scholarly journals Working memory performance is tied to stimulus complexity

2021 ◽  
Author(s):  
Roland Pusch ◽  
Julian Packheiser ◽  
Amir Hossein Azizi ◽  
Celil Semih Sevincik ◽  
Jonas Rose ◽  
...  
Keyword(s):  
Working Memory ◽  
Visual Information ◽  
Neural Coding ◽  
Single Unit ◽  
Memory Performance ◽  
Delay Period ◽  
Memory Representation ◽  
Stimulus Complexity ◽  
Behavioral Experiments ◽  
Complex Stimuli

1.SummaryWorking memory is the cognitive capability to maintain and process information over short periods. Recent behavioral and computational studies have shown that increased visual information of the presented stimulus material is associated with enhanced working memory performance. However, the underlying neural correlates of this association are unknown. To identify how stimuli of different visual information levels affect working memory performance, we conducted behavioral experiments and single unit recordings in the avian analog of the prefrontal cortex, the nidopallium caudolaterale (NCL). On the behavioral level, we confirmed that feature-rich complex stimuli demonstrated higher working memory performance compared to feature-poor simple stimuli. This difference was reflected by distinct neural coding patterns at the single unit level. For complex stimuli, we found a highly multiplexed neuronal code. During the sample presentation, NCL neurons initially reflected both visual and value-related features of the presented stimuli that switched to a representation of the upcoming choice during a delay period. When processing simple stimuli, NCL neurons did not multiplex and represented the upcoming choice already during stimulus presentation and throughout the delay period. It is conceivable that the maintenance of the upcoming choice in working memory was prolonged for simple stimuli due to the early choice representation. This possibly resulted in increased decay of the working memory trace ultimately leading to a decrease in performance. In conclusion, we found that increases in stimulus complexity are associated with increased neuronal multiplexing of the working memory representation. This could possibly allow for a facilitated read-out of the neural code resulting in further enhancements of working memory performance.

Greater Visual Working Memory Capacity for Visually Matched Stimuli When They Are Perceived as Meaningful

2021 ◽  
Vol 33 (5) ◽  
pp. 902-918 ◽  
Author(s):  
Isabel E. Asp ◽  
Viola S. Störmer ◽  
Timothy F. Brady
Keyword(s):  
Working Memory ◽  
Visual Working Memory ◽  
Visual Information ◽  
Memory Performance ◽  
Working Memory Capacity ◽  
Visual Complexity ◽  
Memory Capacity ◽  
Subjective Perception ◽  
Neural Delay ◽  
Meaningful Stimuli

Abstract Almost all models of visual working memory—the cognitive system that holds visual information in an active state—assume it has a fixed capacity: Some models propose a limit of three to four objects, where others propose there is a fixed pool of resources for each basic visual feature. Recent findings, however, suggest that memory performance is improved for real-world objects. What supports these increases in capacity? Here, we test whether the meaningfulness of a stimulus alone influences working memory capacity while controlling for visual complexity and directly assessing the active component of working memory using EEG. Participants remembered ambiguous stimuli that could either be perceived as a face or as meaningless shapes. Participants had higher performance and increased neural delay activity when the memory display consisted of more meaningful stimuli. Critically, by asking participants whether they perceived the stimuli as a face or not, we also show that these increases in visual working memory capacity and recruitment of additional neural resources are because of the subjective perception of the stimulus and thus cannot be driven by physical properties of the stimulus. Broadly, this suggests that the capacity for active storage in visual working memory is not fixed but that more meaningful stimuli recruit additional working memory resources, allowing them to be better remembered.

scholarly journals Early and Late Components of EEG Delay Activity Correlate Differently with Scene Working Memory Performance

2017 ◽  
Author(s):  
Timothy M. Ellmore ◽  
Kenneth Ng ◽  
Chelsea P. Reichert
Keyword(s):  
Working Memory ◽  
Memory Performance ◽  
High Amplitude ◽  
Delay Period ◽  
Spectral Evolution ◽  
Consistent Finding ◽  
Transient Nature ◽  
Neural Transmission ◽  
Source Level ◽  
Short Time

AbstractSustained and elevated activity during the working memory delay period has long been considered the primary neural correlate for maintaining information over short time intervals. This idea has recently been reinterpreted in light of findings generated from multiple neural recording modalities and levels of analysis. To further investigate the sustained or transient nature of activity, the temporal-spectral evolution (TSE) of delay period activity was examined in humans with high density EEG during performance of a Sternberg working memory paradigm with a relatively long six second delay and with novel scenes as stimuli. Multiple analyses were conducted using different trial window durations and different baseline periods for TSE computation. Sensor level analyses revealed transient rather than sustained activity during delay periods. Specifically, the consistent finding among the analyses was that high amplitude activity encompassing the theta range was found early in the first three seconds of the delay period. These increases in activity early in the delay period correlated positively with subsequent ability to distinguish new from old probe scenes. Source level signal estimation implicated a right parietal region of transient early delay activity that correlated positively with working memory ability. This pattern of results adds to recent evidence that transient rather than sustained delay period activity supports visual working memory performance. The findings are discussed in relation to synchronous and desynchronous intra- and inter-regional neural transmission, and choosing an optimal baseline for expressing temporal-spectral delay activity change.

scholarly journals Working memory content is distorted by its use in perceptual comparisons

2020 ◽  
Author(s):  
Keisuke Fukuda ◽  
April Emily Pereira ◽  
Joseph M. Saito ◽  
Ty Yi Tang ◽  
Hiroyuki Tsubomi ◽  
...  
Keyword(s):  
Working Memory ◽  
Individual Differences ◽  
Computational Modeling ◽  
Visual Information ◽  
Dynamic Environment ◽  
Memory Bias ◽  
General Mechanism ◽  
Memory Representation ◽  
Memory Representations ◽  
Memory Content

Visual information around us is rarely static. To carry out a task in such a dynamic environment, we often have to compare current visual input with our working memory representation of the immediate past. However, little is known about what happens to a working memory (WM) representation when it is compared with perceptual input. Here, we tested university students and found that perceptual comparisons retroactively bias working memory representations toward subjectively-similar perceptual inputs. Furthermore, using computational modeling and individual differences analyses, we found that representational integration between WM representations and perceptually-similar input underlies this similarity-induced memory bias. Together, our findings highlight a novel source of WM distortion and suggest a general mechanism that determines how WM representations interact with new perceptual input.

scholarly journals Interhemispheric Connectivity Supports Load-Dependent Working Memory Maintenance for Complex Visual Stimuli

2021 ◽  
Author(s):  
Chelsea Reichert Plaska ◽  
Jefferson Ortega ◽  
Bernard A. Gomes ◽  
Timothy M. Ellmore
Keyword(s):  
Working Memory ◽  
Phase Locking ◽  
Visual Stimuli ◽  
Load Condition ◽  
Brain Regions ◽  
Delay Period ◽  
Temporal Region ◽  
Verbal Rehearsal ◽  
Complex Stimuli ◽  
Low Load

AbstractAn open question in the working memory (WM) field is how information is kept online during the WM delay period. Maintenance of simple stimuli in WM is supported by connectivity between frontal and parietal brain regions. How does delay period activity and connectivity support WM of complex stimuli? Twenty-two participants completed a modified Sternberg WM task with complex stimuli and were told to remember either 2 (low-load) or 5 (high-load) scenes while 32- channel scalp EEG was recorded. During the 6-sec delay period 6 phase-scrambled scenes were presented, which served as interference. While increasing the WM load, particularly with complex stimuli, places a greater demand on attentional resources, interfering stimuli may hijack the available resources. This was confirmed in the examination of theta and alpha amplitude, as amplitude was reduced for the high WM load as compared with the low WM load across frontal, central, and parietal regions. Delay period connectivity was assessed with phase-locking value (PLV). We identified 3 supporting networks that facilitated performance for the low-load condition: 1) increased PLV between left frontal and right posterior temporal in the theta and alpha bands; 2) increased PLV between right anterior temporal and left central in the alpha and lower beta bands; and 3) increased PLV between left anterior temporal and left posterior temporal in theta, alpha, and lower beta bands for the low-load condition. These results suggest that these brain networks facilitated the low-load WM by filtering of interference and the use of verbal rehearsal during the delay period.Impact StatementAlthough, studies of working memory maintenance with simple stimuli have suggested a role of frontal-parietal networks in supporting maintenance, the current study suggests that maintenance of complex visual stimuli with interference present is supported by interhemispheric frontal-posterior temporal and intrahemispheric left temporal region connectivity. These networks support maintenance by filtering of the interfering stimuli, which facilitates the use of verbal rehearsal strategies during the delay period.

scholarly journals Is Long-Term Memory Used in a Visuo-Spatial Change-Detection Paradigm?

2021 ◽  
Author(s):  
Benjamin Goecke ◽  
Klaus Oberauer
Keyword(s):  
Working Memory ◽  
Change Detection ◽  
Memory Performance ◽  
Memory Task ◽  
Repetition Effect ◽  
Long Term Memory ◽  
Memory Representation ◽  
Term Memory ◽  
Hebb Repetition Effect

In tests of working memory with verbal or spatial materials repeating the same memory sets across trials leads to improved memory performance. This well-established “Hebb repetition effect” could not be shown for visual materials. This absence of the Hebb effect can be explained in two ways: Either persons fail to acquire a long-term memory representation of the repeated memory sets, or they acquire such long-term memory representations, but fail to use them during the working memory task. In two experiments, (N1 = 18 and N2 = 30), we aimed to decide between these two possibilities by manipulating the long-term memory knowledge of some of the memory sets used in a change-detection task. Before the change-detection test, participants learned three arrays of colors to criterion. The subsequent change-detection test contained both previously learned and new color arrays. Change detection performance was better on previously learned compared to new arrays, showing that long-term memory is used in change detection.

Specific and Nonspecific Neural Activity during Selective Processing of Visual Representations in Working Memory

2010 ◽  
Vol 22 (2) ◽  
pp. 292-306 ◽  
Author(s):  
Hwamee Oh ◽  
Hoi-Chung Leung
Keyword(s):  
Working Memory ◽  
Neural Activity ◽  
Visual Information ◽  
Posterior Parietal Cortex ◽  
Parietal Lobe ◽  
Response Times ◽  
Temporal Cortex ◽  
Recognition Task ◽  
Delay Period ◽  
The Face

In this fMRI study, we investigated prefrontal cortex (PFC) and visual association regions during selective information processing. We recorded behavioral responses and neural activity during a delayed recognition task with a cue presented during the delay period. A specific cue (“Face” or “Scene”) was used to indicate which one of the two initially viewed pictures of a face and a scene would be tested at the end of a trial, whereas a nonspecific cue (“Both”) was used as control. As expected, the specific cues facilitated behavioral performance (faster response times) compared to the nonspecific cue. A postexperiment memory test showed that the items cued to remember were better recognized than those not cued. The fMRI results showed largely overlapped activations across the three cue conditions in dorsolateral and ventrolateral PFC, dorsomedial PFC, posterior parietal cortex, ventral occipito-temporal cortex, dorsal striatum, and pulvinar nucleus. Among those regions, dorsomedial PFC and inferior occipital gyrus remained active during the entire postcue delay period. Differential activity was mainly found in the association cortices. In particular, the parahippocampal area and posterior superior parietal lobe showed significantly enhanced activity during the postcue period of the scene condition relative to the Face and Both conditions. No regions showed differentially greater responses to the face cue. Our findings suggest that a better representation of visual information in working memory may depend on enhancing the more specialized visual association areas or their interaction with PFC.

scholarly journals Hungarian Structural Focus: Accessibility to Focused Elements and Their Alternatives in Working Memory and Delayed Recognition Memory

2021 ◽  
Vol 12 ◽  
Author(s):  
Tamás Káldi ◽  
Ágnes Szöllösi ◽  
Anna Babarczy
Keyword(s):  
Working Memory ◽  
Recognition Memory ◽  
Sentence Type ◽  
Memory Performance ◽  
Research Question ◽  
Indirect Evidence ◽  
Memory Systems ◽  
Memory Representation ◽  
Original Sentence ◽  
Delayed Recognition

The present work investigates the memory accessibility of linguistically focused elements and the representation of the alternatives for these elements (i.e., their possible replacements) in Working Memory (WM) and in delayed recognition memory in the case of the Hungarian pre-verbal focus construction (preVf). In two probe recognition experiments we presented preVf and corresponding focusless neutral sentences embedded in five-sentence stories. Stories were followed by the presentation of sentence probes in one of three conditions: (i) the probe was identical to the original sentence in the story, (ii) the focused word (i.e., target) was replaced by a semantically related word and (iii) the target word was replaced by a semantically unrelated but contextually suitable word. In Experiment 1, probes were presented immediately after the stories measuring WM performance, while in Experiment 2, blocks of six stories were presented and sentences were probed with a 2-minute delay measuring delayed recognition memory performance. Results revealed an advantage of the focused element in immediate but not in delayed retrieval. We found no effect of sentence type on the recognition of the two different probe types in WM performance. However, results pertaining to the memory accessibility of focus alternatives in delayed retrieval showed an interference effect resulting in a lower memory performance. We conclude that this effect is indirect evidence for the enhanced activation of focus alternatives. The present work is novel in two respects. First, no study has been conducted on the memory representation of focused elements and their alternatives in the case of the structurally marked Hungarian pre-verbal focus construction. Second, to our knowledge, this is the first study that investigates the focus representation accounts for WM and delayed recognition memory using the same stimuli and same measured variables. Since both experiments used exactly the same stimulus set, and they only differed in terms of the timing of recognition probes, the principle of ceteris paribus fully applied with respect to how we addressed our research question regarding the two different memory systems.

scholarly journals When “capacity” changes with set size: Ensemble representations support the detection of across-category changes in visual working memory

2018 ◽  
Author(s):  
Mark Schurgin ◽  
Timothy F. Brady
Keyword(s):  
Working Memory ◽  
Memory Performance ◽  
Working Memory Capacity ◽  
Limited Resource ◽  
Fixed Number ◽  
Stimulus Similarity ◽  
Set Size ◽  
Complex Stimuli ◽  
Potential Use ◽  
Ensemble Representations

Is there a fixed limit on how many objects we can hold actively in mind? Generally, researchers have found participants are able to remember fewer objects if they are more complex, suggesting a limited resource rather than a fixed number of objects best explains working memory performance. However, some evidence has suggested that stimulus similarity better accounts for these effects, and that after accounting for such similarity, the data support a slot-based fixed- item limit for working memory. Much of the evidence used to support the latter claim relies on working memory displays containing different categories of items. It has been found that for large, across-category changes, performance does not differ for different kinds of complex stimuli. However, many of these studies fail to adequately control for the potential use of ensemble information in discriminating such large, across-category changes. Here, we sought to identify how much ensemble representations may explain performance across these tasks. In Experiment 1, we observed that as set size increased from 4 to 12 items, capacity estimates for across-category changes increased linearly as well, providing evidence against the claim of a fixed capacity. In Experiment 2, we controlled for stimulus complexity and similarity but varied the utility of ensemble representations for the change detection task. We observed significantly greater capacity when ensemble information could be used. Altogether, these results are contrary to a slot-like, fixed-object constraint on working memory capacity, and consistent with object complexity and ensemble representations strongly affecting working memory performance.

scholarly journals Is long-term memory used in a visuo-spatial change-detection paradigm?

2021 ◽  
Author(s):  
Benjamin Goecke ◽  
Klaus Oberauer
Keyword(s):  
Working Memory ◽  
Change Detection ◽  
Memory Performance ◽  
Memory Task ◽  
Repetition Effect ◽  
Long Term Memory ◽  
Memory Representation ◽  
Term Memory ◽  
Hebb Repetition Effect

AbstractIn tests of working memory with verbal or spatial materials, repeating the same memory sets across trials leads to improved memory performance. This well-established “Hebb repetition effect” could not be shown for visual materials in previous research. The absence of the Hebb effect can be explained in two ways: Either persons fail to acquire a long-term memory representation of the repeated memory sets, or they acquire such long-term memory representations, but fail to use them during the working memory task. In two experiments (N1 = 18 and N2 = 30), we aimed to decide between these two possibilities by manipulating the long-term memory knowledge of some of the memory sets used in a change-detection task. Before the change-detection test, participants learned three arrays of colors to criterion. The subsequent change-detection test contained both previously learned and new color arrays. Change detection performance was better on previously learned compared with new arrays, showing that long-term memory is used in change detection.

scholarly journals Opposite reactions to loss incentive by young and older adults: Insights from diffusion modeling

2021 ◽  
Author(s):  
Hyesue Jang ◽  
Richard Lewis ◽  
Cindy Lustig
Keyword(s):  
Older Adults ◽  
Working Memory ◽  
Young Adults ◽  
Retention Interval ◽  
Drift Rate ◽  
Memory Performance ◽  
Later Life ◽  
Self Report ◽  
Memory Representation ◽  
Diffusion Modeling

The prospect of loss becomes more salient in later life, and the opportunity to avoid loss is often used to motivate older adults. We examined the effect of loss incentive on working memory in young and older adults. Diffusion-modeling analyses, manipulation of task parameters, and self-report measures identified which aspects of cognitive-motivational processing were most affected within each group. As predicted, loss incentive increased working memory performance and self-reported motivation in young adults, but, consistent with prior work, had the opposite effect in older adults. Diffusion-modeling analyses suggested the primary effect was on the quality of the memory representation (drift rate). Incentive did not interact with retention interval or the number of items in the memory set. Instead, longer retention intervals led to better performance, potentially by improved differentiation between studied items and the unstudied probe as a function of temporal context. Overall, the results do not support theories suggesting that older adults are either more motivated by loss or that they ignore it. Instead, the loss incentive increased young adults' performance and subjective motivation, with opposite effects for older adults. The specific impact on drift rate and lack of interactions with set size or retention interval suggest that rather than affecting load-dependent or strategic processes, the effects occur at a relatively global level related to overall task engagement.

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