Working memory training and perceptual discrimination training impact overlapping and distinct neurocognitive processes: Evidence from event-related potentials and transfer of training gains

Long-term findings on working memory neural dynamics in healthcare workers after mild COVID-19

OBJECTIVE

Understanding the long-term impact of Coronavirus Disease 2019 (COVID-19) on cognitive function, even in mild cases, is critical to the well-being of individuals, especially for healthcare workers who are at increased risk of exposure to the virus. To the best of our knowledge, the electrophysiological activity underlying cognitive functioning has not yet been explored.

METHODS

Seventy-seven healthcare workers took part in the study (43 with mild infection about one year before the study and 34 uninfected). To assess cognitive status, event-related potentials (ERPs) and behavioural responses were recorded while participants performed a working memory task.

RESULTS

COVID-19 participants exhibited a distinct neural pattern with lower parieto-occipital N1 amplitudes and higher frontal P2 amplitudes as compared to non-infected healthcare workers. We found no behavioural differences (reaction times and error rates) in working memory functioning between groups.

CONCLUSIONS

This neural pattern suggests the presence of a decrement of processing resources linked to the encoding of sensory information (N1), followed by the enhanced of the P2 response which could be interpreted as the activation of compensation mechanism in COVID-19 participants.

SIGNIFICANCE

The current findings point out that ERPs could serve as valuable neural indices for detecting distinctive patterns in working memory functioning of COVID-19 participants, even in mild cases. However, further research is required to precisely ascertain the long-term cognitive effects of COVID-19 beyond one-year post-infection.

Lasting enhancements in neural efficiency by multi-session transcranial direct current stimulation during working memory training

The neural basis for long-term behavioral improvements resulting from multi-session transcranial direct current stimulation (tDCS) combined with working memory training (WMT) remains unclear. In this study, we used task-related electroencephalography (EEG) measures to investigate the lasting neurophysiological effects of anodal high-definition (HD)-tDCS applied over the left dorsolateral prefrontal cortex (dlPFC) during a challenging WMT. Thirty-four healthy young adults were randomized to sham or active tDCS groups and underwent ten 30-minute training sessions over ten consecutive days, preceded by a pre-test and followed by post-tests performed one day and three weeks after the last session, respectively, by performing high-load WM tasks along with EEG recording. Multi-session HD-tDCS significantly enhanced the behavioral benefits of WMT. Compared to the sham group, the active group showed facilitated increases in theta, alpha, beta, and gamma task-related oscillations at the end of training and significantly increased P300 response 3 weeks post-training. Our findings suggest that applying anodal tDCS over the left dlPFC during multi-session WMT can enhance the behavioral benefits of WMT and facilitate sustained improvements in WM-related neural efficiency.

A psychometric study of an executive function assessment instrument (TDI-FE)

BACKGROUND

This study aims to present and discuss the psychometric properties of executive functions, which were measured using the TDI-FE instrument. The analysis encompasses its internal structure, potential sensitivity to fatigue factors, relationships with external criteria, and diagnostic accuracy.

METHODS

The study sample comprised 382 students from Brazil, aged 6-8 years. Child development variables were screened using the TDI-FE and gold standard tests (Cancellation Attention and Trail Making Tests). The proposed scale comprised four activities: a test with fruit images with three tasks, and one memory game.

RESULTS

The one-factor model of EF of the TDI-FE failed to fit to the data. However, fit substantially improved once a latent fatigue factor was controlled in the model. The latent factor of EF assessed by the TDI-FE tasks was coherently associated with a series of external variables, including two popular collateral measures of EF. The diagnostic accuracy was reasonable, and a cut-off of 37 points produced 70% of sensitivity and 60% of specificity.

CONCLUSION

Results indicated that the TDI-FE demonstrated sound psychometric properties and diagnostic accuracy, then consisting of an efficient alternative for the assessment of EFs in early childhood education. The study also proved the need to control for response biases such as fatigue in the latent variable models of EF. The TDI-FE is notable because of its low cost and easy application, and it might fulfill a need for instruments for individuals from different contexts at this stage of development in Brazil.

Audiovisual n-Back Training Alters the Neural Processes of Working Memory and Audiovisual Integration: Evidence of Changes in ERPs

(1) Background: This study investigates whether audiovisual n-back training leads to training effects on working memory and transfer effects on perceptual processing. (2) Methods: Before and after training, the participants were tested using the audiovisual n-back task (1-, 2-, or 3-back), to detect training effects, and the audiovisual discrimination task, to detect transfer effects. (3) Results: For the training effect, the behavioral results show that training leads to greater accuracy and faster response times. Stronger training gains in accuracy and response time using 3- and 2-back tasks, compared to 1-back, were observed in the training group. Event-related potentials (ERPs) data revealed an enhancement of P300 in the frontal and central regions across all working memory levels after training. Training also led to the enhancement of N200 in the central region in the 3-back condition. For the transfer effect, greater audiovisual integration in the frontal and central regions during the post-test rather than pre-test was observed at an early stage (80-120 ms) in the training group. (4) Conclusion: Our findings provide evidence that audiovisual n-back training enhances neural processes underlying a working memory and demonstrate a positive influence of higher cognitive functions on lower cognitive functions.

Cognitive skill learning in multiple sclerosis: A meaningful component of the neuropsychological profile

Cognitive skill learning (CSL) refers to the capacity to improve performance on specific cognitive operations through repeated practice. We hypothesized that high CSL aptitude may promote accumulation of cognitive reserve, and resiliency to cognitive decline, in people with Multiple Sclerosis (MS). Using an adaptive working memory training paradigm, we obtained CSL aptitude indices (amount of improvement on the training task over time) in MS patients for a single session of practice (25-30 min), and longer-term practice (twenty sessions). Neuropsychological performance was assessed with the Symbol Digit Modalities Test (SDMT), Paced Auditory Serial Addition Test (PASAT), and the Raven's Advanced Progressive Matrices (RAPM). CSL aptitude measures were positively correlated with neuropsychological performance, and had high diagnostic accuracy for classifying cognitive impairment in MS, defined as 1.5 SD below the demographics-corrected normative mean of the SDMT. Positive relationships between CSL aptitude measures and neuropsychological performance tended to be more pronounced for individuals with high estimated cognitive reserve, suggesting that high CSL aptitude is a a factor that promotes the protective effects of cognitive reserve. Furthermore, regression analyses indicated that CSL aptitude is separable from baseline cognitive capacity. The findings suggest that CSL aptitude impacts the neuropsychological profile in MS, and may be a factor underlying variance in cognitive resiliency.

The effects of first-dose methylphenidate on the neural signatures of visual selective attention in children with attention-deficit/hyperactivity disorder

Although methylphenidate (MPH) has been shown to significantly improve selective attention in children with attention-deficit/hyperactivity disorder (ADHD), the neural mechanism of this effect remains unclear. We investigated the effects of first-dose MPH on the neural signatures of visual selective attention in children with ADHD. We measured the impact of first-dose MPH on electrophysiological indexes from eighteen children with ADHD (8.9-15.2 years; 15 boys) while they performed a visual search task. MPH was administered in a double-blind placebo-controlled crossover design. MPH led to decreases in behavioral error rates and reaction times. For the electrophysiological indexes, MPH significantly increased the target-elicited N2pc amplitude and posterior P3 amplitude during the selective attention process. The trial-based correlation analysis revealed that the enhanced N2pc (more negative) and P3 (more positive) promoted the behavioral response speed for children with ADHD. The lower individual P3 amplitude was associated with higher severity of inattention symptoms. The severer inattention symptoms were related to weaker MPH effect on N2pc amplitude. These findings suggest that N2pc and P3 are closely related to the mechanism of MPH in the ADHD treatment.

Effects of forward and backward span trainings on working memory: Evidence from a randomized controlled trial

Both forward and backward working memory span tasks have been used in cognitive training, but no study has been conducted to test whether the two types of trainings are equally effective. Based on data from a randomized controlled trial, this study (N = 60 healthy college students) tested the effects of backward span training, forward span training, and no intervention. Event-related potential (ERP) signals were recorded at the pre-, mid-, and post-tests while the subjects were performing a distractor version of the change detection task, which included three conditions (2 targets and 0 distractor [2T0D]; 4 targets and 0 distractor [4T0D]; and 2 targets and 2 distractors [2T2D]). Behavioral data were collected from two additional tasks: a multi-object version of the change detection task, and a suppress task. Compared to no intervention, both forward and backward span trainings led to significantly greater improvement in working memory maintenance, based on indices from both behavioral (Kmax) and ERP data (CDA_2T0D and CDA_4T0D). Backward span training also improved interference control based on the ERP data (CDA_filtering efficiency) to a greater extent than did forward span training and no intervention, but the three groups did not differ in terms of behavioral indices of interference control. These results have potential implications for optimizing the current cognitive training on working memory.

Trust violations affect the emotional working memory updating: An event-related brain potential study

Previous studies found that trust violations impaired the ability of working memory (WM) updating, however, these studies did not consider the emotional context in the WM updating. Individuals who experience trust violations have the characteristics of negative bias and enhanced negative emotion. Thus it is necessary to explore how emotional contexts moderate the relationship between trust violations and WM updating. In this study, the trust game was used to manipulate trust violations. Fifty-three participants performed the emotional two-back task while event-related potentials were recorded. Results showed that compared to the control group, the violation group had smaller P2 and P3 amplitudes both in emotional and nonemotional contexts and larger N2 amplitudes in the emotional contexts. There were no significant differences between the two groups on the behavioral data. These results suggest that trust violations result in the inefficient allocation of attention in the early attention (P2) and updating maintenance stages (P3) regardless of the emotional type of the material. Trust violations also improve the abilities of response inhibition, conflict monitoring, or sequential match (N2) when processing emotional material, which may play a compensatory role to maintain a level of behavioral performance comparable to the control group. Together, trust violations affect the sub-processes underlying emotional WM updating differently, and these influences are not valence specific.

An ERP study on the influence of mental abacus calculation on subthreshold arithmetic priming in children

OBJECTIVE

The objective of this study was to investigate the influence of mental abacus calculation training (MACT) on subliminal cognitive processes.

METHODS

Twenty children with intensive MACT (MACT group) and 20 children without MACT (non-MACT group) were selected. The two groups of children were matched in age, sex, handedness and academic grade. The participants were tested with subthreshold arithmetic priming task while their neural activities were recorded with a 32-channel electroencephalogram system.

RESULTS

We found that MACT changed the subliminal cognitive mechanism of computational processing, speeding up the computation. MACT affected the computational processing mode. Specifically, in the identification stage, both groups of children adopted the visual space processing mode, while in the computing stage, the MACT group adopted a visual space processing mode, but the non-MACT group adopted a semantic processing mode. Moreover, MACT improved children's executive functions.

CONCLUSION

These results yielded insights into the effect of early abacus training on children's cognitive processing, providing a theoretical basis for the development and promotion of abacus training.

Short-Term Audiovisual Spatial Training Enhances Electrophysiological Correlates of Auditory Selective Spatial Attention

Audiovisual cross-modal training has been proposed as a tool to improve human spatial hearing. Here, we investigated training-induced modulations of event-related potential (ERP) components that have been associated with processes of auditory selective spatial attention when a speaker of interest has to be localized in a multiple speaker ("cocktail-party") scenario. Forty-five healthy participants were tested, including younger (19-29 years; n = 21) and older (66-76 years; n = 24) age groups. Three conditions of short-term training (duration 15 min) were compared, requiring localization of non-speech targets under "cocktail-party" conditions with either (1) synchronous presentation of co-localized auditory-target and visual stimuli (audiovisual-congruency training) or (2) immediate visual feedback on correct or incorrect localization responses (visual-feedback training), or (3) presentation of spatially incongruent auditory-target and visual stimuli presented at random positions with synchronous onset (control condition). Prior to and after training, participants were tested in an auditory spatial attention task (15 min), requiring localization of a predefined spoken word out of three distractor words, which were presented with synchronous stimulus onset from different positions. Peaks of ERP components were analyzed with a specific focus on the N2, which is known to be a correlate of auditory selective spatial attention. N2 amplitudes were significantly larger after audiovisual-congruency training compared with the remaining training conditions for younger, but not older, participants. Also, at the time of the N2, distributed source analysis revealed an enhancement of neural activity induced by audiovisual-congruency training in dorsolateral prefrontal cortex (Brodmann area 9) for the younger group. These findings suggest that cross-modal processes induced by audiovisual-congruency training under "cocktail-party" conditions at a short time scale resulted in an enhancement of correlates of auditory selective spatial attention.

Training-dependent transfer within a set of nested tasks

Extended practice on a particular cognitive task can boost the performance of other tasks, even though they themselves have not been practised. This transfer of benefits appears to be specific, occurring most when tasks are very similar to those being trained. But what type of similarity is most important for predicting transfer? This question is addressed with a tightly controlled randomised design, with a relatively large sample (N = 175) and an adaptive control group. We created a hierarchical set of nested assessment tasks. Participants then trained on two of the tasks: one was relatively "low" in the hierarchy requiring just simultaneous judgements of shapes' spikiness, whereas the other was relatively "high" requiring delayed judgements of shapes' spikiness or number of spikes in a switching paradigm. Using the full complement of nested tasks before and after training, we could then test whether and how these "low" and "high" training effects cascade through the hierarchy. For both training groups, relative to the control, whether or not an assessment task shared a single specific feature was the best predictor of transfer patterns. For the low-level training group, the overall proportion of feature overlap also significantly predicted transfer, but the same was not true for the high-level training group. Finally, pre-training between-task correlations were not predictive of the pattern of transfer for either group. Together these findings provide an experimental exploration of the specificity of transfer and establish the nature of task overlap that is crucial for the transfer of performance improvements.

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.

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.

Can Working Memory Task-Related EEG Biomarkers Measure Fluid Intelligence and Predict Academic Achievement in Healthy Children?

Background

Educational psychology research has linked fluid intelligence (Gf) with working memory (WM), but it is still dubious whether electroencephalography (EEG) markers robustly indicate Gf. This study addresses this issue and notes the relationship between WM task-related EEG markers with Gf and academic performance.

Method

A sample of 62 healthy children between the ages of 9 and 12 years was selected to perform three tasks: (1) Raven’s Standard Progressive Matrices (RSPM) test to assess Gf; (2) 2-back task to assess central executive system (CES); and (3) delayed match-to-sample task to assess short-term storage. These subjects were divided into high ability (HA) and low ability (LA) groups based on their RSPM scores. Support vector machine and logistic regression were used to train the EEG candidate indicators. A multiple regression was used to predict children’s academic performance using P3 amplitude, P2 latency, and θ-ERS.

Results

Behavioral results demonstrated that the correct rate of the HA group is higher than that of the LA group. The event-related potential results of the 2-back task showed that the P3 amplitude of the HA group was relatively larger and that the P2 latency was shorter than that observed in the LA group. For the delayed matching to sample task, the θ-ERS of the LA group was higher than that of the HA group. However, the area under the curve of these three indicators for Gf was < 0.75 for each and < 0.85 for the combined indicators. In predicting academic performance, only P3 amplitude showed a significant effect.

Conclusion

These results challenge previous findings, which reported that P3, P2, or theta power might be used in standard psychometric tests to assess an individual’s intelligence.

Neural Correlates of Working Memory Deficits in Different Adult Outcomes of ADHD: An Event-Related Potential Study

BACKGROUND

We investigated working memory (WM) processing in a longitudinal sample of young adults with persistent and remittent childhood-onset ADHD to investigate the neural correlates of working memory with adult outcomes of ADHD.

METHODS

Forty-seven young Chinese adults who had been diagnosed with ADHD during childhood underwent follow-up assessments for an average of 9 years. The ADHD sample consisted of 25 ADHD persisters (mean age =18.38 ± 0.5 years) and 22 remitters (mean age = 18.78 ± 1.10 years), who were compared with 25 sex ratio- and IQ-matched healthy adults (mean age = 19.60 ± 1.22 years) in a verbal n-back task.

RESULTS

No differences in behavioral measures were observed across the three groups. Compared with the healthy controls, the ADHD persisters and remitters had larger N1 amplitudes and smaller P2 amplitudes, while no significant differences between the persistence and remission groups were observed. The P3 amplitudes of the remission and control groups were higher than that of the persistence group, but there was no significant difference between the remitters and healthy controls.

CONCLUSION

The P3 amplitudes reflecting postdecisional processing and/or WM updating were sensitive to ADHD remission, as they might improve concurrently with ADHD symptoms. These results indicate that the N1, P2, and P3 components of WM processing might be potential biomarkers for different ADHD outcomes.

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

Improved cognitive performance and event-related potential changes following working memory training in patients with multiple sclerosis

Background

Few studies of cognitive rehabilitation in multiple sclerosis (MS) have targeted working memory specifically.

Objective

We examined the effects of n-back working memory training on cognitive performance and brain function in patients with MS.

Methods

Patients with MS (n = 12) and healthy controls (HC; n = 12) underwent 20 sessions of n-back working memory training. Before and after training (pre- and posttest) cognitive event-related potential (ERP) measures were obtained during a 3-back task. In addition, a battery of cognitive tests was administered.

Results

Following n-back training, both MS patients and HCs showed significant improvement on tests of working memory, processing speed, complex attention, and reasoning ability. MS and HCs also exhibited an enhancement of N2 ERP component amplitude, and earlier N2 and P3 latencies, following n-back training.

Conclusions

Targeted training of working memory with the n-back task may improve cognitive function in MS. Enhancement of N2 ERP component amplitude and shorter N2 and P3 latency following training in patients with MS is consistent with plasticity of neural processes that are involved in working memory.