Increased Working Memory Capacity Research Articles

Interaction between BDNF Val66Met polymorphism and mismatch negativity for working memory capacity in schizophrenia

Both the brain-derived neurotrophic factor (BDNF) valine (Val)/methionine (Met) polymorphism and mismatch negativity (MMN) amplitude are reportedly linked to working memory impairments in schizophrenia. However, there is evident scarcity of research aimed at exploring the relationships among the three factors. In this secondary analysis of a randomized, controlled, double-blind trial, we investigated these relationships. The trial assessed the efficacy of transcranial direct current stimulation for enhancing working memory in clinically stable schizophrenia patients, who were randomly divided into three groups: dorsolateral prefrontal cortex stimulation, posterior parietal cortex stimulation, and sham stimulation groups. Transcranial direct current stimulation was administered concurrently with a working memory task over five days. We assessed the BDNF genotype, MMN amplitude, working memory capacity, and interference control subdomains. These assessments were conducted at baseline with 54 patients and followed up post-intervention with 48 patients. Compared to BDNF Met-carriers, Val homozygotes exhibited fewer positive and general symptoms and increased working memory capacity at baseline. A correlation between MMN amplitude and working memory capacity was noted only in BDNF Val homozygotes. The correlations were significantly different in the two BDNF genotype groups. Furthermore, in the intervention group that showed significant improvement in MMN amplitude, BDNF Val homozygotes exhibited greater enhancement in working memory capacity than Met-carriers. This study provides in vivo evidence for the interaction between MMN and BDNF Val/Met polymorphism for working memory capacity. As MMN has been considered a biomarker of N-methyl-D-aspartate receptor (NMDAR) function, these data shed light on the complex interactions between BDNF and NMDAR in terms of working memory in schizophrenia.

Working Memory Training in Norwegian Children with Cerebral Palsy (CP) Show Minimal Evidence of Near and No Far Transfer Effects

ABSTRACT In children with cerebral palsy (CP), learning disabilities are well documented, and impairments in executive functions, such as attention, inhibition, shifting and working memory, represent significant burdens on patients, their families and the society. The aim of this study was to evaluate whether Cogmed RM working memory training could improve working memory in children with CP and investigate whether increased working memory capacity would generalize to other cognitive functions. Twenty-eight children completed the training and the results were compared to a waitlist control group (n = 32). The results yielded three main findings. First, children with CP improved with practice on trained working memory tasks. Second, the intervention group showed minimal near transfer effects to non-trained working memory tasks. Third, no effects on cognitive and behavioral far transfer measures were found.

Adaptive working memory training does not produce transfer effects in cognition and neuroimaging

Despite growing interest in cognitive interventions from academia and industry, it remains unclear if working memory (WM) training, one of the most popular cognitive interventions, produces transfer effects. Transfer effects are training-induced gains in performance in untrained cognitive tasks, while practice effects are improvements in trained task. The goal of this study was to evaluate potential transfer effects by comprehensive cognitive testing and neuroimaging. In this prospective, randomized-controlled, and single-blind study, we administered an 8-week n-back training to 55 healthy middle-aged (50–64 years) participants. State-of-the-art multimodal neuroimaging was used to examine potential anatomic and functional changes. Relative to control subjects, who performed non-adaptive WM training, no near or far transfer effects were detected in experimental subjects, who performed adaptive WM training. Equivalently, no training-related changes were observed in white matter integrity, amplitude of low frequency fluctuations, glucose metabolism, functional and metabolic connectivity. Exploratory within-group comparisons revealed some gains in transfer tasks, which, however, cannot be attributed to an increased WM capacity. In conclusion, WM training produces transfer effects neither at the cognitive level nor in terms of neural structure or function. These results speak against a common view that training-related gains reflect an increase in underlying WM capacity. Instead, the presently observed practice effects may be a result of optimized task processing strategies, which do not necessarily engage neural plasticity.

80 Hz but not 40 Hz, transcranial alternating current stimulation of 80 Hz over right intraparietal sulcus increases visuospatial working memory capacity

Working memory (WM) is a complex cognitive function involved in the temporary storage and manipulation of information, which has been one of the target cognitive functions to be restored in neurorehabilitation. WM capacity is known to be proportional to the number of gamma cycles nested in a single theta cycle. Therefore, gamma-band transcranial alternating current stimulation (tACS) should be dependent of the stimulation frequency; however, the results of previous studies that employed 40 Hz tACS have not been consistent. The optimal locations and injection currents of multiple scalp electrodes were determined based on numerical simulations of electric field. Experiments were conducted with 20 healthy participants. The order of three stimulation conditions (40 Hz tACS, 80 Hz tACS, and sham stimulation) were randomized but counterbalanced. Visual hemifield-specific visual WM capacity was assessed using a delayed visual match to the sample task. High gamma tACS significantly increased WM capacity, while low gamma tACS had no significant effect. Notably, 80 Hz tACS increased WM capacity on both the left and right visual hemifields, while previous tACS studies only reported the effects of tACS on contralateral hemifields. This is the first study to investigate the frequency-dependent effect of gamma-band tACS on WM capacity. Our findings also suggest that high gamma tACS might influence not only WM capacity but also communication between interhemispheric cortical regions. It is expected that high gamma tACS could be a promising neurorehabilitation method to enhance higher-order cognitive functions with similar mechanisms.

Hospital-Based Modified Cogmed Working Memory Training for Youth With ADHD

Objective: This study evaluated a modified working memory training program, Cogmed, for ADHD youth. Method: Forty youth were randomized to modified Cogmed training (MCT) or treatment as usual (CON). MCT was delivered in an outpatient mental health clinic in 3 weekly 35-minute sessions with a dedicated coach for 10 weeks. Participants completed assessments at baseline, after the intervention, and again 3 months later. Results: After controlling for baseline, groups were comparable on working memory, academics, and ADHD symptoms. The MCT group was rated by parents and teachers as having fewer executive function challenges and youth endorsed better self-concept compared with the CON group. Conclusions: MCT was associated with some improvement, which could not be attributed to increased working memory capacity and may reflect other facets of the program. Results question the usefulness of Cogmed but highlight considerations for optimizing adherence, engagement, and the therapeutic alliance in interventions for ADHD youth.

Effect of one-session focused attention meditation on the working memory capacity of meditation novices: A functional near-infrared spectroscopy study.

IntroductionPrevious studies have revealed that one‐session focused attention meditation (FAM) can improve top‐down attention control, which is one of the factors of working memory capacity (WMC). In addition, FAM shares various neural substrates, including the dorsolateral prefrontal cortex (DLPFC), with WMC. Thus, we hypothesized that one‐session FAM would improve WMC by activating the DLPFC evoked by the top‐down attention control. In this study, we examined whether FAM modified WMC in individuals with little to no meditation experience.MethodsThe participants were randomly assigned to either the FAM group (N = 13) or the control group (N = 17) who engaged in random thinking (i.e., mind‐wandering). Before and after each 15‐min intervention, the participants’ WMC was measured according to the total number of correct answers in the Reading Span Test. During each intervention, functional near‐infrared spectroscopy was employed to measure the blood flow in the participants’ DLPFC and determine the top‐down attention control effect.ResultsIn the FAM group, WMC increased, and the bilateral DLPFC was activated during the intervention. As for the control group, WMC decreased after the intervention, and the bilateral DLPFC was not activated during the intervention. A correlation was also found among all participants between the increase in WMC and the activation of the bilateral DLPFC.ConclusionThe study findings suggest that top‐down attention control during FAM can activate the bilateral DLPFC and increase WMC among meditation novices.

Investigation of a Model-Based Working Memory Training With and Without Distractor Inhibition and Its Comparative Efficacy: A Randomized Controlled Trial on Healthy Old Adults.

Background: Various working memory (WM) trainings have been tested, but differences in experimental designs, the lack of theoretical background, and the need of identifying task-related processes such as filtering efficiency limit conclusions about their comparative efficacy.Objectives: In this study, we compared the efficacy of a model-based WM training with (MB+) and without (MB) distractor inhibition on improving WM capacity to a dual n-back and active control condition.Methods: This randomized clinical trial included 123 healthy elderly adults (78 women, 45 men; aged 64.1 ± 8.3 years). All groups underwent 12 40-min training sessions over 3 weeks and four cognitive testing sessions. The first two sessions served as double baseline to account for practice effects. Primary outcome was WM capacity post-training measured by complex span tasks. Near and far transfer was assessed by simple span, n-back, visuospatial and verbal learning, processing speed, and reasoning tasks.Results: Due to preliminary termination (COVID-19), 93 subjects completed the post-training and 60 subjects the follow-up session. On a whole group level, practice effects occurred from prebaseline to baseline in WM capacity (b = 4.85, t(103) = 4.01, p < 0.001, r = 0.37). Linear mixed-effects models revealed a difference in WM capacity post-training between MB+ and MB (b = −9.62, t(82) = −2.52, p = 0.014, r = 0.27) and a trend difference between MB+ and dual n-back (b = −7.59, t(82) = −1.87, p = 0.065, r = 0.20) and control training (b = −7.08, t(82) = −1.86, p = 0.067, r = 0.20). Univariate analyses showed an increase between pre- and post-training for WM capacity within MB+ (t(22) = −3.34, p < 0.05) only. There was no difference between groups pre- and post-training regarding near and far transfer. Univariate analyses showed improved visuospatial learning within MB+ (t(21) = −3.8, p < 0.05), improved processing speed (t(23) = 2.19, p< 0.05) and n-back performance (t(23) = 2.12, p < 0.05) in MB, and improved n-back performance (t(25) = 3.83, p < 0.001) in the dual n-back training.Interpretation: A model-based WM training including filtering efficacy may be a promising approach to increase WM capacity and needs further investigation in randomized controlled studies.

Affective Modulation of Working Memory Maintenance: The Role of Positive and Negative Emotions.

The present study investigated the impact of task-irrelevant emotional images on the retention of information in spatial working memory (WM). Two experiments employed a delayed matching to-sample task where participants had to maintain the locations of four briefly presented squares. After a short retention interval, a probe item appeared and participants were required to indicate whether the probe position matched one of the previously occupied square positions. During the retention interval, task-irrelevant negative, positive, or neutral emotional pictures were presented. The results revealed a dissociation between negative and positive affect on the participants' ability to hold spatial locations in WM. While negative affective pictures reduced WM capacity, positive pictures increased WM capacity relative to the neutral images. Moreover, the specific valence and arousal of a given emotional picture was also related to WM performance: While higher valence enhanced WM capacity, higher levels of arousal in turn reduced WM capacity. Together, our findings suggest that emotions up- or down-regulate attention to items in WM and thus modulate the short term storage of visual information in memory.

Training-induced improvement in working memory tasks results from switching to efficient strategies

It is debated whether training with a working memory (WM) task, particularly n-back, can improve general WM and reasoning skills. Most training studies found substantial improvement in the trained task, with little to no transfer to untrained tasks. We hypothesized that training does not increase WM capacity, but instead provides opportunities to develop an efficient task-specific strategy. We derived a strategy for the task that optimizes WM resources and taught it to participants. In two sessions, 14 participants who were taught this strategy performed as well as fourteen participants who trained for 40 sessions without strategy instructions. To understand the mechanisms underlying the no-instruction group’s improvement, participants answered questionnaires during their training period. Their replies indicate that successful learners discovered the same strategy and their improvement was associated with this discovery. We conclude that n-back training allows the discovery of strategies that enable better performance with the same WM resources.

Slow Theta tACS of the Right Parietal Cortex Enhances Contralateral Visual Working Memory Capacity.

Recent research suggests alteration of visual working memory capacity by modulation of parietal theta frequency via transcranial alternating current stimulation (tACS). However, it remains to be clarified whether this effect is partly driven by co-stimulation of prefrontal cortex and subcortical structures. It was hypothesized that focal tACS over the parietal lobe without additional prefrontal or subcortical stimulation should lead to similar effects as reported in the literature. Healthy, young participants were tested on a visual working memory paradigm while receiving either focal parietal tACS at 4Hz, at 7Hz or sham stimulation. Focal right posterior 4Hz tACS led to increased working memory capacity strictly for the visual hemifield contralateral to stimulation. Exclusive stimulation of posterior cortex by 4Hz tACS replicates effects recently reported in literature, confirming that stimulation of the prefrontal cortex or subcortical structures are not a primary driver of these observations.

Searching for answers in an uncertain world: Meaning threats lead to increased working memory capacity.

The Meaning Maintenance Model posits that individuals seek to resolve uncertainty by searching for patterns in the environment, yet little is known about how this is accomplished. Four studies investigated whether uncertainty has an effect on people’s cognitive functioning. In particular, we investigated whether meaning threats lead to increased working memory capacity. In each study, we exposed participants to either an uncertain stimulus used to threaten meaning in past studies, or a control stimulus. Participants then completed a working memory measure, where they either had to recall lists of words (Studies 1, 2), or strings of digits (Studies 3, 4). We used both a frequentist approach and Bayesian analysis to evaluate our findings. Across the four studies, we find a small but consistent effect, where participants in the meaning threat condition show improved performance on the working memory tasks. Overall, our findings were consistent with the hypothesis that working memory capacity increases when people experience a meaning threat, which may help to explain improved pattern recognition. Additionally, our results highlight the value of using a Bayesian analytic approach, particularly when studying phenomena with high variance.

Attachment anxiety benefits from security priming: Evidence from working memory performance.

The present study investigates the relationship between the attachment dimensions (anxious vs. avoidance) and the cognitive performance of individuals, specifically whether the attachment dimensions would predict the working memory (WM) performance. In the n-back task, reflecting the WM capacity, both attachment related and non-attachment related words were used. Participants were randomly assigned into two groups that received either the secure or the neutral subliminal priming. In the secure priming condition, the aim was to induce sense of security by presenting secure attachment words prior to the n-back task performance. In neutral priming condition, neutral words that did not elicit sense of security were presented. Structural equation modeling revealed divergent patterns for attachment anxiety and avoidance dimensions under the different priming conditions. In neutral priming condition, WM performance declined in terms of capacity in the n-back task for individuals who rated higher levels of attachment anxiety. However in the secure priming condition, WM performance was boosted in the n-back task for individuals who rated higher levels of attachment anxiety. In other words, the subliminal priming of the security led to increased WM capacity of individuals who rated higher levels of attachment anxiety. This effect, however, was not observed for higher levels of attachment avoidance. Results are discussed along the lines of hyperactivation and deactivation strategies of the attachment system.

ERP and Behavioral Effects of Physical and Cognitive Training on Working Memory in Aging: A Randomized Controlled Study.

Working memory (WM) performance decreases with age. A promising method to improve WM is physical or cognitive training. The present randomized controlled study is aimed at evaluating the effects of different training methods on WM. A sample of 141 healthy older adults (mean age 70 years) was assigned to one of four groups: physical training, cognitive training, a social control group, and a no-contact control group. The participants trained for four months. Before and after the training, n-back task during an EEG recording was applied. The results show that cognitive training enhanced the target detection rate in the 2-back task. This was corroborated by an increased number of repeated digits in the backward digit-span test but not in other memory tests. The improvement of WM was supported by an increased P3a prior to a correct target and an increased P3b both in nontarget and target trials. No ERP effects in the physical and no-contact control groups were found, while a reduction of P3a and P3b was found in the social control group. Thus, cognitive training enhances frontal and parietal processing related to the maintenance of a stored stimulus for subsequent matching with an upcoming stimulus and increases allocation of cognitive resources. These results indicate that multidomain cognitive training may increase WM capacity and neuronal activity in older age.

L’entraînement de la mémoire de travail est-il bénéfique pour les enfants présentant un trouble déficit de l’attention/hyperactivité ?

IntroductionChildhood attention-deficit/hyperactivity disorder is known to be associated with impairment across multiple domains, including social, familial, emotional and academic functioning. Available therapies, and in particular medical treatment, fail to produce lasting improvement in academic and learning outcomes. In this context, recent years have seen a growing interest of experts and practitioners for computer-based cognitive training programs. Indeed, it has been proposed that repeated training of specific executive functions may result in lasting benefits for children with ADHD, especially in the school setting. Cogmed RoboMemo, a program targeting working memory, is the cognitive training that has been the most extensively studied. Literature findingsMeta-analyses have established that the vast majority of children with ADHD present with decreased performance levels compared to typically developing children when performing working memory tasks. Working memory deficits, in turn, have been linked with classroom inattention and decreased academic performance. Based on these findings, models describing working memory deficits as a core feature of ADHD, accounting both for inattentive and hyperactive symptoms, have been proposed. In this theoretical context, interventions specifically targeting working memory deficits in ADHD appear as particularly promising. However, despite this solid theoretical background, meta-analyses of randomized controlled trials relying on the Cogmed RoboMemo program have consistently failed to evidence significant therapeutic effects on key targets, including ADHD symptoms or academic performance. These results suggest that early reports of clinical efficacy with non-blinded assessors were confounded by placebo and expectancy effects. DiscussionDifferent hypotheses have been proposed to explain this lack of significant therapeutic effect. First, it has been observed that Cogmed RoboMemo primarily targets the storage/rehearsal capacity of the child, whereas children with ADHD appear mostly impaired when performing tasks with a strong central executive load (i. e. requiring manipulation and dynamic updating of information). The Cogmed cognitive training program may therefore simply focus on the wrong element of working memory in the context of ADHD. Second, authors have questioned whether RoboMemo practice truly results in increased working memory capacity, proposing that children may simply learn task-specific strategies that they are unable to use in a broader context. In line with this idea, it has also been suggested that training in a non-ecological situation could be insufficient, if children with ADHD do not also learn strategies to apply the capacity acquired in the class context. Finally, one recent randomized control trial suggests that potential methodological limitations (lack of follow-up and/or limited training intensity) may have prevented previous studies from documenting the beneficial effects of the Cogmed program. ConclusionsMeta-analyses available to date indicate that claims regarding the academic, behavioral, and learning benefits associated with Cogmed RoboMemo are unsupported in ADHD. New studies with a follow-up assessment are needed to ensure that beneficial long-term effects of the program have not been overlooked. The development and evaluation of new cognitive training programs targeting the central executive component of working memory is warranted. More research is also necessary to help understand how working memory capacity of children with ADHD could be in improved in an ecological context.

Making working memory work: The effects of extended practice on focus capacity and the processes of updating, forward access, and random access

We investigated the effects of 10h of practice on variations of the N-Back task to investigate the processes underlying possible expansion of the focus of attention within working memory. Using subtractive logic, we showed that random access (i.e., Sternberg-like search) yielded a modest effect (a 50% increase in speed) whereas the processes of forward access (i.e., retrieval in order, as in a standard N-Back task) and updating (i.e., changing the contents of working memory) were executed about 5 times faster after extended practice. We additionally found that extended practice increased working memory capacity as measured by the size of the focus of attention for the forward-access task, but not for variations where probing was in random order. This suggests that working memory capacity may depend on the type of search process engaged, and that certain working-memory-related cognitive processes are more amenable to practice than others.

Working Memory Training May Increase Working Memory Capacity but Not Fluid Intelligence

Working memory is a critical element of complex cognition, particularly under conditions of distraction and interference. Measures of working memory capacity correlate positively with many measures of real-world cognition, including fluid intelligence. There have been numerous attempts to use training procedures to increase working memory capacity and thereby performance on the real-world tasks that rely on working memory capacity. In the study reported here, we demonstrated that training on complex working memory span tasks leads to improvement on similar tasks with different materials but that such training does not generalize to measures of fluid intelligence.

Effect of Relaxation Training on Working Memory Capacity and Academic Achievement in Adolescents

In an experimental study 40 girl students of 7th grade were selected using random cluster sampling from one middle school in Tehran and divided into test and control groups by random assignment. Initially they were assessed by working memory capacity test (Daneman & Carpenter, 1980). Then, the test group through 12 educational sessions (one hour sessions, 3 sessions per week) was taught relaxation techniques, and it is noteworthy that no education was given to a control group. Upon completion of educational sessions, both test and control groups were assessed again with the working memory capacity test. In the case of the academic achievement, the Grade Point Average (GPA) of the first semester for pre-test and the GPA of the second semester for post-test were used. Multivariate analysis of covariance showed that relaxation training increase working memory capacity and its components, storage and processing, and academic achievement. Therefore, relaxation training is a useful technique for student progress.

Enhancing dual-task performance with verbal and spatial working memory training: Continuous monitoring of cerebral hemodynamics with NIRS

To better understand the mechanisms by which working memory training can augment human performance we continuously monitored trainees with near infrared spectroscopy (NIRS) while they performed a dual verbal–spatial working memory task. Linear mixed effects models were used to model the changes in cerebral hemodynamic response as a result of time spent training working memory. Nonlinear increases in left dorsolateral prefrontal cortex (DLPFC) and right ventrolateral prefrontal cortex (VLPFC) were observed with increased exposure to working memory training. Adaptive and yoked training groups also showed differential effects in rostral prefrontal cortex with increased exposure to working memory training. There was also a significant negative relationship between verbal working memory performance and bilateral VLPFC activation. These results are interpreted in terms of decreased proactive interference, increased neural efficiency, reduced mental workload for stimulus processing, and increased working memory capacity with training.

The neuropsychological profile of children at high risk of developing an eating disorder

There is a large body of evidence indicating that eating disorders (EDs) are characterized by particular neuropsychological profiles. We aimed to further explore whether impairments in neuropsychological functioning previously found in ED groups are present prior to onset, or are secondary to the disorder. Method This is the first study to explore neuropsychological functioning in children born to a mother with a lifetime ED, who are therefore at high risk of developing an ED, in a large cohort sample. We investigated intelligence and attention at age 8 years (n=6201) and working memory (WM) and inhibition at age 10 years (6192) in children who are at high risk of developing an ED, compared to children who are not. The children of women with lifetime anorexia nervosa (AN) showed high full-scale and performance IQ, increased WM capacity, better visuo-spatial functioning, and decreased attentional control. The children of women with lifetime bulimia nervosa (BN) showed comparatively poor visuo-spatial functioning. Our findings suggest that high intelligence, increased WM capacity and impaired attentional control might be intermediate phenotypes on the pathway between genetic vulnerability and the development of an ED.

Individual differences in working memory capacity predict action monitoring and the error-related negativity.

Neuroscience suggests that the anterior cingulate cortex (ACC) is responsible for conflict monitoring and the detection of errors in cognitive tasks, thereby contributing to the implementation of attentional control. Though individual differences in frontally mediated goal maintenance have clearly been shown to influence outward behavior in interference-rich contexts, it is unclear whether corresponding differences exist in neural responses that arise out of the ACC. To investigate this possibility, we conducted an electrophysiological study using a variant of the Simon Task, recording event-related potentials (ERPs) in healthy normal individuals with varying working memory capacity (high vs. low spans; a behavioral proxy for variability in goal maintenance). Primary analyses focused on the magnitude of the error-related negativity (ERN), a response-locked ERP component associated with the commission of errors thought to arise because of action monitoring in the ACC. Our results revealed that frontally mediated working memory capacity may alter error monitoring by the ACC, with high spans showing a greater ERN than low spans. These individual differences were also observed in the posterror positivity, a response-locked ERP component associated with updating cognitive strategies, suggesting greater awareness of errors with increased working memory capacity. These results are interpreted within 2-process models of attentional control, suggesting individuals with greater working memory capacity may better maintain task goals by more strongly biasing neural activity in frontal-executive networks.