Working Memory Processes Research Articles

Reading direction interacts with spatial processes of temporal order verbal working memory: evidence from Iranian right-to-left readers

ABSTRACT Reading direction affects cognitive processes such as spatial processing and attention. Testing Farsi right-to-left readers, we investigated the effect of reading direction on the involved spatial and attentional processes in a verbal working memory task. Previous research in left-to-right readers has shown that serial order in verbal WM is encoded spatially from left to right and that mechanisms of spatial attention operate on these mental representations. First, we confirmed that the spatial representation of serial information in WM follows the right-to-left reading direction of Farsi. Second, we demonstrated the influence of reading direction on the distribution of spatial attention over the reading-direction-contingent mental representation of serial information in WM. Behavioural RTs and neural markers of spatial attention shifts (EDAN and ADAN ERPs and lateralised posterior alpha activity) confirm the right-to-left representation of serial order in WM and the involvement of spatial attention in retrieving items from this mnemonic space.

Age differences in the principal temporo-spatial components of EEG activity during a proactive interference task

Proactive interference (PI) is the disruptive effect of no longer relevant information on current working memory (WM) processing. PI effects in EEG data have been previously found to be altered in healthy aging, although it remains unclear the extent to which such changes reflect delayed or different brain mechanisms employed to overcome PI. Hence, we had twenty-six young (18–34 years) and sixteen old (53–68 years) healthy adults complete a Recent Probes task while EEG was recorded. Compared to young adults, old adults were slower, less accurate and less able to discriminate when they last saw a given stimulus, but PI effects on reaction time were greater in the former, likely due to a general difficulty that old adults had in the task. Temporo-spatial principal component analysis of the EEG data showed young and older adults to differ in terms of temporal and spatial characteristics of brain activity associated with resolving PI. YA showed a factor indicative of a medial frontal negativity (MFN) that showed greater amplitude in low compared to high PI trials. OA, in contrast, showed a late positive component (LPC), although similarly with larger amplitude in low compared to high PI trials. The modulation of the MFN component in YA may reflect the recruitment of cognitive control to overcome PI. The modulation of the LPC in OA may represent the detection of conflict between familiarity and context recollection during PI.

Associations of Plasma Glutamatergic Metabolites with Alpha Desynchronization during Cognitive Interference and Working Memory Tasks in Asymptomatic Alzheimer's Disease.

Electroencephalogram (EEG) studies have suggested compensatory brain overactivation in cognitively healthy (CH) older adults with pathological beta-amyloid(Aβ42)/tau ratios during working memory and interference processing. However, the association between glutamatergic metabolites and brain activation proxied by EEG signals has not been thoroughly investigated. We aim to determine the involvement of these metabolites in EEG signaling. We focused on CH older adults classified under (1) normal CSF Aβ42/tau ratios (CH-NATs) and (2) pathological Aβ42/tau ratios (CH-PATs). We measured plasma glutamine, glutamate, pyroglutamate, and γ-aminobutyric acid concentrations using tandem mass spectrometry and conducted a correlational analysis with alpha frequency event-related desynchronization (ERD). Under the N-back working memory paradigm, CH-NATs presented negative correlations (r = ~-0.74--0.96, p = 0.0001-0.0414) between pyroglutamate and alpha ERD but positive correlations (r = ~0.82-0.95, p = 0.0003-0.0119) between glutamine and alpha ERD. Under Stroop interference testing, CH-NATs generated negative correlations between glutamine and left temporal alpha ERD (r = -0.96, p = 0.037 and r = -0.97, p = 0.027). Our study demonstrated that glutamine and pyroglutamate levels were associated with EEG activity only in CH-NATs. These results suggest cognitively healthy adults with amyloid/tau pathology experience subtle metabolic dysfunction that may influence EEG signaling during cognitive challenge. A longitudinal follow-up study with a larger sample size is needed to validate these pilot studies.

Working memory processes and intrinsic motivation: An EEG study

Processes typically encompassed by working memory (WM) include encoding, retention, and retrieval of information. Previous research has demonstrated that motivation can influence WM performance, although the specific WM processes affected by motivation are not yet fully understood. In this study, we investigated the effects of motivation on different WM processes, examining how task difficulty modulates these effects. We hypothesized that motivation level and personality traits of the participants (N = 48, 32 females; mean age = 21) would modulate the parietal alpha and frontal theta electroencephalography (EEG) correlates of WM encoding, retention, and retrieval phases of the Sternberg task. This effect was expected to be more pronounced under conditions of very high task difficulty. We found that increasing difficulty led to reduced accuracy and increased response time, but no significant relationship was found between motivation and accuracy. However, EEG data revealed that motivation influenced WM processes, as indicated by changes in alpha and theta oscillations. Specifically, higher levels of the Resilience trait—associated with mental toughness, hardiness, self-efficacy, achievement motivation, and low anxiety—were related to increased alpha desynchronization during encoding and retrieval. Increased scores of Subjective Motivation to perform well in the task were related to enhanced frontal midline theta during retention. Additionally, these effects were significantly stronger under conditions of high difficulty. These findings provide insights into the specific WM processes that are influenced by motivation, and underscore the importance of considering both task difficulty and intrinsic motivation in WM research.

The independent storage mechanisms of visual and vibrotactile working memory.

Whether information in working memory (WM) is stored in a domain-independent or domain-specific system is still the subject of intense debate. This study used the delayed match-to-sample paradigm, the dual-task paradigm, and the selective interference paradigm to investigate the mechanism of cross-modal storage in visual and vibrotactile WM. We postulated that WM may store cross-modal data from haptics and vision independently, and we proposed domain-specific WM storage. According to the findings, the WM can store cross-modal information from vision and haptics independently, and the storage of visual and tactile WM may be domain-specific. This study provides early support for the hypothesis that haptic and visuospatial sketchpads are dissociated. In addition, the current study provides evidence to elucidate the mechanisms by which WM stores and processes data from different modalities and content. The results also indicate that a cross-modal approach can broaden the cognitive processing bandwidth of WM.

Alpha event-related decreases during encoding in adults with ADHD – An investigation of sustained attention and working memory processes

BackgroundExecutive functioning deficits are central to established neuropsychological models of ADHD. Oscillatory activity, particularly the alpha rhythm (8–12 Hz) has been associated with cognitive impairments in ADHD. However, most studies to date examined such neural mechanisms underlying executive dysfunction in children and adolescents with ADHD, raising the question of whether and to what extent those ADHD-related working memory impairments are still present in adults. To this end, the current study aimed to investigate the role of alpha event-related decreases (ERD) during working memory processes in adults with and without ADHD. MethodsWe collected electroencephalographic (EEG) data from 85 adults with a lifetime diagnosis of ADHD and 105 controls (aged 32–64), while they performed a continuous performance (CPT) and a spatial delayed response working memory task (SDRT). Time-frequency and independent component analysis (ICA) was used to identify alpha (8–12 Hz) clusters to examine group and condition effects during the temporal profile of sustained attention and working memory processes (encoding, maintenance, retrieval), loads (low and high) and trial type (go and nogo). ResultsIndividuals with ADHD exhibited higher reaction time-variability in SDRT, and slower response times in SDRT and CPT, despite no differences in task accuracy. Although working memory load was associated with stronger alpha ERD in both tasks and both groups (ADHD, controls), we found no consistent evidence for attenuated alpha ERD in adults with ADHD, failing to replicate effects reported in children. In contrast, when looking at the whole sample, the correlations of alpha power during encoding with inattention and hyperactivity-impulsivity symptoms were significant, replicating prior findings in children with ADHD, but suggesting an alternate source for these effects in adults. ConclusionsOur results corroborate the robustness of alpha as a marker of visual attention and suggest that occipital alpha ERD normalizes in adulthood, but with unique contributions of centro-occipital alpha ERD, suggesting a secondary source. This implies that deviations in processes other than previously reported visuospatial cortex engagement may account for the persistent symptoms and cognitive deficits in adults with a history of ADHD.

Two are better than one: Differences in cortical EEG patterns during auditory and visual verbal working memory processing between Unilateral and Bilateral Cochlear Implanted children

Despite the proven effectiveness of cochlear implant (CI) in the hearing restoration of deaf or hard-of-hearing (DHH) children, to date, extreme variability in verbal working memory (VWM) abilities is observed in both unilateral and bilateral CI user children (CIs). Although clinical experience has long observed deficits in this fundamental executive function in CIs, the cause to date is still unknown. Here, we have set out to investigate differences in brain functioning regarding the impact of monaural and binaural listening in CIs compared with normal hearing (NH) peers during a three-level difficulty n-back task undertaken in two sensory modalities (auditory and visual). The objective of this pioneering study was to identify electroencephalographic (EEG) marker pattern differences in visual and auditory VWM performances in CIs compared to NH peers and possible differences between unilateral cochlear implant (UCI) and bilateral cochlear implant (BCI) users. The main results revealed differences in theta and gamma EEG bands. Compared with hearing controls and BCIs, UCIs showed hypoactivation of theta in the frontal area during the most complex condition of the auditory task and a correlation of the same activation with VWM performance. Hypoactivation in theta was also observed, again for UCIs, in the left hemisphere when compared to BCIs and in the gamma band in UCIs compared to both BCIs and NHs. For the latter two, a correlation was found between left hemispheric gamma oscillation and performance in the audio task. These findings, discussed in the light of recent research, suggest that unilateral CI is deficient in supporting auditory VWM in DHH. At the same time, bilateral CI would allow the DHH child to approach the VWM benchmark for NH children. The present study suggests the possible effectiveness of EEG in supporting, through a targeted approach, the diagnosis and rehabilitation of VWM in DHH children.

OpenWMB: An open-source and automated working memory task battery for OpenSesame

Working memory capacity (WMC) has been measured with a plethora of cognitive tasks. Several preeminent automated batteries of working memory (WM) tasks have been developed recently. However, despite all their advantages, most batteries were programmed in paid platforms and/or only included a single WM paradigm. To address these issues, we developed the OpenWMB, an automated battery comprising seven tasks from three distinct paradigms (complex spans, updating tasks, and binding tasks) that tap into several functional aspects of WM (simultaneous storage and processing, updating, and binding). The battery runs on open-source software (OpenSesame) and is freely available online in a ready-to-download format. The OpenWMB possesses flexible features and includes a data processing script (that converts data into a format ready for statistical analysis). The instrument is available in Portuguese and English. However, we only assessed the psychometric properties of the former version. The Portuguese version presented good internal consistency and considerable internal and predictive validity: all tasks loaded into a single factor. Additionally, the WMC estimate was strongly correlated with a fluid intelligence factor. This study also tried to contribute to the ongoing debate regarding the best method to assess WMC. We computed a permutation analysis to compare the amount of variance shared between a fluid intelligence factor and (1) each WM task, (2) homogenous WMC factors (based on multiple tasks from the same paradigm), and (3) heterogeneous WMC factors (derived from triplets of tasks from different paradigms). Our results suggested that heterogeneous factors provided the best estimates of WMC.

Unpacking affect maintenance and its association with depressive symptoms: integrating positive and negative affects

ABSTRACT Depression is associated with increased maintenance of negative affect (NA) and reduced – blunted and short-lived – maintenance of positive affect (PA). Studies have focused on factors associated with the maintenance of NA, specifically, the emotion regulation strategy of brooding and the capacity to hold negative affective experiences in working memory (WM). Despite its theoretical importance, less attention has been given to factors associated with the maintenance of PA in depression. This study aims to synthesise factors playing a role in the maintenance of both NA and PA. Specifically, we used self-reported assessment of PA and NA regulation and performance-based measures of NA and PA processing in WM to predict depressive symptoms severity. Participants (N = 219) completed the Affective Maintenance Task (AMT, Mikels et al., 2008), which provided performance-based measures of PA and NA maintenance, and filled out questionnaires assessing brooding, positive rumination and depressive severity. Brooding, positive rumination and AMT-based measures of positive (but not negative) affective information processing were independently associated with depressive symptoms. We highlight the unique contributions of PA processing, as well as of self-reported emotion regulation strategies in understanding depression maintenance.

Cognitive functioning of patients with borderline personality disorder

IntroductionThe neurocognitive deficit model as a characteristic of patients with borderline personality disorder (BPD) has been the focus of research for the past 20 years. However, no such studies have been performed in Russia.ObjectivesThe aim of the present study was to investigate the neurocognitive profile of patients with BPD.MethodsFifty patients with BPD (according to DSM-V criteria) in stable mental state (72% women; mean age 22.44±4.32) were examined. BPD symptom severity was assessed using the Borderline Personality Disorder Questionnaire (PBQ-BPD), which was validated in the Russian population (34 points or more indicated a higher probability of BPD diagnosis). The Brief Assessment of Cognition in Schizophrenia (BACS) was used to assess cognitive function (in order to use these data for differential diagnosis with schizophrenia spectrum disorders). The study was approved by the ethical committee of Saint Petersburg State University.ResultsOn the PBQ-BPD results, 38% of patients (n=19) scored over 34 points, despite being stable. BACS subscales T-scores (presented as median [Q1; Q3]) were within normal limits (Verbal memory - 49.81 [46.56; 53,06]; Working memory - 43.73 [38.0; 47.50]; Motor function - 44.08 [41.0; 47.25]; Coding - 45.56 [42.50; 48.63]; Verbal fluency - 48.14 [46.0; 52.0]; Tower of London test - 52.33 [47.0; 57.0]). A number of patients had low scores on the BACS subscales (T-score < 40), particularly working memory (33.3%), coding (20.8%), and verbal memory (18.8%). The BACS Composite T Score (46.02 [43.65; 48.39]) correlated with the PBQ-BPD score (32.00 [27.00; 36.00]; r=-0.316; p=0.028). To better characterize the cognitive functioning of patients with BPD, patients were divided into two groups: those who scored less than 34 on the PBQ-BPD (group 1) and those who scored more than 34 on the PBQ-BPD (group 2). Group 2 patients had a lower BACS Composite T-score (42.32 [38.06; 46.58]; 48.45 [45.87; 51.03]; p=0.009) and nominally lower mean scores on all BACS subscales, compared with Group 1 patients. We found significant differences in T-scores values on the Working Memory subscale (Group 1 - 45.0 [41.0; 49.0]; Group 2 - 38.0 [33.0; 43.5], p=0.003), Verbal Fluency (49.0 [47.25; 53.75]; 48.0 [44.0; 49.0]; p=0.047), Tower of London Test (57.0 [52.0; 57.0]; 48.0 [42.0; 57.0]; p=0.036).ConclusionsNeurocognitive impairment was detected in 33.3% of patients with BPD. The dominant cognitive impairments in the patients were decreased working and verbal memory and information processing speed. The severity of BPD symptoms has been confirmed to correlate with the neurocognitive functioning of these patients.Disclosure of InterestNone Declared

High-altitude exposure leads to increased modularity of brain functional network with the increased occupation of attention resources in early processing of visual working memory

High-altitude exposure leads to increased modularity of brain functional network with the increased occupation of attention resources in early processing of visual working memory

The relationships among working memory, inhibitory control, and mathematical skills in primary school children: Analogical reasoning matters

The current study examined the mediating role of analogical reasoning in the relationships among working memory, inhibitory control, and children’s mathematical skills. Two hundred fifty-one students from first to third grades were tested on visual-spatial working memory, verbal working memory, inhibitory control, analogical reasoning, and different mathematical skills (i.e., symbolic number processing and mathematical reasoning). After controlling for age and gender, analogical reasoning significantly contributed to both symbolic number processing and mathematical reasoning. The relationship between verbal working memory and symbolic number processing, as well as the relationship between verbal working memory and mathematical reasoning, were significantly mediated by analogical reasoning. The exploratory analyses further revealed that there was no significant age difference in the roles of analogical reasoning. These results highlight the important role of analogical reasoning in explaining the relationships among working memory, inhibitory control, and children’s different mathematical abilities. The findings also indicate that analogical reasoning, the ability of identifying and processing critical relational information, may be a potential avenue to improve children’s mathematical skills.

Perceptual benefits of implicit auditory learning of rule-based nonspeech sound patterns in younger and older adults

Sounds in everyday environments typically precede and follow one another in systematic ways determined by the properties and interactions of corresponding sound sources. Familiar and predictable contextual relationships between consecutive sounds are known to provide perceptual benefit under adverse listening conditions. Previous work has demonstrated implicit learning of arbitrary rule-based sound patterns by young normal hearing adults. However, the role of such rule-based learning on identification of individual sounds within a sound pattern and the effect of listener age has not been investigated. Here younger and older adults with age-appropriate hearing were first familiarized with a set of rule-based nonspeech sound sequences produced by a finite-state machine. Subsequently, they identified individual target sounds within sequences under a range of signal-to-noise ratios (0 to -15 dB). The test sequences were (a) familiar, rule-based; (b) novel, rule-based; or (c) novel, non rule-based. The results for both younger and older listeners revealed superior sound identification in sequences versus in isolation, and a greater overall accuracy of rule-based versus non rule-based sequences. Younger listeners significantly outperformed older listeners. Implicit learning benefit did not correlate with measures of working memory processing. Current findings have implications for audiologic rehabilitation and auditory display design.

A preliminary study of dynamic neurochemical changes in the dorsolateral prefrontal cortex during working memory.

Working memory (WM) is one of the fundamental cognitive functions associated with the dorsolateral prefrontal cortex (DLPFC). However, the neurochemical mechanisms of WM, including the dynamic changes in neurometabolites such as glutamate and GABA in the DLPFC, remain unclear. Here, we investigated WM-related glutamate and GABA changes, alongside hemodynamic responses in the DLPFC, using a combination of functional magnetic resonance spectroscopy (fMRS) and functional magnetic resonance imaging (fMRI). During a WM task, we measured Glx (glutamate + glutamine) and GABA levels using GABA editing MEscher-GArwood Point REsolved Spectroscopy (MEGA-PRESS) sequence and blood-oxygen-level-dependent (BOLD) signal changes. In the DLPFC, we observed elevated Glx levels and increased BOLD signal changes during a 2-back task. Specifically, the Glx levels in the DLPFC were significantly higher during the 2-back task compared with fixation, although this difference was not significant when compared with a 0-back task. However, Glx levels during the 0-back task were higher than during fixation. Furthermore, there was a positive correlation between Glx levels in the DLPFC during the 2-back task and the corresponding BOLD signal changes. Notably, higher Glx increases were associated with increased DLPFC activation and lower WM task performance in individuals. No notable changes in DLPFC GABA levels were observed during WM processing. These findings suggest that the modulation of glutamatergic activity in the DLPFC may play a crucial role in both working memory processing and its associated performance outcomes.

Temporal and Spatial Information Elicit Different Power and Connectivity Profiles during Working Memory Maintenance.

Working memory (WM) is the cognitive ability to store and manipulate information necessary for ongoing tasks. Although frontoparietal areas are involved in the retention of visually presented information, oscillatory neural activity differs for temporal and spatial WM processing. In this study, we corroborated previous findings describing the modulation of neural oscillations and expanded our investigation to the network organization underlying the cognitive processing of temporal and spatial information. We utilized MEG recordings during a Sternberg visual WM task. The spectral oscillatory activity in the maintenance phase revealed increased frontal theta (4-8 Hz) and parietal beta (13-30 Hz) in the temporal condition. Source level coherence analysis delineated the prominent role of parietal areas in all frequency bands during the maintenance of temporal information, whereas frontal and central areas showed major contributions in theta and beta ranges during the maintenance of spatial information. Our study revealed distinct spectral profiles of neural oscillations for separate cognitive subdomains of WM processing. The delineation of specific functional networks might have important implications for clinical applications, enabling the development of stimulation protocols targeting cognitive disabilities associated with WM impairments.

Writing about a stressful experience can impair visual working memory.

Acute stress has been well-established to impair working memory. However, less is known about how writing about an unresolved stressor may influence working memory or working memory processes. We addressed these issues in the present study (N = 282) by randomly assigning participants to write about an unresolved stressful experience (stressful writing condition or the events of the previous day). We then both measured performance on a change detection task and used computational modeling to estimate the processes underlying performance: attention, capacity, and guessing bias. We found that, relative to the control condition, writing about a stressful experience impaired change detection task performance and significantly impaired task attention. These results show that the effects of writing about an unresolved stressor may mimic the effects of acute stress on working memory, rather than conforming to expectations from mood-as-information theory.

Quantifying network behavior in the rat prefrontal cortex.

The question of how consciousness and behavior arise from neural activity is fundamental to understanding the brain, and to improving the diagnosis and treatment of neurological and psychiatric disorders. There is significant murine and primate literature on how behavior is related to the electrophysiological activity of the medial prefrontal cortex and its role in working memory processes such as planning and decision-making. Existing experimental designs, specifically the rodent spike train and local field potential recordings during the T-maze alternation task, have insufficient statistical power to unravel the complex processes of the prefrontal cortex. We therefore examined the theoretical limitations of such experiments, providing concrete guidelines for robust and reproducible science. To approach these theoretical limits, we applied dynamic time warping and associated statistical tests to data from neuron spike trains and local field potentials. The goal was to quantify neural network synchronicity and the correlation of neuroelectrophysiology with rat behavior. The results show the statistical limitations of existing data, and the fact that making meaningful comparison between dynamic time warping with traditional Fourier and wavelet analysis is impossible until larger and cleaner datasets are available.

Age-related alterations in the oscillatory dynamics serving verbal working memory processing.

Working memory (WM) is a foundational cognitive function involving the temporary storage of information. Unfortunately, WM is also one of the most sensitive cognitive functions to the detrimental effects of aging. Expanding the field's understanding of age-related WM changes is critical to advancing the development of strategies to mitigate age-related WM declines. In the current study, we investigated the neural mechanisms serving WM function in seventy-eight healthy aging adults (range: 20.2-65.2 years) using magnetoencephalography (MEG) and a Sternberg WM task with letter stimuli. Neural activity during the different phases of the WM task (i.e., encoding, maintenance, and retrieval) were imaged using a time-frequency resolved beamformer and whole-brain statistics were performed. We found stronger increases in theta activity and stronger decreases in alpha and beta activity (i.e., more negative relative to baseline) as a function of healthy aging. Specifically, age-related increases in theta activity were detected during the encoding period in the primary visual and left prefrontal cortices. Additionally, alpha and beta oscillations were stronger (i.e., more negative) during both encoding and maintenance in the left prefrontal cortex in older individuals. Finally, alpha and beta oscillations during the retrieval phase were stronger (i.e., more negative) in older participants within the prefrontal, parietal, and temporal cortices. Together, these results indicate that healthy aging strongly modulates the neural oscillatory dynamics serving WM function.

Neuromodulator approaches to depression: The potential of transcranial electric stimulation

Depression, a widespread mental health disorder, presents significant challenges in diagnosis and treatment. Amidst the myriad treatments, non-invasive Transcranial Electric Stimulation (tES), encompassing Transcranial Alternating Current Stimulation (tACS) and Transcranial Direct Current Stimulation (tDCS), has emerged as a promising intervention for Major Depressive Disorder (MDD). This review delineates the mechanisms of these modalities, their distinctions, and their potential to modulate neural oscillations and influence cognitive functions. Studies showcased the efficacy of these techniques in ameliorating depressive symptoms, with EEG and fNIRS employed to gauge their neurological impact. Observations suggest the potential in modulating for specific brain rhythms to enhance memory functions in older adults and influence working memory processes. The dynamic interplay between tDCS and tACS in altering cortical activities and their interaction with neurotransmitters like GABA further underscores their potential. However, the need for extensive research, particularly double-blind randomized control trials, remains paramount to ascertain their safety and efficacy. This review provides a comprehensive insight into the prospective role of tES in the clinical landscape of MDD treatment.

The medial prefrontal cortex during flexible decisions: Evidence for its role in distinct working memory processes.

During decisions that involve working memory, task-related information must be encoded, maintained across delays, and retrieved. Few studies have attempted to causally disambiguate how different brain structures contribute to each of these components of working memory. In the present study, we used transient optogenetic disruptions of rat medial prefrontal cortex (mPFC) during a serial spatial reversal learning (SSRL) task to test its role in these specific working memory processes. By analyzing numerous performance metrics, we found: (1) mPFC disruption impaired performance during only the choice epoch of initial discrimination learning of the SSRL task; (2) mPFC disruption impaired performance in dissociable ways across all task epochs (delay, choice, return) during flexible decision-making; (3) mPFC disruption resulted in a reduction of the typical vicarious-trial-and-error rate modulation that was related to changes in task demands. Taken together, these findings suggest that the mPFC plays an outsized role in working memory retrieval, becomes involved in encoding and maintenance when recent memories conflict with task demands, and enables animals to flexibly utilize working memory to update behavior as environments change.