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 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 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 Contralateral Delay Activity Indexes Working Memory Storage, Not the Current Focus of Spatial Attention

2018 ◽  
Vol 30 (8) ◽  
pp. 1185-1196 ◽  
Author(s):  
Tobias Feldmann-Wüstefeld ◽  
Edward K. Vogel ◽  
Edward Awh
Keyword(s):  
Working Memory ◽  
Spatial Attention ◽  
Visual Working Memory ◽  
Memory Load ◽  
Alternative Hypothesis ◽  
Relevant Information ◽  
Alternative Interpretation ◽  
Memory Storage ◽  
Probe Display ◽  
Contralateral Delay Activity

Contralateral delay activity (CDA) has long been argued to track the number of items stored in visual working memory (WM). Recently, however, Berggren and Eimer [Berggren, N., & Eimer, M. Does contralateral delay activity reflect working memory storage or the current focus of spatial attention within visual working memory? Journal of Cognitive Neuroscience, 28, 2003–2020, 2016] proposed the alternative hypothesis that the CDA tracks the current focus of spatial attention instead of WM storage. This hypothesis was based on the finding that, when two successive arrays of memoranda were placed in opposite hemifields, CDA amplitude was primarily determined by the position and number of items in the second display, not the total memory load across both displays. Here, we considered the alternative interpretation that participants dropped the first array from WM when they encoded the second array because the format of the probe display was spatially incompatible with the initial sample display. In this case, even if the CDA indexes active storage rather than spatial attention, CDA activity would be determined by the second array. We tested this idea by directly manipulating the spatial compatibility of sample and probe displays. With spatially incompatible displays, we replicated Berggren and Eimer's findings. However, with spatially compatible displays, we found clear evidence that CDA activity tracked the full storage load across both arrays, in line with a WM storage account of CDA activity. We propose that expectations of display compatibility influenced whether participants viewed the arrays as parts of a single extended event or two independent episodes. Thus, these findings raise interesting new questions about how event boundaries may shape the interplay between passive and active representations of task-relevant information.

scholarly journals On the Role of the Inferior Intraparietal Sulcus in Visual Working Memory for Lateralized Single-feature Objects

2017 ◽  
Vol 29 (2) ◽  
pp. 337-351 ◽  
Author(s):  
Sabrina Brigadoi ◽  
Simone Cutini ◽  
Federica Meconi ◽  
Marco Castellaro ◽  
Paola Sessa ◽  
...  
Keyword(s):  
Working Memory ◽  
Change Detection ◽  
Functional Response ◽  
Visual Working Memory ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Memory Load ◽  
Intraparietal Sulcus ◽  
Posterior Parietal ◽  
Electromagnetic Signals

A consolidated practice in cognitive neuroscience is to explore the properties of human visual working memory through the analysis of electromagnetic signals using cued change detection tasks. Under these conditions, EEG/MEG activity increments in the posterior parietal cortex scaling with the number of memoranda are often reported in the hemisphere contralateral to the objects' position in the memory array. This highly replicable finding clashes with several reported failures to observe compatible hemodynamic activity modulations using fMRI or fNIRS in comparable tasks. Here, we reconcile this apparent discrepancy by acquiring fMRI data on healthy participants and employing a cluster analysis to group voxels in the posterior parietal cortex based on their functional response. The analysis identified two distinct subpopulations of voxels in the intraparietal sulcus (IPS) showing a consistent functional response among participants. One subpopulation, located in the superior IPS, showed a bilateral response to the number of objects coded in visual working memory. A different subpopulation, located in the inferior IPS, showed an increased unilateral response when the objects were displayed contralaterally. The results suggest that a cluster of neurons in the inferior IPS is a candidate source of electromagnetic contralateral responses to working memory load in cued change detection tasks.

scholarly journals Occipital Cortex of Blind Individuals Is Functionally Coupled with Executive Control Areas of Frontal Cortex

2015 ◽  
Vol 27 (8) ◽  
pp. 1633-1647 ◽  
Author(s):  
Ben Deen ◽  
Rebecca Saxe ◽  
Marina Bedny
Keyword(s):  
Working Memory ◽  
Functional Connectivity ◽  
Sentence Comprehension ◽  
Memory Load ◽  
Memory Task ◽  
Occipital Cortex ◽  
Memory Systems ◽  
Functional Responses ◽  
Congenitally Blind ◽  
Blind Individuals

In congenital blindness, the occipital cortex responds to a range of nonvisual inputs, including tactile, auditory, and linguistic stimuli. Are these changes in functional responses to stimuli accompanied by altered interactions with nonvisual functional networks? To answer this question, we introduce a data-driven method that searches across cortex for functional connectivity differences across groups. Replicating prior work, we find increased fronto-occipital functional connectivity in congenitally blind relative to blindfolded sighted participants. We demonstrate that this heightened connectivity extends over most of occipital cortex but is specific to a subset of regions in the inferior, dorsal, and medial frontal lobe. To assess the functional profile of these frontal areas, we used an n-back working memory task and a sentence comprehension task. We find that, among prefrontal areas with overconnectivity to occipital cortex, one left inferior frontal region responds to language over music. By contrast, the majority of these regions responded to working memory load but not language. These results suggest that in blindness occipital cortex interacts more with working memory systems and raise new questions about the function and mechanism of occipital plasticity.

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