Expectation effects in working memory training.

There is a growing body of research focused on developing and evaluating behavioral training paradigms meant to induce enhancements in cognitive function. It has recently been proposed that one mechanism through which such performance gains could be induced involves participants' expectations of improvement. However, no work to date has evaluated whether it is possible to cause changes in cognitive function in a long-term behavioral training study by manipulating expectations. In this study, positive or negative expectations about cognitive training were both explicitly and associatively induced before either a working memory training intervention or a control intervention. Consistent with previous work, a main effect of the training condition was found, with individuals trained on the working memory task showing larger gains in cognitive function than those trained on the control task. Interestingly, a main effect of expectation was also found, with individuals given positive expectations showing larger cognitive gains than those who were given negative expectations (regardless of training condition). No interaction effect between training and expectations was found. Exploratory analyses suggest that certain individual characteristics (e.g., personality, motivation) moderate the size of the expectation effect. These results highlight aspects of methodology that can inform future behavioral interventions and suggest that participant expectations could be capitalized on to maximize training outcomes.

The relation between effortful control and executive function training in preschoolers.

In recent years, the question of whether executive function (EF) is malleable has been widely documented. Despite using the same training tasks, transfer effects remain uncertain. Researchers suggested that the inconsistency might be attributed to individual differences in temperamental traits. In the current study, we investigated how effortful control, a temperamental trait, would affect EF training outcomes in children. Based on parent rating, 79 6-year-old preschoolers were identified as having higher or lower effort control and were assigned to three conditions: working memory (WM) training, inhibitory control (IC) training, and a business-as-usual control group. Children completed assessments at baseline, 1 week after intervention (posttest), and 3 months after intervention (follow-up). As compared with the control group, the WM and IC training groups showed improvement in both trained tasks and nontrained measures. At baseline, children with higher effortful control scores showed greater WM capacity and better IC. Furthermore, effortful control was positively correlated with training gain in both training groups, with children with higher effortful control benefitting more through training. In the WM training group, effortful control was positively correlated with near transfer on WM outcomes both immediately and longitudinally. At posttest, the WM and IC training groups showed a positive correlation between effortful control and fluid intelligence performance. Our results underscore the importance of individual differences in training benefits, in particular the role of effortful control, and further illustrate the potential avenues for designing more effective individualized cognitive training programs to foster learning and optimize children's development.

The Relationship between Socioeconomic Status and Academic Achievement is Mediated and Moderated by Executive Functions.

Executive function is an underlying mechanism linking family socioeconomic status (SES) and academic achievement. Previous studies mainly investigated either the mediating or moderating role of executive function within this relationship, which either overlook the individual differences that are independent of the environment or neglect the influence of the environment on shaping personal factors. To avoid a piecemeal approach to theory, the current study aimed to test the mediating and moderating roles of executive function in a single analytic model. Two hundred and thirty-six Chinese fifth graders (Mage = 10.70 years, SD = 0.49, range = 10.23-11.75 years, and 40.30% girls) were recruited. Their executive function performance was measured using eight different tasks, and their Chinese literacy skills and mathematics achievement were assessed by routine school evaluations. One year after the initial assessment, children's academic achievements were evaluated again. Results demonstrated that parental SES positively predicted children's academic achievement when controlling for prior academic achievement, and children's executive function mediated this relationship. Also, executive function moderated the association between SES and academic achievement in that, the negative predictive effect of low SES on academic achievement was only significant for children with lower levels of executive function, which is not shown in children with higher levels of executive function. By demonstrating the dual roles of executive function in the SES-achievement link, this work provides evidence for supporting the optimal development of children from diverse socioeconomic backgrounds and emphasizes the significance of developing individualized intervention strategies on executive function to mitigate the negative effect of low SES on children's academic achievement.

Effects of Multisession Prefrontal Transcranial Direct Current Stimulation on Long-term Memory and Working Memory in Older Adults.

Transcranial direct current stimulation (tDCS) is a noninvasive form of electrical brain stimulation popularly used to augment the effects of working memory (WM) training. Although success has been mixed, some studies report enhancements in WM performance persisting days, weeks, or even months that are actually more reminiscent of consolidation effects typically observed in the long-term memory (LTM) domain, rather than WM improvements per se. Although tDCS has been often reported to enhance both WM and LTM, these effects have never been directly compared within the same study. However, given their considerable neural and behavioral overlap, this is a timely comparison to make. This study reports results from a multisession intervention in older adults comparing active and sham tDCS over the left dorsolateral pFC during training on both an n-back WM task and a word learning LTM task. We found strong and robust effects on LTM, but mixed effects on WM that only emerged for those with lower baseline ability. Importantly, mediation analyses showed an indirect effect of tDCS on WM that was mediated by improvements in consolidation. We conclude that tDCS over the left dorsolateral pFC can be used as an effective intervention to foster long-term learning and memory consolidation in aging, which can manifest in performance improvements across multiple memory domains.

UCancellation: A new mobile measure of selective attention and concentration.

Measuring selective attention in a speeded task can provide valuable insight into the concentration ability of an individual, and can inform neuropsychological assessment of attention in aging, traumatic brain injury, and in various psychiatric disorders. There are only a few tools to measure selective attention that are freely available, psychometrically validated, and can be used flexibly both for in-person and remote assessment. To address this gap, we developed a self-administrable, mobile-based test called "UCancellation" (University of California Cancellation), which was designed to assess selective attention and concentration and has two stimulus sets: Letters and Pictures. UCancellation takes less than 7 minutes to complete, is automatically scored, has multiple forms to allow repeated testing, and is compatible with a variety of iOS and Android devices. Here we report the results of a study that examined parallel-test reliability and convergent validity of UCancellation in a sample of 104 college students. UCancellation Letters and Pictures showed adequate parallel test reliability (r = .71-.83, p < 0.01) and internal consistency (ɑ = .73-.91). It also showed convergent validity with another widely used cancellation task, d2 Test of Attention (r = .43-.59, p < 0.01), and predicted performance on a cognitive control composite (r = .34-.41, p < 0.05). These results suggest that UCancellation is a valid test of selective attention and inhibitory control, which warrants further data collection to establish norms.

Age differences in functional network reconfiguration with working memory training.

Demanding cognitive functions like working memory (WM) depend on functional brain networks being able to communicate efficiently while also maintaining some degree of modularity. Evidence suggests that aging can disrupt this balance between integration and modularity. In this study, we examined how cognitive training affects the integration and modularity of functional networks in older and younger adults. Twenty three younger and 23 older adults participated in 10 days of verbal WM training, leading to performance gains in both age groups. Older adults exhibited lower modularity overall and a greater decrement when switching from rest to task, compared to younger adults. Interestingly, younger but not older adults showed increased task-related modularity with training. Furthermore, whereas training increased efficiency within, and decreased participation of, the default-mode network for younger adults, it enhanced efficiency within a task-specific salience/sensorimotor network for older adults. Finally, training increased segregation of the default-mode from frontoparietal/salience and visual networks in younger adults, while it diffusely increased between-network connectivity in older adults. Thus, while younger adults increase network segregation with training, suggesting more automated processing, older adults persist in, and potentially amplify, a more integrated and costly global workspace, suggesting different age-related trajectories in functional network reorganization with WM training.

Post-training stimulation of the right dorsolateral prefrontal cortex impairs working memory training performance.

Research investigating transcranial direct current stimulation (tDCS) to enhance cognitive training augments both our understanding of its long-term effects on cognitive plasticity as well as potential applications to strengthen cognitive interventions. Previous work has demonstrated enhancement of working memory training while applying concurrent tDCS to the dorsolateral prefrontal cortex (DLPFC). However, the optimal stimulation parameters are still unknown. For example, the timing of tDCS delivery has been shown to be an influential variable that can interact with task learning. In the present study, we used tDCS to target the right DLPFC while participants trained on a visuospatial working memory task. We sought to compare the relative efficacy of online stimulation delivered during training to offline stimulation delivered either immediately before or afterwards. We were unable to replicate previously demonstrated benefits of online stimulation; however, we did find evidence that offline stimulation delivered after training can actually be detrimental to training performance relative to sham. We interpret our results in light of evidence suggesting a role of the right DLPFC in promoting memory interference, and conclude that while tDCS may be a promising tool to influence the results of cognitive training, more research and an abundance of caution are needed before fully endorsing its use for cognitive enhancement. This work suggests that effects can vary substantially in magnitude and direction between studies, and may be heavily dependent on a variety of intervention protocol parameters such as the timing and location of stimulation delivery, about which our understanding is still nascent.

Neural correlates of working memory training: Evidence for plasticity in older adults.

Brain activity typically increases with increasing working memory (WM) load, regardless of age, before reaching an apparent ceiling. However, older adults exhibit greater brain activity and reach ceiling at lower loads than younger adults, possibly reflecting compensation at lower loads and dysfunction at higher loads. We hypothesized that WM training would bolster neural efficiency, such that the activation peak would shift towards higher memory loads after training. Pre-training, older adults showed greater recruitment of the WM network than younger adults across all loads, with decline at the highest load. Ten days of adaptive training on a verbal WM task improved performance and led to greater brain responsiveness at higher loads for both groups. For older adults the activation peak shifted rightward towards higher loads. Finally, training increased task-related functional connectivity in older adults, both within the WM network and between this task-positive network and the task-negative/default-mode network. These results provide new evidence for functional plasticity with training in older adults and identify a potential signature of improvement at the neural level.

Working memory training restores aberrant brain activity in adult attention-deficit hyperactivity disorder.

The development of treatments for attention impairments is hampered by limited knowledge about the malleability of underlying neural functions. We conducted the first randomized controlled trial to determine the modulations of brain activity associated with working memory (WM) training in adults with attention-deficit hyperactivity disorder (ADHD). At baseline, we assessed the aberrant functional brain activity in the n-back WM task by comparing 44 adults with ADHD with 18 healthy controls using fMRI. Participants with ADHD were then randomized to train on an adaptive dual n-back task or an active control task. We tested whether WM training elicits redistribution of brain activity as observed in healthy controls, and whether it might further restore aberrant activity related to ADHD. As expected, activity in areas of the default-mode (DMN), salience (SN), sensory-motor (SMN), frontoparietal (FPN), and subcortical (SCN) networks was decreased in participants with ADHD at pretest as compared with healthy controls, especially when the cognitive load was high. WM training modulated widespread FPN and SN areas, restoring some of the aberrant activity. Training effects were mainly observed as decreased brain activity during the trained task and increased activity during the untrained task, suggesting different neural mechanisms for trained and transfer tasks.

ERP evidence for the effect of working memory span training on working memory maintenance: A randomized controlled trial.

There is a lot of debate in the literature with regards to whether the effects of working memory span training generalize to working memory tasks that are different from the trained task, however, there is little evidence to date supporting this idea. The present randomized controlled trial included 80 undergraduate students who were randomly assigned to either the experimental group (N = 40) or the control group (N = 40) in order to receive a working memory span intervention for 20 sessions over the course of 4 weeks. Brain electrophysiological signals during a dot pattern expectancy (DPX) task and a change detection task were recorded both before and after the intervention. The amplitudes of characteristic event-related potential (ERP) components reflecting working memory maintenance capability during the delay period of both tasks (i.e., the contingent negative variation or CNV, derived from the DPX task, and the contralateral delay activity or CDA, derived from the change detection task) were used as the primary outcome measures. Our data indicated that the intervention resulted in specific changes in both, the CNV and the CDA, suggesting that working memory span training generalized to working memory maintenance processes as observed in working memory tasks that were different from the trained task. We conclude that working memory span training might serve as a useful tool to improve working memory maintenance capability. Trial Registration: Chinese Clinical Trial Registry (chiCTR-INR-17011728).

Racing dragons and remembering aliens: Benefits of playing number and working memory games on kindergartners' numerical knowledge.

Sources that contribute to variation in mathematical achievement include both numerical knowledge and general underlying cognitive processing abilities. The current study tested the benefits of tablet-based training games that targeted each of these areas for improving the mathematical knowledge of kindergarten-age children. We hypothesized that playing a number-based game targeting numerical magnitude knowledge would improve children's broader numerical skills. We also hypothesized that the benefits of playing a working memory (WM) game would transfer to children's numerical knowledge given its important underlying role in mathematics achievement. Kindergarteners from diverse backgrounds (n = 148; 52% girls; Mage  = 71.87 months) were randomly assigned to either play a number-based game, a WM game, or a control game on a tablet for 10 sessions. Structural equation modeling was used to model children's learning gains in mathematics and WM across time. Overall, our results suggest that playing the number game improved kindergarten children's numerical knowledge at the latent level, and these improvements remained stable as assessed 1 month later. However, children in the WM group did not improve their numerical knowledge compared to children in the control condition. Playing both the number game and WM game improved children's WM at the latent level. Importantly, the WM group continued to improve their WM for at least a month after playing the games. The results demonstrate that computerized games that target both domain-specific and domain-general skills can benefit a broad range of kindergarten-aged children.

The malleability of executive function in early childhood: Effects of schooling and targeted training.

Executive function (EF), its importance for scholastic achievement and the question of whether or not EF is malleable, have become a topic of intense interest. Education or schooling is often seen as effective approaches to enhance EF due to the specific school-related requirements as compared to kindergarten or pre-school. However, no study to date has investigated whether targeted training focusing on those domains might be comparable with regular schooling in improving EF and fluid intelligence (Gf). The aim of the present study was to replicate and extend the previously demonstrated schooling effects on EF by using a school-cutoff design, and to further investigate whether a theoretically motivated intervention targeting specific EF, i.e., working memory (WM) or inhibitory control (IC), could achieve comparable effects with schooling in both, WM and IC, as well as Gf. 91 6-year-old kindergarteners and first-graders with similar chronological age participated the study. We compared the performance of a first-grade schooling group with that of two kindergarten training groups as well as a business-as-usual kindergarten control group. Participants were assessed in WM, IC and Gf at baseline, immediately after the intervention (posttest), as well as 3 months after training completion (follow-up). The results showed that the schooling group indeed outperformed the kindergarten groups at baseline in several cognitive tasks. Furthermore, both the WM and IC training showed pronounced gains in the trained tasks, as well as varying degrees of improvement in non-trained outcome measures. Most importantly, both training groups achieved comparable performance with the schooling group, which was especially apparent in Gf at follow-up. Our findings provide further evidence for the malleability of EF demonstrating that both, long-term and short-term interventions can facilitate the acquisition of those important skills, and as such, our work has important implications for educational practice.

Stress and executive control: Mechanisms, moderators, and malleability.

Stress pervades everyday life and more importantly, affects prefrontal cortices that support executive control functions, processes that are critical to learning and memory as well as a range of life outcomes. The positive or negative effect of stress on cognition depends on an interaction of factors related to the situation and the individual. Research has shown that psychological characteristics related to self-relevance and the availability of resources may lead individuals to perceive a stressor as a threat or challenge, driving performance outcomes. Given that perception is arguably the key to stress reactivity, positive affect and self-belief constructs are discussed in the context of how they may lead to preserved performance in the face of stress. Understanding the underlying mechanisms of stress perception could inform the development of interventions, a socially important endeavor given the impact of stress on health and cognitive functions.

Validation of a matrix reasoning task for mobile devices.

Many cognitive tasks have been adapted for tablet-based testing, but tests to assess nonverbal reasoning ability, as measured by matrix-type problems that are suited to repeated testing, have yet to be adapted for and validated on mobile platforms. Drawing on previous research, we developed the University of California Matrix Reasoning Task (UCMRT)-a short, user-friendly measure of abstract problem solving with three alternate forms that works on tablets and other mobile devices and that is targeted at a high-ability population frequently used in the literature (i.e., college students). To test the psychometric properties of UCMRT, a large sample of healthy young adults completed parallel forms of the test, and a subsample also completed Raven's Advanced Progressive Matrices and a math test; furthermore, we collected college records of academic ability and achievement. These data show that UCMRT is reliable and has adequate convergent and external validity. UCMRT is self-administrable, freely available for researchers, facilitates repeated testing of fluid intelligence, and resolves numerous limitations of existing matrix tests.

Stable long-range interhemispheric coordination is supported by direct anatomical projections.

The functional interaction between the brain's two hemispheres includes a unique set of connections between corresponding regions in opposite hemispheres (i.e., homotopic regions) that are consistently reported to be exceptionally strong compared with other interhemispheric (i.e., heterotopic) connections. The strength of homotopic functional connectivity (FC) is thought to be mediated by the regions' shared functional roles and their structural connectivity. Recently, homotopic FC was reported to be stable over time despite the presence of dynamic FC across both intrahemispheric and heterotopic connections. Here we build on this work by considering whether homotopic FC is also stable across conditions. We additionally test the hypothesis that strong and stable homotopic FC is supported by the underlying structural connectivity. Consistent with previous findings, interhemispheric FC between homotopic regions were significantly stronger in both humans and macaques. Across conditions, homotopic FC was most resistant to change and therefore was more stable than heterotopic or intrahemispheric connections. Across time, homotopic FC had significantly greater temporal stability than other types of connections. Temporal stability of homotopic FC was facilitated by direct anatomical projections. Importantly, temporal stability varied with the change in conductive properties of callosal axons along the anterior-posterior axis. Taken together, these findings suggest a notable role for the corpus callosum in maintaining stable functional communication between hemispheres.

Individual Differences and Long-term Consequences of tDCS-augmented Cognitive Training.

A great deal of interest surrounds the use of transcranial direct current stimulation (tDCS) to augment cognitive training. However, effects are inconsistent across studies, and meta-analytic evidence is mixed, especially for healthy, young adults. One major source of this inconsistency is individual differences among the participants, but these differences are rarely examined in the context of combined training/stimulation studies. In addition, it is unclear how long the effects of stimulation last, even in successful interventions. Some studies make use of follow-up assessments, but very few have measured performance more than a few months after an intervention. Here, we utilized data from a previous study of tDCS and cognitive training [Au, J., Katz, B., Buschkuehl, M., Bunarjo, K., Senger, T., Zabel, C., et al. Enhancing working memory training with transcranial direct current stimulation. Journal of Cognitive Neuroscience, 28, 1419-1432, 2016] in which participants trained on a working memory task over 7 days while receiving active or sham tDCS. A new, longer-term follow-up to assess later performance was conducted, and additional participants were added so that the sham condition was better powered. We assessed baseline cognitive ability, gender, training site, and motivation level and found significant interactions between both baseline ability and motivation with condition (active or sham) in models predicting training gain. In addition, the improvements in the active condition versus sham condition appear to be stable even as long as a year after the original intervention.

Enhanced structural connectivity within a brain sub-network supporting working memory and engagement processes after cognitive training.

The structural connectome provides relevant information about experience and training-related changes in the brain. Here, we used network-based statistics (NBS) and graph theoretical analyses to study structural changes in the brain as a function of cognitive training. Fifty-six young women were divided in two groups (experimental and control). We assessed their cognitive function before and after completing a working memory intervention using a comprehensive battery that included fluid and crystallized abilities, working memory and attention control, and we also obtained structural MRI images. We acquired and analyzed diffusion-weighted images to reconstruct the anatomical connectome and we computed standardized changes in connectivity as well as group differences across time using NBS. We also compared group differences relying on a variety of graph-theory indices (clustering, characteristic path length, global and local efficiency and strength) for the whole network as well as for the sub-network derived from NBS analyses. Finally, we calculated correlations between these graph indices and training performance as well as the behavioral changes in cognitive function. Our results revealed enhanced connectivity for the training group within one specific network comprised of nodes/regions supporting cognitive processes required by the training (working memory, interference resolution, inhibition, and task engagement). Significant group differences were also observed for strength and global efficiency indices in the sub-network detected by NBS. Therefore, the connectome approach is a valuable method for tracking the effects of cognitive training interventions across specific sub-networks. Moreover, this approach allowsfor the computation of graph theoretical network metricstoquantifythetopological architecture of the brain networkdetected. The observed structural brain changes support the behavioral results reported earlier (see Colom, Román, et al., 2013).

Enhancing Working Memory Training with Transcranial Direct Current Stimulation.

Working memory (WM) is a fundamental cognitive ability that supports complex thought but is limited in capacity. Thus, WM training interventions have become very popular as a means of potentially improving WM-related skills. Another promising intervention that has gained increasing traction in recent years is transcranial direct current stimulation (tDCS), a noninvasive form of brain stimulation that can modulate cortical excitability and temporarily increase brain plasticity. As such, it has the potential to boost learning and enhance performance on cognitive tasks. This study assessed the efficacy of tDCS to supplement WM training. Sixty-two participants were randomized to receive either right prefrontal, left prefrontal, or sham stimulation with concurrent visuospatial WM training over the course of seven training sessions. Results showed that tDCS enhanced training performance, which was strikingly preserved several months after training completion. Furthermore, we observed stronger effects when tDCS was spaced over a weekend break relative to consecutive daily training, and we also demonstrated selective transfer in the right prefrontal group to nontrained tasks of visual and spatial WM. These findings shed light on how tDCS may be leveraged as a tool to enhance performance on WM-intensive learning tasks.

Dissociable functional networks of the human dentate nucleus.

The cerebellar dentate nucleus has been reported to project to motor and prefrontal cortical regions in nonhuman primates from 2 anatomically distinct areas. However, despite a wealth of human neuroimaging data implicating the cerebellum in motor and cognitive behaviors, evidence of dissociable motor and cognitive networks comprising the human dentate is lacking. To investigate the existence of these 2 networks in the human brain, we used resting-state functional connectivity magnetic resonance imaging. The resting-state fMRI signal was extracted from regions of interest in the dorsal and ventral dentate nucleus. We report a "motor" network involving the dorsal dentate, anterior regions of the cerebellum, and the precentral gyrus, and a "cognitive" network involving the ventral dentate, Crus I, and prefrontal cortex. The existence of these 2 distinct networks supports the notion that cerebellar involvement in cognitive tasks is above and beyond that associated with motor response components.

Does resting-state connectivity reflect depressive rumination? A tale of two analyses.

Major Depressive Disorder (MDD) is characterized by rumination. Prior research suggests that resting-state brain activation reflects rumination when depressed individuals are not task engaged. However, no study has directly tested this. Here we investigated whether resting-state epochs differ from induced ruminative states for healthy and depressed individuals. Most previous research on resting-state networks comes from seed-based analyses with the posterior cingulate cortex (PCC). By contrast, we examined resting state connectivity by using the complete multivariate connectivity profile (i.e., connections across all brain nodes) and by comparing these results to seeded analyses. We find that unconstrained resting-state intervals differ from active rumination states in strength of connectivity and that overall connectivity was higher for healthy vs. depressed individuals. Relationships between connectivity and subjective mood (i.e., behavior) were strongly observed during induced rumination epochs. Furthermore, connectivity patterns that related to subjective mood were strikingly different for MDD and healthy control (HC) groups suggesting different mood regulation mechanisms.