Objects In Visual Working Memory Research Articles

Occipital, parietal, and frontal cortices selectively maintain task-relevant features of multi-feature objects in visual working memory

Previous studies have shown that information held in visual working memory is represented in the occipital, parietal, and frontal cortices. However, less is known about whether the mnemonic information of multi-feature objects is modulated by task demand in the parietal and frontal regions. To address this question, we asked participants to remember either color or orientation of one of the two colored gratings for a delay. Using fMRI and an inverted encoding model, we reconstructed population-level, feature-selective responses in the occipital, parietal and frontal cortices during memory maintenance. We found that not only orientation but also color information can be maintained in higher-order parietal and frontal cortices as well as the early visual cortex when it was cued to be remembered. Conversely, neither the task-irrelevant feature of the cued object, nor any feature of the uncued object was maintained in the occipital, parietal, or frontal cortices. These results suggest a highly selective mechanism of visual working memory that maintains task-relevant features only.

Feature-based attentional weighting and spreading in visual working memory

Attention can be directed at features and feature dimensions to facilitate perception. Here, we investigated whether feature-based-attention (FBA) can also dynamically weight feature-specific representations within multi-feature objects held in visual working memory (VWM). Across three experiments, participants retained coloured arrows in working memory and, during the delay, were cued to either the colour or the orientation dimension. We show that directing attention towards a feature dimension (1) improves the performance in the cued feature dimension at the expense of the uncued dimension, (2) is more efficient if directed to the same rather than to different dimensions for different objects, and (3) at least for colour, automatically spreads to the colour representation of non-attended objects in VWM. We conclude that FBA also continues to operate on VWM representations (with similar principles that govern FBA in the perceptual domain) and challenge the classical view that VWM representations are stored solely as integrated objects.

What are the effects of attentional prioritization on multifeature objects in WM?

Event Abstract Back to Event What are the effects of attentional prioritization on multifeature objects in WM? Muhammet Ikbal Sahan1, 2*, Andrew D. Sheldon3, 4 and Bradley Postle2, 5 1 Ghent University, Experimental Psychology, Belgium 2 University of Wisconsin-Madison, Psychiatry, United States 3 University of Wisconsin-Madison, Neuroscience Training Program, United States 4 University of Wisconsin-Madison, Medical Scientist Training Program, United States 5 University of Wisconsin-Madison, Psychology, United States Attentional prioritization is a dynamic mechanism for selecting objects in visual working memory (VWM). It has been shown that the content of VWM representations that are in the attentional focus can be flexibly decoded from multivariate pattern activity (Lewis-Peacock, Drysdale, Oberauer & Postle, 2012). However, what is unknown is how this attentional prioritization works for features that are bound to an object themselves. To address this question, two multidimensional objects (colored dots drifting coherently in one direction) were presented as memoranda, followed by retrospective cues instructing the subject to retain either one of the two features that are bound into an object (color and motion direction), or one of the two features across objects (i.e., the color or the motion direction of each object). The aim was to obtain fMRI-based pattern activation reconstructions of the cued and uncued feature representations that were bound into an object. Despite elevated BOLD activity in frontoparietal network during delay, no representational content could be decoded from these regions. To the contrary, we could reconstruct high-fidelity representations in the sensory regions that did not show elevated BOLD activation during delay. While the cued visual feature reconstruction remained robust throughout the whole delay, the uncued feature representation could also be reconstructed though with a decrease in robustness by time. Importantly, this effect was only observed when the features were bound into an object. These results have implications for competing theories about the prioritization of object and feature representations in VWM. References Lewis-Peacock, J. A., Drysdale, A. T., Oberauer, K., & Postle, B. R. (2012). Neural evidence for a distinction between short-term memory and the focus of attention. Keywords: fMRI, inverted encoding model, working memory, short term memory, Attention Conference: 12th National Congress of the Belgian Society for Neuroscience, Gent, Belgium, 22 May - 22 May, 2017. Presentation Type: Poster Presentation Topic: Cognition and Behavior Citation: Sahan M, Sheldon AD and Postle B (2019). What are the effects of attentional prioritization on multifeature objects in WM?. Front. Neurosci. Conference Abstract: 12th National Congress of the Belgian Society for Neuroscience. doi: 10.3389/conf.fnins.2017.94.00062 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Apr 2017; Published Online: 25 Jan 2019. * Correspondence: Mr. Muhammet Ikbal Sahan, Ghent University, Experimental Psychology, Ghent, Belgium, muhammet.sahan@ugent.be Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Muhammet Ikbal Sahan Andrew D Sheldon Bradley Postle Google Muhammet Ikbal Sahan Andrew D Sheldon Bradley Postle Google Scholar Muhammet Ikbal Sahan Andrew D Sheldon Bradley Postle PubMed Muhammet Ikbal Sahan Andrew D Sheldon Bradley Postle Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Occipital, parietal, and frontal cortices maintain only task-relevant features of multi-feature objects in visual working memory

Occipital, parietal, and frontal cortices maintain only task-relevant features of multi-feature objects in visual working memory

Object formation in visual working memory: Evidence from object-based attention

We report on how visual working memory (VWM) forms intact perceptual representations of visual objects using sub-object elements. Specifically, when objects were divided into fragments and sequentially encoded into VWM, the fragments were involuntarily integrated into objects in VWM, as evidenced by the occurrence of both positive and negative object-based attention effects: In Experiment 1, when subjects’ attention was cued to a location occupied by the VWM object, the target presented at the location of that object was perceived as occurring earlier than that presented at the location of a different object. In Experiment 2, responses to a target were significantly slower when a distractor was presented at the same location as the cued object (Experiment 2). These results suggest that object fragments can be integrated into objects within VWM in a manner similar to that of visual perception.

The (Un)Clear Effects of Invalid Retro-Cues.

Studies with the retro-cue paradigm have shown that validly cueing objects in visual working memory long after encoding can still benefit performance on subsequent change detection tasks. With regard to the effects of invalid cues, the literature is less clear. Some studies reported costs, others did not. We here revisit two recent studies that made interesting suggestions concerning invalid retro-cues: One study suggested that costs only occur for larger set sizes, and another study suggested that inclusion of invalid retro-cues diminishes the retro-cue benefit. New data from one experiment and a reanalysis of published data are provided to address these conclusions. The new data clearly show costs (and benefits) that were independent of set size, and the reanalysis suggests no influence of the inclusion of invalid retro-cues on the retro-cue benefit. Thus, previous interpretations may be taken with some caution at present.

Learning changes the attentional status of prospective memories.

Objects in visual working memory (VWM) that are only prospectively relevant can nevertheless affect the guidance of attention in an ongoing visual search task. Here we investigated whether learning changes the attentional status of such prospective memories. Observers performed a visual search while holding an item in memory for a later memory test. This prospective memory was then repeated for several trials. When the memory was new, it interfered with the ongoing search task. However, with repetition, memory performance increased but memory-based interference rapidly diminished, suggesting that observers learned to shield the prospective memory from the ongoing task. This contrasts with earlier findings showing stronger attentional biases from learned memories when these are immediately task-relevant. Interestingly, interference resurfaced again in anticipation of a new memory, suggesting a reactivation of VWM. These effects were sensitive to task context, indicating that the attentional status of prospective memories is flexible.Electronic supplementary materialThe online version of this article (doi:10.3758/s13423-016-1008-7) contains supplementary material, which is available to authorized users.

Ensemble clustering in visual working memory biases location memories and reduces the Weber noise of relative positions

People seem to compute the ensemble statistics of objects and use this information to support the recall of individual objects in visual working memory. However, there are many different ways that hierarchical structure might be encoded. We examined the format of structured memories by asking subjects to recall the locations of objects arranged in different spatial clustering structures. Consistent with previous investigations of structured visual memory, subjects recalled objects biased toward the center of their clusters. Subjects also recalled locations more accurately when they were arranged in fewer clusters containing more objects, suggesting that subjects used the clustering structure of objects to aid recall. Furthermore, subjects had more difficulty recalling larger relative distances, consistent with subjects encoding the positions of objects relative to clusters and recalling them with magnitude-proportional (Weber) noise. Our results suggest that clustering improved the fidelity of recall by biasing the recall of locations toward cluster centers to compensate for uncertainty and by reducing the magnitude of encoded relative distances.

Remembering complex objects in visual working memory: do capacity limits restrict objects or features?

Visual working memory stores stimuli from our environment as representations that can be accessed by high-level control processes. This study addresses a longstanding debate in the literature about whether storage limits in visual working memory include a limit to the complexity of discrete items. We examined the issue with a number of change-detection experiments that used complex stimuli that possessed multiple features per stimulus item. We manipulated the number of relevant features of the stimulus objects in order to vary feature load. In all of our experiments, we found that increased feature load led to a reduction in change-detection accuracy. However, we found that feature load alone could not account for the results but that a consideration of the number of relevant objects was also required. This study supports capacity limits for both feature and object storage in visual working memory.

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.

The Storage Mechanism of Multi-feature Objects in Visual Working Memory

Visual working memory(VWM)is a temporary buffer that maintains a limited set of items(i.e., 3-4 objects) in an "online" state. Luck and Vogel(1997) demonstrated that the capacity was limited by the number of the integrated objects, but not by the number of the individual features. However, with the conjunction of homogenous features served as memory materials, follow-up studies showed that the subjects could retain fewer items than single-feature objects. Some researchers considered that the lower accuracy for conjunction of homogenous features may result from the difference of precision requirement, which was manipulated by the similarity between sample and test array. However, some experiment results showed that higher precision could only affect the accuracy of change detection task, but not the capacity.In present study, we carried out two experiments using change detection paradigm to examine the storage mechanism of multi-feature objects in VWM. In experiment 1, multi-feature and single-feature objects were defined by double-color objects and single-color objects, respectively. To manipulate the precision requirement, we further divide double-color objects into two conditions, that is, a single-change condition in which only one of the two colors changed(high-precision), and a double-change condition in which both colors changed(low-precision). In experiment 2, we focused on the single-change condition, and investigated the units of storage in VWM by manipulating weather there was an arrow indicating the changed color in the test phase. The result would further explain whether the storage mechanism of multi-feature objects is in an integrated manner or in an individual features manner. In experiment 1, we first compared the results of double-color objects and single-color objects to assess the influence of the feature number on the allocation of VWM capacity. Behavioral results showed that double-color objects were responded less accurately than single-color objects. The ERPs results showed that the amplitude of CDA for double-color objects was significantly higher than for single-color objects. Second, we compared the double-change condition and single-change condition to explore the effect of precision requirement. Lower accuracy was found for the single-change condition. CDA amplitudes did not differ between the two conditions. Instead, the amplitude of LPC for the single-change condition was more positive than for the double-change condition. In experiment 2, the accuracy was not modulated by weather there was an arrow or not. These results reveal that the number of features, but not the precision requirement, has an effect on the allocation of VWM capacity. And the units that limit our VWM capacity are the integrated objects instead of the individual features.

How low can you go? Changing the resolution of novel complex objects in visual working memory according to task demands.

In three experiments we manipulated the resolution of novel complex objects in visual working memory (WM) by changing task demands. Previous studies that investigated the trade-off between quantity and resolution in visual WM yielded mixed results for simple familiar stimuli. We used the contralateral delay activity as an electrophysiological marker to directly track the deployment of visual WM resources while participants preformed a change-detection task. Across three experiments we presented the same novel complex items but changed the task demands. In Experiment 1 we induced a medium resolution task by using change trials in which a random polygon changed to a different type of polygon and replicated previous findings showing that novel complex objects are represented with higher resolution relative to simple familiar objects. In Experiment 2 we induced a low resolution task that required distinguishing between polygons and other types of stimulus categories, but we failed in finding a corresponding decrease in the resolution of the represented item. Finally, in Experiment 3 we induced a high resolution task that required discriminating between highly similar polygons with somewhat different contours. This time, we observed an increase in the item’s resolution. Our findings indicate that the resolution for novel complex objects can be increased but not decreased according to task demands, suggesting that minimal resolution is required in order to maintain these items in visual WM. These findings support studies claiming that capacity and resolution in visual WM reflect different mechanisms.

Viewpoint-dependent representation of contextual information in visual working memory

Objects are not represented individually in visual working memory (VWM), but in relation to the contextual information provided by other memorized objects. We studied whether the contextual information provided by the spatial configuration of all memorized objects is viewpoint-dependent. We ran two experiments asking participants to detect changes in locations between memory and probe for one object highlighted in the probe image. We manipulated the changes in viewpoint between memory and probe (Exp. 1: 0°, 30°, 60°; Exp. 2: 0°, 60°), as well as the spatial configuration visible in the probe image (Exp. 1: full configuration, partial configuration; Exp. 2: full configuration, no configuration). Location change detection was higher with the full spatial configuration than with the partial configuration or with no spatial configuration at viewpoint changes of 0°, thus replicating previous findings on the nonindependent representations of individual objects in VWM. Most importantly, the effect of spatial configurations decreased with increasing viewpoint changes, suggesting a viewpoint-dependent representation of contextual information in VWM. We discuss these findings within the context of this special issue, in particular whether research performed within the slots-versus-resources debate and research on the effects of contextual information might focus on two different storage systems within VWM.

Guidance of Working Memory on Attention: The Effects of Inhibition Incentive

Although items matching the contents of visual object working memory(VOWM) could automatically capture attention,whether it is obligatory remains an opening question.With two experiments,we aimed to investigate whether this guidance effect could be affected by top-down inhibitory control.The participants were instructed to remember a visual object item for a change-detection test after a short delay.During the retention interval,the participants were required to seek a target stimulus among five distractors.One of the crucial manipulations was the presence or absence of distractors in the search array matching the memory items.In Experiment 1,we varied the proportion of matching trials across different experimental groups to induce different levels of inhibition incentive.As the memory item would never match the search target,it's highly likely that the participants would draw attention away from the memory-matching distractors.And this effect would be more pronounced in the condition of high inhibition incentive.In Experiment 2,we instructed different proportions of matching trials to different groups while keeping the actual proportion constant across groups to further ruled out the interference of practice.The main results showed,when the level of inhibition incentive was relatively low,search RTs were shorter in matching trials in comparison of that in control trials,demonstrating a classical memory-based attention capture effect by the memory-matching distractors.However,when the level of inhibition incentive was high enough,search RTs were faster in matching trials,suggesting a memory-based attention inhibition effect by the top-down control.Furthermore,the effects of the top-down inhibitory control were more in evidence and appeared earlier,when the inhibition incentive was extremely high.The results,thus,demonstrates:1) the VOWM guidance effect is not obligatory.Instead,it's a flexible mechanism that could be modulated by the top-down inhibitory control.And 2) this top-down control can be modulated by the level of inhibition incentive in terms of its effectiveness,efficiency and time course.

Infants use statistical regularities to chunk items in visual working memory.

Introduction. Infants’ visual working memory (VWM) has a 3-item limit (Feigenson & Carey, 2003), but infants can "chunk" items using perceptually available properties, such as common features or spatial proximity, thereby overcoming that limit (Feigenson & Halberda, 2004; 2008). When such chunking cues are not available, adults can extract statistical regularities between visual arrays presented over time, and use these regularities to more efficiently group items in VWM (Brady, et al, 2009). Here we asked whether 13-month-old infants could also use statistical regularities between objects to increase VWM. Participants & Method. During 10 Familiarization trials, infants (N=21) saw 4 objects (red disk, blue cross, green pentagon, yellow squiggle) placed sequentially on a stage 2 at a time. In the No-Regularity condition, the objects were paired randomly on each Familiarization trial. In the Regularity condition, object identity was yoked such that, across Familiarization trials, the identity of one shape perfectly predicted the identity of the other. Next, infants saw 6 Test Trials in which all 4 objects were sequentially hidden behind an occluder, which was then removed to reveal either all 4 objects (Expected Outcome) or only 3 (Unexpected Outcome), on alternating trials. Results. As predicted by previous findings, infants in the No Regularity condition failed to look longer at the Unexpected Outcome when four objects were hidden and just three were revealed, F(1,10)=0.005, p=n.s.). This finding replicates earlier work demonstrating an upper limit on infants’ VWM. In contrast, infants in the Regularity condition increased their looking to the Unexpected Outcome, F(1,28)=6.37, p=0.024 (see Figure 1). This suggests that seeing statistical regularities between individual objects allowed infants to group or chunk the objects in VWM, and hence to remember more total information about the scene. Conclusions. Infants can chunk items in VWM based on the statistical regularities present as events unfold. Meeting abstract presented at VSS 2013

Visual-object working memory affects aesthetic judgments

Visual-object working memory affects aesthetic judgments

The strategic retention of task-relevant objects in visual working memory.

The serial and spatially extended nature of many real-world visual tasks suggests the need for control over the content of visual working memory (VWM). We examined the management of VWM in a task that required participants to prioritize individual objects for retention during scene viewing. There were 5 principal findings: (a) Strategic retention of task-relevant objects was effective and was dissociable from the current locus of visual attention; (b) strategic retention was implemented by protection from interference rather than by preferential encoding; (c) this prioritization was flexibly transferred to a new object as task demands changed; (d) no-longer-relevant items were efficiently eliminated from VWM; and (e) despite this level of control, attended and fixated objects were consolidated into VWM regardless of task relevance. These results are consistent with a model of VWM control in which each fixated object is automatically encoded into VWM, replacing a portion of the content in VWM. However, task-relevant objects can be selectively protected from replacement.

Selective maintenance in visual working memory does not require sustained visual attention.

In four experiments, we tested whether sustained visual attention is required for the selective maintenance of objects in visual working memory (VWM). Participants performed a color change-detection task. During the retention interval, a valid cue indicated the item that would be tested. Change-detection performance was higher in the valid-cue condition than in a neutral-cue control condition. To probe the role of visual attention in the cuing effect, on half of the trials, a difficult search task was inserted after the cue, precluding sustained attention on the cued item. The addition of the search task produced no observable decrement in the magnitude of the cuing effect. In a complementary test, search efficiency was not impaired by simultaneously prioritizing an object for retention in VWM. The results demonstrate that selective maintenance in VWM can be dissociated from the locus of visual attention.

Competition increases binding errors in visual working memory

When faced with maintaining multiple objects in visual working memory, item information must be bound to the correct object in order to be correctly recalled. Sometimes, however, binding errors occur, and participants report the feature (e.g., color) of an unprobed, non-target item. In the present study, we examine whether the configuration of sample stimuli affects the proportion of these binding errors. The results demonstrate that participants mistakenly report the identity of the unprobed item (i.e., they make a non-target response) when sample items are presented close together in space, suggesting that binding errors can increase independent of increases in memory load. Moreover, the proportion of these non-target responses is linearly related to the distance between sample items, suggesting that these errors are spatially specific. Finally, presenting sample items sequentially decreases non-target responses, suggesting that reducing competition between sample stimuli reduces the number of binding errors. Importantly, these effects all occurred without increases in the amount of error in the memory representation. These results suggest that competition during encoding can account for some of the binding errors made during VWM recall.

Directed forgetting and directed remembering in visual working memory.

A defining characteristic of visual working memory is its limited capacity. This means that it is crucial to maintain only the most relevant information in visual working memory. However, empirical research is mixed as to whether it is possible to selectively maintain a subset of the information previously encoded into visual working memory. Here we examined the ability of participants to use cues to either forget or remember a subset of the information already stored in visual working memory. In Experiment 1, participants were cued to either forget or remember 1 of 2 groups of colored squares during a change-detection task. We found that both types of cues aided performance in the visual working memory task but that observers benefited more from a cue to remember than a cue to forget a subset of the objects. In Experiment 2, we show that the previous findings, which indicated that directed-forgetting cues are ineffective, were likely due to the presence of invalid cues that appeared to cause observers to disregard such cues as unreliable. In Experiment 3, we recorded event-related potentials and show that an electrophysiological index of focused maintenance is elicited by cues that indicate which subset of information in visual working memory needs to be remembered, ruling out alternative explanations of the behavioral effects of retention-interval cues. The present findings demonstrate that observers can focus maintenance mechanisms on specific objects in visual working memory based on cues indicating future task relevance.