Working Memory System Research Articles

Logical Reasoning, Spatial Processing, and Verbal Working Memory: Longitudinal Predictors of Physics Achievement at Age 12-13 Years.

To date, few studies have tried to pinpoint the mechanisms supporting children’s skills in science. This study investigated to what extent logical reasoning, spatial processing, and working memory, tapped at age 9–10 years, are predictive of physics skills at age 12–13 years. The study used a sample of 81 children (37 girls). Measures of arithmetic calculation and reading comprehension were also included in the study. The multiple regression model accounted for 24% of the variation in physics achievement. The model showed that spatial processing (4.6%) and verbal working memory (4.5%) accounted for a similar amount of unique variance, while logical reasoning accounted for 5.7% variance. The measures of arithmetic calculation and reading comprehension did not account for any unique variance. Nine percent of the accounted variance was shared variance. The results demonstrate that physics is a multivariate discipline that draws upon numerous cognitive resources. Logical reasoning ability is a key component in order for children to learn about abstract physics facts, concepts, theories, and applying complex scientific methods. Spatial processing is important as it may sub-serve the assembly of diverse sources of visual-spatial information into a spatial-schematic image. The working memory system provides a flexible and efficient mental workspace that can supervise, coordinate, and execute processes involved in physics problem-solving.

Individual differences in math problem solving and executive processing among emerging bilingual children

This study identified cognitive processes that underlie individual differences in working memory (WM) and mathematical problem-solving accuracy in emerging bilingual children (English learners). A battery of tests was administered in both English and Spanish that assessed problem solving, achievement, and cognitive processing in children in first grade (n = 155), second grade (n = 129), and third grade (n = 110). The results were that (a) the executive component of WM predicted solution accuracy of word problems independent of first language and second language measures of vocabulary, reading, domain-specific knowledge (e.g., calculation, estimation), and short-term memory and (b) first language (Spanish) measures of the executive component of WM and magnitude comparisons were major predictors of math problem-solving accuracy in both languages. The results support the notion that the executive system of WM is a unique predictor of emerging bilingual children’s math problem-solving accuracy in both languages.

Neural architecture of human language: Hierarchical structure building is independent from working memory

Using functional magnetic resonance imaging (fMRI), we show that the neural substrate of language does not overlap with that for verbal working memory when we carefully define verbal working memory in sentence processing. Object-Subject-Verb (OSV) sentences in Japanese were contrasted with canonical Subject-Object-Verb (SOV) sentences, which had less hierarchy in linguistic structure. This contrast revealed the posterior part of Broca's area and the left posterior middle temporal gyrus (pMTG) as the neural bases for hierarchical structure building. Furthermore, we changed verbal working memory load in OSV sentences by adding modifiers to the subject or object noun phrases; this resulted in the activation in the op9, which is situated in the frontal operculum and is adjacent to, but not situated in, Broca's area. The neuroanatomical segregation of language processing from verbal working memory suggests independence of the faculty of language from the verbal working memory system, providing evidence for the domain-specificity of language in human cognition.

Cognitive training for children and adolescents with fragile X syndrome: a randomized controlled trial of Cogmed

BackgroundIndividuals with fragile X syndrome (FXS) typically demonstrate profound executive function (EF) deficits that interfere with learning, socialization, and emotion regulation. We completed the first large, non-pharmacological controlled trial for FXS, designed to evaluate the efficacy of Cogmed, a computer/tablet-based working memory (WM) training program.MethodsThe study was a randomized, blinded, parallel two-arm controlled trial in 100 children and adolescents with FXS (63 male, 37 female; 15.28 ± 3.36 yrs.). Participants were randomized equally to adaptive (difficulty level adjusted to performance) or non-adaptive (control) Cogmed training. Participants were assessed at home using objective measures of WM (primary outcome) and EF at baseline, following 20–25 caregiver-supported sessions over 5–6 weeks, and at follow-up 3 months after cessation of training. Parents and teachers provided ratings of WM, attention, and EF.ResultsThe WM composite and selective domains of EF (distractibility, cognitive flexibility), as well as parent- and teacher-reported attention and EF, significantly improved across the full study sample, with many changes maintained at follow-up. However, comparisons of improvement between adaptive and non-adaptive control conditions did not differ, showing that progressively challenging the WM system by expanding span length did not provide added benefit overall.ConclusionsFurther experimental comparisons are needed before Cogmed working memory training can be considered empirically validated for children with FXS, forming the basis of treatment recommendation. However, given that prior studies show no significant changes on these measures in FXS without treatment, that improvements were maintained for 3 months, and that blinded teachers reported improvements in the classroom, the modest benefits seen in both adaptive and non-adaptive groups overall are unlikely to be attributable to placebo or practice effects alone. Future analyses examining inter-individual differences (e.g., baseline capacity, training efficiency, co-morbidity, training environment, characteristics of training aide) may help to link this intervention to outcomes and potential transfer effects.Trial registrationUS National Institutes of Health (ClinicalTrials.gov), NCT02747394.

The role of context in animal memory.

Past research has shown that testing memory in the same context in which the memory was encoded leads to improved retention relative to testing memory in a new context. Context-dependent memory is directly related to the extent to which the encoding context can be reproduced. An experiment with pigeons is reported in which the context was a colored house-light that completely enveloped the learning and testing contexts. Under this condition, perfect retention of a visual discrimination that reversed at midsession was shown. Beyond reactivation of memory, new research with pigeons suggests that context provides access to different working and reference memory systems. Finally, experiments are reported that suggest context may selectively access information about features from the different dimensions of place, color, and time.

Separation of Tasks Into Distinct Domains, Not Set-Level Compatibility, Minimizes Dual-Task Interference.

Dual-task costs are often significantly reduced or eliminated when both tasks use compatible stimulus-response (S-R) pairs. Either by design or unintentionally, S-R pairs used in dual-task experiments that produce small dual-task costs typically have two properties that may reduce dual-task interference. One property is that they are easy to keep separate; specifically, one task is often visual-spatial and contains little verbal information and the other task is primarily auditory-verbal and has no significant spatial component. The other property is that the two sets of S-R pairs are often compatible at the set-level; specifically, the collection of stimuli for each task is strongly related to the collection of responses for that task, even if there is no direct correspondence between the individual items in the sets. In this paper, we directly test which of these two properties is driving the absence of large dual-task costs. We used stimuli (images of hands and auditory words) that when previously been paired with responses (button presses and vocal utterances) produced minimal dual-task costs, but we manipulated the shape of the hands in the images and the auditory words. If set-level compatibility is driving efficient performance, then these changes should not affect dual-task costs. However, we found large changes in the dual-task costs depending on the specific stimuli and responses. We conclude that set-level compatibility is not sufficient to minimize dual-task costs. We connect these findings to divisions within the working memory system and discuss implications for understanding dual-task performance more broadly.

When working memory is in a mood: Combined effects of induced affect and processing of emotional words

It is already well established that the working memory system can be influenced by moods or emotional stimuli. However, the exact combined impact of these two on the performance of working memory remains a puzzle. To examine the effect that the emotional content of stimuli has on working memory performance, 90 participants performed a 2-back task with emotional content (positive, neutral, and negative words) when they were in a positive, neutral, or negative mood. Repeated-measures ANOVA with mood as between-subjects factor and emotional load as within-subjects factor revealed a main effect of emotional content for both performance accuracy and reaction times in a 2-back task, and a main effect of mood for performance accuracy. Participants reacted significantly faster to negative words independently of their mood state. They were significantly more accurate when they were in the positive mood, but when they processed positive words they were less accurate. Additionally, to test whether loading the working memory system can reset the combined effect of mood and emotional stimuli, we measured the participants’ mood before and after they performed the n-back task; this revealed a significant effect of the n-back task on the mood. Together, these results suggest that although mood and emotional content do have a robust effect on working memory, in some instances combining them does not heighten their individual effects. Moreover, the results also show that participants might be easily distracted from moods by simply performing an n-back task.

Abstract #41: Effects of Bilateral-Frontal tDCS on the Working Memory Network: an fMRI-tDCS Study in Older Adults

Introduction: Working memory is an executive memory process essential for decision-making and problem solving, making it a fundamental process to everyday life. Frontal lobe brain structures are critical for working memory processes (i.e. reorganizing information), which are known to decline with advanced age. Transcranial direct current stimulation (tDCS) shows promise for enhancing working memory in older adults. However, underlying neural mechanisms of tDCS on the working memory system are not well understood. The current study aimed to determine functional connectivity changes in the working memory network using an N-Back working memory task during a tDCS session while inside a 3T Phillips MRI.

Stable Delay Period Representations in the Posterior Parietal Cortex Facilitate Working-Memory-Guided Obstacle Negotiation

In complex environments, information about surrounding obstacles is stored in working memory (WM) and used to coordinate appropriate movements for avoidance. In quadrupeds, this WM system is particularly important for guiding hindleg stepping, as an animal can no longer see the obstacle underneath the body following foreleg clearance. Suchobstacle WM involves the posterior parietal cortex (PPC), as deactivation of area 5 incurs WM deficits,precluding successful avoidance. However, the neural underpinnings of this involvement remain undefined. To reveal the neural substrates of this behavior, microelectrode arrays were implanted to record neuronal activity in area 5 during an obstacle WM task in cats. Early in the WM delay, neurons were modulated generally by obstacle presence or more specifically in relation to foreleg step height. Thus, information about the obstacle or about foreleg clearance can be retained in WM. In a separate set of neurons, this information was recalled later in the delay in order to plan subsequent hindleg stepping. Such early and late delay period signals were temporally bridged by neurons exhibiting obstacle-modulated activity sustained throughout the delay. These neurons represented a specialized subset of all recorded neurons, which maintained stable information coding across the WM delay. Ultimately, these various patterns of task-related modulation enable stable representations of obstacle-related information within the PPC to support successful WM-guided obstacle negotiation in the cat.

Effect of blast-related mTBI on the working memory system: a resting state fMRI study.

Reduced working memory is frequently reported by Veterans with a history of blast-related mild traumatic brain injury (mTBI), but can be difficult to quantify on neuropsychological measures. This study aimed to improve our understanding of the impact of blast-related mTBI on the working memory system by using resting state functional magnetic resonance imaging (fMRI) to explore differences in functional connectivity between OEF/OIF/OND Veterans with and without a history of mTBI. Participants were twenty-four Veterans with a history of blast-related mTBI and 17 Veterans who were deployed but had no lifetime history of TBI. Working memory ability was evaluated with the Auditory Consonants Trigrams (ACT) task. Resting state fMRI was used to evaluate intrinsic functional connectivity from frontal seed regions that are known components of the working memory network. No significant group differences were found on the ACT, but the imaging analyses revealed widespread hyper-connectivity from the frontal seed regions in the Veterans with a history of mTBI relative to the deployed control group. Further, within the mTBI group, but not the control group, better performance on the ACT was associated with increased functional connectivity to multiple brain regions, including cerebellar components of the working memory network. These results were present after controlling for age, PTSD symptoms, and estimated premorbid IQ, and suggest that long-term alterations in the functional connectivity of the working memory network following blast-related mTBI may reflect a compensatory change that contributes to intact performance on an objective measure of working memory.

Modality-Specific Working Memory Systems Verified by Clinical Working Memory Tests

Modality-Specific Working Memory Systems Verified by Clinical Working Memory Tests

Modality-Specific Working Memory Systems Verified by Clinical Working Memory Tests.

ObjectiveThis study was to identify whether working memory (WM) can be clearly subdivided according to auditory and visual modality. To do this, we administered the most recent and universal clinical WM measures in a mixed psychiatric sample.MethodsA total of 115 patients were diagnosed on the basis of DSM-IV diagnostic criteria and with MINI-Plus 5.0, a structured diagnostic interview. WM subtests of Korean version of Wechsler Adult Intelligence Scale-IV and Korean version of Wechsler Memory Scale-IV were administered to assess WM. Confirmatory factor analysis (CFA) was used to observe whether WM measures fit better to a one-factor or two-factor model.ResultsCFA results demonstrated that a two factor model fits the data better than one-factor model as expected.ConclusionOur study supports a modality model of WM, or the existence of modality-specific WM systems, and thus poses a clinical significance of assessing both auditory and visual WM tests.

Pupillometry tracks fluctuations in working memory performance.

In 3 experiments, we examined fluctuations in working memory (WM) performance and associated changes in pretrial and task-evoked pupil diameter. Additionally, we examined whether particularly poor trials were accompanied by self-reports of off-task attentional states. The results demonstrated that task-evoked pupillary responses can be used to measure moment-to-moment fluctuations in the success of WM maintenance during delay intervals. Further, when individuals reported being in an off-task attentional state, their WM performance suffered. Additionally, when probed directly after a particularly poor trial, participants reported being in an off-task attentional state more often than at random intervals throughout the task. So behavioral, subjective, and physiological data converged when people experienced WM failures. Although pretrial pupil diameter did not consistently differentiate between successful and unsuccessful trials, variability in pretrial pupil diameter accounted for a significant portion of variance in WM task performance. This effect persisted after controlling for mean task-evoked pupillary response and variability in task-evoked pupillary responses. Thus, one of the major reasons people varied in the consistency with which they utilized their WM system was variability in arousal. Such variability in arousal is potentially due to variation in the functioning of the locus coeruleus-norepinephrine (LC-NE) neuromodulatory system, and thus may underlie individual differences in WM capacity and attention control.

Individual differences in working memory and general intelligence indexed by P200 and P300: A latent variable model

A robust relationship between working memory (WM) and general intelligence (g) has been well established. Nevertheless, explanations for this relationship in terms of underlying neurocognitive processes are still inadequate. This study addresses this issue using an individual differences approach in which Central Executive System (CES) and Short-Term Storage (STS) components of WM are measured comprehensively and examined for their relationship with g via event-related potentials components (P200 and P300) as mediators. Participants (n = 115) completed tests of the WM, CES and STS, as well as g. P200 and P300 components were recorded during 3-back WM task performance. Structural equation modelling showed significant negative associations between the P200 latency for target stimuli and CES shifting processes, and between the P300 amplitude for target stimuli and CES inhibition and updating processes. The relationship between CES processes and g was mediated in a localized fashion by the P300 amplitude. These findings further support the notion that the CES has a multidimensional structure and, importantly, reveal that the inhibition and updating functions of the CES are crucial in explaining the relationship between WM and g. Negative relations between ERP indices (P200 latency and P300 amplitude for target stimuli) and g support a neural efficiency hypothesis related to high intelligence.

How Working Memory Provides Representational Change During Insight Problem Solving.

Numerous studies of insight problem solving are focused on both the control and storage systems of working memory. We obtained contradictory data about how working memory systems are involved in insight problem solving process. We argue that measuring the dynamics of the control system and storage systems through the course of problem solving can provide a more refined view on the processes involved, as a whole, and explain the existing controversies. We theorize that specific insight mechanisms require varying working memory capacities at different stages of the problem solving process. Our study employed a dual task paradigm to track the dynamics of working memory systems load during problem solving by measuring the reaction time in a secondary probe-task during different stages of problem solving. We varied the modality (verbal, visual) and the complexity of the probe-task during insight and non-insight problem solving. The results indicated that the dynamics of working memory load in insight problems differs from those in non-insight problems. Our first experiment shows that the complexity of the probe-task affects overall probe-task reaction times in both insight and non-insight problem solving. Our second experiment demonstrates that the solution of a non-insight problem is primarily associated with the working memory control system, while insight problems rely on relevant storage systems. Our results confirm that insight process requires access to various systems of working memory throughout the solution. We found that working memory load in non-insight problems increases from stage to stage due to allocation of the attentional control resources to interim calculations. The nature of the dynamics of working memory load in insight problems remains debatable. We claim that insight problem solving demands working memory storage during the entire problem solving process and that control system plays an important role just prior to the solution.

An object-based pointer system in visual working memory

An object-based pointer system in visual working memory

Do complex span and content-embedded working memory tasks predict unique variance in inductive reasoning?

Complex span and content-embedded tasks are two kinds of tasks that are designed to measure maintenance and processing in the working memory system. However, a key functional difference between these task types is that complex span tasks require the maintenance of information that is not relevant to the processing task, whereas content-embedded tasks require the maintenance of task-relevant information. The purpose of the present research was to test the hypothesis that more unique variance in inductive reasoning would be explained by content-embedded tasks than by complex span tasks, given that inductive reasoning requires reasoners to maintain and manipulate task-relevant information in order to arrive to a solution. A total of 384 participants completed three complex span tasks, three content-embedded tasks, and three inductive reasoning tasks. The primary structural equation model explained 51% of the variance in inductive reasoning; 45% of the variance in inductive reasoning was uniquely predicted by the content-embedded latent factor, 6% of the variance was predicted by shared variance between the content-embedded and complex span latent factors, and less than 1% was uniquely predicted by the complex span latent factor. These outcomes provide a novel extension to the small but growing literature showing an advantage of using content-embedded rather than complex span tasks for predicting higher-level cognition.

WOME: Theory-Based Working Memory Training - A Placebo-Controlled, Double-Blind Evaluation in Older Adults.

Background: Scientifically evaluated cognitive intervention programs are essential to meet the demands of our increasingly aging society. Currently, one of the “hottest” topics in the field is the improvement of working memory function and its potential impact on overall cognition. The present study evaluated the efficacy of WOME (WOrking MEmory), a theory-based working memory training program, in a double-blind, placebo-controlled, and randomized controlled trial (www.drks.de, DRKS00013162).Methods: N = 60 healthy older adults were allocated to (1) the WOME intervention, (2) an active low-level intervention, or (3) a passive control group. Overall, the intervention groups practiced twelve sessions of 45 min within 4 weeks of their respective training. Transfer effects were measured via an extensive battery of neuropsychological tests and questionnaires both pre-/post-training and at a 3-month follow-up.Results: WOME led to a significant improvement in working memory function, demonstrated on a non-trained near transfer task and on two different composite scores with moderate to large effect sizes. In addition, we found some indication of relevant impact on everyday life. The effects were short-term rather than stable, being substantially diminished at follow-up with only little evidence suggesting long-term maintenance. No transfer effects on other cognitive functions were observed.Conclusion: WOME is an appropriate and efficient intervention specifically targeting the working memory system in healthy older adults.Trial Registration: German Clinical Trials Register (DRKS), Identifier: DRKS00013162.

Does the structure of working memory in EL children vary across age and two language systems?

ABSTRACTThis study examined the cross-sectional structure of working memory (WM) among elementary school English learners (ELs). A battery of WM tasks was administered in Spanish (L1) and English (L2) within five age groups (ages 6, 7, 8, 9, & 10). Confirmatory factor analysis showed a three-factor structure of WM emerged in both L1 and L2 administrations for each age group. The important findings, however, were: (1) the separation between the executive component and storage component (phonological loop) structure of WM increased as a function of age within both language systems, (2) the structure of WM supported a domain general phonological storage component and a domain general executive system across both language systems, and (3) the visual-spatial WM system shared minimal variance with the executive system. Taken together, the findings support Baddeley’s multicomponent model (e.g., Baddeley & Logie, 1999. The multiple-component model. In A. Miyake & P. Shah (Eds.), Models of working memory: Mechanisms of active maintenance and executive control (pp. 28–61). Cambridge: Cambridge University Press) as a good fit to the structure of WM in EL children’s English and Spanish language system.

A Basal Ganglia Network Centric Reinforcement Learning Model and Its Application in Unmanned Aerial Vehicle

Reinforcement learning brings flexibility and generality for machine learning, while most of them are mathematical optimization driven approaches, and lack of cognitive and neural evidence. In order to provide a more cognitive and neural mechanisms driven foundation and validate its applicability in complex task, we develop a basal ganglia (BG) network centric reinforcement learning model. Compared to existing work on modeling BG, this paper is unique from the following perspectives: 1) the orbitofrontal cortex (OFC) is taken into consideration. OFC is critical in decision making because of its responsibility for reward representation and is critical in controlling the learning process, while most of the BG centric models do not include OFC; 2) to compensate the inaccurate memory of numeric values, precise encoding is proposed to enable working memory system remember important values during the learning process. The method combines vector convolution and the idea of storage by digit bit and is efficient for accurate value storage; and 3) for information coding, the Hodgkin-Huxley model is used to obtain a more biological plausible description of action potential with plenty of ionic activities. To validate the effectiveness of the proposed model, we apply the model to the unmanned aerial vehicle (UAV) autonomous learning process in a 3-D environment. Experimental results show that our model is able to give the UAV the ability of free exploration in the environment and has comparable learning speed as the Q learning algorithm, while the major advances for our model is that it is with solid cognitive and neural basis.