scholarly journals Delay-period activity in frontal, parietal, and occipital cortex tracks noise and biases in visual working memory

PLoS Biology ◽  
2020 ◽  
Vol 18 (9) ◽  
pp. e3000854 ◽  
Author(s):  
Qing Yu ◽  
Matthew F. Panichello ◽  
Ying Cai ◽  
Bradley R. Postle ◽  
Timothy J. Buschman
Keyword(s):  
Working Memory ◽  
Visual Working Memory ◽  
Occipital Cortex ◽  
Delay Period

scholarly journals The Role of Location-Context Binding in Nonspatial Visual Working Memory

2018 ◽  
Author(s):  
Ying Cai ◽  
Qing Yu ◽  
Andrew D. Sheldon ◽  
Bradley R. Postle
Keyword(s):  
Working Memory ◽  
Spatial Attention ◽  
Visual Working Memory ◽  
Parietal Cortex ◽  
Memory Load ◽  
Occipital Cortex ◽  
Delay Period ◽  
Fmri Signal ◽  
Associated Representation ◽  
Unique Context

AbstractSuccessful retrieval of an item from visual working memory (VWM) often requires an associated representation of the trial-unique context in which that item was presented. We dissociated the effects on fMRI signal of memory load versus context binding by comparing nonspatial VWM for one oriented bar vs. three bars individuated by their location on the screen vs. three items drawn from different categories (orientation, color, and luminance), for which location context was superfluous. Delay-period fMRI signal in frontal and parietal cortex was sensitive to stimulus homogeneity rather than to memory load per se. Behavioral performance revealed a broad range in swap errors, an index of the efficacy of context binding, and subjects were classified as high swap error or low swap error. During the delay period, the strength of the representation of stimulus location in parietal cortex predicted individual differences in swap errors. During recall, activity in occipital cortex revealed two dissociable neural correlates of context binding: high swap-error subjects allocated less spatial attention to the location of the probed item and more spatial attention the location of non-probed items; high swap-error subjects also represented the orientation of the probed item more weakly and the orientation of nonprobed items more strongly. Our results suggest context binding is a computation that influences all stages of VWM processing.Significance StatementAlthough we often think of the contents of visual working memory (VWM) as representations of the items that need to be remembered, each item’s trial-unique context is also critical for successful performance. For example, if one observes a red, then a black, then a blue car passing through an intersection, vivid memory for the colors, alone, wouldn’t allow one to execute the instruction “Follow the first of the three cars that just drove by.” Although manipulating load is commonly assumed to isolate storage functions, requiring memory for multiple items drawn from the same category also increases demands on the context binding needed to individuate these items. This experiment tracked the influence of context binding on VWM stimulus processing.

scholarly journals Eye movement-related confounds in neural decoding of visual working memory representations

2017 ◽  
Author(s):  
Pim Mostert ◽  
Anke Marit Albers ◽  
Loek Brinkman ◽  
Larisa Todorova ◽  
Peter Kok ◽  
...  
Keyword(s):  
Working Memory ◽  
Eye Movements ◽  
Eye Movement ◽  
Visual Working Memory ◽  
Delay Period ◽  
Imagery Task ◽  
Neural Decoding ◽  
Neural Signals ◽  
Stable Representation ◽  
Neural Underpinnings

AbstractThe study of visual working memory (VWM) has recently seen revitalization with the emergence of new insights and theories regarding its neural underpinnings. One crucial ingredient responsible for this progress is the rise of neural decoding techniques. These techniques promise to uncover the representational contents of neural signals, as well as the underlying code and the dynamic profile thereof. Here, we aimed to contribute to the field by subjecting human volunteers to a combined VWM/imagery task, while recording and decoding their neural signals as measured by MEG. At first sight, the results seem to provide evidence for a persistent, stable representation of the memorandum throughout the delay period. However, control analyses revealed that these findings can be explained by subtle, VWM-specific eye movements. As a potential remedy, we demonstrate the use of a functional localizer, which was specifically designed to target bottom-up sensory signals and as such avoids eye movements, to train the neural decoders. This analysis revealed a sustained representation for approximately 1 second, but no longer throughout the entire delay period. We conclude by arguing for more awareness of the potentially pervasive and ubiquitous effects of eye movement-related confounds.Significance statementVisual working memory is an important aspect of higher cognition and has been subject of much investigation within the field of cognitive neuroscience. Over recent years, these studies have increasingly relied on the use of neural decoding techniques. Here, we show that neural decoding may be susceptible to confounds induced by stimulus-specific eye movements. Such eye movements during working memory have been reported before, and may in fact be a common phenomenon. Given the widespread use of neural decoding and the potentially contaminating effects of eye movements, we therefore believe that our results are of significant relevance for the field.

scholarly journals The Neural Consequences of Attentional Prioritization of Internal Representations in Visual Working Memory

2019 ◽  
Author(s):  
Muhammet I. Sahan ◽  
Andrew D. Sheldon ◽  
Bradley R. Postle
Keyword(s):  
Working Memory ◽  
Visual Working Memory ◽  
Visual Target ◽  
Human Subjects ◽  
Occipital Cortex ◽  
Neural Representation ◽  
Stimulus Category ◽  
Object Based ◽  
Stimulus Offset ◽  
Selection Of

AbstractAlthough humans can hold multiple items in mind simultaneously, the contents of working memory (WM) can be selectively prioritized to effectively guide behavior in response to rapidly changing exigencies in the environment. Neural evidence for this is seen in studies of dual serial retrocuing of two items held concurrently in visual WM, in which evidence in occipital cortex for the active neural representation of the cued item increases, and evidence for the uncued item decreases, often to levels indistinguishable from empirical baseline. Although this pattern is reminiscent of the effects of selective attention on visual perception, the extent to which more subtle principles of visual attention may also apply to visual working memory remains uncertain. In the present study we explored whether the well-characterized “same-object” benefit in visual target detection, attributed to object-based attention (e.g., Duncan, 1984; Egly, Driver, & Rafal, 1994), may also be observed for information held in visual WM. fMRI data were collected while human subjects (male and female) performed a multi-step serial retrocuing task in which they first viewed two two-dimensional sample stimuli comprised of colored moving dots. After stimulus offset, an initialrelevance cuethen indicated whether both dimensions of only the first or only the second object, or only the color or only the direction-of-motion of both objects, would be relevant for the remainder of the trial, which then proceeded with the standard dual serial retrocuing procedure. Thus, on “object-relevant” trials, the ensuingpriority cuesprompted the selection of one from among two features (“color” or “direction”) bound to the same object, whereas on “feature-relevant” trials thepriority cuesprompted the selection of one from among two features each belonging to a different object. Results of analyses with multivariate inverted encoding models (IEM) revealed a same-object benefit on object-relevant trials: Whereas, on feature-relevant trials, the firstpriority cuetriggered a strengthening of the neural representation of the cued feature and a concomitant weakening-to-baseline of the uncued feature; on object-relevant trials the cued item remained active but did not increase in strength, and the uncued item weakened, but remained significantly elevated throughout the delay period. Of additional interest, on both types of trials the secondpriority cueprompted an active recoding of the uncued item into a different neural representation, perhaps to minimize its ability to interfere with recall of the cued item. Finally, although stimulus-specific representation in parietal and frontal cortex was weak and uneven, these regions closely tracked the higher-order information of which stimulus category was relevant for behavior at all points during the trial, indicating an important role in controlling the prioritization of information in visual working memory.

scholarly journals The Neural Consequences of Attentional Prioritization of Internal Representations in Visual Working Memory

2020 ◽  
Vol 32 (5) ◽  
pp. 917-944 ◽  
Author(s):  
Muhammet I. Sahan ◽  
Andrew D. Sheldon ◽  
Bradley R. Postle
Keyword(s):  
Working Memory ◽  
Visual Working Memory ◽  
Visual Processing ◽  
Delay Period ◽  
Neural Representation ◽  
Fmri Data ◽  
Stimulus Category ◽  
Order Information ◽  
Internal Representations ◽  
Future Behavior

Although humans can hold multiple items in mind simultaneously, the contents of working memory (WM) can be selectively prioritized to guide future behavior. We explored whether the “same-object” benefits in visual processing may also be observed in visual WM. fMRI data were collected while participants performed a multistep serial retrocuing task in which they first viewed two 2-D objects (coherently moving colored dots). During retention, an initial relevance cue then indicated whether only the first or only the second object (“object-relevant”), or only the color of both objects or only their direction of motion would be relevant for the remainder of the trial (“feature-relevant”). On “object-relevant” trials, the ensuing priority cues selected either one of the features (“color” or “direction”) bound to the relevance-cued object, whereas on “feature-relevant” trials, the priority cues selected one of the two relevance-cued features. Using multivariate inverted encoding models, we found a same-object benefit on object-relevant trials in occipitotemporal regions: On feature-relevant trials, the first priority cue triggered a strengthening of the neural representation of the cued feature and a concomitant weakening to baseline of the uncued feature, whereas on object-relevant trials, the cued item remained active but did not increase in strength and the uncued item weakened but remained significantly elevated throughout the delay period. Although the stimulus-specific representation in frontoparietal regions was weak and uneven, these regions closely tracked the higher order information of which stimulus category was relevant for behavior throughout the trial, suggesting an important role in controlling the prioritization of information in visual WM.

scholarly journals Delay-period activity in frontal, parietal, and occipital cortex tracks different attractor dynamics in visual working memory

2020 ◽  
Author(s):  
Qing Yu ◽  
Matthew F. Panichello ◽  
Ying Cai ◽  
Bradley R. Postle ◽  
Timothy J. Buschman
Keyword(s):  
Working Memory ◽  
Parietal Cortex ◽  
Memory Load ◽  
Internal Noise ◽  
Occipital Cortex ◽  
Delay Period ◽  
Attractor Dynamics ◽  
Attractor Model ◽  
New Interpretation ◽  
Memory Precision

AbstractOne important neural hallmark of working memory is persistent elevated delay-period activity in frontal and parietal cortex. In human fMRI, delay-period BOLD activity in frontal and parietal cortex increases monotonically with memory load and asymptotes at an individual’s capacity. Previous work has demonstrated that frontal and parietal delay-period activity correlates with the decline in behavioral memory precision observed with increasing memory load. However, because memory precision can be influenced by a variety of factors, it remains unclear what cognitive processes underlie persistent activity in frontal and parietal cortex. Recent psychophysical work has shown that attractor dynamics bias memory representations toward a few stable representations and reduce the effects of internal noise. From this perspective, imprecision in memory results from both drift towards stable attractor states and random diffusion. Here we asked whether delay-period BOLD activity in frontal and parietal cortex might be explained, in part, by these attractor dynamics. We analyzed data from an existing experiment in which subjects performed delayed recall for line orientation, at different loads, during fMRI scanning. We modeled subjects’ behavior using a discrete attractor model, and calculated within-subject correlation between frontal and parietal delay-period activity and estimated sources of memory error (drift and diffusion). We found that although increases in frontal and parietal activity were associated with increases in both diffusion and drift, diffusion explained the most variance in frontal and parietal delay-period activity. In comparison, a subsequent whole-brain regression analysis showed that drift rather than diffusion explained the most variance in delay-period activity in lateral occipital cortex. These results provide a new interpretation for the function of frontal, parietal, and occipital delay-period activity in working memory.

scholarly journals A between-task consequence of temporal expectations

2021 ◽  
Author(s):  
Daniela Gresch ◽  
Sage Boettcher ◽  
Anna C. Nobre ◽  
Freek van Ede
Keyword(s):  
Working Memory ◽  
Everyday Life ◽  
Visual Working Memory ◽  
Memory Performance ◽  
Memory Task ◽  
Delay Period ◽  
Temporal Expectation ◽  
Memory Probe ◽  
Temporal Predictability ◽  
Memory Contents

In everyday life, we often anticipate the timing of one upcoming task or event while actively engaging in another. Here, we investigated temporal expectations within such a multi-task scenario. In a visual working-memory task, we manipulated whether the onset of a working-memory probe could be predicted in time, while also embedding a simple intervening task within the delay period. We first show that working-memory performance benefitted from temporal predictability, even though an intervening task had to be completed in the interim. Moreover, temporal expectations regarding the upcoming working-memory probe additionally affected performance on the intervening task, resulting in faster responses when the memory probe was anticipated early, and slower responses when the memory probe was expected late, as compared to when it was temporally unpredictable. Because the intervening task always occurred at the same time during the memory delay, differences in performance on this intervening task are attributed to a between-task consequence of temporal expectation. Thus, we show that within multi-task settings, knowing when working-memory contents will be required for an upcoming task not only facilitates performance on the associated working-memory task, but can also influence the performance of other, intervening tasks.

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