Remembering “what” brings along “where” in visual working memory

Does a behavioral and anatomical division exist between spatial and object working memory? In this article, we explore this question by testing human participants in simple visual working memory tasks. We compared a condition in which there was no location change with conditions in which absolute location change and absolute plus relative location change were manipulated. The results showed that object memory was influenced by memory for relative but not for absolute location information. Furthermore, we demonstrated that relative space can be specified by a salient surrounding box or by distractor objects with no touching surfaces. Verbal memory was not influenced by any type of spatial information. Taken together, these results indicate that memory for “where” influences memory for “what.” We propose that there is an asymmetry in memory according to which object memory always contains location information.     

No sex differences in spatial location memory for abstract designs

Previous research has demonstrated a female advantage, albeit imperfectly, on tests of object location memory where object identity information is readily available. However, spatial and visual elements are often confounded in the experimental tasks used. Here spatial and visual memory performance was compared in 30 men and 30 women by presenting 12 abstract designs in a spatial array for recall and recognition (visual memory) and spatial location ("object" location memory). Object location memory was measured via a sensitive absolute displacement score defined as the distance in mms between the position assigned to the object during recall and the actual position it originally occupied. There were no sex differences in either the visual or spatial location tests. Controlling for age and estimated IQ scores made no impact on the results. These data suggest an absence of a sex difference in purely visual and spatial aspects of object location memory.     

Episodic memory for object location versus episodic memory for object identity: do they rely on distinct encoding processes?

Three experiments were conducted to determine whether encoding processes that support episodic memory for object location are distinct from those that support memory for object identity. Guided by transfer-appropriate processing notions, we examined with an incidental learning paradigm whether an attentional focus on object location at encoding promotes subsequent recovery of object location, whereas a focus on object identity promotes recovery of object identity. We found that judging spatial relationships at encoding selectively supports recovery of object location, provided the test assesses memory for these relationships (rather than absolute location); our results also showed that judging physical and semantic object attributes promotes recovery of object identity preferentially. Contrasting with these domain-specific effects was evidence that identification processes involved in object naming boost memory for object identity as well as for absolute object location. Object identification at encoding may support memory performance in both domains by triggering the binding of identity and location information through a mechanism of object-based attentional selection.     

Effects of verbal and nonverbal interference on spatial and object visual working memory

We tested the hypothesis that a verbal coding mechanism is necessarily engaged by object, but not spatial, visual working memory tasks. We employed a dual-task procedure that paired n-back working memory tasks with domain-specific distractor trials inserted into each interstimulus interval of the n-back tasks. In two experiments, object n-back performance demonstrated greater sensitivity to verbal distraction, whereas spatial n-back performance demonstrated greater sensitivity to motion distraction. Visual object and spatial working memory may differ fundamentally in that the mnemonic representation of featural characteristics of objects incorporates a verbal (perhaps semantic) code, whereas the mnemonic representation of the location of objects does not. Thus, the processes supporting working memory for these two types of information may differ in more ways than those dictated by the "what/where" organization of the visual system, a fact more easily reconciled with a component process than a memory systems account of working memory function.     

Coding of spatial location information: an automatic process?

Several researches have claimed that spatial location information is automatically encoded, a claim supported by studies testing several criteria for the identification of automatic processes. However, a careful look at these studies reveals that some have not used appropriate testing methodology, the results of others have not complied with the criteria, and some criteria have not been examined at all. This article includes four experiments in which five criteria for testing the automaticity of cognitive processes were examined. Results show that memory for spatial location information is influenced by intention, age of subjects, competing task loads, practice, strategy manipulations, and individual differences. These results generally hold for memory of absolute location and for relative location information. The reported results are at odds with the claim that memory for spatial location information is exclusively mediated by automatic encoding processes. The concept of automaticity and the appropriateness of the testing criteria are discussed in light of the current results and recent findings on other features of the environment claimed to be automatically encoded.     

Memory for retinotopic locations is more accurate than memory for spatiotopic locations,even for visually guided reaching

To interact successfully with objects, we must maintain stable representations of their locations in the world. However, their images on the retina may be displaced several times per second by large, rapid eye movements. A number of studies have demonstrated that visual processing is heavily influenced by gaze-centered (retinotopic) information, including a recent finding that memory for an object’s location is more accurate and precise in gaze-centered (retinotopic) than world-centered (spatiotopic) coordinates (Golomb & Kanwisher, 2012b). This effect is somewhat surprising, given our intuition that behavior is successfully guided by spatiotopic representations. In the present experiment, we asked whether the visual system may rely on a more spatiotopic memory store depending on the mode of responding. Specifically, we tested whether reaching toward and tapping directly on an object’s location could improve memory for its spatiotopic location. Participants performed a spatial working memory task under four conditions: retinotopic vs. spatiotopic task, and computer mouse click vs. touchscreen reaching response. When participants responded by clicking with a mouse on the screen, we replicated Golomb & Kanwisher’s original results, finding that memory was more accurate in retinotopic than spatiotopic coordinates and that the accuracy of spatiotopic memory deteriorated substantially more than retinotopic memory with additional eye movements during the memory delay. Critically, we found the same pattern of results when participants responded by using their finger to reach and tap the remembered location on the monitor. These results further support the hypothesis that spatial memory is natively retinotopic; we found no evidence that engaging the motor system improves spatiotopic memory across saccades.     

Proactive interference from items previously stored in visual working memory

This study investigates the fate of information that was previously stored in visual working memory but that is no longer needed. Previous research has found inconsistent results, with some showing effective release of irrelevant information and others showing proactive interference. Using change detection tasks of colors or shapes, we show that participants tend to falsely classify a changed item as "no change" if it matches one of the memory items on the preceding trial. The interference is spatially specific: Memory for the preceding trial interferes more if it matches the feature value and the location of a test item than if it does not. Interference results from retaining information in visual working memory, since it is absent when items on the preceding trials are passively viewed, or are attended but not memorized. We conclude that people cannot fully eliminate unwanted visual information from current working memory tasks.     

客体相似性对不同认知方式个体视觉工作记忆表征的影响

采用整体检测的变化察觉范式,探讨客体的相似性对客体—空间型认知方式个体视觉工作记忆表征的影响。行为结果显示,在不相似客体的视觉工作记忆表征任务中,客体型者在长延时条件的成绩优于空间型者,而在相似客体的视觉工作记忆表征任务中,两者无差异;ERP结果显示,在不相似客体视觉工作记忆表征任务中,与客体型者相比,空间型者在大脑皮层诱发出更大的负SP。以上结果表明,客体型者比空间型者对不相似客体视觉工作记忆加工具有优势,其潜在机制可能在于,客体型者对不相似客体视觉工作记忆表征时的神经活动效能更高。     

客体相似性对不同认知方式个体视觉工作记忆表征的影响

采用整体检测的变化察觉范式,探讨客体的相似性对客体—空间型认知方式个体视觉工作记忆表征的影响。行为结果显示,在不相似客体的视觉工作记忆表征任务中,客体型者在长延时条件的成绩优于空间型者,而在相似客体的视觉工作记忆表征任务中,两者无差异;ERP结果显示,在不相似客体视觉工作记忆表征任务中,与客体型者相比,空间型者在大脑皮层诱发出更大的负SP。以上结果表明,客体型者比空间型者对不相似客体视觉工作记忆加工具有优势,其潜在机制可能在于,客体型者对不相似客体视觉工作记忆表征时的神经活动效能更高。     

Developmental Differences in the Influence of Distractors on Maintenance in Spatial Working Memory

This study examined whether attention to a location plays a role in the maintenance of locations in spatial working memory in young children as it does in adults. This study was the first to investigate whether distractors presented during the delay of a spatial working-memory task influenced young children’s memory responses. Across 2 experiments, 3- and 6-year-olds completed a spatial working-memory task featuring a static target location and distractor location. Results indicated a change from 3 years to 6 years of age in how distractors influenced memory. Six-year-olds’ memory responses were biased away from a distractor that was close to the target location and on the outside of the target location relative to the center of the monitor. Distractors that were far from the target or that were toward the center of the monitor relative to the target location had no effect. Three-year-olds’ responses were biased toward a distractor when the distractor was on the outside of the target location and farther from the target. Distractors that were near the target location or toward the center of the monitor had no effect. These biases provide evidence that young children’s maintenance of a location in memory is influenced by attention.     

Ensemble coding remains accurate under object and spatial visual working memory load

A number of studies have provided evidence that the visual system statistically summarizes large amounts of information that would exceed the limitations of attention and working memory (ensemble coding). However the necessity of working memory resources for ensemble coding has not yet been tested directly. In the current study, we used a dual task design to test the effect of object and spatial visual working memory load on size averaging accuracy. In Experiment 1, we tested participants’ accuracy in comparing the mean size of two sets under various levels of object visual working memory load. Although the accuracy of average size judgments depended on the difference in mean size between the two sets, we found no effect of working memory load. In Experiment 2, we tested the same average size judgment while participants were under spatial visual working memory load, again finding no effect of load on averaging accuracy. Overall our results reveal that ensemble coding can proceed unimpeded and highly accurately under both object and spatial visual working memory load, providing further evidence that ensemble coding reflects a basic perceptual process distinct from that of individual object processing.     

Spatial attention based on 2D location and relative depth order modulates visual working memory in a 3D environment

The attentional effect on visual working memory (VWM) has been a heated research topic in the past two decades. Studies show that VWM performance for an attended memory item can be improved by cueing its two-dimensional (2D) spatial location during retention. However, few studies have investigated the effect of attentional selection on VWM in a three-dimensional setting, and it remains unknown whether depth information can produce beneficial attentional effects on 2D visual representations similar to 2D spatial information. Here we conducted four experiments, displaying memory items at various stereoscopic depth planes, and examined the retro-cue effects of four types of cues – a cue would either indicate the 2D or depth location of a memory item, and either in the form of physical (directly pointing to a location) or symbolic (numerically mapping onto a location) cues. We found that retro-cue benefits were only observed for cues directly pointing to a 2D location, whereas a null effect was observed for cues directly pointing to a depth location. However, there was a retro-cue effect when cueing the relative depth order, though the effect was weaker than that for cueing the 2D location. The selective effect on VWM based on 2D spatial attention is different from depth-based attention, and the divergence suggests that an object representation is primarily bound with its 2D spatial location, weakly bound with its depth order but not with its metric depth location. This indicates that attentional selection based on memory for depth, particularly metric depth, is ineffective.     

Different types of working memory binding in epilepsy patients with unilateral anterior temporal lobectomy

The medial temporal lobe is an important structure for long-term memory formation, but its role in working memory is less clear. Recent studies have shown hippocampal involvement during working memory tasks requiring binding of information. It is yet unclear whether this is limited to tasks containing spatial features. The present study contrasted three binding conditions and one single-item condition in patients with unilateral anterior temporal lobectomy.A group of 43 patients with temporal lobectomy (23 left; 20 right) and 20 matched controls were examined with a working memory task assessing spatial relational binding (object–location), non-spatial relational binding (object–object), conjunctive binding (object–colour) and working memory for single items. We varied the delay period (3 or 6 s), as there is evidence showing that delay length may modulate working memory performance.The results indicate that performance was worse for patients than for controls in both relational binding conditions, whereas patients were unimpaired in conjunctive binding. Single-item memory was found to be marginally impaired, due to a deficit on long-delay trials only.In conclusion, working memory binding deficits are found in patients with unilateral anterior temporal lobectomy. The role of the medial temporal lobe in working memory is not limited to tasks containing spatial features. Rather, it seems to be involved in relational binding, but not in conjunctive binding. The medial temporal lobe gets involved when working memory capacity does not suffice, for example when relations have to be maintained or when the delay period is long.     

Life-span development of visual working memory: when is feature binding difficult?

We asked whether the ability to keep in working memory the binding between a visual object and its spatial location changes with development across the life span more than memory for item information. Paired arrays of colored squares were identical or differed in the color of one square, and in the latter case, the changed color was unique on that trial (item change) or was duplicated elsewhere in the array (color-location binding change). Children (8-10 and 11-12 years old) and older adults (65-85 years old) showed deficits relative to young adults. These were only partly simulated by dividing attention in young adults. The older adults had an additional deficiency, specifically in binding information, which was evident only when item- and binding-change trials were mixed together. In that situation, the older adults often overlooked the more subtle, binding-type changes. Some working memory processes related to binding undergo life-span development in an inverted-U shape, whereas other, bias- and salience-related processes that influence the use of binding information seem to develop monotonically.     

视空工作记忆负载对场景主旨加工的影响

本研究采用工作记忆任务和场景辨别任务相结合的双任务范式探究客体工作记忆负载 (实验1)和空间工作记忆负载 (实验2) 对场景主旨辨别的影响。结果发现: (1) 与无负载条件相比, 客体负载条件下的非参辨别力指数(A’)明显下降, 而空间负载条件下A’无明显变化; (2) 随着场景图片呈现时间的延长, 场景辨别任务的A’逐渐提高; (3) 对自然场景和人工场景匹配情况下的A’ 明显高于对自然与自然或者人工与人工匹配情况下的A’。由此可见, 场景主旨识别, 特别是基本水平的场景主旨辨别, 与客体工作记忆共享部分认知资源, 而不与/很少与空间工作记忆共享认知资源; 在识别过程中, 上级水平范畴识别优先于基本水平范畴识别, 进一步支持了上级水平范畴优先的主旨层级加工观点。     

How undistorted spatial memories can produce distorted responses

Reproducing the location of an object from the contents of spatial working memory requires the translation of a noisy representation into an action at a single location—for instance, a mouse click or a mark with a writing utensil. In many studies, these kinds of actions result in biased responses that suggest distortions in spatial working memory. We sought to investigate the possibility of one mechanism by which distortions could arise, involving an interaction between undistorted memories and nonuniformities in attention. Specifically, the resolution of attention is finer below than above fixation, which led us to predict that bias could arise if participants tend to respond in locations below as opposed to above fixation. In Experiment 1 we found such a bias to respond below the true position of an object. Experiment 2 demonstrated with eye-tracking that fixations during response were unbiased and centered on the remembered object’s true position. Experiment 3 further evidenced a dependency on attention relative to fixation, by shifting the effect horizontally when participants were required to tilt their heads. Together, these results highlight the complex pathway involved in translating probabilistic memories into discrete actions, and they present a new attentional mechanism by which undistorted spatial memories can lead to distorted reproduction responses.     

No evidence for binding of items to task-irrelevant backgrounds in visual working memory

When representing visual features such as color and shape in visual working memory (VWM), participants also represent the locations of those features as a spatial configuration of the locations of those features in the display. In everyday life, we encounter objects against some background, yet it is unclear whether the configural representation in memory obligatorily constitutes the entire display, including that (often task-irrelevant) background information. In three experiments, participants completed a change detection task on color and shape; the memoranda were presented in front of uniform gray backgrounds, a textured background (Exp. 1), or a background containing location placeholders (Exps. 2 and 3). When whole-display probes were presented, changes to the objects’ locations or feature bindings impacted memory performance—implying that the spatial configuration of the probes influenced participants’ change decisions. Furthermore, when only a single item was probed, the effect of changing its location or feature bindings was either diminished or completely extinguished, implying that single probes do not necessarily elicit the entire spatial configuration. Critically, when task-irrelevant backgrounds were also presented that may have provided a spatial configuration for the single probes, the effect of location or bindings was not moderated. These findings suggest that although the spatial configuration of a display guides VWM-based recognition, this information does not necessarily always influence the decision process during change detection.     

Interactions between working memory, attention and eye movements

This paper reviews the recent findings on working memory, attention and eye movements. We discuss the research that shows that many phenomena related to visual attention taking place when selecting relevant information from the environment are similar to processes needed to keep information active in working memory. We discuss new data that show that when retrieving information from working memory, people may allocate visual spatial attention to the empty location in space that used to contain the information that has to be retrieved. Moreover, we show that maintaining a location in working memory not only may involve attention rehearsal, but might also recruit the oculomotor system. Recent findings seem to suggest that remembering a location may involve attention-based rehearsal in higher brain areas, while at the same time there is inhibition of specific motor programs at lower brain areas. We discuss the possibility that working memory functions do not reside at a special area in the brain, but emerge from the selective recruitment of brain areas that are typically involved in spatial attention and motor control.     

工作记忆对基于颜色的注意返回抑制的影响

前人研究发现返回抑制与工作记忆间存在特异性关系,即某种特定类型的返回抑制只依赖于此种工作记忆。然而,这些研究都只考察了空间和客体返回抑制。为了验证两者间的这种特异性关系在其他类型的返回抑制中仍然存在,本研究考察了工作记忆对基于颜色的返回抑制的影响。结果发现颜色返回抑制只受颜色工作记忆任务的影响,不受形状工作记忆任务影响,这为返回抑制和工作记忆特异性关系的普适性提供了进一步证据。