Binding In Working Memory Research Articles

Effects of Context Changes on Memory Reactivation.

While the influence of context on long-term memory (LTM) is well documented, its effects on the interaction between working memory (WM) and LTM remain less understood. In this study, we explored these interactions using a delayed match-to-sample task, where participants (6 males, 16 females) encountered the same target object across six consecutive trials, facilitating the transition from WM to LTM. During half of these target repetitions, the background color changed. We measured the WM storage of the target using the contralateral delay activity in electroencephalography. Our results reveal that task-irrelevant context changes trigger the reactivation of long-term memories in WM. This reactivation may be attributed to content-context binding in WM and hippocampal pattern separation.

Unraveling the binding problem in working memory: insights from the hierarchical binding model.

The binding problem is a crucial issue in the study of working memory (WM) and remains a central topic of debate among various WM models. Over the past decade, we have explored feature binding within WM, guided by the Hierarchical Binding Model (HBM). This model suggests that WM binding occurs in two stages: an initial implicit binding involving rapid, coarse feature processing, followed by explicit binding where focused attention refines these features via a reentry process. We found that implicit binding is closely related to the attentional processing of features during the perceptual stage. Basic features that can be rapidly and coarsely processed in parallel through spread attention are involuntarily extracted into WM along with the target features, forming a rough bound representation. For explicit binding, we examined the role of attention in retaining explicit binding in WM, emphasizing the unique role of reentry in the HBM. Our findings indicate that WM binding requires additional object attention through the reentry process. These results demonstrate that both implicit and explicit bindings are integral to WM and that the HBM is effective in elucidating the binding mechanisms within WM.

Evidence Against Effects of Cultural Group and Prior Knowledge on Feature Binding in Working Memory.

Feature binding is the process of integrating features, such as colour and shape, into object representations. A persistent question in the literature concerning whether feature binding is an automatic or resource-demanding process may depend on unitisation, that is, whether the to-be-bound information is intrinsic (belonging to) or extrinsic (contextual). Given extensive evidence showing that Easterners may process information more holistically than Westerners, such cultural differences may be useful to understand the fundamental processes of feature binding in visual working memory (WM). Accordingly, we recruited British and Chinese participants to complete a visual WM task wherein to-be-remembered colours were integrated within (i.e., intrinsic binding) or as backgrounds (i.e., extrinsic binding) of to-be-remembered shapes (Experiments 1 and 2). Experiment 2 further investigated the role of prior knowledge in long-term memory to facilitate feature binding in WM. During retrieval, participants decided among three probes: a target, a lure (i.e., recombination of the presented features), and a new colour/shape. Hierarchical Bayesian multinomial processing tree models were fit to the data to estimate parameters representing binding and item memory. The current results suggest that intrinsic and extrinsic binding memory are similar between the two cultural groups, with no prior knowledge benefits for either intrinsic or extrinsic binding for either cultural group. This result conflicts with the Analytic and Holistic framework and suggests that there are no cultural differences or prior knowledge benefits in feature binding.

Clinical Manifestations.

Associative binding is key to normal memory function and is selectively impaired in Alzheimer's disease (AD).1 Electrophysiological abnormalities are frequently reported in AD including during tasks requiring associative binding.2 We use a precision spatial working memory test to investigate the binding of distinct visual features (object and location) in working memory in AD patients and test the hypothesis that misbinding is related to electrophysiological abnormalities. 36 AD patients and 29 healthy age-matched controls (HC) were tested with a precision working memory paradigm that required the association of object and location information (Fig 1A). Participants were excluded if they were unable to perform the identification element of the task significantly above chance level (p>0.05). High-density eyes-closed resting-state EEG was used to assess changes in electrophysiological power across frequency bands. 25 AD and all HC performed above chance level (Fig 1C). AD patients showed abnormalities in working memory function and made significantly more misbinding errors (p<0.001) than HC (Fig1E) indicating that working memory recall was abnormally biased by the spatial locations of distractor items (Fig 1F). AD patients demonstrated significant reductions in global alpha and increases in global theta (Fig 2A). Channel-wise analysis revealed significant clusters of decreased power in AD across occipital-parietal channels in alpha and beta bands (p<0.05; Fig 2C). Misbinding errors significantly correlated with alpha power in AD but not HC (p<0.05; Fig 2D). These results offer further support for a deficit in working memory binding being a sensitive cognitive biomarker of AD. Pathologically reduced alpha power may offer mechanistic insight into the profound working memory binding impairments seen in AD.

Age-related hearing loss associated with differences in the neural correlates of feature binding in visual working memory

The underlying neural mechanisms underpinning the association between age-related hearing loss (ARHL) and dementia remain unclear. A limitation has been the lack of functional neuroimaging studies in ARHL cohorts to help clarify this relationship. In the present study, we investigated the neural correlates of feature binding in visual working memory with ARHL (controls = 14, mild HL = 21, and moderate or greater HL = 23). Participants completed a visual change detection task assessing feature binding while their neural activity was synchronously recorded via high-density electroencephalography. There was no difference in accuracy scores for ARHL groups compared to controls. There was increased electrophysiological activity in those with ARHL, particularly in components indexing the earlier stages of visual cognitive processing. This activity was more pronounced with more severe ARHL and was associated with maintained feature binding. Source space (sLORETA) analyses indicated greater activity in networks modulated by frontoparietal and temporal regions. Our results demonstrate there may be increased involvement of neurocognitive control networks to maintain lower-order neurocognitive processing disrupted by ARHL.

Working Memory Constrains Long-Term Memory in Children and Adults: Memory of Objects and Bindings

We explored how individual and age-related differences in working memory (WM) capacity affected subsequent long-term memory (LTM) retrieval. Unlike past studies, we tested WM and LTM not only for items, but also for item-color bindings. Our sample included 82 elementary school children and 42 young adults. The participants performed a WM task with images of unique everyday items presented sequentially at varying set sizes in different colors. Later, we tested LTM for items and item-color bindings from the WM task. The WM load during encoding constrained LTM, and participants with a higher WM capacity retrieved more items in the LTM test. Even when accounting for young children's poor item memory by considering only the items that they did remember, they exhibited an exacerbated difficulty with remembering item-color bindings in WM. Their LTM binding performance, however, as a proportion of remembered objects, was comparable to that of older children and adults. The WM binding performance was better during sub-span encoding loads, but with no clear transfer of this benefit to LTM. Overall, LTM item memory performance was constrained by individual and age-related WM limitations, but with mixed consequences for binding. We discuss the theoretical, practical, and developmental implications of this WM-to-LTM bottleneck.

Strategic control of location and ordinal context in visual working memory.

Working memory (WM) requires encoding stimulus identity and context (e.g. where or when stimuli were encountered). To explore the neural bases of the strategic control of context binding in WM, we acquired fMRI while subjects performed delayed recognition of 3 orientation patches presented serially and at different locations. The recognition probe was an orientation patch with a superimposed digit, and pretrial instructions directed subjects to respond according to its location ("location-relevant"), to the ordinal position corresponding to its digit ("order-relevant"), or to just its orientation (relative to all three samples; "context-irrelevant"). Delay period signal in PPC was greater for context-relevant than for "context-irrelevant" trials, and multivariate decoding revealed strong sensitivity to context binding requirements (relevant vs. "irrelevant") and to context domain ("location-" vs. "order-relevant") in both occipital cortex and PPC. At recognition, multivariate inverted encoding modeling revealed markedly different patterns in these 2 regions, suggesting different context-processing functions. In occipital cortex, an active representation of the location of each of the 3 samples was reinstated regardless of the trial type. The pattern in PPC, by contrast, suggested a trial type-dependent filtering of sample information. These results indicate that PPC exerts strategic control over the representation of stimulus context in visual WM.

Working Memory Precision and Associative Binding in Mild Cognitive Impairment

ABSTRACT To better understand working memory (WM) deficits in Mild Cognitive Impairment (MCI), we examined information precision and associative binding in WM in 21 participants with MCI, compared to 16 healthy controls, using an item-location delayed reproduction task. WM, along with other executive functions (i.e. Trail Making Task (TMT) and Stroop task), were measured before and after a 2-h nap. The napping manipulation was intended as an exploratory element to this study exploring potential impacts of napping on executive functions. Compared to healthy participants, participants with MCI exhibited inferior performance not only in identifying encoded WM items but also on item-location associative binding and location precision even when only one item was involved. We also found changes on TMT and Stroop tasks in MCI, reflecting inferior attention and inhibitory control. Post-napping performance improved in most of these WM and other executive measures, both in MCI and their healthy peers. Our study shows that associative binding and WM precision can reliably differentiate MCIs from their healthy peers. Additionally, most measures showed no differential effect of group pre- and post-napping. These findings may contribute to better understanding cognitive deficits in MCI therefore improving the diagnosis of MCI.

Examining the role of attention during feature binding in visuospatial working memory.

The current experiments address the enduring debate regarding the role of attention in feature binding in visuospatial working memory by considering the nature of the to-be-bound features, i.e., whether they are intrinsic (integrated within the object, such as its color and shape) or extrinsic (not part of the object, such as its spatial location). Specifically, arrays of different-colored shapes in different locations were followed by probed recall: One feature of the probed object prompted recall of one of its remaining two features (e.g., a shape probe prompts recall of color, with the probe displayed at the center of the screen (i.e., without spatial information)) to test the retention of intrinsic (shape, color) and extrinsic (location) features. During the retention interval, we manipulated attention via disruption (Experiment 1) and retro-cues (Experiment 2) to determine their impacts on binding errors, as estimated from a three-parameter mixture model fit to recall error (i.e., the distance between the target and response). Disrupting central versus peripheral attention in Experiment 1 did not respectively increase extrinsic and intrinsic binding errors as predicted, but disrupting central attention reduced target memory of the extrinsic feature relative to a no-disruption baseline. Guiding attention via extrinsic and intrinsic retro-cues in Experiment 2 did not respectively reduce extrinsic and intrinsic binding errors as predicted, but we observed retro-cue benefits to target memory that did not distinguish between extrinsic and intrinsic features. Thus, this work highlights that attentional resources aid target memory, with no consistent distinction between intrinsic and extrinsic features.

Role of time in binding features in visual working memory.

Previous research on feature binding in visual working memory has supported a privileged role for location in binding an object's nonspatial features. However, humans are able to correctly recall feature conjunctions of objects that occupy the same location at different times. In a series of behavioral experiments, we investigated binding errors under these conditions, and specifically tested whether ordinal position can take the role of location in mediating feature binding. We performed two dual report experiments in which participants had to memorize three colored shapes presented sequentially at the screen center. When participants were cued with the ordinal position of one item and had to report its shape and color, report errors for the two features were largely uncorrelated. In contrast, when participants were cued, for example, with an item's shape and reported an incorrect ordinal position, they had a high chance of making a corresponding error in the color report. This pattern of error correlations closely matched the predictions of a model in which color and shape are bound to each other only indirectly via an item's ordinal position. In a third experiment, we directly compared the roles of location and sequential position in feature binding. Participants viewed a sequence of colored disks displayed at different locations and were cued either by a disk's location or its ordinal position to report its remaining properties. The pattern of errors supported a mixed strategy with individual variation, suggesting that binding via either time or space could be used for this task. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Pathological Slow-Wave Activity and Impaired Working Memory Binding in Post-Traumatic Amnesia.

Associative binding is key to normal memory function and is transiently disrupted during periods of post-traumatic amnesia (PTA) following traumatic brain injury (TBI). Electrophysiological abnormalities, including low-frequency activity, are common following TBI. Here, we investigate associative memory binding during PTA and test the hypothesis that misbinding is caused by pathological slowing of brain activity disrupting cortical communication. Thirty acute moderate to severe TBI patients (25 males; 5 females) and 26 healthy controls (20 males; 6 females) were tested with a precision working memory paradigm requiring the association of object and location information. Electrophysiological effects of TBI were assessed using resting-state EEG in a subsample of 17 patients and 21 controls. PTA patients showed abnormalities in working memory function and made significantly more misbinding errors than patients who were not in PTA and controls. The distribution of localization responses was abnormally biased by the locations of nontarget items for patients in PTA, suggesting a specific impairment of object and location binding. Slow-wave activity was increased following TBI. Increases in the δ-α ratio indicative of an increase in low-frequency power specifically correlated with binding impairment in working memory. Connectivity changes in TBI did not correlate with binding impairment. Working memory and electrophysiological abnormalities normalized at 6 month follow-up. These results show that patients in PTA show high rates of misbinding that are associated with a pathological shift toward lower-frequency oscillations.SIGNIFICANCE STATEMENT How do we remember what was where? The mechanism by which information (e.g., object and location) is integrated in working memory is a central question for cognitive neuroscience. Following significant head injury, many patients will experience a period of post-traumatic amnesia (PTA) during which this associative binding is disrupted. This may be because of electrophysiological changes in the brain. Using a precision working memory test and resting-state EEG, we show that PTA patients demonstrate impaired binding ability, and this is associated with a shift toward slower-frequency activity on EEG. Abnormal EEG connectivity was observed but was not specific to PTA or binding ability. These findings contribute to both our mechanistic understanding of working memory binding and PTA pathophysiology.

Aging and feature binding in visual working memory.

Older adults have reduced performance in visual working memory tasks in comparison to young adults, but the precipitators of the age-related impairment are not fully understood. The most common interpretation of this difference is that older adults are incapable of maintaining the same amount of object representations as young adults over short intervals (in line with the fixed-slot model of working memory). However, it has remained largely unexplored whether the age-related decline is only due to the number of representations that older individuals can retain in visual working memory, or whether the content of the representation(s) may have an effect as well (in line with the flexible-resource model of working memory). Feature binding studies represent an interesting research line to examine the content of older adults' representations. In this mini-review, we present the main results across feature binding studies in aging, as well as highlight the importance of manipulating both the representation content and number to have a stress test of the various models of working memory and their contribution to aging. Overall, feature binding studies, together with the simultaneous manipulation of set size, will allow us to better understand the nature of the age-related decline of visual working memory.

Intact high-resolution working memory binding in a patient with developmental amnesia and selective hippocampal damage.

Debate continues regarding the possible role of the hippocampus across short‐term and working memory tasks. The current study examined the possibility of a hippocampal contribution to precise, high‐resolution cognition and conjunctive memory. We administered visual working memory tasks featuring a continuous response component to a well‐established developmental amnesic patient with relatively selective bilateral hippocampal damage (Jon) and healthy controls. The patient was able to produce highly accurate response judgments regarding conjunctions of color and orientation or color and location, using simultaneous or sequential presentation of stimuli, with no evidence of any impairment in working memory binding, categorical accuracy, or continuous precision. These findings indicate that hippocampal damage does not necessarily lead to deficits in high‐resolution cognitive performance, even when the damage is severe and bilateral.

The hippocampus supports high-precision binding in visual working memory.

It is well established that the hippocampus is critical for long-term episodic memory, but a growing body of research suggests that it also plays a critical role in supporting memory over very brief delays as measured in tests of working memory (WM). However, the circumstances under which the hippocampus is necessary for WM and the specific processes that it supports remain controversial. We propose that the hippocampus supports WM by binding together high-precision properties of an event, and we test this claim by examining the precision of color-location bindings in a visual WM task in which participants report the precise color of studied items using a continuous color wheel. Amnestic patients with hippocampal damage were significantly impaired at retrieving these colors after a 1-s delay, and these impairments reflected a reduction in the precision of those memories rather than increases in total memory failures or binding errors. Moreover, a parallel fMRI study in healthy subjects revealed that neural activity in the head and body of the hippocampus was directly related to the precision of visual WM decisions. Together, these results indicate that the hippocampus is critical in complex high-precision binding that supports memory over brief delays.

Mechanisms of feature binding in visual working memory are stable over long delays.

The ability to accurately retain the binding between the features of different objects is a critical element of visual working memory. The underlying mechanism can be elucidated by analyzing correlations of response errors in dual-report experiments, in which participants have to report two features of a single item from a previously viewed stimulus array. Results from separate previous studies using different cueing conditions have indicated that location takes a privileged role in mediating binding between other features, in that largely independent response errors have been observed when location was used as a cue, but errors were highly correlated when location was one of the reported features. Earlier results from change detection tasks likewise support such a special role of location, but they also suggest that this role is substantially reduced for longer retention intervals in favor of object-based representation. In the present study, we replicated the findings of previous dual-report tasks with different cueing conditions, using matched stimuli and procedures. Moreover, we show that the observed patterns of error correlations remain qualitatively unchanged with longer retention intervals. Fits with neural population models demonstrate that the behavioral results at long, as well as short, delays are best explained by memory representations in independent feature maps, in which an item's features are bound to each other only via their shared location.

Location-independent feature binding in visual working memory for sequentially presented objects

Spatial location is believed to have a privileged role in binding features held in visual working memory. Supporting this view, Pertzov and Husain (Attention, Perception, & Psychophysics, 76(7), 1914–1924, 2014) reported that recall of bindings between visual features was selectively impaired when items were presented sequentially at the same location compared to sequentially at different locations. We replicated their experiment, but additionally tested whether the observed impairment could be explained by perceptual interference during encoding. Participants viewed four oriented bars in highly discriminable colors presented sequentially either at the same or different locations, and after a brief delay were cued with one color to reproduce the associated orientation. When we used the same timing as the original study, we reproduced its key finding of impaired binding memory in the same-location condition. Critically, however, this effect was significantly modulated by the duration of the inter-stimulus interval, and disappeared if memoranda were presented with longer delays between them. In a second experiment, we tested whether the effect generalized to other visual features, namely reporting of colors cued by stimulus shape. While we found performance deficits in the same-location condition, these did not selectively affect binding memory. We argue that the observed effects are best explained by encoding interference, and that memory for feature binding is not necessarily impaired when memoranda share the same location.

Visual working memory and sensory processing in autistic children

While atypical sensory processing is one of the more ubiquitous symptoms in autism spectrum disorder, the exact nature of these sensory issues remains unclear, with different studies showing either enhanced or deficient sensory processing. Using a well-established continuous cued-recall task that assesses visual working memory, the current study provides novel evidence reconciling these apparently discrepant findings. Autistic children exhibited perceptual advantages in both likelihood of recall and recall precision relative to their typically-developed peers. When autistic children did make errors, however, they showed a higher probability of erroneously binding a given colour with the incorrect spatial location. These data align with neural-architecture models for feature binding in visual working memory, suggesting that atypical population-level neural noise in the report dimension (colour) and cue dimension (spatial location) may drive both the increase in probability of recall and precision of colour recall as well as the increase in proportion of binding errors when making an error, respectively. These changes are likely to impact core symptomatology associated with autism, as perceptual binding and working memory play significant roles in higher-order tasks, such as communication.

Consequence of stroke for feature recall and binding in visual working memory

Visual memory for objects involves the integration, or binding, of individual features into a coherent representation. We used a novel approach to assess feature binding, using a delayed-reproduction task in combination with computational modeling and lesion analysis. We assessed stroke patients and neurotypical controls on a visual working memory task in which spatial arrays of colored disks were presented. After a brief delay, participants either had to report the color of one disk cued by its location or the location of one disk cued by its color. Our results demonstrate that, in the controls, report imprecision and swap errors (non-target reports) can be explained by a single source of variability. Stroke patients showed an overall decrease in memory precision for both color and location, with only limited evidence for deviations from the predicted relationship between report precision and swap errors. These deviations were primarily deficits in reporting items rather than selecting items based on the cue. Atlas-based lesion-symptom mapping showed that selection and reporting deficits, precision in reporting color, and precision in reporting location were associated with different lesion profiles. Deficits in binding are associated with lesions in the left somatosensory cortex, deficits in the precision of reporting color with bilateral fronto-parietal regions, and no anatomical substrates were identified for precision in reporting location. Our results converge with previous reports that working memory representations are widely distributed in the brain and can be found across sensory, parietal, temporal, and prefrontal cortices. Stroke patients demonstrate mostly subtle impairments in visual working memory, perhaps because representations from different areas in the brain can partly compensate for impaired encoding in lesioned areas. These findings contribute to understanding of the relation between memorizing features and their bound representations.

Within and between person effects of sleep quality on daily cognitive performance: Data from the Einstein Aging Study (EAS)

AbstractBackgroundEvidence suggests that sleep disturbance may precede cognitive decline and may thus be a target for early intervention. Few studies have examined the short term (day to day) associations between sleep quality and cognitive performance in older adults. The Einstein Aging Study (EAS) provided the opportunity to examine ambulatory measures of sleep (actigraphy) and smartphone based ecological momentary assessments of cognitive performance to examine between‐ and within‐person effects of sleep quality on cognitive performance the following day.MethodsAnalyses involved 224 participants enrolled in the Einstein Aging Study, a community based longitudinal cohort of older adults free of dementia at enrollment (Mean age 77.3 years; 33% male; 47% White, 39% African American, 13% Hispanic). Participants wore an actiwatch, and completed brief smartphone based cognitive assessments 6 times per day over an 18‐day period. Multilevel models were used to examine between‐person and within‐person associations between objective measures of sleep quality (wake after sleep onset (WASO)), and duration with daily mean cognitive performance, adjusted for age, gender, race/ethnicity, education (years), and learning effects. Cognitive performance was assessed using previously validated smartphone based cognitive tests of processing speed (Symbol Match), working memory (Color Dot) and memory binding (Color Shape).ResultsBetween person results show that older adults with less nightly WASO on average had better processing speed (b=7.18, p=0.001), better working memory (b=0.001, p=0.005), and better memory binding (b= ‐0.003, p&lt;0.001). Within‐person results showed that higher WASO was significantly associated with worse processing speed the next day: A thirty‐minute increase in nightly WASO predicted a 13 millisecond increased response time on the Symbol Match Test (p=0.001). There were no significant within‐person associations between WASO and working memory or memory binding. Sleep duration was not associated with cognitive performance in any of the analyses.ConclusionsWithin individuals, poor sleep quality is associated with worse cognitive processing speed the following day. The cumulative effects of poor sleep may lead to long term cognitive decline. Future work will determine whether individuals susceptible to the adverse effects of sleep from day to day are at increased risk for long term cognitive decline.

Unimodal and crossmodal working memory binding is not differentially affected by age or Alzheimer's disease.

In this study, we investigated whether Crossmodal WMB is differentially affected by normal or pathological aging compared to Unimodal WMB. Experiment 1: 26 older and 26 younger adults recalled the target feature matching the test probe to complete a previously displayed color-shape binding (visually presented in the Unimodal condition; auditorily and visually presented in the Crossmodal condition). Experiment 2: 35 older and 35 younger adults undertook the same paradigm while carrying out articulatory suppression to limit verbal recoding. Experiment 3: 24 Alzheimer's disease (AD) patients and two groups of 24 healthy matched controls (tested respectively with the same and an increased memory load compared to the patients) were recruited to perform a similar task. Results show no age-related additional cost in Crossmodal WMB in respect to Unimodal WMB. AD patients had poor attainment in both WMB tasks regardless of specific binding condition. These findings provide evidence identifying WMB per se to be impaired in AD, regardless of the type of to-be-bound material. This supports the view that WMB is a suitable cognitive marker for AD. (PsycInfo Database Record (c) 2020 APA, all rights reserved).