Visual Working Memory Maintenance Research Articles

Hearing fearful prosody impairs visual working memory maintenance

Interference by distractors has been associated multiple times with diminished visual and auditory working memory (WM) performance. Negative emotional distractors in particular lead to detrimental effects on WM. However, these associations have only been seen when distractors and items to maintain in WM are from the same sensory modality. In this study, we investigate cross-modal interference on WM. We invited 20 participants to complete a visual change-detection task, assessing visual WM (VWM), while hearing emotional (fearful) and neutral auditory distractors. Electrophysiological activity was recorded to measure contralateral delay activity (CDA) and auditory P2 event-related potentials (ERP), indexing WM maintenance and distractor salience respectively. At the behavioral level, fearful prosody didn't decrease significantly working memory accuracy, compared to neutral prosody. Regarding ERPs, fearful distractors evoked a greater P2 amplitude than neutral distractors. Correlations between the two ERP potentials indicated that P2 amplitude difference between the two types of prosody was associated with the difference in CDA amplitude for fearful and neutral trials. This association suggests that cognitive resources required to process fearful prosody detrimentally impact VWM maintenance. That result provides a piece of additional evidence that negative emotional stimuli produce greater interference than neutral stimuli and that the cognitive resources used to process stimuli from different modalities come from a common pool.

Stunting in infancy is associated with atypical activation of working memory and attention networks

Stunting is associated with poor long-term cognitive, academic and economic outcomes, yet the mechanisms through which stunting impacts cognition in early development remain unknown. In a first-ever neuroimaging study conducted on infants from rural India, we demonstrate that stunting impacts a critical, early-developing cognitive system—visual working memory. Stunted infants showed poor visual working memory performance and were easily distractible. Poor performance was associated with reduced engagement of the left anterior intraparietal sulcus, a region involved in visual working memory maintenance and greater suppression in the right temporoparietal junction, a region involved in attentional shifting. When assessed one year later, stunted infants had lower problem-solving scores, while infants of normal height with greater left anterior intraparietal sulcus activation showed higher problem-solving scores. Finally, short-for-age infants with poor physical growth indices but good visual working memory performance showed more positive outcomes suggesting that intervention efforts should focus on improving working memory and reducing distractibility in infancy.

Encoding specificity instead of online integration of real-world spatial regularities for objects in working memory

Most objects show high degrees of spatial regularity (e.g. beach umbrellas appear above, not under, beach chairs). The spatial regularities of real-world objects benefit visual working memory (VWM), but the mechanisms behind this spatial regularity effect remain unclear. The “encoding specificity” hypothesis suggests that spatial regularity will enhance the visual encoding process but will not facilitate the integration of information online during VWM maintenance. The “perception-alike” hypothesis suggests that spatial regularity will function in both visual encoding and online integration during VWM maintenance. We investigated whether VWM integrates sequentially presented real-world objects by focusing on the existence of the spatial regularity effect. Throughout five experiments, we manipulated the presentation (simultaneous vs. sequential) and regularity (with vs. without regularity) of memory arrays among pairs of real-world objects. The spatial regularity of memory objects presented simultaneously, but not sequentially, improved VWM performance. We also examined whether memory load, verbal suppression and masking, and memory array duration hindered the spatial regularity effect in sequential presentation. We found a stable absence of the spatial regularity effect, suggesting that the participants were unable to integrate real-world objects based on spatial regularities online. Our results support the encoding specificity hypothesis, wherein the spatial regularity of real-world objects can enhance the efficiency of VWM encoding, but VWM cannot exploit spatial regularity to help organize sampled sequential information into meaningful integrations.

Neural basis of distractor resistance during visual working memory maintenance

Visual working memory representations must be protected from the intervening irrelevant visual input. While it is well known that interference resistance is most challenging when distractors match the prioritised mnemonic information, its neural mechanisms remain poorly understood. Here, we identify two top-down attentional control processes that have opposing effects on distractor resistance. We reveal an early selection negativity in the EEG responses to matching as compared to non-matching distractors, the magnitude of which is negatively associated with behavioural distractor resistance. Additionally, matching distractors lead to reduced post-stimulus alpha power as well as increased fMRI responses in the object-selective visual cortical areas and the inferior frontal gyrus. However, the congruency effect found on the post-stimulus periodic alpha power and the inferior frontal gyrus fMRI responses show a positive association with distractor resistance. These findings suggest that distractor interference is enhanced by proactive memory content-guided selection processes and diminished by reactive allocation of top-down attentional resources to protect memorandum representations within visual cortical areas retaining the most selective mnemonic code.

Object-based encoding in visual working memory: A critical revisit.

Visual working memory (VWM) is responsible for the temporal retention and manipulation of visual information. It has been suggested that VWM employs an object-based encoding (OBE) manner to extract highly discriminable information from visual perception: Whenever one feature dimension of the objects is selected for entry into VWM, the other task-irrelevant highly discriminable dimension is also extracted into VWM involuntarily. However, the task-irrelevant feature in OBE studies might reflect a high capacity fragile VWM (FVWM) trace that stores maskable sensory representations. To directly compare the VWM storage hypothesis and the FVWM storage hypothesis, we used a unique characteristic of FVWM that the representations in FVWM could be erased by backward masks presented at the original locations of the memory array. We required participants to memorise the orientations of three coloured bars while ignoring their colours, and presented backward masks during the VWM maintenance interval. In four experiments, we consistently observed that the OBE occurs regardless of the presentation of the backward masks, except when even the task-relevant features in VWM were significantly interrupted by immediate backward masks, suggesting that the task-irrelevant features of objects are stored in VWM rather than in FVWM.

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).

Spatial specificity of feature-based interaction between working memory and visual processing.

Visual working memory interacts with ongoing visual processing in a stimulus-specific manner, potentially through a common neural substrate supporting visual perception and working memory maintenance. The spatial specificity of this effect, however, remains unknown. The current study tested whether features in working memory influence perception in a spatially specific or global fashion. Across four experiments, subjects performed perceptual discrimination tasks on orientation or on contrast while concurrently holding an orientation in working memory. Experiments 1 and 2 revealed that memory content boosted the perceived contrast of the discrimination stimulus when the two matched in orientation, but only when the locations of the memorandum and the discriminandum also matched. In turn, feature-based influence on memory precision was also greater when locations matched. Experiments 3 and 4 demonstrated that the spatial specificity of this interaction was influenced by task demands. When encoding of location was discouraged in Experiment 3, memory interacted with perception in a global fashion, whereas when location was task-relevant in otherwise very similar Experiment 4, the feature-based enhancement was again modulated by location. These results suggest that context-binding demand is an important determinant of the spatial specificity of memory-perception interaction and highlight the flexible configurability of working memory representations. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Frontoparietal Beta Amplitude Modulation and its Interareal Cross-frequency Coupling in Visual Working Memory

Visual working memory (VWM) relies on sustained neural activities that code information via various oscillatory frequencies. Previous studies, however, have emphasized time–frequency power changes, while overlooking the possibility that rhythmic amplitude variations can also code frequency-specific VWM information in a completely different dimension. Here, we employed the recently-developed Holo-Hilbert spectral analysis to characterize such nonlinear amplitude modulation(s) (AM) underlying VWM in the frontoparietal systems. We found that the strength of AM in mid-frontal beta and gamma oscillations during late VWM maintenance and VWM retrieval correlated with people’s VWM performance. When behavioral performance was altered with transcranial electric stimulation, AM power changes during late VWM maintenance in beta, but not gamma, tracked participants’ VWM variations. This beta AM likely codes information by varying its amplitude in theta period for long-range propagation, as our connectivity analysis revealed that interareal theta-beta couplings—bidirectional between mid-frontal and right-parietal during VWM maintenance and unidirectional from right-parietal to left-middle-occipital during late VWM maintenance and retrieval—underpins VWM performance and individual differences.

Delay-dependent cholinergic modulation of visual short-term memory in rhesus macaques

Cholinergic neuromodulation is known to play a key role in visual working memory (VWM) – keeping relevant stimulus representations available for cognitive processes for short time periods (up to a few minutes). Despite the growing body of evidence on how the neural and cognitive mechanisms of VWM dynamically change over retention time, there is mixed evidence available on cholinergic effects as a function of VWM delay period in non-human primates. Using the delayed matching to sample VWM task in rhesus macaques (N = 6), we aimed to characterize VWM maintenance in terms of performance changes as a function of delay duration (across a wide range of delays from 1 to 76 s). Then, we studied how cholinergic neuromodulation influences VWM maintenance using the muscarinic receptor antagonist scopolamine administered alone as transient amnestic treatment, and in combination with two doses of the acetylcholinesterase inhibitor donepezil, a widely used Alzheimer’s medication probing for the reversal of scopolamine-induced impairments. Results indicate that scopolamine-induced impairments of VWM maintenance are delay-dependent and specifically affect the 15−33 s time range, suggesting that scopolamine worsens the normal decay of VWM with the passage of time. Donepezil partially rescued the observed scopolamine-induced impairments of VWM performance. These results provide strong behavioral evidence for the role of increased cholinergic tone and muscarinic neuromodulation in the maintenance of VWM beyond a few seconds, in line with our current knowledge on the role of muscarinic acetylcholine receptors in sustained neural activity during VWM delay periods.

Attention for action in visual working memory

From the conception of Baddeley's visuospatial sketchpad, visual working memory and visual attention have been closely linked concepts. An attractive model has advocated unity of the two cognitive functions, with attention serving the active maintenance of sensory representations. However, empirical evidence from various paradigms and dependent measures has now firmly established an at least partial dissociation between visual attention and visual working memory maintenance – thus leaving unclear what the relationship between the two concepts is. Moreover, a focus on sensory storage has treated visual working memory as a reflection of the past, with attention as a limiting resource. This view ignores what storage is for: immediate or future action. We argue that rather than serving sensory storage, attention emerges from coupling relevant sensory and action representations within working memory. Importantly, this coupling is bidirectional: First, through recurrent feedback mechanisms, action coupling results in the enhancement of the appropriate sensory memory representation. Under this view, unattended memories are currently not coupled to an action plan, but are not necessarily lost and remain available for future tasks when necessary. Second, through the very same feedback projections, attention serves as the credit assignment mechanism for the action's outcome. When the action is successful, the associated representations are being reinforced, leading to more robust consolidation and more rapid retrieval in the future – thus explaining performance benefits for attended memories without assuming that attention serves as the maintenance mechanism. By firmly grounding VWM in the action system, the new framework integrates a range of behavioural and neurophysiological findings and avoids circularity in explaining the role of attention in working memory.

Functional dissociation of anterior cingulate cortex and intraparietal sulcus in visual working memory

Previous electrophysiological studies of lateralized visual working memory (VWM) identified an ERP component, defined as contralateral delay activity (CDA), directly modulated by the number of items held in memory. One of the main candidate as the cortical source of this ERP component is the inferior intraparietal sulcus (IPS). Moreover, previous neuroimaging studies put forth evidence for the presence of a distributed VWM network involving also prefrontal areas and in particular the anterior cingulate cortex (ACC). Nonetheless, the understanding of the functional role of ACC is still debated. We recorded the high-density EEG in 20 healthy participants undergoing a VWM and a control task. Explorative cluster-based permutation statistics confirmed the posterior memory load dependent CDA modulation, but also identified an additional anterior cluster of electrodes whose amplitude was modulated by memory load. The source reconstruction revealed a memory load dependent activation in the IPS but also in the ACC, suggesting that these two areas might be nodes of a fronto-parietal circuit underlying VWM maintenance. Crucially, parietal and prefrontal areas showed a temporal dissociation, since IPS was more engaged in the early phase of visual information storage while the ACC was more active during the late phase. This pattern suggests a functional dissociation between the parietal cortex, which is involved in encoding and storage of information, and prefrontal areas, subserving cognitive control processes, including the boosting and protection of information from decay. Remarkably, the connection strength between IPS and ACC predicted the individual number of items held in memory. These findings are discussed within the theoretical account of a neural distributed model of VWM.

Neural markers of visual working memory encoding and maintenance track attentional prioritization

Neural markers of visual working memory encoding and maintenance track attentional prioritization

Attention induces surround suppression in visual working memory.

Controversy currently exists regarding whether visual working memory (VWM) maintains sensory or non-sensory representations. Here, we tested the nature of VWM representations by leveraging a perceptual surround suppression effect when an item is attended. Participants performed a delayed-estimation task in which they memorized an array of six colors. A cue indicated which location was most likely probed. In separate experiments, we manipulated external attention (via a precue) or internal attention (via a retrocue). Both types of attention elicited a surround suppression effect, such that memory performance showed a Mexican-hat profile as a function of cue-probe offsets. Given the sensory origin of the surround suppression effect, our results thus provide compelling evidence that VWM maintenance relies on sensory mechanisms.

Trait anxiety is associated with a decreased visual working memory capacity for faces

Recent work has suggested that anxiety restricts working memory capacity, which may underlie a wide range of cognitive symptoms in anxiety. However, previous literature on the anxiety-visual working memory association yielded mixed results, with some studies demonstrating an anxiety-related increase in visual working memory capacity. In an attempt to gain a more thorough understanding of the relationship between anxiety and visual working memory maintenance function, the current study examined the influence of trait anxiety on visual working memory capacity and resolution for negative, positive, and neutral faces in a large unselected sample, by conducting two different experiments. Experiment 1 used a change-detection task to estimate visual working memory capacity, while Experiment 2 used a modified time-delay estimation task to measure memory precision. Hierarchical linear modeling was used to analyze the relationship between trait anxiety, emotional valence, and visual working memory. Results showed that trait anxiety was associated with decreased visual working memory capacity for faces in a valence-independent manner, whereas anxiety-related change in visual working memory resolution was not significant. This pattern of results was discussed in light of the theories of anxiety and visual working memory.

Temporal-Order-Based Attentional Priority Modulates Mnemonic Representations in Parietal and Frontal Cortices.

The respective roles of occipital, parietal, and frontal cortices in visual working memory maintenance have long been under debate. Previous work on whether parietal and frontal regions convey mnemonic information has yielded mixed findings. One possibility for this variability is that the mnemonic representations in high-level frontoparietal regions are modulated by attentional priority, such as temporal order. To test this hypothesis, we examined whether the most recent item, which has a higher attentional priority in terms of temporal order, is preferentially encoded in frontoparietal regions. On each trial, participants viewed 2 gratings with different orientations in succession, and were cued to remember one of them. Using fMRI and an inverted encoding model, we reconstructed population-level, orientation representations in occipital (V1-V3), parietal (IPS), and frontal (FEF) areas during memory maintenance. Unlike early visual cortex where robust orientation representations were observed regardless of serial order, parietal, and frontal cortices showed stronger representations when participants remembered the second grating. A subsequent experiment using a change detection task on color rings excluded the possibilities of residual stimulus-driven signals or motor preparative signals for responses. These results suggest that mnemonic representations in parietal and frontal cortices are modulated by temporal-order-based attentional priority signals.

Concussion Alters the Functional Brain Processes of Visual Attention and Working Memory.

Millions of North Americans sustain a concussion or a mild traumatic brain injury annually, and are at risk of cognitive, emotional, and physical sequelae. Although functional MRI (fMRI) studies have provided an initial framework for examining functional deficits induced by concussion, particularly working memory and attention, the temporal dynamics underlying these deficits are not well understood. We used magnetoencephalography (MEG), a modality with millisecond temporal resolution, in conjunction with a 1-back visual working memory (VWM) paradigm using scenes from everyday life to characterize spatiotemporal functional differences at specific VWM stages, in adults had had or had not had a recent concussion. MEG source-level differences between groups were determined by whole-brain analyses during encoding and recognition phases. Despite comparable behavioral performance, abnormal hypo- and hyperactivation patterns were found in brain areas involving frontoparietal, ventral occipitotemporal, temporal, and subcortical areas in concussed patients. These patterns and their timing varied as a function of VWM stagewise processing, linked to early attentional control, visuoperceptual scene processing, and VWM maintenance and retrieval processes. Parietal hypoactivation, starting at 60 ms during encoding, was correlated with symptom severity, possibly linked to impaired top-down attentional processing. Hyperactivation in the scene-selective occipitotemporal areas, the medial temporal complex, specifically the right hippocampus and orbitofrontal areas during encoding and/or recognition, lead us to posit inefficient but compensatory visuoperceptual, relational, and retrieval processing. Although injuries sustained after the concussion were considered "mild," these data suggest that they can have prolonged effects on early attentional and VWM processes.

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

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

Object maintenance beyond their visible parts in working memory.

Completion of a partially occluded object requires that a representation of the whole is constructed based on the information provided by the physically specified parts of the stimulus. Such processes of amodal completion rely on the generation and maintenance of a mental image that renders the completed object in visual working memory (VWM). The present study examined this relationship between VWM storage and processes of object completion. We recorded event-related potentials to track VWM maintenance by means of the contralateral delay activity (CDA) during a change detection task in which composite objects (notched shapes abutting an occluding shape) to be memorized were primed to induce either a globally completed object or a noncompleted, mosaic representation. The results revealed an effect of completion in VWM despite physically identical visual input: change detection was more accurate for completed compared with mosaic representations when observers were required to memorize two objects, and these differences were reduced with four memorized items. At the electrophysiological level, globally completed (vs. mosaic) objects gave rise to a corresponding increase in CDA amplitudes. These results indicate that although incorporating the occluded portions of the presented shapes requires mnemonic resources, the complete object representations thus formed in VWM improve change detection performance by providing a more simple, regular shape. Overall, these findings demonstrate that mechanisms of object completion modulate VWM, with the memory load being determined by the structured representations of the memorized stimuli. NEW & NOTEWORTHY This study shows that completion of partially occluded objects requires visual working memory (VWM) resources. In the experiment reported, we induced observers to memorize a given visual input either as completed or as noncompleted objects. The results revealed both a behavioral performance advantage for completed vs. noncompleted objects despite physically identical input, and an associated modulation of an electrophysiological component that reflects VWM object retention, thus indicating that constructing an integrated object consumes mnemonic resources.

Heterogeneity in development of aspects of working memory predicts longitudinal attention deficit hyperactivity disorder symptom change.

The current study uses an accelerated longitudinal design and latent trajectory growth mixture models in a sample of children ages 7-13 years carefully characterized as with (n = 437) and without (n = 297) ADHD to (a) identify heterogeneous developmental trajectories for response inhibition, visual spatial working memory maintenance, and delayed reward discounting and (b) to assess the relationships between these cognitive trajectories and ADHD symptom change. Best-fitting models indicated multiple trajectory classes in both the ADHD and typically developing samples, as well as distinct relationships between each cognitive process and ADHD symptom change. Developmental change in response inhibition and delayed reward discounting were unrelated to ADHD symptom change, while individual differences in the rate of visual spatial working memory maintenance improvement predicted symptom remission in ADHD. Characterizing heterogeneity in cognitive development will be crucial for clarifying mechanisms of symptom persistence and recovery. Results here suggest working memory maintenance may be uniquely related to ADHD symptom improvement. (PsycINFO Database Record

Pupillary correlates of covert shifts of attention during working memory maintenance.

The pupillary light reflex (PLR) was used to track covert shifts of attention to items maintained in visual working memory (VWM). In three experiments, participants performed a change detection task in which rectangles appeared on either side of fixation and at test participants indicated if the cued rectangle changed its orientation. Prior to presentation or during the delay, participants were cued to the light or dark side of the screen. When cued to the light side, the pupil constricted, and when cued to the dark side, the pupil dilated, suggesting that the PLR tracked covert shifts of attention. Similar covert shifts of attention were seen when the target stimuli remained onscreen and during a blank delay period, suggesting similar effects for attention to perceptual stimuli and attention to stimuli maintained in VWM. Furthermore, similar effects were demonstrated when participants were pre-cued or retro-cued to the prioritized location, suggesting that shifts of covert attention can occur both before and after target presentation. These results are consistent with prior research, suggesting an important role of covert shifts of attention during VWM maintenance and that the PLR can be used to track these covert shifts of attention.