刺激冲突和反应冲突的事件相关电位特征:中顶部P3

在色-词Flanker任务中,研究者采用2:1映射设计能构造两类冲突:刺激冲突和反应冲突。然而,这两类冲突所涉及的神经机制还不清楚。本研究采用2:1映射设计,记录了31个健康成人被试完成色-词Flanker任务时的行为和脑电数据。反应时数据显示了明显的刺激冲突和反应冲突。事件相关电位结果表明,中顶部P3峰值与刺激冲突有关,峰潜伏期能预测反应冲突。所以,中顶部P3反映了刺激冲突和反应冲突的神经机制。     

冲突观察范式下冲突适应的机制

冲突观察诱发的冲突适应不受反应执行的影响,因此更纯净。该研究分别采用Stroop任务、单词Flanker任务和字母Flanker任务的冲突观察范式,在三个实验中考察了冲突适应的机制。在三个实验中,冲突适应都表现在反应任务中的一致试次和不一致试次上;不一致试次之后的干扰效应显著小于一致试次之后的干扰效应;冲突适应量服从正态分布。因此,该研究首次在冲突观察范式下揭示了冲突适应的分布特征,为认知控制研究提供了新思路。     

冲突水平的变化诱发冲突适应

冲突适应是重要的认知控制现象, 反映了认知控制的动态过程。然而, 目前为止对于冲突水平上的差异能否诱发冲突适应尚不清楚。本研究采用字母Flanker的变式, 通过改变目标-分心物的一致性操纵冲突水平, 探究冲突水平的变化对认知控制调整的影响。结果发现被试的反应时间随冲突水平的提高而增加; 而且先前试次的一致性影响当前试次的干扰效应, 无冲突和低冲突、无冲突和高冲突、低冲突和高冲突条件之间均出现了典型的冲突适应。本研究结果表明, 除了冲突的有无, 冲突水平的变化也能诱发冲突适应, 支持更大的冲突驱动更强的认知控制, 而且冲突诱发的认知控制的功能可能通过注意聚焦实现。这一发现为冲突监测理论的注意调节机制提供了直接的支持证据, 对于促进冲突适应的相关研究具有重要意义。     

6～12岁儿童Flanker任务下的冲突适应效应

为了探讨6～12岁儿童冲突适应能力的发展,本研究使用经典的Flanker任务,考察了181名一至六年级小学生在冲突任务中的成绩。结果发现,冲突效应在各个年龄段都显著,但是冲突效应大小在不同年龄段之间没有显著差异;对于冲突适应效应,在反应时和准确率上都发现了冲突适应的证据,表现为不一致试次后的冲突效应减小和错误率降低,并且,冲突适应效应的大小在各个年龄段也没有差异。以上结果表明,对于6～12岁左右的小学生,冲突适应效应已经稳定存在,并且,不存在年龄差异。     

不同任务难度条件下认知老化对冲突适应能力的影响

采用任务冲突范式考察在不同任务难度条件下认知老化对个体冲突适应能力的影响。实验1采用经典Flanker任务考察在需要较少认知资源的低难度任务上,老年人与年轻人的冲突适应能力是否有差异;实验2则进一步采用Flanker与Simon任务的交叉整合任务,探讨在需要更多认知资源的高难度任务上,认知老化对冲突适应能力的影响。结果表明在低难度任务条件下,认知老化并未对冲突适应能力产生影响;而当冲突调控所需认知资源超出老化大脑最大代偿潜能时,老年人的冲突适应能力受损严重,认知老化会显著影响冲突适应能力。本研究最终支持了脑功能代偿说和资源限制理论。     

无意识冲突的发生机制：基于Stroop范式的探讨

无意识信息对人们的行为有着十分重要的影响,它不仅能触发相对低级的认知功能而且也能触发冲突控制等相对高级的认知功能。尽管已有研究从行为和认知神经研究两个方面强有力地证实了无意识冲突的存在,但对无意识冲突是源自中枢加工产生的语义冲突还是晚期动作选择中产生的反应冲突存在激烈的争议。本研究采用分离语义冲突和反应冲突的实验逻辑在Stroop掩蔽启动任务中探讨了无意识冲突的机制。结果发现,无意识Stroop效应中既包含语义冲突又包含反应冲突。这说明无意识冲突可能由语义冲突和反应冲突共同构成。实验结果也进一步支持了无意识刺激可以加工到语义水平的观点。     

无意识信息的刺激表征及其时间特性

无意识信息是否存在刺激表征有待解决。实验采用字母Flanker任务, 通过目标和flanker在刺激水平和反应水平上的冲突效应, 重点考察阈下flanker在刺激水平的表征。在相同的实验设计下, flanker可觉察时(实验1A), 观察到经典的刺激冲突效应和反应冲突效应; 而flanker无意识时(实验1B), 重复了反应冲突效应, 却观察到刺激冲突效应发生反转, 提示了无意识信息的反应加工及刺激加工。实验2采用符号材料促使刺激−反应的自动联结, 减少刺激−反应规则的难度, 结果重复了实验1B的发现--无意识信息引起反转的刺激冲突。刺激冲突下反转效应的一致结果表明无意识信息的刺激表征影响了认知加工。实验3考察这种影响在时间进程上的特点。无意识刺激表征的影响随反应时变化：在快速反应中观察到刺激冲突效应, 之后该效应发生反转且反转量随反应时增加而增大。相反, 无意识反应表征的影响在不同反应时下保持稳定。以上结果提供了无意识信息存在刺激表征的行为学证据并揭示了其时间特性, 提供了无意识领域中不一致研究结果的整合思路。     

冲突适应效应是领域特定的

本研究采用整合的交叉任务范式,通过任务类型的操纵,对冲突适应效应是领域一般的还是领域特定的问题进行了探讨。结果发现当时,在刺激-反应集为4的字母flanker+Simon的整合交叉任务中和刺激-反应集为4的Stroop+Simon的整合交叉任务中,冲突适应效应都是仅存在于任务内,不存在于任务间。说明在控制了重复启动效应且排除了任务之间维度重叠的影响后,两种类型的整合交叉任务都只在任务内观察到冲突适应效应。这表明在控制特征整合的影响后,冲突适应效应是领域特定的,同时说明冲突监测系统不仅是对冲突进行监测,也对冲突的来源进行识别。     

情绪冲突控制过程的脑电特征研究

应用Flanker研究范式探讨了正常成人被试在情绪冲突控制过程中的脑电特征.结果发现:干扰刺激的特征主要在P200上得到体现,判断刺激的特征主要在N300上得到体现,干扰刺激与判断刺激的特征体现了个体注意控制的过程.积极情绪和消极情绪在判断过程中发挥着不同的作用,但无论是作为干扰刺激还是作为判断刺激,消极情绪都使任务难度增大,对加工过程造成干扰;积极情绪则不然.     

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。     

高、低趋近积极情绪对不同注意加工阶段的影响

本研究采用事件相关电位(ERP)技术和Flanker任务, 探讨由甜点和风景图片分别诱发的高、低趋近积极情绪对注意的早期和晚期加工的影响。同时, 为更精细考察情绪对视觉注意范围早期加工阶段的影响, 在75%的Flanker试次中加入了一个白色方块探测刺激, 该刺激位于中央Flanker字母的左侧或右侧。研究结果表明, 在注意加工的早期感知阶段, 高趋近积极情绪下, 带有白色探测刺激的Flanker字母比低趋近积极情绪条件下诱发了更小的P1, 表明高趋近积极情绪窄化了早期注意加工范围; 在注意加工的晚期选择阶段, 高趋近积极情绪下的Flanker字母诱发了更大的N2b成分, 低趋近积极情绪下诱发了更大的P3成分, 表明高趋近积极情绪增强了对干扰的抑制能力, 而低趋近积极情绪下个体调用了更多的注意资源用以加工周边刺激。     

基于Flanker、Stroop和Simon多重冲突驱动的认知控制机制

认知控制是维持和调整多任务目标导向的加工策略,而基于多任务冲突的认知控制是一般领域上还是特定领域上,即一种冲突是否会影响另一种冲突的解决,已有研究并没有得到统一的结论。本研究运用事件相关电位（ERP）方法考察了同一任务中不同类型冲突（Stroop、Simon和Flanker冲突）驱动认知控制调节的脑机制。数据显示：各冲突都出现了一致性效应和冲突适应性效应;实验中每种冲突的上一个trial只与该类冲突的当前trial的交互效应显著,而与其他类型冲突的当前trial的交互效应不显著;几乎所有冲突都发现了P300、N450、SP成分一致性效应。结果表明：在不同类型冲突驱动条件下,人脑能够同时监控并解决不同类型的冲突;冲突驱动的认知控制系统以局部的控制方式工作;人脑是基于多冲突驱动的认知控制系统的灵活性和某类型冲突所特有的控制机制来解决冲突,且冲突解决机制是相互独立、互不干扰的。     

The effect of memory load on reaction time in character classification

In order to investigate the effect of memory load on reaction time (RT), choice RT trials were embedded in a binary character classification task using the varied set procedure. Twelve Ss performed in experimental blocks, as well as in control blocks consisting of character classification trials only. In experimental blocks, every trial began as a classification trial with the presentation of a new positive set. On a random half of these trials, however, a choice RT stimulus was presented instead of a probe letter and S simply made the indicated response. Results indicated that memory load had no effect on the choice RT trials. Embedding choice RT trials in the classification task affected the intercept (but not the slope) of the function relating classification RT to memory load. This result implies that the increase in latency usually obtained in classification experiments is entirely due to an increase in the duration of the memory searching stage of processing.     

Influence of stimulus type on effects of flanker,flanker position,and trial sequence in a saccadic eye movement task

Using the flanker paradigm in a task requiring eye movement responses, we examined how stimulus type (arrows vs. letters) modulated effects of flanker and flanker position. Further, we examined trial sequence effects and the impact of stimulus type on these effects. Participants responded to a central target with a left- or rightward saccade. We reasoned that arrows, being overlearned symbols of direction, are processed with less effort and are therefore linked more easily to a direction and a required response than are letters. The main findings demonstrate that (a) flanker effects were stronger for arrows than for letters, (b) flanker position more strongly modulated the flanker effect for letters than for arrows, and (c) trial sequence effects partly differed between the two stimulus types. We discuss these findings in the context of a more automatic and effortless processing of arrow relative to letter stimuli.     

Functionally lateralised information processing and its allocation to response: Inferences from three measures of letter identification performance following lateralised visual input

Identification errors were analysed for single letters presented in each visual hemi-field. The kinds of errors occurring reflected both how the letters were made difficult to see, and the informational relationships among the possible stimulus letters. The particular pattern of errors was different in the two hemifields, with the direction of that difference suggesting the letters were better differentiated following left half-brain input. But this left-sided superiority in letter differentiation was only sometimes reflected in faster or more accurate responses overall. Instead, the extent of left-sided performance superiority in RT and accuracy depended in a complex way on the degree of difficulty of the task. This influence of task difficulty on the RT and accuracy measures of functional laterality was considered to reflect a greater or lesser allocation to response of the lateralised letter-differentiation process revealed by the errors analysis.     

Wholistic and analytic stimulus processing: The development of selective perceptual strategies

This experiment reports an investigation of the development of selective processing strategies as subjects become increasingly more practised at a serial self-paced RT task. It demonstrates the effect a preceding stimulus can have on the analysis of a current signal and the development of active analytic strategies in favour of passive wholistic processing, with practice. The stimuli used were letters with irrelevant visual noise dot patterns superimposed on them. The letter, or the dot pattern, or both, could be repeated on successive trials. Early in practice repetition of both stimulus components simultaneously produced short reponse latencies relative to repetition of the letter alone. The number of noise dots markedly affected RT. Late in practice, however, letter repetition RTs were small, irrespective of whether or not the noise dot pattern was repeated. Furthermore, the number of noise dots no longer had an effect on the RT to these stimulus transitions. The results suggest that subjects appear to be able to select relevant information to process as they become progressively more practised, even though there is evidence that they compare the current stimulus with an iconic representation of the immediately preceding one.     

Changes in same-different laterality patterns as a function of practice and stimulus quality

Accuracy and reaction time (RT) of judgments about sameness vs. difference of (a) names of two letters and (b) shapes of two nonverbal forms were examined for stimuli presented to the center, left (LVF), and right (RVF) visual fields. For same-name letter pairs during Experiment I, responses were more accurate and faster for LVF than for RVF trials on an initial 90-trial block, but this difference was reversed by a third 90-trial block. The RVF advantage for RT was maintained over Trial Blocks 4 and 5, given during a second session, but had disappeared on Trial Blocks 6 through 9 as RT reached the same asymptotic level for both visual fields. No LVF-RVF differences were obtained at any level of practice for different-name letter pairs or for any of the form pairs. Experiment II replicated the shift from LVF toward RVF advantage that occurred over the first three trial blocks of Experiment I and demonstrated that such a shift does not occur when the letters are perceptually degraded. The results were discussed in terms of differences in cerebral hemisphere specialization for visuospatial vs. abstract stages of letter processing and changes with practice in the relative difficulty of these stages.     

Specialization of the cerebral hemispheres in scanning for information in short-term memory

Lateral specialization of function in the cerebral hemispheres was investigated in the context of a memory scanning paradigm. The S first memorized a set of letters (the memory set) and then indicated whether or not a subsequent test stimulus, presented in either the right or left visual field, matched any letter in the set. The test stimulus was either a letter or a picture of some common object; for the picture, S’s response was based on the initial letter of the name of that object. Reaction time was recorded and plotted as a function of the number of letters in the memory set. The results support the hypothesis that in a memory scanning task of this type, letter and picture test stimuli are spatially and verbally represented, respectively, and are processed in different cerebral hemispheres.     

特质自我控制个体在多源干扰任务下的认知神经机制

本研究采用事件相关电位技术(ERPs)结合多源干扰任务(MSIT)范式来探讨特质自我控制个体的认知神经机制。考察了高、低自我控制者各26名在MSIT任务上的差异。结果：高自我控制者的反应时显著长于低自我控制者。在MSIT冲突条件下,高自我控制者的N2和P3(LPC)波幅比无冲突条件更大。结论：高自我控制者较低自我控制者处理冲突干扰更慢,需要的注意资源较多,激活前额叶中部脑区。