Age Differences in the Transfer and Maintenance of Practice-Induced Improvements in Task Switching: The Impact of Working-Memory and Inhibition Demands

The effect of age on task switching: updated and extended meta-analyses

Cognitive flexibility is one of the crucial abilities for human survival. As people get older, whether their flexibility ability will be affected is one of the core research topics in aging research. Researchers have developed a task-switch paradigm in laboratories to mimic daily-life shifting task-set scenarios. However, the empirical evidence is equivocal. Considering every single study may have a biased sample; therefore, we hoped to combine smaller studies, making them into one extensive investigation, which may help show an actual effect. In the current study, we used two meta-analysis techniques, the Brinley plot (along with the State-trace plot) and conventional meta-analysis, to re-evaluate whether healthy aging influences cognitive flexibility. The results of the Brinley plot analysis showed no evidence of switch-specific age-related impairment as indexed by the local switch cost. Yet, older adults performed more slowly than younger adults across task conditions. The conventional meta-analysis further showed that the currently available findings were heterogenous and exhibited publication bias. Therefore, this study suggests that researchers should interpret their results cautiously while using a task-switching paradigm to address older adults' shifting abilities. More parametric variables must be considered and developed in a task-switching paradigm to enhance its sensitivity and reveal older adults' actual shifting ability.

Effects of anodal tDCS stimulation in predictable and unpredictable task switching performance: The possible involvement of the parietal cortex

Transcranial direct current stimulation (tDCS) has been used to explore the causal relationship between specific brain regions and task switching. However, most studies have focused on the frontal cortex, and only few have examined other related cortices, e.g., the parietal cortex. However, no prior study has systematically explored the tDCS-induced effect of the parietal cortex in different task switching types. Therefore, the current study mainly used the unilateral anodal-tDCS (a-tDCS) stimulation setting to investigate the possible involvement of the parietal cortex in predictable and unpredictable task switching. It was noted that compared with sham group, significantly higher switch cost reaction time of right anode tDCS (RA) group was found in predictable task but not unpredictable task. No interaction effect was observed between congruence and tDCS groups in predictable task. These findings suggested that a-tDCS over right parietal cortex could markedly decrease the predictable task-switching performance in both congruent and incongruent trials, and indicated that parietal cortex is more likely to be involved in the proactive cognitive processes, such as endogenous preparation.

Feasibility of a Home-Based Task-Switching Training in Middle-Aged Caregivers

The current study aimed at investigating feasibility of a self-administered task-switching training in a middle-aged working population. Eighty-one caregivers (41–62 years old) were instructed to train at home 8 times either within a 7- or 14-day interval. Only 56.7% performed more than 50% of the instructed number of training sessions. However, compliant caregivers (who completed more than 4 training sessions) showed significant training gains and transfer to an untrained task-switching task. Although transfer effects to other cognitive tasks were not found, trained participants tended to report fewer everyday memory failures than a control group. In conclusion, the implementation of a home-based task-switching training in everyday life of caregivers is possible. However, there is only limited evidence for generalization of results of previous laboratory studies. Adherence and transfer to other cognitive tasks are discussed as important challenges in conveying laboratory findings into real life.

Cognitive training using the abacus: a literature review study on the benefits for different age groups

The literature indicates that cognitive stimulation interventions have shown promising results. Abacus represents a tool with great potential in such interventions.

Anodal Transcranial Direct Current Stimulation-Induced Effects Over the Right Dorsolateral Prefrontal Cortex: Differences in the Task Types of Task Switching

Transcranial direct current stimulation (tDCS) has been previously used to investigate the causal relationships between the dorsolateral prefrontal cortex (DLPFC) and task switching but has delivered inconclusive results that may be due to different switching tasks involving different cognitive control processes. In the current study, we manipulated task types and task predictability to investigate the role of DLPFC in task-switching performances. Notably, we distinguished the specific effects of anodal-tDCS on two types of tasks (parity/magnitude and parity/vowel-consonant tasks). Forty-eight participants were randomly assigned to four task groups as follows; Group I who was assigned right anode (RA) parity/magnitude tasks, Group II who were assigned sham parity/magnitude tasks, Group III who were assigned RA parity/vowel-consonant tasks, and Group IV who were assigned sham parity/vowel-consonant tasks. Participants were asked to complete both predictable and unpredictable tasks. In the parity/magnitude task, we demonstrated a lower switch cost for the RA group compared to the sham group for unpredictable tasks. In contrast, in the parity/vowel-consonant task, the switch cost was higher for the RA group compared to the sham group for unpredictable and predictable tasks. These findings confirmed an anodal-tDCS-induced effect over the right DLPFC both in the parity/magnitude and parity/vowel-consonant tasks. Our data indicated that anodal tDCS may have a stronger influence on task-switching performance over the right DLPFC by changing the irrelevant task-set inhibition process. Also, the right DLPFC is unlikely to act by performing exogenous adjustment of predictable task switching.

Cross-Modal Transfer Following Auditory Task-Switching Training in Old Adults

Maintaining and coordinating multiple task-sets is difficult and leads to costs, however task-switching training can reduce these deficits. A recent study in young adults demonstrated that this training effect occurs at an amodal processing level. Old age is associated with reduced cognitive plasticity and further increases the performance costs when mixing multiple tasks. Thus, cognitive aging might be a limiting factor for inducing cross-modal training effects in a task-switching environment. We trained participants, aged 62-83 years, with an auditory task-switching paradigm over four sessions (2880 total trials), to investigate whether training-related reductions in task-switching costs would also manifest in an untrained visual modality version of the task. Two control groups trained with single tasks (active control) or not trained (passive control) allowed us to identify improvements specific to task-switching training. To make statistical evaluations of any age differences in training and cross-modal transfer, the data from the Kattner cohort were incorporated into the present analysis. Despite the tendency for older adults to respond more cautiously, task-switching training specifically led to a mixing cost reduction in both trained and untrained modalities, the magnitude of which was statistically similar regardless of age. In line with a growing body of research, we failed to observe any far transfer effects in measures of inhibition, working memory or fluid intelligence. Overall, we conclude that any apparent cognitive limitations associated with aging do not prevent cognitive control processes which support set-shifting from improving at an amodal level.

Training and Transfer of Cue Updating in Older Adults Is Limited: Evidence From Behavioral and Neuronal Data

Cognitive control processes, such as updating task-relevant information while switching between multiple tasks, are substantially impaired in older adults. However, it has also been shown that these cognitive control processes can be improved by training interventions, e.g., by training in task switching. Here, we applied an event-related potential (ERP) approach to identify whether a cognitive training improves task-preparatory processes such as updating of relevant task goals. To do so, we applied a pretest-training-posttest design with eight training sessions. Two groups of older adults were either trained in task switching (treatment group) or in performing single tasks (control group) and we compared their performance to a group of untrained younger adults. To foster cue updating in the treatment group, we applied a cue-based switching task in which the two task cues were randomly selected prior to target presentation so that participants had time to prepare for the upcoming task. In contrast, the control group also received task cues but those were redundant as only one task had to be performed. We also examined whether training in cue updating during task switching can be transferred to a similar cognitive control task measuring updating of context information, namely a modified version of the AX-Continuous Performance Task (AX-CPT). The results revealed training-specific improvements in task switching, that is, a larger improvement in blocks requiring switching in comparison to single tasks at the behavioral level. In addition, training specific-effects were also found at the neuronal level. Older adults trained in cue updating while switching showed a reduction in mixing costs in the cue-related P3, indicating an improvement in preparatory updating processes. Additionally, P3 topography changed with training from a very broad to a parietally focused scalp distribution similar to the one found in younger adults. However, we did not obtain training-specific improvements in context updating in the AX-CPT neither at the behavioral level nor at the neuronal level. Results are discussed in the context of the ongoing debate on whether transfer of cognitive training improvements is possible.

The Effect of Baseline Performance and Age on Cognitive Training Improvements in Older Adults: A Qualitative Review

Findings that the brain is capable of plasticity up until old age have led to interest in the use of cognitive training as a potential intervention to delay the onset of dementia. However, individuals participating in training regimens differ greatly with respect to their outcomes, demonstrating the importance of considering individual differences, in particular age and baseline performance in a cognitive domain, when evaluating the effectiveness of cognitive training. In this review, we summarize existing literature on cognitive training in adults across the domains of episodic memory, working memory and the task-switching component of executive functioning to clarify the picture on the impact of age and baseline performance on cognitive training-related improvements. Studies targeting episodic memory induced greater improvements in younger adults with more intact cognitive abilities, explained in part by factors specific to episodic memory training. By contrast, older, lower baseline performance adults improved most in several studies targeting working memory in older individuals as well as in the majority of studies targeting executive functioning, suggesting the preservation of neural plasticity in these domains until very old age. Our findings can have important implications for informing the design of future interventions for enhancing cognitive functions in individuals at the prodromal stage of Alzheimer's Disease and potentially delaying the clinical onset of Alzheimer's Disease. Future research should more clearly stratify individuals according to their baseline cognitive abilities and assign specialized, skill-specific cognitive training regimens in order to directly answer the question of how individual differences impact training effectiveness.

Working memory training format in older adults: individual versus group sessions

Working memory (WM) training has been shown to increase the performance of participants in WM tasks and in other cognitive abilities, but there has been no study comparing directly the impact of training format (individual vs. group) using the same protocol. Therefore, the aim of this study was to compare the efficacy of the Borella et al. three session verbal WM training offered in two different formats on target and transfer tasks. This study was conducted in two waves. In the first wave, participants were randomized into individual training (n = 11) and individual control conditions (n = 15). In the second wave, participants were randomized into group training (n = 16) and group control conditions (n = 17). Training consisted of three sessions of WM exercises and participants in the active control condition responded to questionnaires during the same time. There was significant improvement for both training conditions at post-test and maintenance at follow-up for the target task, other WM tasks, processing speed, and executive functions tasks. The ANOVA results showed that the training gains did not depend on the WM training format. However, the effect size analyses suggested that this intervention can be more effective, at short term and follow-up, when provided individually. To conclude, this study showed that providing this training collectively or individually does not change the training benefits, which increases the possibilities of its use in different contexts.

Does attention switching between multiple tasks affect gait stability and task performance differently between younger and older adults?

Gait stability and secondary task performance are affected by the need to share attention when dual-tasking. Further decrements may result from the need to switch attention between multiple secondary tasks. The aim of the current study was to determine the effects of attention switching upon gait stability and task performance in healthy younger and older adults. Ten healthy younger and ten healthy older adults walked on a treadmill at their preferred speed during three trials including: (1) baseline walking; (2) non-switching task walking, requiring response to an auditory-spatial or visual-spatial cue presented in an expected order; and (3) switching task walking, which required response to an auditory-spatial or visual-spatial cue presented in an unexpected order. Response time and accuracy, the margin of stability in the frontal (MoS_ML) and sagittal planes (MoS_A: anterior, MoS_P: posterior), step width and step length were calculated for non-switching and switching tasks. The MoS_ML, MoS_A, MoS_P, step width and step length during non-switching and switching tasks were normalized to baseline walking. Older adults took significantly longer to respond to cues and made more errors during the switching task compared to younger adults. Younger adults took narrower steps (p < 0.01) and displayed a reduction in MoS_ML (p < 0.01) during the switching task compared with the non-switching task. Conversely, older adults displayed no differences in MoS_ML between tasks. These findings suggest that attention switching results in different task prioritization strategies in younger and older adults during walking.

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.

Goal-Oriented Attention Self-Regulation (GOALS) training in older adults

Objectives: A common cognitive complaint of older adulthood is distractibility, or decline in ability to concentrate and maintain focus, yet few evidence-based interventions exist to address these deficits. We implemented s pilot trial of an evidence-based executive function training program, to investigate whether training in applied goal-directed attention regulation and problem solving would enhance executive control abilities in a sample of cognitively normal older adults with self-reported complaints of concentration problems.Method: Consecutively recruited participants were placed into small groups and randomized to either Goal-Oriented Attentional Self-Regulation training (GOALS; N = 15) or a closely matched Brain Health Education program (BHE; N = 15).Results: GOALS participants significantly improved on: neurocognitive measures of mental flexibility (p = 0.03, partial eta squared = 0.23); real-world setting functional performance measures of: task failures (p = 0.02, Cohen's d = 0.88), task rule breaks (p = 0.02, Cohen's d = 1.06), and execution (p = 0.04, Cohen's d = 0.76); and in-lab functional assessment of goal-directed behaviour divergent thinking scale (p = 0.03, Cohen's d = 0.95). All participants improved on a neurocognitive measure of planning (p = 0.01, partial eta squared = 0.031). BHE participants' improvement over and above GOALS participants was limited to: rule adherence on the real world task (p = 0.04, Cohen's d = 0.99), and evaluator rating (p = 0.03, Cohen's d = 0.56), and average score (p = 0.02, Cohen's d = 0.71) on the in-lab functional task.Conclusion: Participation in GOALS training can enhance executive control, and lead to real-world functional improvements, for cognitively normal older adults with self-reported attention difficulties.

Verbal working memory training in older adults: an investigation of dose response

The WM training protocol proposed by Borella et al. found specific and transfer effects among seniors, however, the studies were carried out in the same socio-cultural context and variations in the procedure were never tested. The present study aimed at analyzing the efficacy of Borella et al.'s training, in terms of short and long-term benefits, in a different socio-cultural context (Study 1), and the effect of change in the training's length (duplicating the number of sessions (Study 2). Participants were randomly assigned to a trained group (N = 18 for Study 1, and N = 23 for Study 2) and active control group (N = 28 for Study 1, and N = 27 for Study 2), and evaluated at pre, post-test and six-month follow-up for verbal WM task (criterion task), and for visuospatial and verbal WM, inhibition, processing speed, executive function, and fluid intelligence measures (transfer tasks). The trained groups had higher performance in all tasks when compared with active control groups after training and at 6 month follow-up. The longer training (Study 2) generated similar gains as the original protocol, with some advantage in far transfer tasks at post-test and follow-up. Study limitations include the small sample sizes. In conclusion, this training was effective in a different socio-cultural context and adding three sessions to the protocol did not significantly change training impact.

Spatio-Temporal Neural Changes After Task-Switching Training in Old Age

In the present study, we aimed at examining selective neural changes after task-switching training in old age by not only considering the spatial location but also the timescale of brain activation changes (i.e., sustained/block-related or transient/trial-related timescales). We assigned a sample of 50 older adults to a task-switching training or an active single-task control group. We administered two task paradigms, either sensitive to transient (i.e., a context-updating task) or sustained (i.e., a delayed-recognition working-memory task) dynamics of cognitive control. These dynamics were captured by utilizing an appropriate event-related or block-related functional magnetic resonance imaging design. We captured selective changes in task activation during the untrained tasks after task-switching training compared to an active control group. Results revealed changes at the neural level that were not evident from only behavioral data. Importantly, neural changes in the transient-sensitive context updating task were found on the same timescale but in a different region (i.e., in the left inferior parietal lobule) than in the task-switching training task (i.e., ventrolateral PFC, inferior frontal junction, superior parietal lobule), only pointing to temporal overlap, while neural changes in the sustained-sensitive delayed-recognition task overlapped in both timescale and region with the task-switching training task (i.e., in the basal ganglia), pointing to spatio-temporal overlap. These results suggest that neural changes after task-switching training seem to be critically supported by the temporal organization of neural processing.

Aging of the frontal lobe

Healthy aging is associated with numerous deficits in cognitive function, which have been attributed to changes within the prefrontal cortex (PFC). This chapter summarizes some of the most prominent cognitive changes associated with age-related alterations in the anatomy and physiology of the PFC. Specifically, aging of the PFC results in deficient aspects of cognitive control, including sustained attention, selective attention, inhibitory control, working memory, and multitasking abilities. Yet, not all cognitive functions associated with the PFC exhibit age-related declines, such as arithmetic, comprehension, emotion perception, and emotional control. Moreover, not all older adults exhibit declines in cognition. Multiple life-course and lifestyle factors, as well as genetics, play a role in the trajectory of cognitive performance across the life span. Thus many adults retain cognitive function well into advanced age. Moreover, the brain remains plastic throughout life and there is increasing evidence that most age-related declines in cognition can be remediated by various methods such as physical exercise, cognitive training, or noninvasive brain stimulation. Overall, because cognitive aging is associated with numerous life-course and lifestyle factors, successful aging likely begins in early life, while maintaining cognition or remediating declines is a life-long process.

Cognitive Training Does Not Enhance General Cognition

Due to potential theoretical and societal implications, cognitive training has been one of the most influential topics in psychology and neuroscience. The assumption behind cognitive training is that one's general cognitive ability can be enhanced by practicing cognitive tasks or intellectually demanding activities. The hundreds of studies published so far have provided mixed findings and systematic reviews have reached inconsistent conclusions. To resolve these discrepancies, we carried out several meta-analytic reviews. The results are highly consistent across all the reviewed domains: minimal effect on domain-general cognitive skills. Crucially, the observed between-study variability is accounted for by design quality and statistical artefacts. The cognitive-training program of research has showed no appreciable benefits, and other more plausible practices to enhance cognitive performance should be pursued.

Training and transfer effects of extensive task-switching training in students

The capacity to switch between tasks is a central component of executive functioning. Previous studies assessing effects of task-switch training have revealed mixed results, both in terms of processes that may be improved and the extent of beneficial effects on non-trained tasks. These studies primarily used few training sessions, which may have limited training and transfer effects. Here, 31 students were trained for 21 days on a cued switching task. Both the trained group and an active control group (n = 29) performed a number of cognitive tasks before and after training. Training reduced both switch and mixing costs, which mostly reached an asymptote after approximately four to six training sessions, although there were residual costs at the end of training. The switch cost reduction was restricted to trials with a short cue–stimulus onset interval (CSI). Training benefitted performance on another switching task, reflecting near transfer. However, this benefit was limited to the switch cost and to trials with a short CSI. There were no beneficial effects on far-transfer tasks measuring interference control, response inhibition, working memory, and general IQ. The results suggest that the present extensive training protocol, implicating overtraining, specifically enhanced the efficiency of processes involved in preparing for the relevant upcoming task set and/or inhibition of the previous task set. However, the lack of beneficial far-transfer effects is in line with previous cognitive training studies employing fewer training sessions, suggesting that the extent of training is not critical for (not) finding transfer effects.