had been found in the 600-800 ms time window, and it distributed mainly on left temporo-parietal areas.(6) In counting Stroop task, the neural mechanism of conflict monitoring in the context of multiple distractor stimuli was the same as that in single distractor case, and Stroop N450 were found at midline sites reversing polarity over the lateral frontal regions under both of these contexts. But the conflict resolution of cognitive control in multiple distractors situation was a longer-lasting continuous process, which was different from that in the single distractor situation. This process consisted of three sub-components of executive function, i.e. episodic control, context control and sensory control. Each of them respectively executed the conflict resolution in different periods. Specifically, episodic control reduced perceptual conflict at 300-390ms over the temporo-parietal regions; context control reinforced conflict monitoring and it started with 400ms and could lasted around 600-800ms; and sensory control regulated response conflict and completed motor response selection at 600-800ms over the midline sites.更多还原