Visual working memory capacity for color is independent of representation resolution

Influence of presentation duration on filtering of irrelevant stimuli in visual working memory

In environments teeming with distractions, the ability to selectively focus on relevant information is crucial for advanced cognitive processing. Existing research using event-related potential (ERP) technology has shown active suppression of irrelevant stimuli during the consolidation phase of visual working memory (VWM). In previous studies, participants have always been given sufficient time to consolidate VWM, while suppressing distracting information. However, it remains unclear whether the suppression of irrelevant distractors requires continuous effort throughout their presence or whether this suppression is only necessary after the consolidation of task-relevant information. To address this question, our study examines whether distractor suppression is necessary in scenarios where consolidation time is limited. This research investigates the effect of varying presentation durations on the filtering of distractors in VWM. We tasked participants with memorizing two color stimuli and ignoring four distractors, presented for either 50 ms or 200 ms. Using ERP technology, we discovered that the distractor-induced distractor positivity (PD) amplitude is larger during longer presentation durations compared to shorter ones. These findings underscore the significant impact of presentation duration on the efficacy of distractor suppression in VWM, as prolonged exposure results in a stronger suppression effect on distractors. This study sheds light on the temporal dynamics of attention and memory, emphasizing the critical role of stimulus timing in cognitive tasks. These findings provide valuable insights into the mechanisms underlying VWM and have significant implications for models of attention and memory.

A negative emotional state impairs individuals' ability to filter distractors from working memory: an ERP study

Capacity-limited visual working memory (VWM) requires that individuals have sufficient memory space and the ability to filter distractors. Negative emotional states are known to impact VWM storage, yet their influence on distractor filtering within VWM remains underexplored. We conducted direct neural measurement of participants (n = 56) who conducted a lateralized change detection task with distractors, while manipulating the emotional state by presenting neutral or negative images before each trial. We found a detrimental effect of distractors on memory accuracy under both neutral and negative emotional states. Using the event-related potential (ERP) component, contralateral delay activity (CDA; sensitive to VWM load), to observe the VWM load in each condition, we found that in the neutral state, the participants showed significantly higher late CDA amplitudes when remembering 4 targets compared with 2 targets and 2 targets with 2 distractors but no significant difference when remembering 2 targets compared with 2 targets with 2 distractors. In the negative state, no significant CDA amplitude differences were evident when remembering 4 targets and 2 targets, but CDA was significantly higher when remembering 2 targets with 2 distractors compared with 2 targets. These results suggest that the maximum number of items participants could store in VWM was lower under negative emotional states than under neutral emotional states. Importantly, the participants could filter out distractors when in a neutral emotional state but not in a negative emotional state, indicating that negative emotional states impair their ability to filter out distractors in VWM.

Exploring retro-cue effects on visual working memory: insights from double-cue paradigm

In the realm of visual working memory research, the retro-cue paradigm helps us study retro-cue effects such as retro-cue benefit (RCB) and retro-cue cost (RCC). RCB reflects better performance with cued items, while RCC indicates poorer performance with uncued items. Despite consistent evidence for RCB, it's still uncertain whether it remains when previously uncued items are cued afterward. Additionally, research findings have been inconsistent. This study combines prior experiments by controlling the proportion of cue types and the number of memory items. Besides, using a CDA index to assess the status of items after the cue appeared. Results showed better performance under the double-cue condition (involving two cues pointing inconsistently with only the second cue being valid) compared to the neutral-cue condition, and better performance under the single-cue condition compared to double-cue. EEG data revealed that after the appearance of the second cue in the double-cue condition, there was a significant increase in CDA wave amplitude compared to the single-cue condition. Behavior results suggests that RCB occurs under double-cue but to a lesser extent than the single-cue. And EEG outcomes indicates that individuals did not remove the uncued item from their visual working memory after the first cue. Instead, they kept it in a passive state and then shifted it to an active state after the appearance of the second cue.

Sustained attention required for effective dimension-based retro-cue benefit in visual working memory

In visual working memory (VWM) tasks, participants' performances can be improved through the use of dimension-based retro-cues, which direct internal attention to prioritize a particular dimension (e.g., color or orientation) of VWM representations even after the stimuli disappear. This phenomenon is known as the dimension-based retro-cue benefit (RCB). The present study investigates whether sustained attention is required for the dimension-based RCB by inserting interference or interruption between the retro-cue and the test array to distract attention. We tested the effects of perceptual interference or cognitive interruption on dimension-based RCB when the interference (Experiments 1 and 2 with masks) or interruption (Experiments 3 and 4 with an odd-even task) occurred concurrently with the stages for the maintenance of prioritized information (long cue-and-interference/interruption interstimulus interval, e.g., Experiments 1 and 3) or the deployment of attention (short cue-and-interference/interruption interstimulus interval, e.g., Experiments 2 and 4). Our results demonstrate that perceptual interference or cognitive interruption attenuates the dimension-based RCB. These findings suggest that sustained attention is necessary for the effective prioritization of a specific dimension of VWM representations.

Active inhibition of the retro-cue effect in visual working memory: Evidence from event-related potential

This study used the event-related potential (ERP) technique to investigate whether active inhibition exists in retro-cue Effect (RCE) in visual working memory using modified retro-cue tasks. In this modified task, the participants were first asked to memorize six color blocks and then presented with directed remembering or directed forgetting cues; finally, their working memory performance was tested. For behavioral results, due to the extension of the memory interval, this study did not find RCE in accuracy but reflected it in the total reaction time. For ERP results, the frontal late positive potential (LPP) followed by the directed forgetting condition was larger than that followed by directed remembering and baseline conditions, and there was no significant difference between directed remembering and baseline conditions. There was no significant difference in parietal P3 followed by both the directed remembering and directed forgetting conditions, which were significantly larger than the baseline condition. This result reveals that active inhibition plays an important role in directed forgetting RCE. There was a correlation between parietal P3 and frontal LPP with the same time window but different scalp regions in the directed forgetting condition, indicating a potential relationship between active inhibition and retelling in directed forgetting RCE.

Alterations in working memory maintenance of fearful face distractors in depressed participants: An ERP study

Task-irrelevant threatening faces (e.g., fearful) are difficult to filter from visual working memory (VWM), but the difficulty in filtering non-threatening negative faces (e.g., sad) is not known. Depressive symptoms could also potentially affect the ability to filter different emotional faces. We tested the filtering of task-irrelevant sad and fearful faces by depressed and control participants performing a color-change detection task. The VWM storage of distractors was indicated by contralateral delay activity, a specific event-related potential index for the number of objects stored in VWM during the maintenance phase. The control group did not store sad face distractors, but they automatically stored fearful face distractors, suggesting that threatening faces are specifically difficult to filter from VWM in non-depressed individuals. By contrast, depressed participants showed no additional consumption of VWM resources for either the distractor condition or the non-distractor condition, possibly suggesting that neither fearful nor sad face distractors were maintained in VWM. Our control group results confirm previous findings of a threat-related filtering difficulty in the normal population while also suggesting that task-irrelevant non-threatening negative faces do not automatically load into VWM. The novel finding of the lack of negative distractors within VWM storage in participants with depressive symptoms may reflect a decreased overall responsiveness to negative facial stimuli. Future studies should investigate the mechanisms underlying distractor filtering in depressed populations.

The impact of retro-cue validity on working memory representation: Evidence from electroencephalograms

Visual working memory (VWM) performance can be improved by retrospectively cueing an item. The validity of retro-cues has an impact on the mechanisms underlying the retro-cue effect, but how non-cued representations are handled under different retro-cue validity conditions is not yet clear. Here, we used electroencephalograms to investigate whether retro-cue validity can affect the fate of non-cued representations in VWM. The participants were required to perform a change-detection task using a retro-cue with 80% or 20% validity. Contralateral delay activity and the lateralized alpha power were used to assess memory storage and selective attention, respectively. The retro-cue could redirect selective attention to the cued item under both validity conditions; however, the participants maintained the non-cued representations under the low-validity condition but dropped them from VWM under the high-validity condition. These results suggest that the maintenance of non-cued representations in VWM is affected by the expectation of cue validity and may be partially strategically driven. DATA AVAILABILITY: The datasets generated/analyzed during this study and experimental script have been added to https://osf.io/qtwc9/.

Systematic Review of the Longitudinal Sensitivity of Precision Tasks in Visual Working Memory

Precision of working memory (WM) refers to the objective performance of individuals when trying to recall the features of the encoded WM items. Studies of precision in VWM aim to identify whether differences in WM performance within individuals are sensitive to individual states or traits. In this systematic review, we study VWM precision and whether it reflects true differences in ability to accurately store information, and thereby possibly a more sensitive measure than discrete VWM span alone. Sifting through 327 abstracts, we identified 34 relevant articles. After assessing these articles with regard to our inclusion criteria to test participants at two separate time points and have a sample size of at least fifteen participants, we found four longitudinal studies regarding VWM precision. One review author and two reviewers independently assessed all studies in the screening and selection process and extracted outcome measures, study characteristics, and, when possible, test-retest reliability metrics. Given the small and heterogeneous sample, this systematic review could not yet provide conclusive evidence on the sensitivity of VWM precision paradigms. Future research of VWM should include longitudinal studies of precision, and address both test-retest reliability in healthy adults and changes in precision during key developmental trajectory periods and in clinical populations.

Intermittent theta burst stimulation over the parietal cortex has a significant neural effect on working memory

The crucial role of the parietal cortex in working memory (WM) storage has been identified by fMRI studies. However, it remains unknown whether repeated parietal intermittent theta‐burst stimulation (iTBS) can improve WM. In this within‐subject randomized controlled study, under the guidance of fMRI‐identified parietal activation in the left hemisphere, 22 healthy adults received real and sham iTBS sessions (five consecutive days, 600 pulses per day for each session) with an interval of 9 months between the two sessions. Electroencephalography signals of each subject before and after both iTBS sessions were collected during a change detection task. Changes in contralateral delay activity (CDA) and K‐score were then calculated to reflect neural and behavioral WM improvement. Repeated‐measures ANOVA suggested that real iTBS increased CDA more than the sham one (p = .011 for iTBS effect). Further analysis showed that this effect was more significant in the left hemisphere than in the right hemisphere (p = .029 for the hemisphere‐by‐iTBS interaction effect). Pearson correlation analyses showed significant correlations for two conditions between CDA changes in the left hemisphere and K score changes (ps <.05). In terms of the behavioral results, significant K score changes after real iTBS were observed for two conditions, but a repeated‐measures ANOVA showed a nonsignificant main effect of iTBS (p = .826). These results indicate that the current iTBS protocol is a promising way to improve WM capability based on the neural indicator (CDA) but further optimization is needed to produce a behavioral effect.

A relational account of visual short-term memory (VSTM)

Visual short-term memory (VSTM) is an important resource that allows temporarily storing visual information. Current theories posit that elementary features (e.g., red, green) are encoded and stored independently of each other in VSTM. However, they have difficulty explaining the similarity effect, that similar items can be remembered better than dissimilar items. In Experiment 1, we tested (N = 20) whether the similarity effect may be due to storing items in a context-dependent manner in VSTM (e.g., as the reddest/yellowest item). In line with a relational account of VSTM, we found that the similarity effect is not due to feature similarity, but to an enhanced sensitivity for detecting changes when the relative colour of a to-be-memorised item changes (e.g., from reddest to not-reddest item; than when an item underwent the same change but retained its relative colour; e.g., still reddest). Experiment 2 (N = 20) showed that VSTM load, as indexed by the CDA amplitude in the EEG, was smaller when the colours were ordered so that they all had the same relationship than when the same colours were out-of-order, requiring encoding different relative colours. With this, we report two new effects in VSTM - a relational detection advantage that describes an enhanced sensitivity to relative changes in change detection, and a relational CDA effect, which reflects that VSTM load, as indexed by the CDA, scales with the number of (different) relative features between the memory items. These findings support a relational account of VSTM and question the view that VSTM stores features such as colours independently of each other.

Action Real-Time Strategy Gaming Experience Related to Enhanced Capacity of Visual Working Memory

Action real-time strategy gaming (ARSG)—a major genre of action video gaming (AVG)—has both action and strategy elements. ARSG requires attention, visual working memory (VWM), sensorimotor skills, team cooperation, and strategy-making abilities, thus offering promising insights into the learning-induced plasticity. However, it is yet unknown whether the ARSG experience is related to the development of VWM capacity. Using both behavioral and event-related potential (ERP) measurements, this study tested whether ARSG experts had larger VWM capacity than non-experts in a change detection task. The behavioral results showed that ARSG experts had higher accuracy and larger VWM capacity than non-experts. In addition, the ERP results revealed that the difference wave of the contralateral delay activity (CDA) component (size 4–size 2) elicited by experts was significantly larger than that of non-experts, suggesting that the VWM capacity was higher in experts than in non-experts. Thus, the findings suggested that prolonged ARSG experience is correlative with the enhancement of VWM.

The two-stage process in visual working memory consolidation

Two hypotheses have been proposed to explain the formation manner for visual working memory (VWM) representations during the consolidation process: an all-or-none process hypothesis and a coarse-to-fine process hypothesis. However, neither the all-or-none process hypothesis nor the coarse-to-fine process hypothesis can stipulate clearly how VWM representations are formed during the consolidation process. In the current study, we propose a two-stage process hypothesis to reconcile these hypotheses. The two-stage process hypothesis suggests that the consolidation of coarse information is an all-or-none process in the early consolidation stage, while the consolidation of detailed information is a coarse-to-fine process in the late consolidation stage. By systematically manipulating the encoding time of memory stimuli, we asked participants to memorize one (Experiment 1) or two (Experiment 2) orientations in different encoding time intervals. We found that the memory rate increased linearly as the encoding time increased. More importantly, VWM precision remained constant when the encoding time was short, while the precision increased linearly as the encoding time increased when the encoding time was sufficient. These results supported the two-stage process hypothesis, which reconciles previous conflicting findings in the literature.

The transition from feature to object: Storage unit in visual working memory depends on task difficulty

Visual working memory (VWM) is a cognitive memory buffer for temporarily processing and storing visual information. Previous studies suggest that its capacity is severely limited, and there is an ongoing debate on whether the storage capacity is object-based or feature-based in VWM. In this study, a change-detection task was employed to investigate whether and how task difficulty can affect VWM, specifically, its capacity and the unit of storage. Task difficulty was manipulated through the set size of memory items, memory fidelity required by the resolution of representation and the type of feature tested. We examined two types of stimuli: the single-feature type, where each memory item was composed of a single feature (color or shape), and the conjunctive-feature type, where each item was composed of a conjunction of two features (colored shape). Experiment 1 replicated the previous findings that memory capacity for colors was larger than shapes, and decreased with the resolution demand regardless of the type of stimuli. In Experiment 2, we analyzed and compared the results from single-feature items and conjunctive-feature items in the low- and high-resolution conditions while controlling for the number of to-be-remembered features. By directly matching the estimated capacity based on an object-unit and a feature-unit with the theoretical prediction, the results showed that the unit storage in VWM tended to be feature-based with low task difficulty, and to be object-based with high task difficulty. This suggests that VWM is dynamic and flexible, dependent on the load of the current task.

Negative emotional state modulates visual working memory in the late consolidation phase

Although a considerable literature has grown up around the interactions between emotional state and visual working memory (VWM) performance, the mechanism underlying the impact of the negative emotional state on VWM remains unclear. The present study aimed to test whether the influence of emotional state is related to the early phase or late phase of VWM consolidation process. Across three experiments, we found that the negative emotional state did not affect VWM performance when the presentation time of stimuli was short. However, when the presentation time was long, the negative emotional state increased the VWM precision and reduced the VWM number. According to the two-phase model proposed by Ye et al. (2017. A two-phase model of resource allocation in visual working memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 43(10), 1557-1566. doi: 10.1037/xlm0000376), the results suggested that negative emotional state could affect the late phase of resource allocation in VWM consolidation process, but it has no impact on the early consolidation phase. The findings from this study make important contributions to the current literature regarding the emotional modulation of VWM.

Working memory capacity affects trade-off between quality and quantity only when stimulus exposure duration is sufficient: Evidence for the two-phase model

The relation between visual working memory (VWM) capacity and attention has attracted much interest. In this study, we investigated the correlation between the participants’ VWM capacity and their ability to voluntarily trade off the precision and number of items remembered. The two-phase resource allocation model proposed by Ye et al. (2017) suggests that for a given set size, it takes a certain amount of consolidation time for an individual to control attention to adjust the VWM resources to trade off the precision and number. To verify whether trade-off ability varies across VWM capacity, we measured each individual’s VWM capacity and then conducted a colour recall task to examine their trade-off ability. By manipulating the task requirement, participants were instructed to memorise either more colours in a low-precision way or fewer colours in a high-precision way. We conducted two experiments by adjusting stimulus duration to be longer than predicted critical value (Experiment 1) and duration shorter than predicted critical value (Experiment 2). While the results of Experiment 1 showed a positive correlation between the VWM capacity and trade-off ability, the results of Experiment 2 showed a lack of such correlation. These results are consistent with the prediction from the two-phase model.

Neural evidence for an object-based pointer system underlying working memory

To accomplish even rudimentary tasks, our cognitive system must update its representation of the changing environment. This process relies on visual working memory (VWM), which can actively modify its representations. We argue that this ability depends on a pointer system, such that each representation is stably and uniquely mapped to a specific stimulus. Without these pointers, VWM representations are inaccessible and therefore unusable. In three Electroencephalogram (EEG) experiments, we examined whether the pointers are allocated in an object-based, featural, or spatial manner: three factors that were confounded in previous studies. We used a feature change-detection task, in which objects moved and could separate into independently-moving parts. Despite the movement and separation being completely task-irrelevant, we found that the separation invalidated the pointers. This happened in a shape task, where the separation changed both the objects and the task-relevant features, but importantly, also in a color task, where the separation destroyed the objects while leaving the task-relevant features intact. Furthermore, even in a color task where all items had identical shapes, object-separation invalidated the pointers. This suggests that objects and not task-relevant features underlie the pointer system. Finally, when each object-part could be individuated already before the separation, the pointers were maintained, suggesting that the pointers are specifically tied to objects rather than locations. These results shed new light on the pointers which underlie VWM performance, demonstrating that the pointer system is object-based regardless of the task requirements.

The impact of visual working memory capacity on the filtering efficiency of emotional face distractors

Emotional faces can serve as distractors for visual working memory (VWM) tasks. An event-related potential called contralateral delay activity (CDA) can measure the filtering efficiency of face distractors. Previous studies have investigated the influence of VWM capacity on filtering efficiency of simple neutral distractors but not of face distractors. We measured the CDA indicative of emotional face filtering during a VWM task related to facial identity. VWM capacity was measured in a separate colour change detection task, and participants were divided to high- and low-capacity groups. The high-capacity group was able to filter out distractors similarly irrespective of its facial emotion. In contrast, the low-capacity group failed in filtering the neutral and angry face distractors, while the filtering was efficient for the happy face distractors. The results indicate that potentially threatening faces are particularly difficult to filter if VWM capacity is limited.

Dissociations of the number and precision of visual short-term memory representations in change detection

The present study dissociated the number (i.e., quantity) and precision (i.e., quality) of visual short-term memory (STM) representations in change detection using receiver operating characteristic (ROC) and experimental manipulations. Across three experiments, participants performed both recognition and recall tests of visual STM using the change-detection task and the continuous color-wheel recall task, respectively. Experiment 1 demonstrated that the estimates of the number and precision of visual STM representations based on the ROC model of change-detection performance were robustly correlated with the corresponding estimates based on the mixture model of continuous-recall performance. Experiments 2 and 3 showed that the experimental manipulation of mnemonic precision using white-noise masking and the experimental manipulation of the number of encoded STM representations using consolidation masking produced selective effects on the corresponding measures of mnemonic precision and the number of encoded STM representations, respectively, in both change-detection and continuous-recall tasks. Altogether, using the individual-differences (Experiment 1) and experimental dissociation (Experiment 2 and 3) approaches, the present study demonstrated the some-or-none nature of visual STM representations across recall and recognition.

Delineating resetting and updating in visual working memory based on the object-to-representation correspondence

When an object we represent in visual working memory (VWM) changes, its representation is modified accordingly. VWM can either access and change the existing representation by an updating process, or it can reset, by encoding the object in its novel status as a new representation. Our goal was to show that the determining factor of updating versus resetting is the availability of a stable correspondence between the object and its VWM representation. Here, we demonstrate that updating relies on the object-to-representation mapping to access and modify the appropriate representation, while losing this mapping triggers a resetting process. We compared very similar situations of object separation that either allowed the mapping to hold, or caused it to be lost. When an object that was mapped to one representation separated, VWM reset, manifested by a sharp drop in the contralateral delay activity (CDA) amplitude (an electrophysiological marker of VWM contents; Experiment 1), and a behavioral cost to detect salient changes that co-occurred with the resetting-triggering event (Experiment 2). When each part was mapped to a different representation, the separation resulted in updating, with a gradual rise in CDA amplitude (Experiment 1), and a reduced behavioral cost (Experiment 2). Thus, while updating and resetting resulted in similar final representations (corresponding to the post-change objects), their dynamics were different, depending on the availability of the mapping. Our results reveal the triggering conditions of resetting and updating, establish methods to study these online processes, and highlight the importance of the object-to-representation correspondence in VWM.

The bilateral field advantage effect in memory precision

Previous research has demonstrated that visual working memory performance is better when visual items are allocated in both left and right visual fields than within only one hemifield. This phenomenon is called the bilateral field advantage (BFA). The BFA is thought to be driven by an enhanced probability of storage, rather than by greater precision. In the present experiments, we sought to test whether the BFA can also extend to precision when the parameters of the task are modified. Using a moderate number of to-be-remembered items and 400 ms presentation time, we found better precision in the bilateral condition than in the unilateral condition. The classic BFA was still found in the form of an enhanced probability of storage, when presentation time was 200 ms. Thus, the BFA appears to convey both enhanced precision and greater probability of storage. The BFA is most likely due to the allocation of more attentional resources, when items are presented in both left and right visual fields.

The bandwidth of VWM consolidation varies with the stimulus feature: Evidence from event-related potentials

Our previous work suggests that 2 colors can be consolidated into visual short-term memory (VSTM) in parallel without a loss of memory precision, whereas consolidation of 2 orientations is performed in a strictly serial manner. Those experiments compared VSTM performance for simultaneously and sequentially presented stimuli. However, there is still controversy about whether the bandwidth for consolidation is determined by the type of information. To further investigate this issue, here we measured electroencephalography while participants attempted to consolidate 1, 2 or 4 simultaneously presented colors (Experiment 1) or orientations (Experiment 2) under limited presentation times. We used the contralateral delay activity (CDA) as an electrophysiological marker of the number of items that were consolidated. For colored stimuli, the CDA amplitude increased between set-size 1 and 2 but did not further increase for set size 4. By contrast, for orientation, the CDA amplitude remained at the set size 1 amplitude as set size increased to 2 or 4 items. Furthermore, in a long exposure duration (300 ms) condition that did not limit the consolidation process, the CDA amplitude pattern indicated that VSTM capacity is limited to about 3 colored items and about 2 orientation items in our paradigm. Thus, the CDA effects observed in the short presentation time was not limited by VSTM storage, but rather by consolidation. These results are consistent with our previous behavioral research and suggest that the bandwidth of VSTM consolidation is determined by the stimulus feature. (PsycINFO Database Record

EEG correlates of visual short-term memory in older age vary with adult lifespan cognitive development

Visual short-term memory (vSTM) is a cognitive resource that declines with age. This study investigated whether electroencephalography (EEG) correlates of vSTM vary with cognitive development over individuals' lifespan. We measured vSTM performance and EEG in a lateralized whole-report task in a healthy birth cohort, whose cognitive function (intelligence quotient) was assessed in youth and late-middle age. Higher vSTM capacity (K; measured by Bundesen's theory of visual attention) was associated with higher amplitudes of the contralateral delay activity (CDA) and the central positivity (CP). In addition, rightward hemifield asymmetry of vSTM (K_λ) was associated with lower CDA amplitudes. Furthermore, more severe cognitive decline from young adulthood to late-middle age predicted higher CDA amplitudes, and the relationship between K and the CDA was less reliable in individuals who show higher levels of cognitive decline compared to individuals with preserved abilities. By contrast, there was no significant effect of lifespan cognitive changes on the CP or the relationship between behavioral measures of vSTM and the CP. Neither the CDA, nor the CP, nor the relationships between K or K_λ and the event-related potentials were predicted by individuals' current cognitive status. Together, our findings indicate complex age-related changes in processes underlying behavioral and EEG measures of vSTM and suggest that the K-CDA relationship might be a marker of cognitive lifespan trajectories.

A two-phase model of resource allocation in visual working memory

Two broad theories of visual working memory (VWM) storage have emerged from current research, a discrete slot-based theory and a continuous resource theory. However, neither the discrete slot-based theory or continuous resource theory clearly stipulates how the mental commodity for VWM (discrete slot or continuous resource) is allocated. Allocation may be based on the number of items via stimulus-driven factors, or it may be based on task demands via voluntary control. Previous studies have obtained conflicting results regarding the automaticity versus controllability of such allocation. In the current study, we propose a two-phase allocation model, in which the mental commodity could be allocated only by stimulus-driven factors in the early consolidation phase. However, when there is sufficient time to complete the early phase, allocation can enter the late consolidation phase, where it can be flexibly and voluntarily controlled according to task demands. In an orientation recall task, we instructed participants to store either fewer items at high-precision or more items at low-precision. In 3 experiments, we systematically manipulated memory set size and exposure duration. We did not find an effect of task demands when the set size was high and exposure duration was short. However, when we either decreased the set size or increased the exposure duration, we found a trade-off between the number and precision of VWM representations. These results can be explained by a two-phase model, which can also account for previous conflicting findings in the literature. (PsycINFO Database Record

The contralateral delay activity as a neural measure of visual working memory

The contralateral delay activity (CDA) is a negative slow wave sensitive to the number of objects maintained in visual working memory (VWM). In recent years, a growing number of labs started to use the CDA in order to investigate VWM, leading to many fascinating discoveries. Here, we discuss the recent developments and contribution of the CDA in various research fields. Importantly, we report two meta-analyses that unequivocally validate the relationship between the set-size increase in the CDA amplitude and the individual VWM capacity, and between the CDA and filtering efficiency. We further discuss how the CDA was used to study the role of VWM in visual search, multiple object tracking, grouping, binding, and whether VWM capacity allocation is determined by the items' resolution or instead by the number of objects regardless of their complexity. In addition, we report how the CDA has been used to characterize specific VWM deficits in special populations.