任务优势度影响任务转换的认知神经机制

发布时间：2018-05-05 05:24

本文选题：任务优势度 + 任务转换　；参考：《西南大学》2017年硕士论文

【摘要】：任务转换是个体按照情境线索,从一种任务转向另一种任务的转换加工过程。任务转换体现了个体认知灵活性,是我们生存和适应社会的重要能力。但是个体如何在任务之间发生转换,什么因素会影响个体的任务转换过程?任务转换研究有利于我们更好地理解人类的这种认知灵活性和目标导向行为。在实验室中,常常采用任务转换范式(task switching paradigm)来研究任务转换背后的心理机制。任务转换范式要求被试按照实验要求执行任务,如果当前试次和先前试次的任务类型一致,我们称当前试次为“任务重复”,如果不一致,我们称之为“任务转换”。众多研究发现相比重复任务,个体执行转换任务的反应时更长、正确率更低,研究者将两者之间的差异称为转换代价(switch cost)。任务优势度是指任务自动化加工水平的高低,通常表现为任务间干扰的不对称性。有研究发现转换代价受任务优势度的调节,即劣势任务的转换代价显著小于优势任务的转换代价,也称不对称转换代价(asymmetric switch cost)。Allport最早提出任务设置惯性理论来解释此现象,认为不对称转换代价源于先前试次的持续性抑制作用。但是目前不少研究发现操纵一些变量,如改变任务类型,降低任务间的干扰量等,会出现不对称转换代价的减小、甚至反转。因此目前对于任务优势度影响任务转换的内在机制还存在争议,争议的焦点主要在于不对称转换代价是否由先前任务设置的负启动效应(抑制过程)导致,是否还涉及其他认知控制过程?n-2任务重复代价(n-2 task repetition cost)是任务转换中抑制过程的直接证据,所以本研究基于第n-2个试次的任务类型将任务转换(如任务序列AB)分为交替任务转换(第n-2个试次与第n个试次任务类型相同,BAB)和单任务转换(第n-2个试次的任务类型与第n个试次任务类型不同,AAB),其中交替转换(BAB)是启动先前被抑制的任务设置(克服先前任务设置的负启动效应),代表任务转换的抑制过程,单转换(AAB)是启动一个未被抑制的任务设置(重构过程),代表任务转换的非抑制过程。本研究试图分离任务转换的抑制过程和非抑制过程,分别分析两者在不对称任务转换中的作用。此外我们还借助空间分辨率较高的功能性磁共振(functional magnetic resonance imaging,f MRI)技术,力求从行为和脑机制角度深入探索任务优势度影响任务转换的认知神经机制。本研究包括三部分:实验1主要验证变式stroop刺激的颜色任务和文字任务是否是一对具有不同任务优势度的任务。通过分析任务类型(颜色辨别任务、文字判断任务)和试次一致性的交互作用,检验颜色辨别任务和文字判断任务是不是表现任务干扰的不对称性?结果表明,颜色辨别任务和文字判断任务均存在显著的一致性效应,且颜色辨别任务的一致性效应显著大于文字判断任务的一致性效应,在这里我们可以称颜色辨别任务为劣势任务,文字判断任务为优势任务。基于实验1,实验2采用color-word stroop刺激和线索任务转换范式相结合的方法,探究任务优势度对转换代价的调节效应,并通过分离任务转换的单转换和交替转换过程,考察这两个过程分别在不对称任务转换中的作用。行为结果表明,虽然整体上文字任务的转换代价显著大于颜色任务的转换代价,进一步分析转换代价的成分发现,文字任务的交替转换代价显著大于颜色任务的交替转换代价,而颜色任务的单转换代价显著大于文字任务的单转换代价。实验3采用f MRI技术,验证了实验2的行为结果,同时脑成像结果表明:与任务重复相比,相比交替任务转换显著激活外侧前额叶皮质(lateral prefrontal cortex,LPFC)、前扣带回(anterior cingulate cortex,ACC)和左侧颞下回(inferior temporal gyrus:ITG),说明这些脑区参与了任务转换的抑制控制过程;而单任务转换过程并没有显著激活,说明执行控制网络(双侧额下回bilateral inferior frontal cortex:IFG,左侧顶下小叶left inferior parietal cortex:IPL,双侧颞中回bilateral middle temporal gyrus:MTG)具有基于领域的冲突适应性,转换到新任务设置可能使执行控制网络暂时“瘫痪”而导致行为反应变慢。当进一步考虑不同任务类型的任务转换效应时,发现文字任务的交替转换过程在海马旁回(parahippocampal gyrus)出现激活降低,在壳核(putamen)出现明显激活,文字任务的交替转换代价可能源于从长时记忆检索相关刺激-反应映射的过程受阻,反应冲突增大导致。而颜色任务的单转换过程在相关执行控制网络(脑岛insula,壳核putamen)的“失活”程度明显大于文字任务的单转换过程,表现出颜色任务设置的重构过程要难于文字任务。综上,本文结合行为和脑成像技术说明任务优势度对任务转换的影响不仅体现在抑制过程上(先前任务设置的负启动效应),也体现在非抑制过程上(重构新任务设置),而且这两个过程受到任务优势度不同方向的调节,不对称转换代价由这两者共同决定。
[Abstract]:Task conversion is the process of transformation from one task to another. Task transformation embodies individual cognitive flexibility and is an important ability for us to survive and adapt to society. But how does the individual change between tasks and what factors affect individual task conversion process? Task transformation research It is good for us to better understand the cognitive flexibility and goal oriented behavior of human beings. In the laboratory, the task transformation paradigm (task switching paradigm) is often used to study the psychological mechanism behind the task transformation. The task transformation paradigm requires the trial to perform the task according to the experimental requirements, if the current trial and previous trial tasks are in the task. We call the current trial the "task repetition". If we do not agree, we call it "task conversion". Many studies find that the response of the individual to the task is longer and the correct rate is lower than the repetitive task. The researchers call the difference between the two as the conversion cost (switch cost). Task dominance refers to the task. The level of automatic processing is usually characterized by the asymmetry between tasks. It is found that the conversion cost is regulated by the task dominance, that is, the conversion cost of the disadvantaged task is significantly less than the conversion cost of the dominant task. It is also known as the asymmetric conversion cost (asymmetric switch cost).Allport first proposed the task setting inertia theory To explain this phenomenon, it is considered that the cost of asymmetric conversion is derived from the persistent inhibition effect of previous trials. However, many studies have found that manipulating some variables, such as changing task types and reducing the amount of interference between tasks, will reduce the cost of asymmetric conversion and even reverse. So the task dominance affects task conversion at present. The internal mechanism is still controversial, and the focus of the dispute lies mainly in whether the cost of the asymmetric conversion is caused by the negative start effect (inhibition process) of the previous task, and does it involve other cognitive control processes? The N-2 task repeat cost (n-2 task repetition cost) is the direct evidence of the suppression process in the task transfer, so this study is based on the first. The task type of the N-2 test times divides task conversion (such as task sequence AB) into alternating task conversion (n-2 trial and N trial task type, BAB) and single task conversion (the N-2 test task type is different from that of the N trial task type, AAB), and the alternate conversion (BAB) is a previously suppressed task setting (Overcoming) The negative startup effect of the previous task setting, representing the suppression process of task transformation, the single conversion (AAB) is the non suppressed process that starts an unsuppressed task setting (refactoring process) and represents the task transformation. This study attempts to separate the suppression and non restraining processes of the task transformation, and analyze the roles of the two in the conversion of asymmetric tasks, respectively. In addition, we also use the functional magnetic resonance imaging (f MRI) technology to explore the cognitive neural mechanism of task dominance affecting task conversion from the perspective of behavior and brain mechanism. This study includes three parts: Experiment 1 mainly verifies the color task of variable Stroop stimuli. Whether a text task is a pair of tasks with different task dominance. By analyzing the interaction of task types (color discrimination tasks, word judgment tasks) and trial consistency, does the color discrimination task and word judgment task show the asymmetry of the task interference? Results show that the color discrimination task and the word judgment are responsible for the task. There is a significant consistency effect, and the consistency effect of color discrimination task is significantly greater than the consistency effect of the word judgment task. Here we can call the color discrimination task as the inferior task and the word judgment task is the dominant task. Based on Experiment 1, the experiment 2 uses the color-word Stroop stimulus and the clue task transformation paradigm phase. By combining the method, we explore the adjustment effect of task dominance to the conversion cost, and examine the role of the two processes in the conversion of asymmetric tasks through the single conversion and alternate conversion process of the separation of tasks. The results show that the conversion cost of the text task is significantly greater than the cost of the conversion of color tasks on the whole. One step analysis of the composition of the conversion cost is found that the alternate conversion cost of the text task is significantly greater than the alternate conversion cost of the color task, while the single conversion cost of the color task is significantly greater than the single conversion cost of the text task. Experiment 3 uses f MRI technology to verify the behavior results of Experiment 2, and the brain imaging results show that the duplication of the task is with the task repetition. Compared to that, the alternation task shift significantly activates the lateral prefrontal cortex (lateral prefrontal cortex, LPFC), the anterior cingulate gyrus (anterior cingulate cortex, ACC) and the left temporal gyrus (inferior temporal gyrus:ITG), indicating that these brain regions are involved in the suppression control of the task transformation, while the single task conversion process has not been significantly activated, indicating that the single task conversion process is not significantly activated. The execution control network (bilateral bilateral inferior frontal cortex:IFG, left top and lower lobule left inferior parietal cortex:IPL, dual temporal gyrus bilateral middle temporal gyrus:MTG) has domain based conflict adaptability, and conversion to the new task setting may cause the execution control network to temporarily "paralyze" and cause the behavior to reverse. When further consideration is given to the task conversion effect of different task types, it is found that the alternate conversion process of the word task is activated in the parahippocampal gyrus (parahippocampal gyrus) and is activated in the putamen (putamen). The alternate conversion cost of the text task can be derived from the retrieval of the related stimulus response mapping from the long time memory. The process is blocked and the reaction conflict increases. And the single conversion process of the color task in the related executive control network (insula, shell putamen) is obviously greater than the single conversion process of the text task, showing that the reconstruction process of the color task setting is difficult for the text task. To sum up, this paper combines behavior and brain imaging technology. It shows that the effect of task dominance on task conversion is not only reflected in the process of suppression (the negative startup effect of previous task setting), but also in the non inhibition process (reconstructing the new task setting), and the two processes are regulated by different directions of task dominance, and the cost of asymmetric conversion is determined by the two.

【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：B842

【参考文献】