客体复杂度影响工作记忆可存储的客体数目

采用变化觉察范式,以对侧延迟活动（contralateral delay activity,CDA）的幅值为指标,通过操纵记忆刺激的复杂程度,对视觉工作记忆中可存储的客体数目（即工作记忆容量）问题进行了探讨。结果表明,2个复杂客体条件下的CDA幅值与4个复杂客体条件无显著差异,而4个简单客体条件的CDA幅值显著高于2个简单客体条件,即CDA的幅值受客体复杂度的调节。基于该结果推论：并非视觉工作记忆总能存储4个客体,其可存储的客体数目受客体复杂度影响。     

线条朝向的空间构型对视觉工作记忆表征的影响

采用行为实验和事件相关电位技术(ERP),通过整体检测的变化觉察范式,探讨线条朝向的空间构型对视觉工作记忆表征的影响及机制。行为结果发现,水平排列线条朝向的视觉工作记忆成绩高于杂乱排列; 水平排列线条朝向有框时的视觉工作记忆成绩低于无框条件; ERP结果发现,无框条件下水平排列的线条朝向诱发的对侧延迟活动的波幅小于有框条件。以上结果说明,水平排列的空间构型能够促进线条朝向的视觉工作记忆表征,这一促进作用的潜在机制可能是水平排列的空间构型能够降低信息表征的负荷。     

视觉工作记忆中基于客体的存储机制：来自ERPs的证据

该研究以简单形状和颜色构成的客体为材料,采用延迟匹配范式,通过记录事件相关电位,以反映工作记忆表征与知觉输入间冲突的N270为指标,就视觉工作记忆中的客体存储机制进行了探讨。结果发现,无关维度特征变化与目标维度特征变化均可诱发N270。该结果表明,视觉工作记忆对客体目标特征进行存储时,无关特征亦自动得到选择加工,支持基于客体的存储说。     

客体运动方向的视觉工作记忆存储方式

采用变化觉察范式,以独立运动的客体为对象,通过两个实验,探讨多个客体的运动方向在视觉工作记忆中的存储机制,即单个对象独立存储,抑或其存储受多个客体构型的影响。实验一和实验二相继考察了非目标客体运动方向变化,以及是否存在非目标客体对觉察目标客体运动方向的影响。结果发现,非目标客体运动方向变化条件下的觉察正确率显著低于不变的条件,然而只呈现目标客体条件下的觉察正确率与同时呈现目标和非目标条件无显著差异。该结果与前人在静态条件下对目标客体的觉察受目标客体和非目标客体整体构型影响的结论不一致。本研究的结果支持多个客体的运动方向信息在工作记忆中是以独立方式存储的假设。     

两维特征图形的客体和空间工作记忆存储研究

研究采用单探测变化检测范式,考察了两维特征图形在视觉客体和视觉空间工作记忆中的存储机制,并对其容量进行测定。40名被试(平均年龄20.56±1.73岁)随机分为两个等组,分别完成实验一和实验二。实验一的刺激图形由颜色和形状两基本特征组成,实验二的刺激为由不同颜色和开口朝向组成的兰道环。两个实验结果均显示:(1)特征交换变化条件下的记忆成绩与单特征变化条件下最差的记忆成绩差异不显著;(2)空间工作记忆任务的成绩显著优于客体工作记忆任务;(3)被试在视觉工作记忆中能存储2~3个客体和3~4个空间位置。这表明,由两种不同维度特征组成的图形在视觉客体和视觉空间工作记忆中均以整合方式进行存储,空间工作记忆的容量大于客体工作记忆。     

客体运动速度的视觉工作记忆容量

自Luck等人的研究以来,诸多研究者对客体信息在视觉工作记忆中的表征与存储问题进行了探讨。现有研究主要采用呈现于静态场景的客体作为刺激材料,而不涉及对客体运动特征信息的短时存储。本研究结合多客体追踪范式和视觉工作记忆的变化觉察范式,通过比较检测项全部呈现方式与单检测项呈现方式条件下,客体运动速度的视觉工作记忆绩效,探讨了多个客体的运动速度信息在工作记忆中的存储方式和容量问题。结果表明,在工作记忆中能够存储约3仑独立客体的运动速度信息。     

工作记忆内容对无意视盲的改善作用

无意视盲是注意捕获失败的一种现象.研究发现:工作记忆内容对视觉注意的引导可以影响视觉注意的捕获.本研究以此为基础探讨了工作记忆内容能否影响无意视盲.本研究采用了静态无意视盲典型范式,通过两个实验分别探讨了工作记忆对无意视盲的引导作用以及在不同知觉负荷下引导作用的自动性,进而研究工作记忆内容对无意视盲的改善作用.实验1结果表明,当非期望刺激与工作记忆内容属于同一类别时,对非期望刺激的觉察率显著高于当非期望刺激与工作记忆内容不属于同一类别的情况,说明在纯语义的水平上工作记忆内容可以引导视觉注意捕获,进而改善无意视盲.实验2发现,当知觉负荷由低到高变化时,非期望刺激与工作记忆内容同类属时,觉察率无显著变化,说明工作记忆内容对无意视盲引导不受知觉负荷的调节,是一种自动化的过程.     

三维图形的视空间工作记忆容量研究

采用三维几何图形为材料,通过单探测变化觉察范式来测定视觉工作记忆的存储容量,并比较客体工作记忆和空间工作记忆容量的差异。实验1、2的材料分别为由颜色和形状两个基本特征组成的三维图形和由一个基本特征和一个细节特征组成的三维图形。两个实验结果显示,被试能在视觉工作记忆中存储约2-3个客体和4个空间位置,空间工作记忆容量显著大于客体工作记忆容量。进一步的比较发现,被试对由两个基本特征组成的三维图形的存储容量大于由一个基本特征和一个细节特征组成的三维图形。这表明,组成三维图形的特征类型对视空间工作记忆的存储容量有显著影响。     

客体在视觉工作记忆中的存储机制

采用变化觉察范式,通过两个实验对不同类型视觉信息在工作记忆中的存储机制进行了探讨。实验一中要求记忆的客体由颜色和形状两基本特征构成;实验二中的客体为具有不同颜色及开口朝向的兰道环。通过观察检测项变化方式对记忆绩效的影响,获得以下结论:（1）对颜色和形状两基本特征的存储以整合客体为单位;（2）兰道环的颜色与开口朝向信息难以以整合客体方式存储。笔者推测,视觉工作记忆中存储的整合客体并非如现有理论假设的,是在集中注意参与下创建的,而是由并行加工阶段所获信息构成;客体中所含需集中注意提取的细节特征信息难以与其基本特征信息整合于该客体表征     

本族和异族面孔的视觉工作记忆容量:面孔特征的影响

采用延迟探测刺激匹配再认任务,考察面孔种族和内外部特征是否会影响面孔视觉工作记忆容量。被试先识记2或4张中国人或白人的真实面孔图片,一半有内部特征(眼睛、鼻子和嘴巴),另一半有内部和外部特征(脸型、发型),再进行面孔再认判断。采用Cowan’s K值的分析显示,我国被试对本族和异族面孔的视觉工作记忆容量没有差异,但面孔数量与特征多少会影响面孔工作记忆容量,表明对本族和异族面孔的视觉加工不同。     

视觉工作记忆的同类别存储优势

概念规律如记忆项间的类别关系如何影响视觉工作记忆容量是一个有争议的问题。针对该问题, 学界存在两种预测截然不同的假说：(1)混合类别优势假说, (2)同类别优势假说。综述文献发现, 该类研究均采用带有细节特征的真实客体作为实验材料, 因此前人研究中发现的混合类别优势效应或同类别优势效应中必然混有低水平知觉特征的影响。故本研究采用去除细节信息的动物剪影作为记忆材料来排除上述因素的影响, 旨在厘清上述两种假设, 并采用对侧延迟活动作为神经指标, 来进一步探讨概念规律影响工作记忆容量的内在机制。两个行为实验发现, 不论记忆项同时呈现还是序列呈现, 均存在同类别记忆优势效应。脑电实验结果发现相比记忆不同类别客体, 记忆同等数量的同类别客体诱发的对侧延迟活动的幅值更小。上述结果一致表明, 视觉工作记忆可借助概念的方式将同类别客体加以组织, 从而有效扩大视觉工作记忆容量, 支持了同类别优势假说。     

The effects of direction similarity in visual working memory: Behavioural and event-related potential studies

Object similarity can improve visual working memory (VWM) performance in the change-detection task, but impair the recognition performance when it occurs at retrieval of VWM in the recognition task. The effect of direction similarity is an issue that has not been well resolved. Furthermore, electrophysiological evidence in support of the mechanisms that underlie the effects of similarity is still scarce. In the current study, we conducted three behavioural experiments to examine the effects of direction similarity on memory performance with regard to both the encoding and retrieval phases of VWM and one event-related potential (ERP) experiment to explore the neural signatures of direction similarity in VWM. Our behavioural studies indicated that direction similarity improved performance when it occurred at the encoding phase but impaired performance when it occurred at the retrieval phase. Moreover, the ERP experiment showed that the amplitude of the contralateral delay activity (CDA) increased with the increasing set size for similar but not dissimilar directions. In addition, the CDA amplitude for similar directions was lower than that for dissimilar directions at set size 2. Taken together, these findings suggest that direction similarity at encoding has a positive effect on VWM performance and at retrieval has a negative effect. Given that VWM capacity depends on information load and the number of objects, the positive effect of similarity may be attributed to reduced information load of memory objects.     

客体同维度特征的视觉工作记忆存储机制

客体理论认为视觉工作记忆的存储单位是客体, 人类能够把组成物体的所有特征整合成一个单元进行记忆, 不管这些特征是来自不同维度还是同一维度。然而同一维度多个特征可以被整合成客体记忆的结果只被少数研究证实, 大量研究发现同一维度的多个特征不能被整合记忆, 这形成了弱客体理论的基本观点。为了解决两大理论之间的争议, 本研究主要探究同维度特征能否被整合记忆。通过分析以往研究, 我们认为实验范式和物体意义两个因素可能是导致之前大部分研究没有发现维度内特征能够被整合记忆的原因。因此, 实验1采用回忆报告范式替代以往研究经常使用的变化觉察范式, 结果发现, 同一维度的多个特征难以被整合记忆。实验2以记忆无意义物体的特征为基线, 探究在记忆有意义物体的特征时是否可能将多个特征进行整合记忆。结果发现, 对于有意义物体的特征的记忆成绩并没有显著好于记忆无意义物体特征的成绩, 说明即使采用具有较强整合线索的有意义物体作为载体, 同一维度多个特征也难以被整合记忆。两个实验结果进一步支持了弱客体理论。     

Visual working memory for dynamic objects: Impaired binding between object feature and location

In daily life, people frequently need to observe dynamic objects and temporarily maintain their representations in visual working memory (VWM). The present study explored the mechanism underlying the binding between perceptual features and locations of dynamic objects in VWM. In three experiments, we measured and compared the memory performance for feature-location binding of multiple dynamic and static objects. The results showed that the feature-location binding was impaired for the dynamic objects compared with the static objects. The impairment persisted when the global spatial configuration of the objects remained intact during the motion, as well as when the binding task was relatively easy, such as binding between single-feature objects and coarse locations. The results indicate that object features and locations are not maintained in VWM as well-integrated object files; rather, the formation of feature-location binding may require additional processes, which are disrupted by the constant change of locations in dynamic circumstances. We propose a consolidation process as possible underlying mechanism, and discuss factors that may influence the strength of feature-location binding in dynamic circumstances.     

Reward-priming impacts visual working memory maintenance: Evidence from human electrophysiology

Reward can benefit visual processing of reward-associated objects in a non-strategic way. Recent studies have suggested that such influence extends also to visual working memory (VWM) representations of reward-associated stimuli. However, it is not clear yet which mechanisms underlie the behavioural effects in VWM tasks: reward could directly impact on our ability to maintain representations in VWM or it could influence memory indirectly via priming of attentional selection. To distinguish between these alternatives we measured event-related potential indices of selective attention – the N2pc – and VWM maintenance – the CDA (contralateral delay activity) – while participants completed a VWM task. Results show that reward outcome in one trial caused similarly coloured targets to be strongly represented in VWM in subsequent trials, as expressed in a larger-amplitude CDA This was not preceded by a corresponding effect on attentional selection, in so far as our key manipulation had no impact on the N2pc. In a second experiment, we found that reward priming produced a behavioural benefit that emerged over time, suggesting that the representations of reward-associated items stored in VWM are more resistant to interference and decay. We conclude that when the task stresses VWM maintenance, it is at this representational level that reward will have impact.     

Does maintaining bindings in visual working memory require more attention than maintaining features?

ABSTRACT

Whether more attention is required for maintaining bindings than maintaining features in visual working memory (VWM) remains an open question. If maintaining bindings in VWM does not require more attention than maintaining features, is it related to the stability of binding representations? In this study, we explored whether maintaining bindings requires more attention than maintaining features for similar and dissimilar objects by inserting a feature report task into the maintenance phase of VWM in Experiments 1 and 2. We also investigated whether the effect of similarity on the attentional requirement for maintaining bindings and features is due to the stability of VWM representations by inserting a suffix during the maintenance phase of VWM in Experiment 3. The results showed that when object-based attention was consumed, bindings were more impaired than features for dissimilar objects but not for similar objects. We also found that the bindings of similar objects were less interfered by the suffix than those of dissimilar objects. Our findings suggest that maintaining bindings does not require more attention than maintaining features when the binding representations are stable in VWM and similarity improves the stability of binding representations.     

Storage of features, conjunctions and objects in visual working memory

Working memory can be divided into separate subsystems for verbal and visual information. Although the verbal system has been well characterized, the storage capacity of visual working memory has not yet been established for simple features or for conjunctions of features. The authors demonstrate that it is possible to retain information about only 3-4 colors or orientations in visual working memory at one time. Observers are also able to retain both the color and the orientation of 3-4 objects, indicating that visual working memory stores integrated objects rather than individual features. Indeed, objects defined by a conjunction of four features can be retained in working memory just as well as single-feature objects, allowing many individual features to be retained when distributed across a small number of objects. Thus, the capacity of visual working memory must be understood in terms of integrated objects rather than individual features.     

Visual working memory for simple and complex visual stimuli

Does the magical number four characterize our visual working memory (VWM) capacity for all kinds of objects, or is the capacity of VWM inversely related to the perceptual complexity of those objects? To find out how perceptual complexity affects VWM, we used a change detection task to measure VWM capacity for six types of stimuli of different complexity: colors, letters, polygons, squiggles, cubes, and faces. We found that the estimated capacity decreased for more complex stimuli, suggesting that perceptual complexity was an important factor in determining VWM capacity. However, the considerable correlation between perceptual complexity and VWM capacity declined significantly if subjects were allowed to view the sample memory display longer. We conclude that when encoding limitations are minimized, perceptual complexity affects, but does not determine, VWM capacity.