Working memory training revisited: A multi-level meta-analysis of n-back training studies

Working memory training impacts neural activity during untrained cognitive tasks in people with multiple sclerosis

The identification of effective cognitive rehabilitation strategies for people with multiple sclerosis (MS) is critically important, as cognitive difficulties are prevalent in MS. Relatively few cognitive rehabilitation studies in MS have examined working memory (WM) training specifically, and the extent that WM training may impact neural activity on untrained tasks is not well understood. In the present study, we examined the effects of 20 sessions of adaptive WM training (using an n-back task with visually presented letter stimuli) on neural indices of the transfer of training gains to untrained tasks in MS and healthy control participants. Event-Related Potential (ERP) measures were obtained before (pretest) and after training (posttest) on untrained visual tasks of spatial WM (Spatial 3-back task), cognitive control (Go/Nogo Flanker task), and processing speed and selective attention (Search task). At posttest compared to pretest, MS and control groups exhibited enhancement of N1 amplitude for the Spatial 3-back; attenuation of P2 amplitude, and enhancement of N2 amplitude for the Go/NoGo Flanker task; and enhancement of P2 and N2 amplitude for the Search task. These findings suggest that MS participants had enhancement of attention and cognitive control on untrained tasks following WM training that was similar to the effects that were observed in controls. In contrast, only the control group exhibited pretest-to-posttest enhancement of a late positive potential on the Spatial 3-back, as well as enhancement of P3 amplitude across all of the untrained outcome tasks. These latter findings suggest that there may be potential limitations in the neural plasticity induced by WM training in MS. Overall, the present study identified neural indices of the transfer of WM training gains that were responsive in MS and potentially resilient to disease processes, as well as those that were not.

Disentangling the Role of Working Memory in Parkinson's Disease

Working memory (WM) represents a core cognitive function with a major striatal contribution, and thus WM deficits, commonly observed in Parkinson’s disease (PD), could also relate to many other problems in PD patients. Our online study aimed to determine the subdomains of WM that are particularly affected in PD and to clarify the links between WM and everyday cognitive deficits, other executive functions, psychiatric and PD symptoms, as well as early cognitive impairment. Fifty-two mild-to-moderate PD patients and 54 healthy controls performed seven WM tasks tapping selective updating, continuous monitoring, or maintenance of currently active information. Self-ratings of everyday cognition, depression, and apathy symptoms, as well as screenings of global cognitive impairment, were also collected. The data were analyzed using structural equation modeling. Of the three WM domains, only selective updating was directly predictive of PD group membership. More widespread WM deficits were observed only in relation to global cognitive impairment in PD patients. Self-rated everyday cognition or psychiatric symptoms were not linked to WM performance but correlated with each other. Our findings suggest that WM has a rather limited role in the clinical manifestation of PD. Nevertheless, due to its elementary link to striatal function, the updating component of WM could be a candidate for a cognitive marker of PD also in patients who are otherwise cognitively well-preserved.

Individual Baseline Performance and Electrode Montage Impact on the Effects of Anodal tDCS Over the Left Dorsolateral Prefrontal Cortex

Anodal transcranial direct current stimulation (tDCS), applied over the left dorsolateral prefrontal cortex (lDLPFC), can produce significant effects on working memory (WM) performance and associated neurophysiological activity. However, results from previous studies are inconsistent and occasionally contradictory. This inconsistency may be attributed to methodological and individual differences during experiments. This study therefore investigated two hypotheses: (1) A multichannel-optimized montage was expected to be more effective than a classical bipolar montage, because of increased focality. (2) The subjects were expected to benefit differently from the stimulation depending on their initial task performance. In a sham-controlled crossover study, 24 healthy participants received bipolar, multichannel, and sham stimulation for 20 min in randomized order, targeting the lDLPFC while performing a 2-back WM task. After stimulation, electroencephalography (EEG) was recorded at rest and during 2-back and nontarget continuous performance task (CPT) performance. Bipolar and multichannel stimulations were both well tolerated and effectively blinded. We found no effect of stimulation on behavioral performance or neuronal oscillations comparing the classical bipolar or multichannel montage with sham stimulation. We did, however, find an interaction between stimulation and initial task performance. For multichannel stimulation, initially low-performing participants tended to improve their WM performance while initially high-performing participants tended to worsen their performance compared to sham stimulation. Both tDCS montages induced changes in neural oscillatory power, which correlated with baseline performance. The worse the participants’ initial WM performance was, the more task-related theta power was induced by multichannel and bipolar stimulation. The same effect was observed for alpha power in the nontarget task following multichannel stimulation. Notably, we were not able to show a superiority of multichannel stimulation compared to bipolar stimulation. Still, comparing both montages with sham stimulation, multichannel stimulation led to stronger effects than bipolar stimulation. The current study highlights the importance of investigating different parameters with potential influence on tDCS effects in combination. Our results demonstrate how individual differences in cognitive performance and electrode montages influence effects of tDCS on neuropsychological performance. These findings support the idea of an individualized and optimized stimulation setting, potentially leading to increased tDCS effects.

The effect of n-back training during hemodialysis on cognitive function in hemodialysis patients: a non-blind clinical trial

Background

Traditional vascular risk factors such as hypertension, diabetes mellitus, hyperlipidemia, cigarette smoking, and cardiovascular disease with myocardial infarction and atrial fibrillation have been linked to cognitive impairment in patients with chronic kidney disease. Therefore, interventions for cognitive function that can be performed during hemodialysis are needed. In this regard, n-back training has been demonstrated to be effective in patients with cognitive impairment.

Methods

In this pre-post study, 12 patients underwent n-back training during hemodialysis. The patients, aged 52–80 years, had mild cognitive impairment and were tested before and after a 3-month training period. This study was carried out in a single dialysis center. The Mini-Mental State Examination, Montreal Cognitive Assessment-Japanese version, Benton Visual Retention Test, Trail Making Test, visual cancelation task, Symbol Digit Modality Test, and Paced Auditory Serial Addition Task were used as outcome measures.

Results

All patients completed the 3-month training program. Improvements were seen in scores for the Mini-Mental State Examination (P = 0.01), Montreal Cognitive Assessment-Japanese version (P = 0.01), Benton Visual Retention Test (P = 0.02), Trail Making Test-B (P = 0.01), and Paced Auditory Serial Addition Task 1 s (P = 0.01) and 2 s (P = 0.01) from baseline to 3 months.

Conclusions

Cognitive training during hemodialysis improved cognitive and attention function in patients with mild cognitive impairment. This suggests that the simultaneous provision of n-back training and hemodialysis can be effective for treating chronic kidney disease with cognitive impairment.

Trial registration

UMIN Clinical Trials Registry (UMIN000033742); retrospectively registered on August 13, 2018.

Strategy mediation in working memory training in younger and older adults

Working memory (WM) training with the N-Back task has been argued to improve cognitive capacity and general cognitive abilities (the Capacity Hypothesis of training), although several studies have shown little or no evidence for such improvements beyond tasks that are very similar to the trained task. Laine et al. demonstrated that instructing young adult participants to use a specific visualisation strategy for N-back training resulted in clear, generalised benefits from only 30 min of training (Strategy Mediation Hypothesis of training). Here, we report a systematic replication and extension of the Laine et al. study, by administering 60 younger and 60 older participants a set of WM tasks before and after a 30-min N-back training session. Half the participants were instructed to use a visualisation strategy, the others received no instruction. The pre-post test battery encompassed a criterion task (digit N-back), two untrained tasks N-back tasks (letters and colours), and three structurally different WM tasks. The instructed visualisation strategy significantly boosted at least some measures of N-back performance in participants of both age groups, although the strategy generally appeared more difficult to implement and less beneficial for older adults. However, the strategy did not improve performance on structurally different WM tasks. We also found significant associations between N-back performance and the type and level of detail of self-generated strategies in the uninstructed participants, as well as age group differences in reported strategy types. WM performance appeared to partly reflect the application of strategies, and Strategy Mediation should be considered to understand the mechanisms of WM training. Claims of efficient training should demonstrate useful improvement beyond task-specific strategies.

Application of Machine Learning Models for Tracking Participant Skills in Cognitive Training

A key need in cognitive training interventions is to personalize task difficulty to each user and to adapt this difficulty to continually apply appropriate challenges as users improve their skill to perform the tasks. Here we examine how Bayesian filtering approaches, such as hidden Markov models and Kalman filters, and deep-learning approaches, such as the long short-term memory (LSTM) model, may be useful methods to estimate user skill level and predict appropriate task challenges. A possible advantage of these models over commonly used adaptive methods, such as staircases or blockwise adjustment methods that are based only upon recent performance, is that Bayesian filtering and deep learning approaches can model the trajectory of user performance across multiple sessions and incorporate data from multiple users to optimize local estimates. As a proof of concept, we fit data from two large cohorts of undergraduate students performing WM training using an N-back task. Results show that all three models predict appropriate challenges for different users. However, the hidden Markov models were most accurate in predicting participants' performances as a function of provided challenges, and thus, they placed participants at appropriate future challenges. These data provide good support for the potential of machine learning approaches as appropriate methods to personalize task performance to users in tasks that require adaptively determined challenges.

Changes in Error Patterns during N-back Training Indicate Reliance on Subvocal Rehearsal

Contemporary cognitive training literature suggests that training on an adaptive task produces improvements only in the trained task or near transfer effects. No study has yet systematically explained the mechanism behind improved performance on the N-back. In this study, we first investigated how improvements in an N-back task using eight pairs of phonologically similar words as stimuli occurred by examining error distributions of the task over training sessions. Nineteen participants (non-native English speakers) trained for 20 sessions over 5 weeks. We observed a reduction in false alarms to non-target words and fewer missed target words. Though the absolute number of phonological-based errors reduced as training progressed, the proportion of this error type did not decrease over time suggesting participants increasingly relied on subvocal rehearsal in completing the N-back. In the second experiment, we evaluated if improvements developed during N-back training transferred to tasks that relied on serial order memory using simple span tasks (letter span with phonologically distinct letters, letter span with phonologically similar letters, digit span forward, and digit span backward). Twenty-nine participants trained on the N-back and 16 trained on the Operation Span (OSPAN) for 15 sessions over 4 weeks. Neither group of participants showed improvements on any of the simple span tasks. In the third experiment, 20 participants (16 native English speakers) trained on the N-back for 15 sessions over 4 weeks also showed increasing reliance on subvocal rehearsal as they progressed through training. Self-report strategy use did not predict improvements on the N-back.

Does Blindness Boost Working Memory? A Natural Experiment and Cross-Cultural Study

Intelligence requires sufficient working-memory capacity. Traditionally, working memory was seen as a process and as a prerequisite for fluid intelligence. Working memory was assumed to be determined by maturation and health. There is a gap in the literature: It is still not fully understood to which extent and how working memory can be influenced. So this study tested how visual impairment and the extent of visual impairment are related to working memory capacity. In our study we compared N = 249 children (6–16 years) with and without visual impairment (blind, visually impaired, and sighted) in two countries (South Africa and Austria) at different development levels on their working-memory capacity and verbal comprehension. Using the WISC-IV, blind and visually impaired children showed higher working-memory capacity than sighted children (r = + 0.35, 14, and 3 IQ points, respectively). On the other hand, visually impaired children showed a weakness in verbal comprehension (r = −0.39, on average 13 IQ points lower). The pattern remained robust when SES and race-ethnicity were controlled. Our natural (quasi-)experiment shows a pattern, which is unlikely to be genetic, and so supports the view that working memory and intelligence scores can be modified.

Autonomic/central coupling benefits working memory in healthy young adults

Working memory (WM) is an executive function that can improve with training. However, the precise mechanism for this improvement is not known. Studies have shown greater WM gains after a period of sleep than a similar period of wake, and correlations between WM improvement and slow wave activity (SWA; 0.5-1 Hz) during slow wave sleep (SWS). A different body of literature has suggested an important role for autonomic activity during wake for WM. A recent study from our group reported that the temporal coupling of Autonomic/CentralEvents (ACEs) during sleep was associated with memory consolidation. We found that heart rate bursts (HR bursts) during non-rapid eye movement (NREM) sleep are accompanied by increases in SWA and sigma (12-15 Hz) power, as well as increases in the high-frequency (HF) component of the RR interval, reflecting vagal rebound. In addition, ACEs predict long-term, episodic memory improvement. Building on these previous results, we examined whether ACEs also contribute to gains in WM. We tested 104 young adults in an operation span task (OSPAN) in the morning and evening, with either a nap (n = 53; with electroencephalography (EEG) and electrocardiography (ECG)) or wake (n = 51) between testing sessions. We identified HR bursts in the ECG and replicated the increases in SWA and sigma prior to peak of the HR burst, as well as vagal rebound after the peak. Furthermore, we showed sleep-dependent WM improvement, which was predicted by ACE activity. Using regression analyses, we discovered that significantly more variance in WM improvement could be explained with ACE variables than with overall sleep activity not time-locked with ECG. These results provide the first evidence that coordinated autonomic and central events play a significant role in sleep-related WM improvement and implicate the potential of autonomic interventions during sleep for cognitive enhancement.

Enhancing task-demands disrupts learning but enhances transfer gains in short-term task-switching training

Content variability was previously suggested to promote stronger learning effects in cognitive training whereas less variability incurred transfer costs (Sabah et al. Psychological Research, 10.1007/s00426-018-1006-7, 2018). Here, we expanded these findings by additionally examining the role of learners’ control in short-term task-switching training by comparing voluntary task-switching to a yoked control forced task-switching condition. To this end, four training conditions were compared: (1) forced fixed content, (2) voluntary fixed content, (3) forced varied content, and (3) voluntary varied content. To further enhance task demands, bivalent stimuli were used during training. Participants completed baseline assessment commencing with task-switching and verbal fluency blocks, followed by seven training blocks and last by task-switching (near transfer) and verbal fluency (far transfer) blocks, respectively. For the baseline and transfer task-switching blocks, we used the exact same baseline and first transfer block from Sabah et al. (Psychological Research, 10.1007/s00426-018-1006-7, 2018), employing univalent stimuli and alternating-runs task sequence. Our results pointed again to the contribution of content variability to task-switching performance. No indications for far transfer were observed. Allowing for learners’ control was not found to produce additional transfer gains beyond content variability. A between-study comparison suggests that enhanced task demands, by means of bivalency, promoted higher transfer gains in the current study when compared to Sabah et al. (Psychological Research, 10.1007/s00426-018-1006-7, 2018). Taken together, the current results provide further evidence to the beneficial impact of variability on training outcomes. The lack of modulatory effect for learners’ control is discussed in relation to possible methodological limitations.

The effects of transcranial direct current stimulation on within- and cross-paradigm transfer following multi-session backward recall training

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Randomised controlled trial combining backward recall memory training and tDCS.

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Systematic investigation into task features constraining training transfer.

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Measurement of potential benefits of tDCS for training and for transfer across tasks with varying degrees of overlap with training task.

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Training transfer is constrained by paradigm but not task materials.

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tDCS over left DLPFC (1 mA, 10 min) does not enhance training or transfer.

Transcranial direct current stimulation (tDCS) has been shown to enhance the efficacy and generalisation of working memory (WM) training, but there has been little systematic investigation into how coupling task-specific WM training with stimulation impacts more specifically on transfer to untrained tasks. This randomised controlled trial investigated the boundary conditions to transfer by testing firstly whether the benefits of training on backward digit recall (BDR) extend to untrained backward recall tasks and n-back tasks with different materials, and secondly which, if any, form of transfer is enhanced by tDCS. Forty-eight participants were allocated to one of three conditions: BDR training with anodal (10 min, 1 mA) or sham tDCS, or visual search training with sham tDCS, applied over the left dorsolateral prefrontal cortex. Transfer was assessed on within- (backward recall with digits, letters, and spatial locations) and cross-paradigm (n-back with digits and letters) transfer tests following three sessions of training and stimulation. On-task training gains were found, with transfer to other backward span but not n-back tasks. There was little evidence that tDCS enhanced on-task training or transfer. These findings indicate that training enhances paradigm-specific processes within WM, but that tDCS does not enhance these gains.

Post-training Load-Related Changes of Auditory Working Memory - An EEG Study

Working memory (WM) refers to the temporary retention and manipulation of information, and its capacity is highly susceptible to training. Yet, the neural mechanisms that allow for increased performance under demanding conditions are not fully understood. We expected that post-training efficiency in WM performance modulates neural processing during high load tasks. We tested this hypothesis, using electroencephalography (EEG) (N = 39), by comparing source space spectral power of healthy adults performing low and high load auditory WM tasks. Prior to the assessment, participants either underwent a modality-specific auditory WM training, or a modality-irrelevant tactile WM training, or were not trained (active control). After a modality-specific training participants showed higher behavioral performance, compared to the control. EEG data analysis revealed general effects of WM load, across all training groups, in the theta-, alpha-, and beta-frequency bands. With increased load theta-band power increased over frontal, and decreased over parietal areas. Centro-parietal alpha-band power and central beta-band power decreased with load. Interestingly, in the high load condition a tendency toward reduced beta-band power in the right medial temporal lobe was observed in the modality-specific WM training group compared to the modality-irrelevant and active control groups. Our finding that WM processing during the high load condition changed after modality-specific WM training, showing reduced beta-band activity in voice-selective regions, possibly indicates a more efficient maintenance of task-relevant stimuli. The general load effects suggest that WM performance at high load demands involves complementary mechanisms, combining a strengthening of task-relevant and a suppression of task-irrelevant processing.

N-Back Task Training Helps to Improve Post-error Performance

Improved performance on working memory (WM) through training has been widely expected to transfer to other domains. Recent studies have proposed that WM training could enhance the autonomous coordination of WM processes. Based on the shared processes between WM and error processing, our present study explored the transfer effect of 15 days of training on post-error performance, during the n-back task, compared to a simple visual search task. Participants were randomly assigned to either the training (N = 22) or control (N = 18) group. We found that WM training successfully improved WM performance. After training, compared with the control group, the training group showed a significant reduction in post-error slowing (PES); however, post-error accuracy and the flanker effect were not modulated by WM training. Moreover, we observed a significant, negative correlation between the changes in PES and WM from pretest to posttest and classified two groups based on these changes in PES with 70% accuracy. Thus, in our present sample, WM training improved post-error performance. We propose that the skill of controlling information flow, developed during WM training, is transferable to other tasks and discuss the implications of current findings for understanding the generation of PES.

Locating neural transfer effects of n-back training on the central executive: a longitudinal fMRI study

The large number of behavioral studies testing whether working memory training improves performance on an untrained task have yielded inconclusive results. Moreover, some studies have investigated the possible neural changes during the performance of untrained tasks after training. Here, we studied the transfer from n-back training to the Paced Auditory Serial Addition Test (PASAT), two different tasks that use the central executive system to maintain verbal stimuli. Participants completed fMRI sessions at baseline, immediately after one week of training, and at the five-week follow-up. Although behavioral transfer effects were not obtained, training was associated with decreased activation in the anterior dorsolateral prefrontal cortex (DLPFC; BA 9/46) while performing the PASAT that remained stable five weeks later. Consistent with our hypothesis, the changes in the anterior DLFPC largely overlapped with the n-back task fMRI activations. In conclusion, working memory training improves efficiency in brain areas involved in the trained task that may affect untrained tasks, specifically in brain areas responsible for the same cognitive processes.

Verbal Working Memory as Emergent from Language Comprehension and Production

This article reviews current models of verbal working memory and considers the role of language comprehension and long-term memory in the ability to maintain and order verbal information for short periods of time. While all models of verbal working memory posit some interaction with long-term memory, few have considered the character of these long-term representations or how they might affect performance on verbal working memory tasks. Similarly, few models have considered how comprehension processes and production processes might affect performance in verbal working memory tasks. Modern theories of comprehension emphasize that people learn a vast web of correlated information about the language and the world and must activate that information from long-term memory to cope with the demands of language input. To date, there has been little consideration in theories of verbal working memory for how this rich input from comprehension would affect the nature of temporary memory. There has also been relatively little attention to the degree to which language production processes naturally manage serial order of verbal information. The authors argue for an emergent model of verbal working memory supported by a rich, distributed long-term memory for language. On this view, comprehension processes provide encoding in verbal working memory tasks, and production processes maintenance, serial ordering, and recall. Moreover, the computational capacity to maintain and order information varies with language experience. Implications for theories of working memory, comprehension, and production are considered.

Acute increases in brain-derived neurotrophic factor in plasma following physical exercise relates to subsequent learning in older adults

Multidomain lifestyle interventions represents a promising strategy to counteract cognitive decline in older age. Brain-derived neurotrophic factor (BDNF) is essential for experience-dependent plasticity and increases following physical exercise, suggesting that physical exercise may facilitate subsequent learning. In a randomized-controlled trial, healthy older adults (65–75 years) completed a 12-week behavioral intervention that involved either physical exercise immediately before cognitive training (n = 25; 13 females), physical exercise immediately after cognitive training (n = 24; 11 females), physical exercise only (n = 27; 15 females), or cognitive training only (n = 21; 12 females). We hypothesized that cognition would benefit more from cognitive training when preceded as opposed to followed by physical exercise and that the relationship between exercise-induced increases in peripheral BDNF and cognitive training outcome would be greater when cognitive training is preceded by physical exercise. Greater increases of plasma BDNF were associated with greater cognitive training gains on trained task paradigms, but only when such increases preceded cognitive training (ß = 0.14, 95% CI [0.04, 0.25]). Average cognitive training outcome did not differ depending on intervention order (ß = 0.05, 95% CI [−0.10, 0.20]). The study provides the first empirical support for a time-critical but advantageous role for post-exercise increases in peripheral BDNF for learning at an interindividual level in older adults, with implications for future multidomain lifestyle interventions.

Neurophysiological indices of the transfer of cognitive training gains to untrained tasks

Targeted training of working memory (WM) may improve performance and modulate brain function in untrained cognitive modalities. Demanding cognitive training protocols that do not target WM may also improve performance on untrained cognitive tests, but the delineation between transfer effects that are unique to WM training and effects that are shared among different cognitive training modalities has not been well-established. To address this, we examined the effects of twenty sessions of either WM training (visual n-back task with letter stimuli) or selective attention training (visual search task with letter array stimuli) on brain function during untrained WM and cognitive control tasks. Event-related potentials (ERPs) were obtained at baseline (pretest) and after the training period (posttest) for two untrained tasks - a Spatial 3-back task measuring spatial WM, and a Go/NoGo Flanker task measuring cognitive control. The n-back training group had more pronounced pretest-to-posttest performance improvements on the Spatial 3-back task compared to the search training group. N-back training was also associated with pretest-to-posttest enhancement of N1 amplitude and reduced N2 latency on trials of the task in which where there was a stimulus match, as well as enhancement of a late positive potential (550-750 msec post-stimulus) for all trials of the task. These ERP effects suggest that n-back training resulted in enhancement of attention to spatial locations, earlier onset of conflict monitoring processes, and changes in the engagement of neural activity during the retention interval, respectively. Both groups had faster reaction time on Go trials of the Go/NoGo Flanker task at posttest compared to pretest. Relatively subtle training-related effects were observed for N2 amplitude on this task, in line with the notion that training (particularly n-back training) was associated with improved conflict monitoring. Further, search training resulted in earlier onset of P2 and P3 latency at posttest compared to pretest. Taken together, the ERP findings for both tasks identify specific cognitive processes that are associated with transfer to untrained tasks after distinct forms of cognitive training.

Exploring N-Back Cognitive Training for Children With ADHD

Objective: The efficacy of n-back training for children with attention deficit hyperactivity disorder (ADHD) was tested in a randomized controlled trial. Method: 41 children aged 7 to 14 years with ADHD were trained on an n-back task, and their performance was compared with that of an active control group (n = 39) who were trained on a general knowledge and vocabulary task. Results: The experimental group demonstrated transfer of training to a nontrained n-back task as well as to a measure of inhibitory control. These effects were correlated with the magnitude of training gains. Conclusion: Our results suggest that n-back training may be useful in addressing some of the cognitive and behavioral issues associated with ADHD.

Effects of working memory training in patients with Parkinson's disease without cognitive impairment: A randomized controlled trial

OBJECTIVE

To determine the feasibility and evaluate effects of a computerized working memory (WM) training (WMT) in patients with Parkinson's Disease (PD) on cognitive and clinical outcomes.

METHODS

76 patients with PD without cognitive impairment were randomized to either the WMT group (n = 37), who participated in a 5-week adaptive WMT, or a passive waiting-list control group (CG, n = 39). Patients underwent clinical and neuropsychological examination at baseline, after training, and at 3-months follow-up, with verbal WM and non-verbal WM as primary outcomes. Outcome assessors were blinded for group allocation.

RESULTS

All WMT participants completed the training successfully and reported high levels of motivation for and satisfaction with the training. Repeated-measures, linear mixed-effects models revealed positive training effects for the WMT group compared to the CG in verbal working memory with a small relative effect size 0.39 [95%CI 0.05; 0.76] for the 3-months follow-up only. No other reliable training effects in cognitive and clinical variables were found for either point of time.

CONCLUSIONS

In this randomized controlled trial, WMT was feasible and yielded some evidence for 3-months follow-up training gains in patients with PD. WMT might be an effective intervention to prevent cognitive decline in this patient group, however, more longitudinal studies with longer follow-up periods and more sensitive assessment tools will have to proof this concept.

TRIAL REGISTRATION

German Clinical Trials Register (DRKS00009379).

Causal underpinnings of working memory and Stroop interference control: Testing the effects of anodal and cathodal tDCS over the left DLPFC

By means of transcranial direct current stimulation applied to the left dorsolateral prefrontal cortex, we investigated the causal role of increased or decreased excitability of this brain region for two facets of executive functions: working memory and Stroop interference control. We tested 1) whether anodal tDCS of the left DLPFC enhances working memory 15 minutes after termination of stimulation and in the absence of direct task practice under stimulation; 2) whether anodal tDCS of the left DLPFC enhances interference control, as evidenced by Stroop performance and Stroop sequence effects; and 3) whether cathodal tDCS leads to compromised executive functioning compared to anodal stimulation. In a between-subject design with 88 healthy psychology students, we compared the impact of anodal and cathodal stimulation against a sham condition, on performance on a Stroop task (during active stimulation) and on an n-back task (completed 15 minutes after active stimulation ended). We found significantly enhanced accuracy in the n-back task after anodal stimulation compared with sham, as well as speeded reactions in the Stroop tasks independent of trial type. By contrast, we found no modulation of Stroop interference effects or Stroop sequence effects. No inhibitory effects of cathodal stimulation were observed. These results support the causal role of the left DLPFC in working memory but lend no support to its involvement in Stroop interference control.

Quantifying the Difference between Active and Passive Control Groups in Cognitive Interventions Using two Meta-Analytical Approaches

Despite promising reports of broad cognitive benefit in studies of cognitive training, it has been argued that the reliance of many studies on no-intervention control groups (passive controls) make these reports difficult to interpret because placebo effects cannot be ruled out. Although researchers have recently been trying to incorporate more active controls, in which participants engage in an alternate intervention, previous work has been contentious as to whether this actually yields meaningfully different results. To better understand the influence of passive and active control groups on cognitive interventions, we conducted two meta-analyses to estimate their relative effect sizes. While the first one broadly surveyed the literature by compiling data from 34 meta-analyses, the second one synthesized data from 42 empirical studies that simultaneously employed both types of controls. Both analyses showed no meaningful performance difference between passive and active controls, suggesting that current active control placebo paradigms might not be appropriately designed to reliably capture these non-specific effects or that these effects are minimal in this literature.

Early Attentional Modulation by Working Memory Training in Young Adult ADHD Patients during a Risky Decision-Making Task

Background: Working memory (WM) deficits and impaired decision making are among the characteristic symptoms of patients affected by attention deficit/hyperactivity disorder (ADHD). The inattention associated with the disorder is likely to be due to functional deficits of the neural networks inhibiting irrelevant sensory input. In the presence of unnecessary information, a good decisional process is impaired and ADHD patients tend to take risky decisions. This study is aimed to test the hypothesis that the level of difficulty of a WM training (WMT) is affecting the top-down modulation of the attentional processes in a probabilistic gambling task. Methods: Event-related potentials (ERP) triggered by the choice of the amount wagered in the gambling task were recorded, before and after WMT with a the dual n-back task, in young ADHD adults and matched controls. For each group of participants, randomly assigned individuals were requested to perform WMT with a fixed baseline level of difficulty. The remaining participants were trained with a performance-dependent adaptive n-level of difficulty. Results: We compared the ERP recordings before and after 20 days of WMT in each subgroup. The analysis was focused on the time windows with at least three recording sites showing differences before and after training, after Bonferroni correction ( p < 0.05 ). In ADHD, the P1 wave component was selectively affected at frontal sites and its shape was recovered close to controls' only after adaptive training. In controls, the strongest contrast was observed at parietal level with a left hemispheric dominance at latencies near 900 ms, more after baseline than after adaptive training. Conclusion: Partial restoration of early selective attentional processes in ADHD patients might occur after WMT with a high cognitive load. Modified frontal sites' activities might constitute a neural marker of this effect in a gambling task. In controls, conversely, an increase in late parietal negativity might rather be a marker of an increase in transfer effects to fluid intelligence.

Cognitive training as a component of treatment of alcohol use disorder: A review

OBJECTIVE

Cognitive training is an effective means of improving performance in a range of populations. Whether it may serve to facilitate cognitive recovery and longer-term outcomes in persons with alcohol use disorders (AUDs) is unclear. Here, we review historical and current literature and offer perspectives for model development and potential implementation.

METHOD

We considered a large literature regarding the nature of alcohol-related compromise, early efforts to clarify the nature of recovery and current models and methods underlying cognitive training paradigms. We then constructed a narrative review demonstrating evolving frameworks and empirical data informing the critical review of cognitive training methods as a means of mitigating compromise and facilitating functional outcomes.

RESULTS

Cognitive improvement with abstinence is generally noted, but training protocols may enhance performance and generalize benefit to untrained, but highly similar, tasks. Transfer of training to dissimilar tasks and functional outcomes is uncommonly reported. It is noteworthy that some work suggests that clinician ratings for participants are improved. Inconsistency in sample characteristics, training protocols, and outcome measures constrain general conclusions while suggesting opportunities for study and development.

CONCLUSIONS

Cognitive training protocols have shown benefit in a variety of populations but have been examined infrequently in persons with AUDs. This overview indicates significant opportunity for cognitive improvement and recovery and thus a strong potential role for training protocols. However, supportive data are not robustly obtained. We suggest that one step in bridging this gap is the implementation of a conceptual framework incorporating contextual, behavioral, and neurobiological variables. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Training Three Facets of Executive Functions

Given the importance of executive functions for everyday life, recent years have seen a tremendous interest in whether the basic cognitive abilities involved can be improved by training. The present research investigated whether, compared to an active control group, the three main facets of executive cognitive functions - task switching, updating, and inhibition (Miyake, Friedman, Emerson, Witzki, & Howerter, 2000) - can be trained jointly via intense adaptive online training of 5 weeks. Using a large sample and two training tasks per facet, we obtained clear evidence for increased task performance on all six tasks, suggesting that the three facets can be trained simultaneously, with some tasks showing very large in-task training gains. However, the evidence for correlated in-task training gains and for intermediate transfer effects on related but untrained tasks from pre- to posttest was very weak. Further random slopes analyses suggested that individuals benefit differently from training. These results warrant caution against general and sweeping claims about the far-reaching impact of cognitive training. They rather are in line with a more nuanced view according to which the training of executive functions is specific in at least three important ways.

Effects of virtual reality-based cognitive training in older adults living without and with mild dementia: a pretest-posttest design pilot study

OBJECTIVE

Modern technologies are increasingly used in the development of cognitive interventions for older adults. Research into possible applications of virtual reality in such interventions has begun only recently. The aim of present study was to evaluate the effects of 8 sessions of VR-based cognitive training using the GRADYS game in healthy older adults (n = 72; aged 60-88) and older adults living with mild dementia (n = 27; aged 60-89).

RESULTS

Older adults with mild dementia demonstrated worse baseline cognitive performance than participants without dementia. Both groups showed progress in training, which was greater in healthy older adults. There were also significant differences in cognitive functioning before and after the training. However, positive changes were revealed almost exclusively in the group of older adults without dementia. Based on the findings, we can recommend the GRADYS game for cognitive enhancement and as a possible counter-measure for cognitive decline experienced in normal cognitive ageing. Our results provide also support for the usefulness of VR technology in cognitive interventions in older adults. The use of the GRADYS game in persons living with dementia, however, would require several of the hardware and software modifications. Trial registration ISRCTN17613444, date of registration: 10.09.2019. Retrospectively registered.

The remediation effects of working memory training in schizophrenia patients with prominent negative symptoms

Introduction: Negative symptoms, particularly amotivation and anhedonia, are important predictors of poor functional outcome in patients with schizophrenia. There has been interest in the efficacy and mechanism of non-pharmacological interventions to alleviate these symptoms. The present study aimed to examine the remediation effect of working memory (WM) training in patients with schizophrenia with prominent negative symptoms.Methods: Thirty-one schizophrenia patients with prominent negative symptoms were recruited and assigned to either a WM training group or a treatment-as-usual (TAU) control group. The WM training group underwent 20 sessions of training using the dual n-back task over one month. A functional neuroimaging paradigm of the Affective Incentive Delay (AID) task was administered before and after the training intervention to evaluate the remediation effect of the intervention.Results: Our results showed that the WM training group demonstrated significant improvement in the WM training task and inattention symptoms. Compared with the TAU group, increased brain activations were observed at the right insula and the right frontal sub-gyral after WM training in the training group.Conclusions: These findings support the efficacy of WM training in ameliorating hedonic dysfunction in schizophrenia patients with prominent negative symptoms.

Does Working Memory Moderate the Within-Person Associations Between Pain Intensity and Negative Affect and Pain's Interference With Work Goal Pursuit?

OBJECTIVES

Chronic pain exerts a pervasive negative influence on workers' productivity. However, a paucity of research has addressed the mechanisms underlying the pain → productivity relation. In the present study using intensive daily diary data, we examined whether working memory (WM) moderates the positive within-person associations between (1) morning pain intensity and (2) morning negative affect (NA) and later day pain's interference of work-goal (WG) pursuit.

METHODS

A community sample of 131 adults with chronic pain completed a battery of questionnaires, laboratory-measured WM, and a 21-day daily diary.

RESULTS

WM did not moderate the positive within-person association between morning pain intensity and afternoon/evening ratings of pain's interference with work goal pursuit. However, individuals with higher WM showed significantly attenuated positive within-person association between morning negative affect and pain's interference with afternoon/evening work goal pursuit.

DISCUSSION

WM appears to protect goal-relevant information from distractions due to negative affective arousal. The continued use of ecologically valid observational and intervention studies would shed further light on the influence of WM on the pursuit of valued work goals in the face of pain and negative affect.

Enhanced decision-making through multimodal training

A central aim of research in the psychological and decision sciences is to establish interventions that enhance performance, investigating the efficacy of modern approaches to improve human inference and decision-making. Whereas the decision sciences have established interventions to reduce decision biases by promoting strategies for critical thought and reasoning, methods from psychology have instead focused on enhancing cognition through skill-based training of executive functions. Contemporary research in psychology has engaged these operations through multi-modal interventions designed to enhance cognition and physical health through training of executive functions, mindfulness meditation, and physical fitness. Despite the comparable aims of research in the psychological and decision sciences, the efficacy of multi-modal interventions to enhance decision-making remain to be established. We therefore conducted a comprehensive, 16-week, randomized controlled trial (RCT) to investigate this issue, enrolling 160 healthy adults in one of four interventions: (1) high-intensity cardioresistance fitness training (HICRT); (2) HICRT and cognitive training of core executive functions; (3) HICRT and cognitive training, along with mindfulness meditation training; or (4) active control training. The results of our RCT demonstrate that HICRT training and multi-modal interventions that also incorporate cognitive training and mindfulness meditation have beneficial effects on decision-making competence. The observed pattern of findings motivate the application of modern interventions from psychology and cognitive neuroscience to enhance human judgment and decision-making in complex, real-world environments.

Mapping differential responses to cognitive training using machine learning

We used two simple unsupervised machine learning techniques to identify differential trajectories of change in children who undergo intensive working memory (WM) training. We used self‐organizing maps (SOMs)—a type of simple artificial neural network—to represent multivariate cognitive training data, and then tested whether the way tasks are represented changed as a result of training. The patterns of change we observed in the SOM weight matrices implied that the processes drawn upon to perform WM tasks changed following training. This was then combined with K‐means clustering to identify distinct groups of children who respond to the training in different ways. Firstly, the K‐means clustering was applied to an independent large sample (N = 616, M_age = 9.16 years, range = 5.16–17.91 years) to identify subgroups. We then allocated children who had been through cognitive training (N = 179, M_age = 9.00 years, range = 7.08–11.50 years) to these same four subgroups, both before and after their training. In doing so, we were able to map their improvement trajectories. Scores on a separate measure of fluid intelligence were predictive of a child's improvement trajectory. This paper provides an alternative approach to analysing cognitive training data that go beyond considering changes in individual tasks. This proof‐of‐principle demonstrates a potentially powerful way of distinguishing task‐specific from domain‐general changes following training and of establishing different profiles of response to training.

A Large-Scale, Cross-Sectional Investigation Into the Efficacy of Brain Training

Brain training is a large and expanding industry, and yet there is a recurrent and ongoing debate concerning its scientific basis or evidence for efficacy. Much of evidence for the efficacy of brain training within this debate is from small-scale studies that do not assess the type of “brain training,” the specificity of transfer effects, or the length of training required to achieve a generalized effect. To explore these factors, we analyze cross-sectional data from two large Internet-cohort studies (total N = 60,222) to determine whether cognition differs at the population level for individuals who report that they brain train on different devices, and across different timeframes, with programs in common use circa 2010–2013. Examining scores for an assessment of working-memory, reasoning and verbal abilities shows no cognitive advantages for individuals who brain train. This contrasts unfavorably with significant advantages for individuals who regularly undertake other cognitive pursuits such as computer, board and card games. However, finer grained analyses reveal a more complex relationship between brain training and cognitive performance. Specifically, individuals who have just begun to brain train start from a low cognitive baseline compared to individuals who have never engaged in brain training, whereas those who have trained for a year or more have higher working-memory and verbal scores compared to those who have just started, thus suggesting an efficacy for brain training over an extended period of time. The advantages in global function, working memory, and verbal memory after several months of training are plausible and of clinically relevant scale. However, this relationship is not evident for reasoning performance or self-report measures of everyday function (e.g., employment status and problems with attention). These results accord with the view that although brain training programs can produce benefits, these might extend to tasks that are operationally similar to the training regime. Furthermore, the duration of training regime required for effective enhancement of cognitive performance is longer than that applied in most previous studies.

Working memory training and high magnitude incentives for youth cannabis use: A SMART pilot trial

The purpose of this sequential multiple-assignment randomization treatment pilot study was to examine if (a) adding working memory training to contingency management (CM) for youth with cannabis use disorder (CUD) and (b) switching nonresponding youth to higher magnitude CM incentives boosts outcomes. In Phase 1, youth with CUD (n = 59, M age = 16, male = 71%) attending an intensive outpatient program were randomly assigned to 14 weeks of CM only or CM plus working memory training (WMT). In Week 4, a Phase 2 treatment was assigned. Those with negative urine drug tests (responders) continued in their Phase 1 treatment. Those who were drug positive (nonresponders) were randomly assigned to remain in their Phase 1 treatment or to higher magnitude CM. Zero-inflated negative binomial models comparing those assigned to CM versus CM + WMT indicated no differences in the likelihood of having ≥ 1 week of continuous abstinence or longer abstinence duration. Those assigned to WMT showed greater but nonsignificant improvements in working memory (n = 35; β = .69, p = .06). Working memory improvements were associated with achieving any abstinence (odds ratio = 3.50, 95% CI [1.01, 12.10], p = .05). Phase 2 randomization to higher magnitude CM did not boost outcomes. Overall results suggest that WMT appears promising, but the sample size was small, attrition was high, and replication is important. Alternative strategies should continue to be explored to improve outcomes for adolescent substance use disorders, such as different approaches for nonresponders, tailoring to other baseline or response characteristics, or more robust first-line interventions. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

The academic outcomes of working memory and metacognitive strategy training in children: A double-blind randomized controlled trial

Working memory training has been shown to improve performance on untrained working memory tasks in typically developing children, at least when compared to non‐adaptive training; however, there is little evidence that it improves academic outcomes. The lack of transfer to academic outcomes may be because children are only learning skills and strategies in a very narrow context, which they are unable to apply to other tasks. Metacognitive strategy interventions, which promote metacognitive awareness and teach children general strategies that can be used on a variety of tasks, may be a crucial missing link in this regard. In this double‐blind randomized controlled trial, 95 typically developing children aged 9–14 years were allocated to three cognitive training programmes that were conducted daily after‐school. One group received Cogmed working memory training, another group received concurrent Cogmed and metacognitive strategy training, and the control group received adaptive visual search training, which better controls for expectancy and motivation than non‐adaptive training. Children were assessed on four working memory tasks, reading comprehension, and mathematical reasoning before, immediately after, and 3 months after training. Working memory training improved working memory and mathematical reasoning relative to the control group. The improvements in working memory were maintained 3 months later, and these were significantly greater for the group that received metacognitive strategy training, compared to working memory training alone. Working memory training is a potentially effective educational intervention when provided in addition to school; however, future research will need to investigate ways to maintain academic improvements long term and to optimize metacognitive strategy training to promote far‐transfer. A video abstract of this article can be viewed at https://youtu.be/-7MML48ZFgw

A classroom-based intervention targeting working memory, attention and language skills in 4-5 year olds (RECALL): study protocol for a cluster randomised feasibility trial

BACKGROUND

There is international recognition of the need for creative, classroom-based interventions to support children at risk of low academic achievement and well-being, due to poor attention and language skills on school entry. Working memory (WM) is a cognitive skill that is strongly associated with attention and language skills. There has been speculation that WM training, embedded within typical educational activities, may improve children's WM skills and produce transfer effects to real-world skills such as attention and language. However, little is known about the effectiveness of this approach.'Recall to Enhance Children's Attention, Language and Learning' (RECALL) is a novel, 6-week, classroom-based intervention targeting WM, attention and language skills in 4-5 year olds. RECALL was co-produced with health professionals, teachers and parents. This protocol describes the rationale, methods and analysis plan for a proposed cluster randomised feasibility trial of this RECALL programme.

METHODS

This is a three-arm, cluster randomised feasibility trial comparing RECALL to an existing programme (active control), and no-intervention (education as usual). We will recruit six schools in socially disadvantaged areas in one region of the UK. Two schools will be randomly allocated to each arm of the trial. In each school, one class of children (ages 4-5 years) of approx. 30 children will be involved in this study. Ten children in each class will be sampled purposefully for outcome measurement including: standardised assessments of WM, language and attention skills; teacher ratings of attention; and parent ratings of functional communication skills. These will be administered at baseline and 1-week post-intervention in order to test the acceptability of the measures. A process evaluation using semi-structured interviews with participants will explore the acceptability of RECALL and the procedures employed in this trial.

DISCUSSION

This feasibility study will explore the acceptability of RECALL to the health professionals and teachers who will deliver it and inform the optimal design of the programme. The inclusion of an active control group and the blinding of outcomes assessors enhance rigour in this study. The findings will determine whether this study can be scaled-up into a definitive cluster randomised trial to evaluate the effectiveness of RECALL.

TRIAL REGISTRATION

ISRCTN13633886. Registered 7 Sept 2018.

Effects of Left Versus Right Dorsolateral Prefrontal Cortex Repetitive Transcranial Magnetic Stimulation on Affective Flexibility in Healthy Women: A Pilot Study

OBJECTIVE

To determine the antidepressant mechanism of action for repetitive transcranial magnetic stimulation (rTMS) to the left dorsolateral prefrontal cortex (DLPFC) in healthy women. Our primary hypothesis was that a single session of left DLPFC rTMS, compared with a session of right DLPFC rTMS, would result in better (reduced) negative nonaffective switch costs in healthy women.

BACKGROUND

The antidepressant mechanism of action for rTMS is not clear. It is possible that rTMS to the DLPFC improves emotion regulation, which could be a part of its antidepressant mechanism.

METHODS

Twenty-five healthy women were randomized to receive left high-frequency (HF) rTMS versus right HF rTMS in one session and then contralateral stimulation during a second session. Emotion regulation was assessed via switch costs for reappraisal of negatively valenced information on an affective flexibility task.

RESULTS

For negative nonaffective switch costs, the interaction effect in the two-way ANOVA was not significant (F1,19=3.053, P=0.097). Given that left HF rTMS is the approved treatment for depression, post hoc t tests were completed with particular interest in the left-side findings. These tests confirmed that negative nonaffective switch costs significantly improved immediately after left rTMS (t1,19=2.664, P=0.015) but not right rTMS.

CONCLUSIONS

These findings suggest that left DLPFC HF rTMS may lead to antidepressant effects by improving the regulation of emotion.

Interventions targeting working memory in 4-11 year olds within their everyday contexts: A systematic review

It has been suggested that diverse interventions applied within children's everyday contexts have the potential to improve working memory (WM) and produce transfer to real-world skills but little is known about the effectiveness of these approaches. This review aims to examine systematically the effectiveness of non-computerised interventions with 4-11 year olds to identify: (i) their effects on WM; (ii) whether benefits extend to near- and far-transfer measures; (iii) if gains are sustained over time; (iv) the active ingredients; and (v) the optimum dosage. Searches were conducted across 12 electronic databases using consistent keywords. Papers were screened by title and abstract (n = 6212) and judged against pre-defined eligibility criteria (n = 63). Eighteen papers were included in the review. They used a range of non-computerised WM intervention approaches that included: (i) adapting the environment to reduce WM loads; (ii) direct WM training with and without strategy instruction; and (iii) training skills which may indirectly impact on WM (physical activity, phonological awareness, fantastical play and inhibition). Both direct training on WM tasks and practicing certain skills that may impact indirectly on WM (physical activity, fantastical play and inhibition) produced improvements on WM tasks, with some benefits for near-transfer activities. The common ingredient across effective interventions was the executive-loaded nature of the trained task i.e., training on a task that taps into attentional and processing resources under executive control and not just the storage of information. Few studies reported dosage effects, measured far-transfer effects (n = 4), or tested the durability of gains over time (n = 4). The lack of a clear theoretical framework in many of the included studies resulted in ambiguous predictions about training and transfer effects, and inadequate use of outcome measures. Methodological issues also constrain the strength of the evidence, including: small samples sizes; an absence of blinding of participant and outcome assessors; and lack of active control groups. Further well-designed and controlled studies with clear theoretical underpinnings are required to expand and enhance the evidence base. The heterogeneity of the interventions and of the study designs (randomised and non-randomised) in the included papers limited the synthesis of evidence across studies. However, this diversity enabled the identification of key ingredients, notably the training of executive-loaded WM tasks, which can help inform novel approaches to WM intervention in everyday contexts.

The Influence of Individual Differences in Cognitive Ability on Working Memory Training Gains

Working memory training research has produced mixed results in terms of finding benefits beyond the trained tasks (i.e., transfer). One potential limitation is that the research thus far has failed to isolate the specific combination of factors that makes working memory training work best. Individual differences in cognitive ability at pretest may be an important factor, suggesting possible aptitude-by-treatment interactions. Baseline cognitive ability could be (a) positively related, (b) negatively related, or (c) unrelated to training task improvements. The relationship between ability and training gains is important given the idea that larger training improvements should lead to greater transfer. However, the majority of training studies tend to be under-powered to examine individual differences. We pooled studies conducted in related labs to increase power while minimizing differences between studies. In the studies that were identified for this project, young adults completed complex span training and working memory and/or fluid intelligence as pretest measures. The combined samples from seven studies resulted in a sample of 192 participants. Analyses focused on the relationship between pretest cognitive ability and training performance across training days. There was no evidence that individuals lower in cognitive ability improved more than high-ability subjects on the training tasks. Instead, we found a positive relationship for both working memory and fluid intelligence measured at pretest with the amount of training improvement. In addition, the association between pretest working memory and working memory training performance appears to be domain-general - verbal and visuospatial content do not produce differential relationships.

Working Memory Capacity as a Predictor of Cognitive Training Efficacy in the Elderly Population

Aging is associated with a decline in a wide range of cognitive functions and working memory (WM) deterioration is considered a main factor contributing to this. Therefore, any attempt to counteract WM decline seems to have a potential benefit for older adults. However, determination of whether such methods like WM trainings are effective is a subject of a serious debate in the literature. Despite a substantial number of training studies and several meta-analyses, there is no agreement on the matter of their effectiveness. The other important and still not fully explored issue is the impact of the preexisting level of intellectual functioning on the training's outcome. In our study we investigated the impact of WM training on variety of cognitive tasks performance among older adults and the impact of the initial WM capacity (WMC) on the training efficiency. 85 healthy older adults (55-81 years of age; 55 female, 30 males) received 5 weeks of training on adaptive dual N-back task (experimental group) or memory quiz (active controls). Cognitive performance was assessed before and after intervention with measures of WM, memory updating, inhibition, attention shifting, short-term memory (STM) and reasoning. We found post-intervention group independent improvements across all cognitive tests except for inhibition and STM. With multi-level analysis individual learning curves were modeled, which enabled examining of the intra-individual change in training and inter-individual differences in intra-individual changes. We observed a systematic and positive, but relatively small, learning trend with time. Moderator analyses with demographic characteristics as moderators showed no additional effects on learning curves. Only initial WMC level was a significant moderator of training effectiveness. Older adults with initially lower WMC improved less and reached lower levels of performance, compared to the group with higher WMC. Overall, our findings are in accordance with the research suggesting that post-training gains are within reach of older adults. Our data provide evidence supporting the presence of transfer after N-back training in older adults. More importantly, our findings suggest that it is more important to take into account an initial WMC level, rather than demographic characteristics when evaluating WM training in older adults.

Are Working Memory Training Effects Paradigm-Specific?

A randomized controlled trial compared complex span and n-back training regimes to investigate the generality of training benefits across materials and paradigms. The memory items and training intensities were equated across programs, providing the first like-with-like comparison of transfer in these two widely used training paradigms. The stimuli in transfer tests of verbal and visuo-spatial n-back and complex span differed from the trained tasks, but were matched across the untrained paradigms. Participants were randomly assigned to one of three training groups: complex span training, n-back training, or no training. Pre- to- post training changes were observed for untrained n-back tasks following n-back training. Following complex span training there was equivocal evidence for improvements on a verbal complex span task, but no evidence for changes on an untrained visuo-spatial complex span activity. Relative to a no intervention group, the evidence supported no change on an untrained verbal complex span task following either n-back or complex span training. Equivocal evidence was found for improvements on visuo-spatial complex span and verbal and visuo-spatial n-back tasks following both training regimes. Evidence for selective transfer (comparing the two active training groups) was only found for an untrained visuo-spatial n-back task following n-back training. There was no evidence for cross-paradigm transfer. Thus transfer is constrained by working memory paradigm and the nature of individual processes executed within complex span tasks. However, within-paradigm transfer can occur when the change is limited to stimulus category, at least for n-back.

The Hype Cycle of Working Memory Training

Seventeen years and hundreds of studies after the first working memory training journal article was published, evidence for the efficacy of working memory training is still wanting. Numerous studies show that individuals who repeatedly practice computerized working memory tasks improve on those tasks and closely related variants. Critically, although individual studies have claimed improvements in untrained abilities and behaviors, systematic reviews of the broader literature show that studies producing large, positive findings are often those with the most methodological shortcomings. The current review discusses the past, present, and future status of working memory training, including consideration of factors that might influence working memory training and transfer efficacy.

Divergent Research Methods Limit Understanding of Working Memory Training

Working memory training has been a hot topic over the last decade. Although studies show benefits in trained and untrained tasks as a function of training, there is an ongoing debate on the efficacy of working memory training. There have been numerous meta-analyses put forth to the field, some finding overall broad transfer effects while others do not. However, discussion of this research typically overlooks specific qualities of the training and transfer tasks. As such, there has been next to no discussion in the literature on what training and transfer tasks features are likely to mediate training outcomes. To address this gap, here, we characterized the broad diversity of features employed in N-back training tasks and outcome measures in published working memory training studies. Extant meta-analyses have not taken into account the diversity of methodology at this level, primarily because there are too few studies using common methods to allow for a robust meta-analysis. We suggest that these limitations preclude strong conclusions from published data. In order to advance research on working memory training, and in particular, N-back training, more studies are needed that systematically compare training features and use common outcome measures to assess transfer effects.

Effects of neurofeedback and working memory-combined training on executive functions in healthy young adults

Given the interest in improving executive functions, the present study examines a promising combination of two training techniques: neurofeedback training (NFT) and working memory training (WMT). NFT targeted increasing the amplitude of individual's upper Alpha frequency band at the parietal midline scalp location (Pz), and WMT consisted of an established computerized protocol with working memory updating and set-shifting components. Healthy participants (n = 140) were randomly allocated to five combinations of training, including visual search training used as an active control training for the WMT; all five groups were compared to a sixth silent control group receiving no training. All groups were evaluated before and after training for resting-state electroencephalogram (EEG) and behavioral executive function measures. The participants in the silent control group were unaware of this procedure, and received one of the training protocols only after study has ended. Results demonstrated significant improvement in the practice tasks in all training groups including non-specific influence of NFT on resting-state EEG spectral topography. There was only a near transfer effect (improvement in working memory task) for WMT, which remained significant in the delayed post-test (after 1 month), in comparison to silent control group but not in comparison to active control training group. The NFT + WMT combined group showed improved mental rotation ability both in the post-training and in the follow-up evaluations. This improvement, however, did not differ significantly from that in the silent control group. We conclude that the current training protocols, including their combination, have very limited influence on the executive functions that were assessed in this study.