Phases Of Working Memory Research Articles

Working memory limitations constrain visual episodic long-term memory at both specific and gist levels of representation.

Limitations in one's capacity to encode information in working memory (WM) constrain later access to that information in long-term memory (LTM). The present study examined whether these WM constraints on episodic LTM are limited to specific representations of past episodes or also extend to gist representations. Across three experiments, young adult participants (n = 40 per experiment) studied objects in set sizes of two or six items, either sequentially (Experiments 1a and 1b) or simultaneously (Experiment 2). They then completed old/new recognition tests immediately after each sequence (WM tests). After a long study phase, participants completed LTM conjoint recognition tests, featuring old but untested items from the WM phase, lures that were similar to studied items at gist but not specific levels of representation, and new items unrelated to studied items at both specific and gist levels of representation. Results showed that LTM estimates of specific and gist memory representations from a multinomial-processing-tree model were reduced for items encoded under supra-capacity set sizes (six items) relative to within-capacity set sizes (two items). These results suggest that WM encoding capacity limitations constrain episodic LTM at both specific and gist levels of representation, at least for visual objects. The ability to retrieve from LTM each type of representation for a visual item is contingent on the degree to which the item could be encoded in WM.

P157 Neurocognitive insights: functional magnetic resonance imaging of spatial working memory and sustained attention in people with systemic lupus erythematous

Abstract Background/Aims Cognitive impairment (CI) is common in people with systemic lupus erythematosus (pwSLE). Treatment options are limited and the effects upon the brain is unclear. Differences in brain structure seen in SLE do not always associate with CI, however significant associations have been found with functional magnetic resonance imaging (fMRI). Using fMRI, this study aims to further explore potential compensatory brain mechanisms used in SLE that help with cognitive function. Methods Participants were recruited into one of two groups;pwSLE (meeting EULAR/ACR criteria) or healthy controls(HC). Demographic, clinical and psychiatric data and patient reported outcome measures were collected.Cognitive function was assessed using the ACR Neuropsychological Battery. Brain scans included two structural and two fMRI scans done during stage 1 and 2 of a cognitive task. Stage 1 of the task had an encoding, retention and working memory (WM) component. Stage 2 of the task examined long-term memory. Differences between task performances were examined using t-tests. The fMRI data was modelled using SPM12 to look for differences in blood-oxygen-level-dependent (BOLD) brain responses between the study groups during the different stages/components of the task. Results To-date 37 pwSLE and 10 HCs have been recruited. The median ages were 36 (HC) and 40 (pwSLE) years. From the pwSLE group the average disease duration was 15 years, the average SLEDAI-2K score was 5 and percentages of those on antimalarials, corticosteroids, and immunosuppressants and biologics were 66%, 32%, and 54%, respectively. There were no differences on task performance between the two groups. Greater BOLD responses were seen in the HC compared to the pwSLE group during stage 1 encoding and WM phases as well as during stage 2 (long-term memory). pwSLE had less attenuated BOLD signals during the stage 1 retention phase compared to HCs (Table 1). Conclusion We found altered brain responses to our cognitive task between pwSLE and HCs. Predominantly the HC group had greater BOLD responses in cognitive regions during the task compared to the pwSLE group. However, we did not find any difference between the two groups in regards to cognitive performance. This study is still ongoing and additional results are expected. Disclosure M. Barraclough: None. M. McCowen: None. S. McKie: None. A. Kafkas: None. B. Parker: None. J. Diaz-Martinez: None. A. Knight: None. K. Bingham: None. M. Li: None. J. Su: None. M. Kakvan: None. C. Munoz Grajales: None. M. Tartaglia: None. L. Ruttan: None. J. Wither: None. D. Bonilla: None. N. Anderson: None. D. Montaldi: None. R. Elliott: None. P. Katz: None. D. Beaton: None. R. Green: None. I. Bruce: None. Z. Touma: None.

Gender-dependent variations in optical illusions: evidence from N400 waveforms

Objective: The cognitive mechanisms (especially the gender-related ones) underlying optical illusion processing remain elusive. Since the N400 component of event-related potentials (ERPs) is an index of the semantic integration of information processing tasks, the present study focuses on gender-related differences in N400 waveforms elicited during the reasoning process applied to reach a valid conclusion of optical illusions engaging working memory (WM). Approach: Fifty-one healthy participants (28 males, age = 34.25 years ± 10.25, years of education = 16.00 years ± 1.78; and 23 females, age = 33.43 ± 7.93, years of education = 15.56 ± 1.82) were measured. The N400 ERP component was evoked by 39 optical illusions adjusted to induce WM. We compared brain activation patterns while participants maintained conclusions of the optical illusions in WM. The N400 of ERPs was recorded during the WM phase, during which participants were required to draw a logical conclusion regarding the correctness of the optical illusions. Main results: Analysis revealed that females compared to males exhibited significantly increased N400 amplitudes located at parietal and occipital sites, whereas males exhibited significantly higher N400 amplitudes located at frontal areas. Furthermore, females compared to males demonstrated significantly prolonged latencies of the N400 component located at right frontotemporal abductions. Significance: These results suggest that coupling of optical illusions with WM engages distinct gender-related variations of brain semantic processing as reflected by the N400 ERP component. Based on the dual process account, our study gives support to the notion that women tend to employ a more deliberate and slower semantic reasoning than the men who tend to employ an automatic and fast one. Topographically, within the network sub-serving the semantic operation, the posterior brain areas responsible for sensorimotor integration-related processes elicit a greater brain activation among females while the anterior brain areas responsible for control and storage/retrieval operation elicit a greater brain activation among males.

The Modulation of Spatial Working Memory by Emotional Stickers and Facial Expressions.

This article aims to investigate the interaction effects of emotional valence (negative, positive) and stimulus type (sticker, face) on attention allocation and information retrieval in spatial working memory (WM). The difference in recognition of emotional faces and stickers was also further explored. Using a high-resolution event-related potential (ERP) technique, a time-locked delayed matching-to-sample task (DMST) was employed that allowed separate investigations of target, delay, and probe phases. Twenty-two subjects participated in our experiment. The results indicated that negative face can catch early attention in information encoding, which was indicated by the augmentation of the attention-related P200 amplitude. In the delay phase, the N170 component represents facial specificity and showed a negative bias against stickers. For information retrieval, the increase in the emotion-related late positive component (LPC) showed that positive emotion could damage spatial WM and consume more cognitive resources. Moreover, stickers have the ability to catch an individual’s attention throughout the whole course of spatial WM with larger amplitudes of the attention-related P200, the negative slow wave (NSW), and the LPC. These findings highlight the role of stickers in different phases of spatial WM and provide new viewpoints for WM research on mental patients.

Neural activity during working memory encoding, maintenance, and retrieval: A network-based model and meta-analysis.

It remains unclear whether and to what extent working memory (WM) temporal subprocesses (i.e., encoding, maintenance, and retrieval) involve shared or distinct intrinsic networks. To address this issue, I constructed a model of intrinsic network contributions to different WM phases and then evaluated the validity of the model by performing a quantitative meta-analysis of relevant functional neuroimaging data. The model suggests that the transition from the encoding to maintenance and to retrieval stages involves progressively decreasing involvement of the dorsal attention network (DAN), but progressively increasing involvement of the frontoparietal control network (FPCN). Separate meta-analysis of each phase effect and direct comparisons between them yielded results that were largely consistent with the model. This evidence included between-phase double dissociations that were consistent with the model, such as encoding > maintenance contrast showing some DAN, but no FPCN, regions, and maintenance > encoding contrast showing the reverse, that is, some FPCN, but no DAN, regions. Two closely juxtaposed regions that are members of the DAN and FPCN, such as inferior frontal junction versus caudal prefrontal cortex and superior versus inferior intraparietal sulcus, showed a high degree of functional differentiation. Although all regions identified in the present study were already identified in previous WM studies, this study uniquely enhances our understating of their roles by clarifying their network membership and specific associations with different WM phases.

Different Topological Properties of EEG-Derived Networks Describe Working Memory Phases as Revealed by Graph Theoretical Analysis.

Several non-invasive imaging methods have contributed to shed light on the brain mechanisms underlying working memory (WM). The aim of the present study was to depict the topology of the relevant EEG-derived brain networks associated to distinct operations of WM function elicited by the Sternberg Item Recognition Task (SIRT) such as encoding, storage, and retrieval in healthy, middle age (46 ± 5 years) adults. High density EEG recordings were performed in 17 participants whilst attending a visual SIRT. Neural correlates of WM were assessed by means of a combination of EEG signal processing methods (i.e., time-varying connectivity estimation and graph theory), in order to extract synthetic descriptors of the complex networks underlying the encoding, storage, and retrieval phases of WM construct. The group analysis revealed that the encoding phase exhibited a significantly higher small-world topology of EEG networks with respect to storage and retrieval in all EEG frequency oscillations, thus indicating that during the encoding of items the global network organization could “optimally” promote the information flow between WM sub-networks. We also found that the magnitude of such configuration could predict subject behavioral performance when memory load increases as indicated by the negative correlation between Reaction Time and the local efficiency values estimated during the encoding in the alpha band in both 4 and 6 digits conditions. At the local scale, the values of the degree index which measures the degree of in- and out- information flow between scalp areas were found to specifically distinguish the hubs within the relevant sub-networks associated to each of the three different WM phases, according to the different role of the sub-network of regions in the different WM phases. Our findings indicate that the use of EEG-derived connectivity measures and their related topological indices might offer a reliable and yet affordable approach to monitor WM components and thus theoretically support the clinical assessment of cognitive functions in presence of WM decline/impairment, as it occurs after stroke.

Aristotle Meets Zeno: Psychophysiological Evidence.

This study, a tribute to Aristotle's 2400 years, used a juxtaposition of valid Aristotelian arguments to the paradoxes formulated by Zeno the Eleatic, in order to investigate the electrophysiological correlates of attentional and /or memory processing effects in the course of deductive reasoning. Participants undertook reasoning tasks based on visually presented arguments which were either (a) valid (Aristotelian) statements or (b) paradoxes. We compared brain activation patterns while participants maintained the premises / conclusions of either the valid statements or the paradoxes in working memory (WM). Event-related brain potentials (ERPs), specifically the P300 component of ERPs, were recorded during the WM phase, during which participants were required to draw a logical conclusion regarding the correctness of the valid syllogisms or the paradoxes. During the processing of paradoxes, results demonstrated a more positive event-related potential deflection (P300) across frontal regions, whereas processing of valid statements was associated with noticeable P300 amplitudes across parieto-occipital regions. These findings suggest that paradoxes mobilize frontal attention mechanisms, while valid deduction promotes parieto-occipital activity associated with attention and/or subsequent memory processing.

Cognition–emotion interactions in schizophrenia: Emerging evidence on working memory load and implicit facial-affective processing

Although much is known about working memory (WM) and emotion perception deficits in schizophrenia, little is known of how these deficits interact. We sought to address this gap by conducting a narrative review of relevant literatures and distilling core themes. First, people with schizophrenia have difficulty with high load and during initial phases of WM (e.g., encoding, early rehearsal), yet are able to activate WM-related prefrontal brain regions to the same maximal degree as comparison controls under certain circumstances. Second, people with schizophrenia have difficulty identifying and expressing facial emotions, yet demonstrate heightened automatic/implicit processing of facial emotions. Third, people with schizophrenia behaviourally demonstrate intact cognition–emotion interactions on laboratory tasks wherein emotional processing is automatic/implicit, yet demonstrate cognition–emotion disconnections in other levels of analysis. Insights are drawn from basic science showing interdependency between WM load and implicit emotion. Future research questions are raised regarding interactions between WM load and implicit facial-affective processing in schizophrenia.

Working Memory Encoding and Maintenance Deficits in Schizophrenia: Neural Evidence for Activation and Deactivation Abnormalities

Substantial evidence implicates working memory (WM) as a core deficit in schizophrenia (SCZ), purportedly due to primary deficits in dorsolateral prefrontal cortex functioning. Recent findings suggest that SCZ is also associated with abnormalities in suppression of certain regions during cognitive engagement--namely the default mode system--that may further contribute to WM pathology. However, no study has systematically examined activation and suppression abnormalities across both encoding and maintenance phases of WM in SCZ. Twenty-eight patients and 24 demographically matched healthy subjects underwent functional magnetic resonance imaging at 3T while performing a delayed match-to-sample WM task. Groups were accuracy matched to rule out performance effects. Encoding load was identical across subjects to facilitate comparisons across WM phases. We examined activation differences using an assumed model approach at the whole-brain level and within meta-analytically defined WM areas. Despite matched performance, we found regions showing less recruitment during encoding and maintenance for SCZ subjects. Furthermore, we identified 2 areas closely matching the default system, which SCZ subjects failed to deactivate across WM phases. Lastly, activation in prefrontal regions predicted the degree of deactivation for healthy but not SCZ subjects. Current results replicate and extend prefrontal recruitment abnormalities across WM phases in SCZ. Results also indicate deactivation abnormalities across WM phases, possibly due to inefficient prefrontal recruitment. Such regional deactivation may be critical for suppressing sources of interference during WM trace formation. Thus, deactivation deficits may constitute an additional source of impairments, which needs to be further characterized for a complete understanding of WM pathology in SCZ.

Hemodynamic correlates of brain electrical oscillations related with working memory

Event Abstract Back to Event Hemodynamic correlates of brain electrical oscillations related with working memory Itır Kaşıkçı1*, Ali Bayram2, 3, Esin Karahan2, Başar Bilgiç4, Ahmet Ademoğlu2 and Tamer Demiralp5 1 Istanbul University, Turkey 2 Bogazici University, Institute of Biomedical Engineering, Turkey 3 NPISTANBUL Neuropsychiatry Hospital, Turkey 4 Istanbul University, Istanbul Faculty of Medicine, Neurology Department, Turkey 5 Istanbul University, Istanbul Faculty of Medicine, Physiology Department, Turkey Majority of EEG studies related with working memory (WM) report increased amplitudes of posterior alpha and frontal theta in the retention phase and in many fMRI studies prefrontal and posterior parietal cortex activations were observed. Although posterior alpha oscillations during the retention phase might be associated with parietal regions and frontal theta oscillation with frontal regions, validity of such assumptions that do not rely on direct EEG/fMRI integration is questionable. In this study, simultaneous EEG-fMRI recordings were carried out while 18 healthy volunteers were performing a version of Sternberg paradigm. EEG signals obtained during the retention phase of WM were decomposed into topographical components using independent component analysis (ICA). Components with significantly different power between the retention phase and other phases of WM have been identified. From this set of components those that significantly differed among different memory load conditions (2/6) and the control condition were theta and alpha components with frontal distributions. The temporal courses of these components were used as regressors in fMRI analysis. Change of the frontal alpha oscillation due to WM retention phase was found correlated with fMRI activations in right orbitofrontal and dorsolateral prefrontal areas, while frontal theta was found correlated with activations in bilateral inferior temporal gyri and left inferior frontal cortex. These results shed light on the temporal dynamics of the neuronal assemblies residing in these brain areas that are closely related with memory processes. Keywords: multimodal integration, working memory Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Multimodal Integration of EEG, MEG and fMRI data Citation: Kaşıkçı I, Bayram A, Karahan E, Bilgiç B, Ademoğlu A and Demiralp T (2011). Hemodynamic correlates of brain electrical oscillations related with working memory. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00096 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 16 Nov 2011; Published Online: 25 Nov 2011. * Correspondence: Dr. Itır Kaşıkçı, Istanbul University, Istanbul, Turkey, itirk@istanbul.edu.tr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Itır Kaşıkçı Ali Bayram Esin Karahan Başar Bilgiç Ahmet Ademoğlu Tamer Demiralp Google Itır Kaşıkçı Ali Bayram Esin Karahan Başar Bilgiç Ahmet Ademoğlu Tamer Demiralp Google Scholar Itır Kaşıkçı Ali Bayram Esin Karahan Başar Bilgiç Ahmet Ademoğlu Tamer Demiralp PubMed Itır Kaşıkçı Ali Bayram Esin Karahan Başar Bilgiç Ahmet Ademoğlu Tamer Demiralp Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Cortical Oscillatory Activity Is Critical for Working Memory as Revealed by Deficits in Early-Onset Schizophrenia

Impairments in working memory (WM) are a core cognitive deficit in schizophrenia. Neurophysiological models suggest that deficits during WM maintenance in schizophrenia may be explained by abnormalities in the GABAergic system, which will lead to deficits in high-frequency oscillations. However, it is not yet clear which of the three WM phases (encoding, maintenance, retrieval) are affected by dysfunctional oscillatory activity. We investigated the relationship between impairments in oscillatory activity in a broad frequency range (3-100 Hz) and WM load in the different phases of WM in 14 patients with early-onset schizophrenia and 14 matched control participants using a delayed matching to sample paradigm. During encoding, successful memorization was predicted by evoked theta, alpha, and beta oscillatory activity in controls. Patients showed severe reductions in the evoked activity in these frequency bands. During early WM maintenance, patients showed a comparable WM load-dependent increase in induced alpha and gamma activity to controls. In contrast, during the later maintenance phase, patients showed a shift in the peak of induced gamma activity to the lower WM load conditions. Finally, induced theta and gamma activity were reduced in patients during retrieval. Our findings suggest that the WM deficit in schizophrenia is associated with impaired oscillatory activity during all phases of the task and that the cortical storage system reaches its capacity limit at lower loads. Inability to maintain oscillatory activity in specific frequency bands could thus result in the information overload that may underlie both cognitive deficits and psychopathological symptoms of schizophrenia.

A dopaminergic basis for working memory, learning and attentional shifting in Parkinsonism

Parkinson's disease (PD) patients exhibit cognitive deficits, including reinforcement learning, working memory (WM) and set shifting. Computational models of the basal ganglia–frontal system posit similar mechanisms for these deficits in terms of reduced dynamic range of striatal dopamine (DA) signals in both medicated and non-medicated states. Here, we report results from the first study that tests PD patients on and off dopaminergic medications in a modified version of the AX continuous performance (AX-CPT) working memory task, consisting of three performance phases and one phase requiring WM associations to be learned via reinforcement feedback. Patients generally showed impairments relative to controls. Medicated patients showed deficits specifically when having to ignore distracting stimuli during the delay. Our models suggest that this impairment is due to medication causing excessive WM updating by enhancing striatal “Go” signals that facilitate such updating, while concurrently suppressing “NoGo” signals. In contrast, patients off medication showed deficits consistent with an overall reduction in striatal DA and associated Go updating signals. Supporting this dichotomy, patients on and off medication both showed attentional shifting deficits, but for different reasons. Deficits in non-medicated patients were consistent with an inability to update the new attentional set, whereas those in medicated patients were evident when having to ignore distractors that had previously been task relevant. Finally, in the feedback-based WM phase, medicated patients were better than unmedicated patients, suggesting a key role of striatal DA in using feedback to update information into WM. These results lend further insight into the role of basal ganglia dopamine in WM and broadly support predictions from neurocomputational models.

The influence of working memory load on phase specific patterns of cortical activity

This study investigated patterns of cortical activity associated with the temporally separated encoding, maintenance and retrieval phases of a working memory (WM) task. Eighteen healthy subjects completed a variable load version of the Sternberg Item Recognition Task. Brain regions showing activity on average across load were determined for each task phase. In addition, brain regions showing activity that increased linearly with load were determined for encoding and retrieval. Although previous fMRI studies have used event-related designs to isolate phase specific activity, this study differed in that design and analysis methods were optimized to ensure low multicollinearity between the conditions of interest: the duration of the intermediate phase (maintenance) was varied and load was selectively modeled for the encoding and retrieval phases. The brain areas showing activity on average across load for each phase combine to encompass regions identified in previous studies that have not attempted to separate phase specific activity. Encoding is associated with extensive load dependent activity, with the most robust activity in bilateral occipital and posterior parietal regions. Retrieval is associated with more selective load dependent activity, primarily in the anterior supplementary motor region and the right posterior cerebellum. The analysis strategies employed in this study could be used to further delineate the phases of WM that are most severely compromised in clinical populations with WM disturbances.