ISSN 0439-755X
CN 11-1911/B

心理学报 ›› 2008, Vol. 40 ›› Issue (05): 562-570.

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  1. 首都师范大学心理系,北京 100037
  • 收稿日期:2007-06-20 修回日期:1900-01-01 发布日期:2008-05-30 出版日期:2008-05-30
  • 通讯作者: 郭春彦

Endogenous Preparation and Exogenous Adjustment in Task Switching Under Foreknowledge

SUN Tian-Yi;XIAO Xin;GUO Chun-Yan   

  1. Department of Psychology, Capital Normal University, Beijing, 100037, China
  • Received:2007-06-20 Revised:1900-01-01 Online:2008-05-30 Published:2008-05-30
  • Contact: Guo Chunyan

摘要: 采用ERP探究在预知条件下任务转换的神经机制。使用“任务转换”实验范式,以汉字(名词/动词)或数字(奇数/偶数)的归类为任务。被试执行任务重复(AA,BB,…)或在两个任务间转换(AB,BA,…),每个任务序列为连续的两个任务(任务1,任务2)。结果发现,任务1中,在刺激呈现后300ms左右,数、词的转换序列与重复序列出现显著差异;在中央区,320ms左右,任务1中转换序列比重复序列、任务2中转换任务比重复任务都产生一个更为负走向的波。这些结果表明,在预知条件下,简单任务转换的内源性准备可能开始于任务1呈现后300ms左右;内源性准备和外源性调节可能都反映了认知冲突过程,此认知冲突可能是转换代价的主要来源

关键词: 任务转换, 转换代价, 内源性准备, 外源性调节, ERPs

Abstract: Task switching is the basic method in human cognitive activities, and the switching process is an important aspect of executive control, which is responsible for controlling the switching course between two tasks competing for the same cognitive resources in working memory. Switching costs refer to longer reaction times for switching items (e.g., AB), as compared to repeating items (e.g., BB) as an indicator of executive control. The course of switching is involved in both endogenous preparation without an external stimulus and exogenous adjustment in response to the external stimulus.
The event-related potentials (ERPs) of participants were recorded to investigate task switching, by using the “task-switching” paradigm. Tasks included a simple classification of Chinese characters (noun/verb) or that of digits (odd/even). For each task, the stimulus picture consisted of one Chinese character and a two-digit natural number on the same background (red and blue were used for the digit and character tasks respectively). We aimed to detect task switching under foreknowledge conditions. Participants consecutively performed two tasks (tasks 1 and 2) that involved either task repetition (i.e. AA、BB,…) or task switching (i.e. AB、BA,…), including four blocks respectively. All these blocks were presented with the sequence ABBAABBA. The participants were 17 healthy and right-handed undergraduates (10 males and 7 females). Their eyesight was either normal or corrected-to-normal, and their ages ranged from 19 to 23 (mean age = 20.24). An ANOVA with repeated measures was used to analyze the data.
The ERPs of task 1 in repeating trial and switching trials (e.g., AA to AB) were analyzed, and the ERPs of task 2 in repeat tasks and switching tasks (e.g., AA to BA) were also analyzed. The authors found that the differences between ERPs in task 1 were significant at about 300 ms after the stimulus onset. There was a late slow negative-going wave that was larger for switching trials than for repeating trials during 500~800 ms. A larger P3b deflection was found for repeating tasks than for switching tasks, and the Chinese characters were different from numerals in the cerebral regions. In Cz, at about 320 ms, the switching trials evoked a larger negative wave as compared to the repeating trials in task 1; and in task 2, the switching tasks produced a larger negative-going wave as compared to the repeating tasks. The difference wave was a N320.
These results suggest the following: (1) under foreknowledge conditions, for simple task switching, the endogenous preparation for task 2 started at 300 ms after the appearance of task 1; (2) the P3b in the switching tasks may reflect the differences in the frequency of the occurrence of these events but not the differences in the cognitive resources of task switching. Moreover, the N320 reflected the cognitive conflict that may be the main source of the switching cost; (3) the material specificity during task switching may be one of the reasons that lead to the difference in the same experimental paradigm

Key words: task switching, switching cost, endogenous preparation, exogenous adjustment, ERPs