Information In Visual Working Memory Research Articles

Discriminating orientation information with phase consistency in alpha and low-gamma frequency bands: an EEG study

Recent studies suggest that noninvasive imaging methods (EEG, MEG) in the human brain scalp can decode the content of visual features information (orientation, color, motion, etc.) in Visual-Working Memory (VWM). Previous work demonstrated that with the sustained low-frequency Event-Related Potential (ERP under 6 Hz) of scalp EEG distributions, it is possible to accurately decode the content of orientation information in VWM during the delay interval. In addition, previous studies showed that the raw data captured by a combination of the occi-parietal electrodes could be used to decode the orientation. However, it is unclear whether the orientation information is available in other frequency bands (higher than 6 Hz) or whether this information is feasible with fewer electrodes. Furthermore, the exploration of orientation information in the phase values of the signal has not been well-addressed. In this study, we propose that orientation information is also accessible through the phase consistency of the occipital region in the alpha band frequency. Our results reveal a significant difference between orientations within 200 ms after stimulus offset in early visual sensory processing, with no apparent effect in power and Event-Related Oscillation (ERO) during this period. Additionally, in later periods (420–500 ms after stimulus offset), a noticeable difference is observed in the phase consistency of low gamma-band activity in the occipital area. Importantly, our findings suggest that phase consistency between trials of the orientation feature in the occipital alpha and low gamma-band can serve as a measure to obtain orientation information in VWM. Furthermore, the study demonstrates that phase consistency in the alpha and low gamma band can reflect the distribution of orientation-selective neuron numbers in the four main orientations in the occipital area.

Just-in-Time Encoding Into Visual Working Memory Is Contingent Upon Constant Availability of External Information.

Humans maintain an intricate balance between storing information in visual working memory (VWM) and just-in-time sampling of the external world, rooted in a trade-off between the cost of maintaining items in VWM versus retrieving information as it is needed. Previous studies have consistently shown that one prerequisite of just-in-time sampling is a high degree of availability of external information, and that introducing a delay before being able to access information led participants to rely less on the external world and more on VWM. However, these studies manipulated availability in such a manner that the cost of sampling was stable and predictable. It is yet unclear whether participants become less reliant on external information when it is more difficult to factor in the cost of sampling that information. In two experiments, participants copied an example layout from the left to the right side of the screen. In Experiment 1, intermittent occlusion of the example layout led participants to attempt to encode more items per inspection than when the layout was constantly available, but this did not consistently result in more correct placements. However, these findings could potentially be explained by inherent differences in how long the example layout could be viewed. Therefore in Experiment 2, the example layout only became available after a gaze-contingent delay, which could be constant or variable. Here, the introduction of any delay led to increased VWM load compared to no delay, although the degree of variability in the delay did not alter behaviour. These results reaffirm that the nature of when we engage VWM is dynamical, and suggest that any disruption to the continuous availability of external information is the main driver of increased VWM usage relative to whether availability is predictable or not.

External cues improve visual working memory encoding in the presence of salient distractors in schizophrenia.

People with schizophrenia (PSZ) are impaired in attentional prioritization of non-salient but relevant stimuli over salient distractors during visual working memory (VWM) encoding. Conversely, guidance of top-down attention by external predictive cues is intact. Yet, it is unknown whether this preserved ability can help PSZ encode more information in the presence of salient distractors. We employed a visuospatial change-detection task using four Gabor patches with differing orientations in 66 PSZ and 74 healthy controls (HCS). Two Gabor patches flickered which were designated either as targets or distractors and either a predictive or a non-predictive cue was displayed to manipulate top-down attention, resulting in four conditions. We observed significant effects of group, salience and cue as well as significant interactions of salience by cue, group by salience and group by cue. Across all conditions, PSZ stored significantly less information in VWM than HCS. PSZ stored significantly less non-flickering than flickering information with a non-predictive cue. However, PSZ stored significantly more flickering and non-flickering information with a predictive cue. Our findings indicate that control of attentional selection is impaired in schizophrenia. We demonstrate that additional top-down information significantly improves performance in PSZ. The observed deficit in attentional control suggests a disturbance of GABAergic inhibition in early visual areas. Moreover, our findings are indicative of a mechanism for enhancing attentional control in PSZ, which could be utilized by pro-cognitive interventions. Thus, the current paradigm is suitable to reveal both preserved and compromised cognitive component processes in schizophrenia.

Which factor affects the storage of real-world object information in visual working memory: perceptual or conceptual information?

Visual working memory (VWM) is a limited dynamic memory system where people temporarily store and process visual information. Previous research showed that real-world objects do not have a fixed capacity compared to simple ones. In konkle's study, they found that the conceptual information and perception information of real-world objects had different effects on visual long-term memory (VLTM) capacity. VLTM capacity was more dependent on conceptual information than the perceptual distinctiveness of real-world objects. However, we did not know how the intrinsic attribute of real-world objects affects VWM capacity yet. In the current research, we set five experiments to explore the comparative effects of conceptual vs. perceptual information of real-world objects in VWM capacity. Our results suggested that VWM capacity was more dependent on the perceptual distinctiveness of real-world objects than on conceptual structure. These data provide evidence that VWM capacity for real-world objects depends more on perceptual information than on conceptual structure.

Mountains of memory in a sea of uncertainty: Sampling the external world despite useful information in visual working memory

A large part of research on visual working memory (VWM) has traditionally focused on estimating its maximum capacity. Yet, humans rarely need to load up their VWM maximally during natural behavior, since visual information often remains accessible in the external world. Recent work, using paradigms that take into account the accessibility of information in the outside world, has indeed shown that observers utilize only one or two items in VWM before sampling from the external world again. One straightforward interpretation of this finding is that, in daily behavior, much fewer items are memorized than the typically reported capacity limits. Here, we first investigate whether this lower reliance on VWM when information is externally accessible might instead reflect resampling before VWM is actually depleted. To this aim we devised an online task, in which participants copied a model (six items in a 4x4 grid; always accessible) in an adjacent empty 4x4 grid. A key aspect of our paradigm is that we (unpredictably) interrupted participants just before inspection of the model with a 2-alternative-forced-choice (2-AFC) question, probing their VWM content. Critically, we observed above-chance performance on probes appearing just before model inspection. This finding shows that the external world was resampled, despite VWM still containing relevant information. We then asked whether increasing the cost of sampling causes participants to load up more information in VWM or, alternatively, to squeeze out more information from VWM (at the cost of making more errors). To manipulate the cost of resampling, we made it more difficult (specifically, more time-consuming) to access the model. We show that with increased cost of accessing the model (which lead to fewer, but longer model inspections), participants could place more items correctly immediately after sampling, and they kept attempting to place items for longer after their first error. These findings demonstrate that participants both encoded more information in VWM and made attempts to squeeze out more information from VWM when sampling became more costly. We argue that human observers constantly evaluate how certain they are of their VWM contents, and only use that VWM content of which their certainty exceeds a context-dependent “action threshold”. This threshold, in turn, depends on the trade-off between the cost of resampling and the benefits of making an action. We argue that considering the interplay between the available VWM contents and a context-dependent action threshold, is key for reconciling the traditional VWM literature with VWM use in our day-to-day behavior.

Manipulating information in visual working memory

Manipulating information in visual working memory

Perceptual comparisons modulate memory biases induced by new visual inputs.

It is well-established that stimulus-specific information in visual working memory (VWM) can be systematically biased by new perceptual inputs. These memory biases are commonly attributed to interference that arises when perceptual inputs are physically similar to VWM contents. However, recent work has suggested that explicitly comparing the similarity between VWM contents and new perceptual inputs modulates the size of memory biases above and beyond stimulus-driven effects. Here, we sought to directly investigate this modulation hypothesis by comparing the size of memory biases following explicit comparisons to those induced when new perceptual inputs are ignored (Experiment 1) or maintained in VWM alongside target information (Experiment 2). We found that VWM reports showed larger attraction biases following explicit perceptual comparisons than when new perceptual inputs were ignored or maintained in VWM. An analysis of participants' perceptual comparisons revealed that memory biases were amplified after perceptual inputs were endorsed as similar-but not dissimilar-to one's VWM representation. These patterns were found to persist even after accounting for variability in the physical similarity between the target and perceptual stimuli across trials, as well as the baseline memory precision between the distinct task demands. Together, these findings illustrate a causal role of perceptual comparisons in modulating naturally-occurring memory biases.

Unintended emotions in the laboratory: Emotions incidentally induced by a standard visual working memory task relate to task performance.

The ability to temporarily hold information in visual working memory (VWM) is among the most crucial and most extensively examined human cognitive functions. Here, we empirically confirm previous speculations (a) that a standard VWM task arouses emotions in participants and (b) that these task-induced emotions are related to VWM performance. In a first qualitative study (N = 19), by adapting a qualitative method of inquiry, the think-aloud technique, we found that the task induced different positive and negative emotions, such as joy and anger, which varied on the inter- as well as on the intraindividual level. The emotional experiences seemed to be tied to the implicit achievement requirement of the VWM task (getting it right vs. wrong). Encouraged by these findings, two quantitative studies (N = 45, and N = 44, respectively) revealed that VWM performance was positively linked to joy and pride, and negatively linked to anger, frustration, and boredom on the inter- and on the intraindividual level. Notably, these emotions were also affected by an experimental manipulation of task difficulty (set size 4 vs. 8). Further, the findings from Study 3 were replicated in a fourth high-powered online study (N = 110). This research is the first to demonstrate that a task designed to measure VWM in itself triggers emotions, specifically achievement emotions, which, in turn, are linked with VWM performance. Our findings suggest that these task-induced emotions should be considered as potential confounding variables in future research on VWM and in cognitive research in general. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Recruitment of a long-term memory supporting neural network during repeated maintenance of a multi-item abstract visual image in working memory

Humans can flexibly transfer information between different memory systems. Information in visual working memory (VWM) can for instance be stored in long-term memory (LTM). Conversely, information can be retrieved from LTM and temporarily held in WM when needed. It has previously been suggested that a neural transition from parietal- to midfrontal activity during repeated visual search reflects transfer of information from WM to LTM. Whether this neural transition indeed reflects consolidation and is also observed when memorizing a rich visual scene (rather than responding to a single target), is not known. To investigate this, we employed an EEG paradigm, in which abstract six-item colour-arrays were repeatedly memorized and explicitly visualized, or merely attended to. Importantly, we tested the functional significance of a potential neural shift for longer-term consolidation in a subsequent recognition task. Our results show a gradually enhanced- and sustained modulation of the midfrontal P170 component and a decline in parietal CDA, during repeated WM maintenance. Improved recollection/visualization of memoranda upon WM-cueing, was associated with contralateral parietal- and right temporal activity. Importantly, only colour-arrays previously held in WM, induced a greater midfrontal P170-response, together with left temporal- and late centro-parietal activity, upon re-exposure. These findings provide evidence for recruitment of an LTM-supporting neural network which facilitates visual WM maintenance.

The extrastriate symmetry response is robust to variation in visual memory load.

An Event Related Potential response to visual symmetry, known as the Sustained Posterior Negativity (SPN), is generated whether symmetry is task relevant or not, and whether symmetry is attended or not. However, no study has yet examined interference from concurrent memory tasks. To answer this fundamental question, we investigated whether the SPN is robust to variation in Visual Working Memory (VWM) load. In Experiment 1 (N=24), each trial involved a sample display, a probe and a test display. Sample and test displays contained either four colors or four black shapes, and the probe was either a symmetrical or random pattern. We compared a memory task and a passive viewing task. In the memory task, participants held color or shape information in VWM when the probe was presented. In the passive viewing task, there were no memory demands. Contrary to our predictions, there was no evidence that VWM interfered with the symmetry response. Instead, there was a general SPN enhancement during both color and shape memory tasks compared to passive viewing. In Experiment 2 (N=24), we used symmetrical patterns themselves as sample and test to maximize interference. Again, the SPN was enhanced in the memory task compared to passive viewing. We conclude that the visual symmetry response is not impaired by concurrent VWM tasks, even when these tasks involve remembering symmetry itself. It seems that the SPN is not only attention-proof, but also memory-proof. This adds to evidence that symmetry perception is robust and automatic.

Classification images reveal uniform decay of facial feature information in visual working memory

Classification images reveal uniform decay of facial feature information in visual working memory

Towards a better understanding of information storage in visual working memory

ABSTRACT Chota, S., & Van der Stigchel, S. (2021). Dynamic and flexible transformation and reallocation of visual working memory representations (this issue); Iamshchinina, P., Christophel, T. B., Gayet, S., & Rademaker, R. L. (2021). Essential considerations for exploring visual working memory storage in the human brain (this issue); Lorenc, E. S., & Sreenivasa, K. K. (2021). Reframing the debate: the distributed systems view of working memory (this issue); and Teng, C., & Postle, B. R. (2021). Understanding occipital and parietal contributions to visual working memory: Commentary to Xu (2020) (this issue) each present a commentary regarding Xu, Y. (2020). Revisit once more the sensory storage account of visual working memory. Visual Cognition, 28(5-8), 433–446. https://doi.org/10.1080/13506285.2020.1818659 where I conclude that sensory regions are nonessential for the storage of information in visual working memory (VWM). They argue instead that sensory regions are critical to VWM storage. Here I briefly reiterate some of the key evidence against this account, some of which has not been accounted by the four commentaries. I also provide a detailed reanalysis of why the main evidence supporting this account may be problematic. Collectively, existence evidence from human neuroimaging and TMS studies and that from monkey neurophysiology studies does not provide strong support for the sensory storage account of VWM. To form an accurate understanding of the distinctive role each brain region may play in perception and VWM as well as how they may interact to collectively support a VWM task, it is important that we properly survey and evaluate all the available evidence.

Can valuable information be prioritized in verbal working memory?

Though there is substantial evidence that individuals can prioritize more valuable information in visual working memory (WM), little research has examined this in the verbal domain. Four experiments were conducted to investigate this and the conditions under which effects emerge. In each experiment, participants listened to digit sequences and then attempted to recall them in the correct order. At the start of each block, participants were either told that all items were of equal value, or that an item at a particular serial position was worth more points. Recall was enhanced for these higher value items (Experiment 1a), a finding that was replicated while rejecting an alternative account based on distinctiveness (Experiment 1b). Thus, valuable information can be prioritized in verbal WM. Two further experiments investigated whether these boosts remained when participants completed a simple concurrent task disrupting verbal rehearsal (Experiment 2), or a complex concurrent task disrupting verbal rehearsal and executive resources (Experiment 3). Under simple concurrent task conditions, prioritization boosts were observed, but with increased costs to the less valuable items. Prioritization effects were also observed under complex concurrent task conditions, although this was accompanied by chance-level performance at most of the less valuable positions. A substantial recency advantage was also observed for the final item in each sequence, across all conditions. Taken together, this indicates that individuals can prioritize valuable information in verbal WM even when rehearsal and executive resources are disrupted, though they do so by neglecting or abandoning other items in the sequence. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The locus of proactive interference in visual working memory.

Recent studies showed that proactive interference (PI) impairs visual working memory (WM), as performance is better when the memory items are unique rather than repeated throughout the experiment. To scrutinize the mechanisms driving this effect, we tested how it affects the stages of encoding, retention, and testing. Experiment 1 instructed participants to make speeded responses and found that reaction time was slower in the repeated than in the unique condition, suggesting memory source confusion during testing. Experiment 2 showed that a retention interval manipulation did not affect the magnitude of the PI effect. Finally, Experiment 3 found that the PI effect did not increase when the encoding interval was short. Instead, the difference between the repeated and unique conditions was reduced, probably because the increased familiarity with the memory items in the repeated condition facilitated consolidation. Taken together, these results suggest that the main locus of PI in visual WM is during testing and that encoding and retaining information in visual WM are hardly affected by no longer needed information. Consequently, these data support the involvement of long-term memory in the effect. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Assessing the robustness of feature-based selection in visual working memory.

Visual working memory (VWM) is a capacity-limited system to temporarily maintain visual information. Attending to information in VWM conveys a benefit, as revealed by the retro-cue effect. For example, when the location of one memory item is retro-cued during VWM maintenance, memory accuracy for that item improves. Attentional selection in VWM can also be feature-based: One feature (e.g., shape) may serve as a retrieval cue for another feature (e.g., color) of the same item. Here, we assessed the scope of feature retro-cue benefits with continuous report of colors and orientations. Across six experiments, we observed robust feature retro-cue benefits with manipulations of the cued and recalled feature dimensions, as well as against different baselines controlling for temporal and interference effects. Furthermore, we replicated with continuous report the hallmark of external feature-based attention-concurrent selection of multiple items. Mixture modeling indicated that feature retro-cue benefits increased recall probability and sometimes precision, paralleling findings on spatial attention. Importantly, cuing multiple items did not produce costs, indicating that concurrently attended items did not interfere with each other. Lastly, manipulation constraining spatial location to a single position suggested that feature retro-cue benefits persist even when spatial context is not singular, but take longer to emerge. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Massive Effects of Saliency on Information Processing in Visual Working Memory

Limitations in the ability to temporarily represent information in visual working memory (VWM) are crucial for visual cognition. Whether VWM processing is dependent on an object’s saliency (i.e., how much it stands out) has been neglected in VWM research. Therefore, we developed a novel VWM task that allows direct control over saliency. In three experiments with this task (on 10, 31, and 60 adults, respectively), we consistently found that VWM performance is strongly and parametrically influenced by saliency and that both an object’s relative saliency (compared with concurrently presented objects) and absolute saliency influence VWM processing. We also demonstrated that this effect is indeed due to bottom-up saliency rather than differential fit between each object and the top-down attentional template. A simple computational model assuming that VWM performance is determined by the weighted sum of absolute and relative saliency accounts well for the observed data patterns.

Social anxiety is related to impaired ability to filter out irrelevant information but not reduced storage capacity

Individuals with social anxiety have deficits in inhibiting task-irrelevant threatening information, but the mechanism is poorly understood. In this study, we instructed participants with high and low social anxiety to perform a variant change-detection task, recording their accuracy and electrophysiological data. The results indicated that individuals with high social anxiety showed impaired ability to filter out irrelevant information in disgust facial expression condition rather than neutral facial expression. While individuals with low social anxiety didn’t show filter efficiency defects under both disgust and neutral facial expressions. Furthermore, we found high socially anxious individuals could hold more information in visual working memory than low socially anxious individuals. These results suggest that the abundance of cognitive resources in socially anxious individuals compensates the presumed weak performance in accuracy produced by impaired filter efficiency. These results provide support for the claims of efficiency and effectiveness in attentional control theory.

Working memory limits severely constrain long-term retention

There has been considerable controversy in recent years as to whether information held in working memory (WM) is rapidly forgotten or automatically transferred to long-term memory (LTM). Although visual WM capacity is very limited, we appear able to store a virtually infinite amount of information in visual LTM. Still, LTM retrieval often fails. Some view visual WM as a mental sketchpad that is wiped clean when new information enters, but not a consistent precursor of LTM. Others view the WM and LTM systems as inherently linked. Distinguishing between these possibilities has been difficult, as attempts to directly manipulate the active holding of information in visual WM has typically introduced various confounds. Here, we capitalized on the WM system's capacity limitation to control the likelihood that visual information was actively held in WM. Our young-adult participants (N = 103) performed a WM task with unique everyday items, presented in groups of two, four, six, or eight items. Presentation time was adjusted according to the number of items. Subsequently, we tested participants' LTM for items from the WM task. LTM was better for items presented originally within smaller WM set sizes, indicating that WM limitations contribute to subsequent LTM failures, and that holding items in WM enhances LTM encoding. Our results suggest that a limit in WM capacity contributes to an LTM encoding bottleneck for trial-unique familiar objects, with a relatively large effect size.

Functional difference between the ventral visual cortex and the intraparietal sulcus in visual working memory of material properties.

A recent study showed that objects' roughness (smooth or rough) was held in visual working memory (VWM) in the ventral visual cortex and the intraparietal sulcus (IPS). Here, we investigated the functional differences between these areas in the context of VWM of material properties. We focused on the process in which participants accurately extracted and maintained in their memories the glossiness and roughness of a sphere. Human participants performed two types of delayed material (glossiness or roughness) discrimination tasks in which they judged which task was to be performed based on the differences in the material properties of two sequentially presented sample spheres. This task allowed us to investigate how the visual system in the human brain could properly extract a material property and hold the information in VWM. By decoding the task information (glossiness or roughness) from the brain activity patterns in the delay period, we found that both the ventral visual cortex and the IPS contributed to maintenance in memory of material properties. We also showed different decoding patterns in the areas over the course of each trial; the ventral visual cortex performed at levels above chance performance in extracting a material property, and the IPS performed at levels above chance performance in maintaining the property in memory. These results suggest that, in VWM, material properties are visually processed in the ventral visual cortex, and the visual information is sent to the IPS to be robustly maintained.

Coding of featural information in visual working memory in 2.5-year-old toddlers

The number of objects that infants can remember in visual working memory (VWM) increases rapidly during the first few years of life (Kaldy & Leslie, 2005; Ross-Sheehy, Oakes, & Luck, 2003). However, less is understood about the representational format of VWM: whether storage is determined by fixed-precision memory slots, or the allocation of a limited continuous resource. In the current study, we adapted the Delayed Match Retrieval eye-tracking paradigm (Kaldy, Guillory, & Blaser, 2016), to test 2.5-year-old toddlers’ ability to remember three object-location bindings when the to-be-remembered objects were all unique (Experiment 1) versus when they shared features such as color or shape (Experiment 2). 2.5-year-olds succeeded in Experiment 1, but only performed marginally better than chance in Experiment 2. Interestingly, when incorrect, participants in Experiment 2 were no more likely to select a decoy item that shared a feature with the target item. It seems that the increased similarity of to-be-remembered objects did not impair memory for the objects directly, but instead increased the likelihood of catastrophic forgetting.