人类工作记忆的某些神经影像研究

采用神经影像技术研究人类工作记忆的脑机理是目前一个十分活跃的研究领域。研究表明存在负责不同信息加工的工作记忆系统 ,如词语工作记忆、空间工作记忆等 ,其中词语工作记忆主要由大脑左半球参与 ,空间工作记忆主要由大脑右半球参与。前额叶在工作记忆中的作用相当复杂 ,包括对记忆信息的注意和抑制、管理、整合等功能。合理巧妙的实验设计、多种研究手段的综合应用必将使人类工作记忆的脑机理得到充分阐明。     

知觉表征精度对工作记忆中抑制干扰能力的影响

工作记忆的容量十分有限,需要选择性地抑制与目标无关信息的干扰,工作记忆容量高的个体,其抑制干扰的能力也更强。本研究采用带有不同形状干扰刺激的色块颜色回忆任务考察干扰对工作记忆容量和表征精度的影响,结果发现,当负荷超出工作记忆容量范围时,干扰减少了记忆所能表征客体的个数;当负荷在工作记忆容量范围内时,干扰降低了记忆中表征客体的精度。更进一步,研究采用独立的知觉任务来测量知觉表征的精度,并探讨作为信息加工的初始阶段的知觉表征如何影响工作记忆加工过程中抑制干扰的能力。将实验中收集的48名有效被试按照知觉表征精度的高低平均分为两组,结果发现上述干扰效应主要表现在知觉表征精度较低的组中,并且该组中知觉表征精度越高的个体,其工作记忆抑制干扰的能力也越强。本研究为实践中通过知觉训练来提升工作记忆的抑制干扰能力提供了理论指导。     

工作记忆内容对视知觉的功能性影响

工作记忆和知觉是人类信息加工系统中的两个基本认知结构, 阐明两者之间的功能关系对于揭示人类信息加工的本质规律具有重要和根本的科学意义。工作记忆和知觉可以在多个方面发生交互作用, 其中工作记忆内容对视知觉的影响就是一个很重要的方面。文章在系统回顾工作记忆内容影响视知觉的相关研究的基础上, 提出工作记忆内容可以引导知觉选择、增强知觉表征和改变知觉经验, 指出工作记忆中的自上而下调控机制可能是工作记忆内容影响知觉的神经基础。     

抑制控制与高级认知功能的关系

近年来抑制控制与高级认知功能关系的研究受到了越来越多的重视。大量实证研究表明, 抑制控制是解释工作记忆、阅读理解、液态智力等高级认知功能个体差异的一个重要机制。脑成像研究表明, 抑制控制与工作记忆和液态智力等高级认知功能都激活了前额叶和顶叶等共同脑区。同时, 认知发展和认知老化, 以及认知干预领域的研究都一致表明, 抑制控制与高级认知功能关系密切。未来研究应注意抑制控制的定义和测量问题, 以及脑机制和训练干预等方面的问题。     

抑郁症患者工作记忆内情绪刺激加工的特点及其机制

抑郁症患者在工作记忆内情绪刺激加工的特点为倾向于加工与负性心境一致的材料, 被认为是抑郁症认知易感性的核心特征。目前研究者们围绕抑郁症工作记忆中央执行系统三个子功能的情绪刺激加工特点及其作用机制进行了大量研究, 发现在更新功能上, 患者难以移除负性情绪信息, 且在正性信息的加工上存在缺损; 在抑制功能上, 患者难以抑制无关负性情绪信息进入工作记忆; 在转换功能上, 患者情绪材料转换困难的研究证据尚不充分。神经生理与脑成像的研究初步表明, 工作记忆中的情绪刺激加工与抑郁症患者背外侧前额叶和前扣带回的功能激活水平异常有关。未来研究需评估工作记忆三个子功能对抑郁症状的差异性贡献及在情绪刺激加工上的统一性, 并探究其随疾病发生发展变化的轨迹, 谨慎选取并评估不同情绪刺激材料指标的诱发效应及其对工作记忆功能的独特影响。在此基础上, 深入探究工作记忆内情绪刺激加工的神经机制, 为工作记忆偏向矫正干预的临床应用及其预期效果提供理论依据和方向。     

工作记忆负荷对无意注意的影响

通过探讨工作记忆负荷对无意注意的影响,考察工作记忆的认知控制功能对选择性注意的作用机制。为了避免工作记忆和选择注意的目标或者干扰子之间的知觉注意资源的竞争,采用言语工作记忆任务和视觉空间位置辨别任务,同时视觉干扰刺激采用被试无法识别的韩语。结果发现,在高负荷条件下,干扰效应显著;而在低和中负荷条件下,没有观察到干扰效应。说明在高负荷条件下,被试没有额外的资源来抑制干扰加工,从而出现了显著的干扰效应。由此,本研究支持负荷理论的观点：工作记忆在选择性注意中执行认知控制功能。     

执行功能与儿童数学认知

儿童数学认知能力的发展与儿童执行功能之间有着密切的联系.这种联系不仅仅表现在认知加工机制方面,如工作记忆、抑制控制等,还涉及到深层的认知神经机制,如前额叶皮质等.此外,儿童数学认知和执行功能在研究范式上也存在着一些共同的模式,例如冲突抑制任务和规则转换任务等.     

基本心理能力老化的认知机制

基本心理能力老化机制是认知老化领域研究热点之一。横断研究与追踪研究表明, 感觉功能、加工速度、工作记忆等信息加工资源的衰退导致了基本心理能力的衰退。但由于相关研究不能进行因果推论, 基本心理能力老化的认知机制尚存在争论。因此本项目拟采用实验室研究和干预实验设计, 通过操纵感觉功能(知觉压力水平)、干预加工速度与工作记忆, 考察基本心理能力的年龄差异的变化, 以期为认知老化理论的深化和拓展提供实验依据。     

视觉工作记忆的过滤效能

过滤效能反映了视觉工作记忆的干扰抑制功能, 研究者可基于储存容量或表征精度对其进行测量, 其神经加工过程主要分为觉察分心项目、过滤启动、实现过滤或储存, 涉及前额叶皮层和基底核、后顶叶皮层的协同作用。过滤效能的变化方向受到年龄、特殊障碍、情绪、认知特点等因素的影响。未来研究仍需解决的问题包括厘清过滤效能与工作记忆容量的关系, 辨明过滤效能的心理实现过程, 探索不同年龄、特殊障碍和职业等群体过滤效能的脑机制以及提升基础研究范式的生态学效度。     

工作记忆训练对认知功能和大脑神经系统的影响

工作记忆训练成为近年来提升个体认知绩效的一种有效方式。工作记忆训练主要是指采用工作记忆广度任务、刷新任务以及各种复杂工作记忆任务在计算机上以循序渐进的方式进行训练。近年来的研究发现, 工作记忆训练能提升工作记忆、流体智力、抑制、注意、阅读和数学等认知功能。神经机制的研究发现：工作记忆训练引起大脑额-顶区域激活减弱, 而皮层下结构包括纹状体和尾状核区域的激活增强; 工作记忆训练减少了大脑灰质的数量, 增强了大脑白质的功能连通性; 工作记忆训练引起尾状核上多巴胺受体的变化。未来的研究需要在研究设计、被试人群、研究手段上进一步确认和扩展工作记忆训练的有效性和内在认知神经机制。     

额叶在启动效应中的作用机制：对额叶损伤病人颜色命名和词命名任务的分析

以额叶损伤病人为被试,探讨在知觉型联想启动和知觉启动中,额叶的作用及其内在机制。实验任务包括颜色命名和词命名任务,以及相应的再认任务。结果表明,额叶损伤病人在颜色命名和词命名任务中,对旧词和重组颜色词的命名时间都没有明显差别,联想启动和颜色启动效应受损,但轻度记忆损伤病人与正常对照组之间的再认成绩相似。相关分析发现联想启动和颜色启动与额叶的多项功能有中度相关。这表明,额叶参与了知觉型联想启动效应和知觉启动,并且与其抑制和注意等执行功能有关。     

小学儿童执行功能与问题解决能力的关系

本研究选取小学二、四、六年级儿童为被试,采用计算机操作的方式,考察小学生执行功能中抑制、工作记忆和认知灵活性与4类伦敦塔问题解决表现之间的关系。结果表明在问题解决的计划方面,抑制能力较高的被试体现出良好的适应性解决能力,而工作记忆高的被试更能有效的利用资源;根据问题解决路径的不同划分了三大伦敦塔问题解决表现类型,工作记忆和抑制在问题解决中均起到重要作用。     

分心抑制的年龄差异

通过对负启动范式的说明,从年龄发展的角度对分心抑制作了理论上的探讨,介绍了几个有代表性的理论与假说,包括抑制衰退理论、多样化抑制系统模型和最佳测试时间假说;并从工作记忆能量与分心抑制的关系上探讨了基于年龄发展的资源依赖抑制模型和抑制控制假说。     

Genetic Mediation of the Associations Among Motor and Perceptual Speed and Adult Cognitive Abilities

Quantitative genetic analyses were conducted to determine the genetic mediation of the associations among motor speed, perceptual speed, and cognitive abilities in normal aging. Measures of motor performance, perceptual speed, and cognitive functioning in four domains (crystallized, fluid, spatial, and memory) were available from the Swedish Adoption/Twin Study of Aging. The sample included 206 twin pairs ranging in age from 44 to 82 years. A Motor Speed factor was constructed from 17 timed measures of motor performance. Heritability of Motor Speed was .26 in middle-aged twins and .00 in older twins. Results indicated that genetic variance in cognitive functioning in the middle-aged cohort may be defined by working memory, whereas genetic variance in the older cohort was defined by perceptual speed. Indications of a nonshared environmental component in the association among motor speed, perceptual speed, and spatial abilities suggest possible frontal lobe involvement.     

提取学习有利于学习与记忆的认知神经基础

研究表明提取学习相比简单重复学习更加益于记忆的保持。近期的脑成像研究发现, 与简单重复学习相比, 提取学习时前额叶、顶下叶、颞叶及一些皮层下结构的脑激活更大, 这些脑区的激活也能预测随后的记忆成绩。这些研究表明, 在更多认知资源的投入和工作记忆系统的参与下, 提取学习是一个获得、加工、整合和巩固语义关系的过程。提取学习充分调用认知和情感、皮层与皮层下机能, 同时还发挥语义和情景记忆优势来促进学习与记忆。     

Improved segregation of simultaneous talkers differentially affects perceptual and cognitive capacity demands for recognizing speech in competing speech

Perception of speech in competing speech is facilitated by spatial separation of the target and distracting speech, but this benefit may arise at either a perceptual or a cognitive level of processing. Load theory predicts different effects of perceptual and cognitive (working memory) load on selective attention in flanker task contexts, suggesting that this paradigm may be used to distinguish levels of interference. Two experiments examined interference from competing speech during a word recognition task under different perceptual and working memory loads in a dual-task paradigm. Listeners identified words produced by a talker of one gender while ignoring a talker of the other gender. Perceptual load was manipulated using a nonspeech response cue, with response conditional upon either one or two acoustic features (pitch and modulation). Memory load was manipulated with a secondary task consisting of one or six visually presented digits. In the first experiment, the target and distractor were presented at different virtual locations (0° and 90°, respectively), whereas in the second, all the stimuli were presented from the same apparent location. Results suggest that spatial cues improve resistance to distraction in part by reducing working memory demand.     

High working memory load leads to more Ebbinghaus illusion

The evidence that distractor processing increases with greater load on working memory has come mainly from Stroop-type interference tasks, making it difficult to establish whether cognitive load affects distractor processing at the perceptual level or during response selection. We measured the Ebbinghaus illusion under varying levels of working memory load to test whether cognitive control is also relevant for preventing processing of distractors that do not produce any response conflict, and instead affect target processing at the perceptual level. The Ebbinghaus illusion was greater under high working memory load, suggesting that availability of cognitive control functions is critical to reduce distractor processing even for distractors that are not associated with a response. We conclude that the effect of loading working memory during selective attention leads to greater distractor perception.     

Effects of frontal lobe damage on interference effects in working memory

Working memory is hypothesized to comprise a collection of distinct components or processes, each of which may have a unique neural substrate. Recent neuroimaging studies have isolated a region of the left inferior frontal gyrus that appears to be related specifically to one such component: resolving interference from previous items in working memory. In the present study, we examined working memory in patients with unilateral frontal lobe lesions by using a modified version of an item recognition task in which interference from previous trials was manipulated. In particular, we focused on patient R.C., whose lesion uniquely impinged on the region identified in the neuroimaging studies of interference effects. We measured baseline working memory performance and interference effects in R.C. and other frontal patients and in age-matched control subjects and young control subjects. Comparisons of each of these groups supported the following conclusions. Normal aging is associated with changes to both working memory and interference effects. Patients with frontal damage exhibited further declines in working memory but normal interference effects, with the exception of R.C., who exhibited a pronounced interference effect on both response time and accuracy. We propose that the left inferior frontal gyrus subserves a general, nonmnemonic function of selecting relevant information in the face of competing alternatives and that this function may be required by some working memory tasks.     

Load theory of selective attention and cognitive control

A load theory of attention in which distractor rejection depends on the level and type of load involved in current processing was tested. A series of experiments demonstrates that whereas high perceptual load reduces distractor interference, working memory load or dual-task coordination load increases distractor interference. These findings suggest 2 selective attention mechanisms: a perceptual selection mechanism serving to reduce distractor perception in situations of high perceptual load that exhaust perceptual capacity in processing relevant stimuli and a cognitive control mechanism that reduces interference from perceived distractors as long as cognitive control functions are available to maintain current priorities (low cognitive load). This theory resolves the long-standing early versus late selection debate and clarifies the role of cognitive control in selective attention.