【作者】 杜英春；

【导师】 吴仁华； 张学新；

【作者基本信息】 汕头大学 ， 病理学与病理生理学， 2008， 博士

【摘要】 工作记忆是顺利完成高级认知任务的基础。前摄干扰(proactive interference)是对工作记忆具有影响的因素之一,因此考察干扰刺激表征的作用及人们如何克服干扰具有重要的研究意义。本研究包含三个实验。实验一采用工作记忆的选择任务,通过一系列行为实验,系统地考察了靶刺激表征与干扰刺激表征之间的竞争。首先让被试学习一系列字母,接着通过提示刺激指示被试记住一部分字母并忽略其余的字母。被记住的字母成为靶刺激系列,被忽略的字母成为干扰刺激系列。当提示刺激为靶刺激系列时,我们把这种条件叫做“记住”条件;当提示刺激为干扰刺激系列时,我们把这种条件叫做“忘记”条件。提示刺激消失后,屏幕上出现探测刺激,要求被试判断探测刺激是否属于靶刺激系列。研究中,通过调控提示刺激类型和提示刺激与探测刺激之间的时间间隔来检测工作记忆选择的难度。研究发现,在“记住”条件下,提示刺激通过重复呈现靶刺激,增强了靶刺激表征,从而促进了工作记忆的选择,使被试对探测刺激做出更快的判断。然而,“忘记”条件下,尽管提示刺激重复呈现了干扰刺激使干扰刺激的表征得到增强,但却并没有阻碍工作记忆的选择加工过程。这一研究结果为相对激活假说提供了部分支持,说明工作记忆的选择也许更多依赖于靶刺激表征的激活增强,而不是依赖于干扰刺激表征的激活减弱。实验二和实验三采用事件相关电位技术(event-related potential,ERP),分别考察了指导性遗忘任务和最近探测刺激任务中前摄干扰效应的电生理指标及其相关意义。指导性遗忘任务相当于实验一中的“忘记”条件。根据探测刺激的选择将实验条件分为三类。当探测刺激属于靶刺激系列,为正反应条件;当探测刺激是当前测试中没有出现过的项目,为负反应条件;当探测刺激是被“忘记”的项目,则为干扰条件。我们认为干扰条件与负反应条件之间的差异就是前摄干扰效应。最近探测刺激任务中,首先要求被试学习四个字母,随后出现探测刺激,要求被试判断探测刺激是否属于刚才学习过的字母。在这个任务中,为了控制探测刺激的熟悉性,使每个测试中的2个学习字母都与上一轮测试中的两个字母相同,从而形成以下几种实验条件:如果探测刺激在前一个测试及当前测试中都出现过,就属于熟悉性正反应;如果探测刺激仅在当前测试中出现过,属于非熟悉性正反应;如果探测刺激在前一个测试中出现过,但不属于当前测试中的学习项目,属于熟悉性负反应;如果探测刺激在当前测试及最近的前两个测试中都没有出现过,属于非熟悉性负反应。在这个任务中,熟悉性负反应与非熟悉性负反应的差异反映了前摄干扰效应。实验二的结果发现,干扰条件比负反应条件有更大的错误率和延长的反应时。电生理证据方面,在额中央区发现一个N2成分,其波峰在探测刺激出现后300毫秒左右达到最大,并且N2波幅在不同的实验条件下有一定差异,其中干扰条件的N2波幅显著小于负反应条件下的N2波幅。随后的P3波幅对不同的实验条件无差异,但正反应条件的潜伏期要早于负反应和干扰条件。通过分析,我们认为这个分布在额中央区的N2成分代表了前摄干扰的解决。同时,这个负波也说明干扰的解决过程与靶/非靶刺激的辨别发生在同一时间窗口。本研究为基于脑成像研究的偏向竞争模型提供了初步的电生理证据。实验三也发现了位于脑前部区域的N2和P3成分。对于N2波幅,发现了显著的正、负反应条件差异,正反应条件的N2波幅要小于负反应条件。而两种正条件之间与两种负条件之间没有N2波幅的显著差异。此外,两种正反应的P3潜伏期均显著小于两种负反应下的P3潜伏期。对熟悉性负反应和非熟悉性负反应的P3波幅进行分析,发现涉及前摄干扰的熟悉性负反应P3波幅减小。因此我们认为,在这个任务中,P3的波幅变化反映了前摄干扰的解决过程。结合实验二和实验三的结果,我们认为在本研究中,前部N2和P3成分分别代表了双重加工理论中的两个过程:熟悉性信息加工和信息回忆。根据双重加工理论,再认是基于熟悉度及信息回忆的一种综合判断,并且对熟悉度信息的提取要早于对情境信息的提取。由于指导性遗忘任务和最近探测刺激任务中的记忆负荷不同,并且干扰刺激的表征激活强度也不同,因此两种任务中前摄干扰发生作用和被解决的时程也有所不同。在两个实验中,反映干扰效应的电生理成分波幅都有所减小,说明干扰的解决也许并非需要额外心理努力的抑制过程。这与实验一的结果也是一致的,即正确的工作记忆选择是通过对靶刺激表征的激活增强来实现的,而不是依靠干扰刺激表征的激活减小。更多还原

【Abstract】 Working memory is central to successful cognition. As proactive interference (PI) is one of the critical factors which exert significant control over the amount of information that can be retrieved from working memory, it is important to investigate the effect of distractor representation and how can we overcome this negative effect.This study includes three experiments. Working memory selection task was used in experiment one and the competition between target stimuli representation and distractors representation was fully examined through a series of behavioral tasks. Participants were told to remember a set of letters in the study display and later were cued to select half of the letters and to forget the others. The selected letters were the target stimuli and were called as the to-be-remember (TBR) set and the other letters were distractors and were named as to-be-forgotten (TBF) set. Soon after the selection cue, the probe was displayed on the screen and participants had to make a“yes/no”judgment as to whether the probe was one of the three target stimuli.We modulated the types of selection cues and the cue-to-probe intervals to test selection difficulty in working memory. It was found that when selection cues represented target stimuli, the target representation became more active and made it easier for the target to be selected. However, even though the level of activation of the distractor representation increased with cues reinstating the TBF set, it did not make selection more difficult. These results provided partial support to the relative activation hypothesis-- the level of target representation had a significant impact on selection difficulty, that of the distractor representation did not.Using event-related potential (ERP) technique, experiment two and three investigated the eletrophysiological signature of PI in directed-forgetting task and recent probes task, respectively. Directed-forgetting task equals with TBF cue condition in experiment one. The probe was selected in different ways in this study. The probes were in the memory set for the“Yes”trials, in the recently ignored set for the“Lure”condition and out of the initial memory set for“No”trials. Proactive interference was indexed as delayed response to probes in the Lure condition than in the No condition and differences between Lure and No waveforms. In the recent probes task, participants were presented with a study display including four letters. They were to judge whether the following probe was in the study display or not. To manipulate the familiarity of the probes, each trial was composed of 2 letters from the previous trial and 2 letters that had not been presented in the previous two trials. This allowed some probes were members of the current trial and the last trial (Recent Positive probes); some were members of the current trial but not the last two trial (Non-Recent Positive probes); some were members of the previous trial but not the current trial (Familiar Negative probes); and some had not been presented in the current trial and the previous two trials (Non-familiar Negative probes). Proactive interference effect was thought to be indexed by differences between the two kinds of negative probes in this study.As the results of experiment two showed, error rate was increased and reaction time was delayed for the Lure condition relative to No condition. A fronto-central N2 component peaking around 300 ms post-probe-onset differentiated among different types of probes, with Lure N2 significantly reduced when compared with No condition. There was no difference between P3 amplitudes, but P3 latency was earlier for Yes condition than for Lure and No condition. The study identifies N2 as the ERP signature for proactive interference resolution. It also indicates that the resolution process occurs in the same time window as target/non-target discrimination and provides the first piece of electrophysiological evidence supporting biased competition model based on localization data.The anterior N2 and P3 component were consistently found in experiment three. N2 component differentiated between yes/no responses, with yes trials induced reduced N2. There was no difference between Familiar and Non-familiar positive trials and between Familiar and Non-familiar negative trials. Moreover, the latencies of P3 components were earlier for positive trials than for negative trials. Further comparison of P3 amplitudes between Familiar and Non-familiar negative conditions found decreased amplitude for Familiar negative trials. We inferred the modulation of P3 amplitudes indexed proactive interference resolution.Combining evidences from experiment two and experiment three, it is postulated that the anterior N2 and P3 component correspond to the two processes in the dual-process theory, i.e., judgment of familiarity and information collection. Dual-process theory assumes that recognition reflects a mixture of judgments based on familiarity and recollection of specific episodic information. The two tasks used in ERP studies have different memory load and different level of distractor representation activation. Maybe these differences lead to different timing course of online processing of PI. The ERP components reflecting PI resolution had reduced amplitudes in experiment two and experiment three, indicating the resolution of PI does not need inhibition with extra mental effort. The electrophysiological evidences are consistent with results from experiment one, that is, successful selection in working memory depends on increased activation of target representation but not decreased activation of distracor representation.更多还原