任务切换机制研究的理论争议与整合

任务切换是执行控制的一种重要功能。切换代价是量化执行控制持续时间的指标。并广泛应用于各个研究领域。但是切换代价在多大程度上体现了执行控制的作用,仍然还存在争论．当前主要存在任务设置重构、任务设置惯性和联结竞争三种理论。本文首先介绍了三种理论的基本观点和实验证据,以及对任务切换加工机制的分析;其次阐明了对三种理论进行整合的相关研究;最后分析了进一步研究的方向。     

任务转换加工机制的研究述评

本文重点介绍了任务转换加工机制的三种主要假设：任务重建、任务重复优势和线索重复优势。任务重建假设认为转换加工是一种根据个体行为意图的自上而下的执行控制过程,而任务重复优势假设和线索重复优势假设均认为转换加工是一种由外部刺激启动的自下而上的自动控制过程。三者差异的焦点在于：转换加工过程中是否有执行控制参与。本文围绕这一争论进行了讨论和分析,并对相关领域进行了展望。     

Age-related changes in duration reproduction: involvement of working memory processes

The aim of the present research was to study age-related changes in duration reproduction by differentiating the working memory processes underlying this time estimation task. We compared performances of young and elderly adults in a duration reproduction task performed in simple and concurrent task conditions. Participants were also administered working memory tests to measure storage and central executive functions. Findings indicated a differential involvement of working memory storage and central executive functions in age-related differences in temporal tasks. The limited storage capacities explained age-related changes in the simple task of duration reproduction, and the dysfunctioning of central executive functions accounted for age-related changes in duration reproduction performed in a concurrent task condition, which involves greater attentional resources.     

The role of the executive system in visuo-spatial memory functioning

Participants were presented with a spatial sequence in which between 4 and 10 cells were highlighted. On each trial list length was unknown to the participant who was required to serially recall the last four cells. Processing of longer lists is assumed to call upon the executive system, which is thought to be involved in updating the contents of the short-term visuo-spatial store. Study 1 revealed that loading the executive system with concurrent random letter generation impaired performance on the spatial task especially recall of the early serial positions. However, contrary to expectation the degree of impairment was no greater on the longer lists, where it had been assumed that updating would be occurring. Study 2 confirmed this finding and demonstrated that relative to sequences of known length, under conditions of uncertainty when the list length was unknown, spatial recall was impaired even on short sequences. The present results support the growing consensus, which is suggestive of closer links between visuo-spatial and executive processes. However, it remains unclear whether or not updating is actually occurring on the longer sequences, and if it is, what specific executive processes are involved.     

The personality-related implications of Stroop performance: Stress-contingent self-control in daily life

People with higher levels of executive control, relative to low levels, should be more capable of responding to the problems and stressors of their lives, yet we know very little concerning this lab-to-life interface. Two studies (total N = 254) sought to speak to questions of this type using the Stroop task, a classic measure of executive control. Individual differences in Stroop costs were assessed in the laboratory, following which the same people completed daily diary protocols for two weeks. Consistent with neurocognitive theories of executive control, both studies found that people capable of overriding the Stroop effect tended to recruit self-control in response to the stressful circumstances of their lives. By contrast, people with high Stroop costs did not exhibit this problem-focused form of recruitment. The findings extend our knowledge of individual differences in executive control and the manner in which they operate in daily life.     

Task Switching and Attention Deficit Hyperactivity Disorder

The main goal of the present set of studies was to examine the efficiency of executive control processes and, more specifically, the control processes involved in task set inhibition and preparation to perform a new task in attention deficit hyperactivity disorder (ADHD) and non-ADHD children. This was accomplished by having ADHD children, both on and off medication, and non-ADHD children perform the task-switching paradigm, which involves the performance of two simple tasks. In nonswitch trials, an individual task is performed repeatedly for a number of trials. In switch trials, subjects must rapidly and accurately switch from one task to the other, either in a predictable or unpredictable sequence. Switch costs are calculated by subtracting performance on the nonswitch trials from performance on the switch trials. These costs are assumed to reflect the executive control processes required for the coordination of multiple tasks. ADHD children showed substantially larger switch costs than non-ADHD children. However, when on medication, the ADHD children's switch performance was equivalent to control children. In addition, medication was observed to improve the ADHD children's ability to inhibit inappropriate responses. These data are discussed in terms of models of ADHD and cognition.     

Input monitoring and response selection as components of executive control in pro-saccades and anti-saccades

Several studies have shown that anti-saccades, more than pro-saccades, are executed under executive control. It is argued that executive control subsumes a variety of controlled processes. The present study tested whether some of these underlying processes are involved in the execution of anti-saccades. An experiment is reported in which two such processes were parametrically varied, namely input monitoring and response selection. This resulted in four selective interference conditions obtained by factorially combining the degree of input monitoring and the presence of response selection in the interference task. The four tasks were combined with a primary task which required the participants to perform either pro-saccades or anti-saccades. By comparison of performance in these dual-task conditions and performance in single-task conditions, it was shown that anti-saccades, but not pro-saccades, were delayed when the secondary task required input monitoring or response selection. The results are discussed with respect to theoretical attempts to deconstruct the concept of executive control.     

Priming or executive control? Associative priming of cue encoding increases “switch costs” in the explicit task-cuing procedure

The explicit task-cuing procedure involves presenting a cue that indicates which task to perform on a target. Responses are typically faster when tasks repeat than when they alternate, and this difference is often interpreted as a measure of the time required for executive control processes to change task set. This article suggests that the difference reflects priming of cue encoding when successive cues are identical or associatively related. Subjects responded to task repetitions more quickly when the cue on the current trial was associatively related to the cue on the previous trial (e.g., day --> night) than when the cues were unrelated (e.g., verb --> night). Models applied to the time course function--generated by manipulating the interval between the onsets of the cue and the target--showed that the facilitation was due to cue encoding, a process that does not require online executive control.     

社会性信息对Flanker效应的影响

研究显示,面孔Flanker任务中,经典Flanker效应会消失,但其机制还不明确。本文在ANT-I范式的基础上,除常规的箭头Flanker,增加面孔Flanker、两侧为箭头中间为面孔和两侧为面孔中间为箭头的混合Flanker,探究造成该现象的可能原因。结果发现,当Flanker任务中的干扰刺激为箭头时,Flanker效应存在;而干扰刺激为面孔时,Flanker效应则消失了。提示,Flanker任务中干扰刺激的社会性可能是造成Flanker效应消失的原因。这为冲突信息加工中社会性与非社会性信息的控制机制提供了新的视角。     

挫折情境下自我肯定对执行功能的影响

为探讨挫折情境下自我肯定对执行功能的影响,创设挫折和非挫折情境,采用价值观自我肯定干预,通过Stroop范式和2-back范式分别测量抑制控制和工作记忆的刷新能力。结果发现,挫折情境下的Stroop任务和2-back任务反应时均高于非挫折情境;挫折情境下自我肯定组在Stroop任务和2-back任务上的反应时均显著低于非自我肯定组,而非挫折情境下两组的反应时没有显著性差异;Stroop效应量在情境与肯定条件上的交互作用不显著。结果表明挫折降低了执行功能的任务表现,自我肯定干预能够改善挫折情境下执行功能相关的任务成绩,促进了个体对工作记忆任务的刷新能力和Stroop任务的认知表现,但对抑制控制能力的改善没有明显作用。     

Assessment and development of executive function (EF) during childhood.

This review paper outlines the issues associated with the assessment of executive function (EF) in children and adolescents, and describes the developmental profile of executive processes across childhood. At the outset, EF is defined, and cognitive and behavioral impairments associated with executive dysfunction (EDF) are described. A developmental model of EF is proposed incorporating four discrete but inter-related executive domains (attentional control, cognitive flexibility, goal setting, and information processing) which operate in an integrative manner to enable "executive control". Characteristics that constitute traditional EF measures are discussed, as are the problems associated with test interpretation. The ecological validity of EF tests and neuropsychological assessment procedures are examined, and adjunct methods of measurement are presented to enable a more comprehensive and valid assessment of EF. Based on developmental and normative studies, the maturation of executive domains is mapped. Attentional control appears to emerge in infancy and develop rapidly in early childhood. In contrast, cognitive flexibility, goal setting, and information processing experience a critical period of development between 7 and 9 years of age, and are relatively mature by 12 years of age. A transitional period is thought to occur at the beginning of adolescence, and shortly after "executive control" is likely to emerge. In order to confirm our current understanding of EF development and further enhance our understanding of brain-behavior relationships, longitudinal studies incorporating structural and functional neuroimaging are required.     

睡眠对儿童执行功能的影响

近期研究表明, 睡眠总量和睡眠质量都会对儿童执行功能的发展造成影响, 在自然睡眠条件下, 睡眠质量的影响倾向于即时性, 睡眠总量的影响具有滞后性, 在实验干预条件下, 少量的睡眠延长提高了儿童的执行功能表现。睡眠问题中研究最为广泛的睡眠呼吸障碍也会对儿童的执行功能带来危害, 但由于方法的不同, 目前的研究在结论上并不一致。随着年龄的增长, 睡眠对儿童执行功能的影响会逐步降低。此外, 基因、家庭社会经济地位等内外部因素也会对研究结果产生影响。未来的研究应针对执行功能中认知灵活性这一成分进行加强。     

Are bilingual advantages dependent upon specific tasks or specific bilingual experiences?

Paap and Greenberg concluded that there is no coherent evidence for bilingual advantages in executive processing. More optimistic researchers believe that the advantages may be restricted to certain types of bilinguals. Recent large-scale and lifespan investigations that tested highly fluent bilinguals from communities where the same two languages are spoken by most residents reported no bilingual advantages in any age group or in any of the tasks used to measure executive functioning. The present study takes a complementary approach by examining a sample that is quite homogeneous in terms of current life experiences, but heterogeneous in terms of its exposure to second languages. The composite database of 168 bilinguals and 216 monolinguals is used to explore for differences based on: (1) the age of acquiring a second language (L2), (2) the relative proficiency of an L2 and (3) the number of languages used. Across 12 different measures of executive function, derived from 4 different nonverbal tasks, there was no consistent evidence supporting the hypotheses that either early bilingualism, highly fluent balanced bilingualism, or trilingualism enhances inhibitory control, monitoring or switching. In fact, when statistically significant effects did occur, they more often disconfirmed than confirmed these hypotheses.     

Assessment and Development of Executive Function (EF) During Childhood

This review paper outlines the issues associated with the assessment of executive function (EF) in children and adolescents, and describes the developmental profile of executive processes across childhood. At the outset, EF is defined, and cognitive and behavioral impairments associated with executive dysfunction (EDF) are described. A developmental model of EF is proposed incorporating four discrete but inter-related executive domains (attentional control, cognitive flexibility, goal setting, and information processing) which operate in an integrative manner to enable “executive control”. Characteristics that constitute traditional EF measures are discussed, as are the problems associated with test interpretation. The ecological validity of EF tests and neuropsychological assessment procedures are examined, and adjunct methods of measurement are presented to enable a more comprehensive and valid assessment of EF. Based on developmental and normative studies, the maturation of executive domains is mapped. Attentional control appears to emerge in infancy and develop rapidly in early childhood. In contrast, cognitive flexibility, goal setting, and information processing experience a critical period of development between 7 and 9 years of age, and are relatively mature by 12 years of age. A transitional period is thought to occur at the beginning of adolescence, and shortly after “executive control” is likely to emerge. In order to confirm our current understanding of EF development and further enhance our understanding of brain-behavior relationships, longitudinal studies incorporating structural and functional neuroimaging are required.     

Executive Function and the Frontal Lobes: A Meta-Analytic Review

Currently, there is debate among scholars regarding how to operationalize and measure executive functions. These functions generally are referred to as “supervisory” cognitive processes because they involve higher level organization and execution of complex thoughts and behavior. Although conceptualizations vary regarding what mental processes actually constitute the “executive function” construct, there has been a historical linkage of these “higher-level” processes with the frontal lobes. In fact, many investigators have used the term “frontal functions” synonymously with “executive functions” despite evidence that contradicts this synonymous usage. The current review provides a critical analysis of lesion and neuroimaging studies using three popular executive function measures (Wisconsin Card Sorting Test, Phonemic Verbal Fluency, and Stroop Color Word Interference Test) in order to examine the validity of the executive function construct in terms of its relation to activation and damage to the frontal lobes. Empirical lesion data are examined via meta-analysis procedures along with formula derivatives. Results reveal mixed evidence that does not support a one-to-one relationship between executive functions and frontal lobe activity. The paper concludes with a discussion of the implications of construing the validity of these neuropsychological tests in anatomical, rather than cognitive and behavioral, terms.     

Space Fortress game training and executive control in older adults: a pilot intervention

We investigated the feasibility of using the Space Fortress (SF) game, a complex video game originally developed to study complex skill acquisition in young adults, to improve executive control processes in cognitively healthy older adults. The study protocol consisted of 36 one-hour game play sessions over 3 months with cognitive evaluations before and after, and a follow-up evaluation at 6 months. Sixty participants were randomized to one of three conditions: Emphasis Change (EC)--elders were instructed to concentrate on playing the entire game but place particular emphasis on a specific aspect of game play in each particular game; Active Control (AC)--game play with standard instructions; Passive Control (PC)--evaluation sessions without game play. Primary outcome measures were obtained from five tasks, presumably tapping executive control processes. A total of 54 older adults completed the study protocol. One measure of executive control, WAIS-III letter-number sequencing, showed improvement in performance from pre- to post-evaluations in the EC condition, but not in the other two conditions. These initial findings are modest but encouraging. Future SF interventions need to carefully consider increasing the duration and or the intensity of the intervention by providing at-home game training, reducing the motor demands of the game, and selecting appropriate outcome measures.     

经颅直流电刺激对健康人群反应抑制的影响

反应抑制是指抑制不恰当的或不符合当前需要的行为的能力, 研究表明反应抑制主要与额下回、背外侧前额叶和前辅助运动区的功能有关。经颅直流电刺激(tDCS)是一种非侵入式脑刺激技术, 近年来对健康人群使用tDCS刺激相应脑区从而影响反应抑制功能的研究日益增多, 但主要研究结果不一致。阐明tDCS影响反应抑制具体的神经机制、减少tDCS研究的异质性、探索更有效的tDCS刺激方式和确定tDCS效果的年龄依赖性差异已成为目前亟待解决的问题。     

Prospective duration judgments: The role of temporality and executive demands of concurrent tasks

It is known that concurrent non-temporal tasks shorten reproduced temporal durations in prospective duration judgments. Two experiments were carried out, one comparing a concurrent temporal task to a minimally demanding concurrent task (Experiment 1) and one comparing an executive concurrent (Simon) task with a less demanding non-executive concurrent task (Experiment 2). An effect of the concurrent task type on temporal reproductions was found. Furthermore, a duration length effect was found, where longer durations were underestimated more than shorter durations. This effect tended to be stronger for the experiments that included a concurrent task that demanded high attention.     

中央执行子功能对预期式时距估计的作用——基于结构方程模型的结果

采用结构方程模型的方法探讨中央执行系统与时距加工过程的关系,考察三种中央执行子功能(转换,抑制,刷新)对预期式长、短时距估计(两种标准时距:2s,5s)的作用模式。结果发现刷新功能对长、短时距估计任务都产生影响;抑制功能只作用于长时距估计;转换功能不参与单独的预期式时距估计过程。结果表明,三种执行子功能对预期式短时距加工和长时距加工的作用不同,支持时距加工的差异机制假设。     

Mental fatigue and the control of cognitive processes: effects on perseveration and planning

We tested whether behavioural manifestations of mental fatigue may be linked to compromised executive control, which refers to the ability to regulate perceptual and motor processes for goal-directed behaviour. In complex tasks, compromised executive control may become manifest as decreased flexibility and sub-optimal planning. In the study we use the Wisconsin Card Sorting Test (WCST) and the Tower of London (TOL), which respectively measure flexibility (e.g., perseverative errors) and planning. A simple memory task was used as a control measure. Fatigue was induced through working for 2 h on cognitively demanding tasks. The results showed that compared to a non-fatigued group, fatigued participants displayed more perseveration on the WCST and showed prolonged planning time on the TOL. Fatigue did not affect performance on the simple memory task. These findings indicate compromised executive control under fatigue, which may explain the typical errors and sub-optimal performance that are often found in fatigued people.