Testing the limits of cognitive plasticity in older adults: application to attentional control

The assessment of executive function abilities in healthy and neurodegenerative aging-A selective literature review

Numerous studies have examined executive function (EF) abilities in cognitively healthy older adults and those living with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Currently, there are no standard accepted protocols for testing specific EFs; thus, researchers have used their preferred tool, which leads to variability in assessments of decline in a particular ability across studies. Therefore, there is a need for guidance as to the most sensitive tests for assessing EF decline. A search of the most current literature published between 2000 and 2022 on EF studies assessing cognitively healthy older adults and individuals living with MCI and AD was conducted using PubMed/Medline, PsycINFO, Embase, Web of Science, and Google Scholar. Emphasis was placed on the EF's dual-tasking, inhibition, shifting or switching, and working memory updating. Many tasks and their outcomes were reviewed. Of particular importance was the difference in outcomes for tasks applied to the same group of participants. These various EF assessment tools demonstrate differences in effectively identifying decline in EF ability due to the aging process and neurodegenerative conditions, such as MCI and AD. This review identifies various factors to consider in using particular EF tasks in particular populations, including task demand and stimuli factors, and also when comparing differing results across studies.

A mechanism underlying improved dual-task performance after practice: Reviewing evidence for the memory hypothesis

Extensive practice can significantly reduce dual-task costs (i.e., impaired performance under dual-task conditions compared with single-task conditions) and, thus, improve dual-task performance. Among others, these practice effects are attributed to an optimization of executive function skills that are necessary for coordinating tasks that overlap in time. In detail, this optimization of dual-task coordination skills is associated with the efficient instantiation of component task information in working memory at the onset of a dual-task trial. In the present paper, we review empirical findings on three critical predictions of this memory hypothesis. These predictions concern (1) the preconditions for the acquisition and transfer of coordination skills due to practice, (2) the role of task complexity and difficulty, and (3) the impact of age-related decline in working memory capacity on dual-task optimization.

Age does not modify the processing architecture of dual memory retrieval: an investigation of age-related effects on dual-retrieval practice in younger and older adults

The present study investigated the cognitive processing architecture of dual(-memory) retrieval from a single cue across two distinct age groups: younger and older adults. Previous research has shown that younger adults can exhibit learned parallel retrieval, but only if they synchronize response execution. This phenomenon has not been demonstrated with older adults. Experiment 1 functioned as an extension of previous studies to assess whether the finding of learned retrieval parallelism in younger adults could be observed in older adults as well. The experiment used a dual retrieval task that involved the retrieval of two responses, one vocal and one keypress, from a single cue. Experiment 2 further assessed whether the cognitive processing architecture underlying the occurrence of learned retrieval parallelism in dual memory retrieval could be influenced by the number of cues in single-retrieval practice. The results of both experiments showed that learned retrieval parallelism occurs in older as well as younger adults and that the processing mechanisms involved in dual memory retrieval are relatively stable across age groups.

Exercise-Induced Elevated BDNF Concentration Seems to Prevent Cognitive Impairment after Acute Exposure to Moderate Normobaric Hypoxia among Young Men

Memory impairment, reduced learning ability, decreased concentration, and psychomotor performance can be all signs of deleterious impact of hypoxia on cognitive functioning. In turn, physical exercise can improve performance and enhance cognitive functions. The purpose of this study was to investigate whether the potential positive effects of exercise performed under normobaric hypoxia can counteract the negative effects of hypoxia on cognitive function, and whether these changes correlate with brain-derived neurotrophic factor (BDNF) concentrations. Seventeen healthy subjects participated in a crossover study where they performed two sessions of single breathing bouts combined with moderate intensity exercise under two conditions: normoxia (NOR EX) and normobaric hypoxia (NH EX). To assess cognitive function, Stroop test was applied. There were no significant differences in any part of the Stroop interference test regardless of the conditions (NOR, NH), despite a statistical decrease in SpO2 (p < 0.0001) under normobaric hypoxic conditions. In addition, a statistical increase (p < 0.0001) in BDNF concentration was observed after both conditions. Acute exercise under normobaric hypoxia did not impair cognitive function despite a significant decrease in SpO2. Exercise in such conditions may offset the negative effects of hypoxia alone on cognitive function. This may be related to the significant increase in BDNF concentration and, as a consequence, positively affect the executive functions.

A Comparison of the Effect of Physical Activity and Cognitive Training on Dual-Task Performance in Older Adults

OBJECTIVES

Studies suggest that cognitive training and physical activity can improve age-related deficits in dual-task performances. However, both of these interventions have never been compared in the same study. This article investigates the improvement in dual-task performance in 2 types of exercise training groups and a cognitive training group and explores if there are specific dual-task components that are more sensitive or more likely to improve following each type of training.

METHODS

Seventy-eight healthy inactive participants older than the age of 60 (M = 69.98, SD = 5.56) were randomized to one of three 12-week training programs: aerobic training (AET) = 26, gross motor abilities (GMA) = 27, and cognition (COG) = 25. Before and after the training program, the participants underwent physical fitness tests, and cognitive evaluations involving a computerized cognitive dual task. The AET consisted of high- and low-intensity aerobic training, the GMA of full-body exercises focusing on agility, balance, coordination, and stretching, and the COG of tablet-based exercises focusing on executive functions.

RESULTS

Repeated-measures analysis of variance on reaction time data revealed a group × time interaction (F(2,75) = 11.91, p < .01) with COG having the greatest improvement, followed by a significant improvement in the GMA group. Secondary analysis revealed the COG to also improve the intraindividual variability in reaction time (F(1,24) = 8.62, p < .01), while the GMA improved the dual-task cost (F(1,26) = 12.74, p < .01).

DISCUSSION

The results show that physical and cognitive training can help enhance dual-task performance by improving different aspects of the task, suggesting that different mechanisms are in play.

Protocol for SYNchronising Exercises, Remedies in GaIt and Cognition at Home (SYNERGIC@Home): feasibility of a home-based double-blind randomised controlled trial to improve gait and cognition in individuals at risk for dementia

INTRODUCTION

Physical exercise and cognitive training have the potential to enhance cognitive function and mobility in older adults at risk of Alzheimer's disease and related dementia (ADRD), but little is known about the feasibility of delivering multidomain interventions in home settings of older adults at risk of ADRD. This study aims to assess the feasibility of home-based delivery of exercise and cognitive interventions, and to evaluate the relationship between participants' intervention preferences and their subsequent adherence. Secondary objectives include the effect of the interventions on ADRD risk factors, including frailty, mobility, sleep, diet and psychological health.

METHODS AND ANALYSIS

The SYNchronising Exercises, Remedies in GaIt and Cognition at Home (SYNERGIC@Home) feasibility trial is a randomised control trial that follows a 2×2 factorial design, with a 16-week home-based intervention programme (3 sessions per week) of physical exercises and cognitive training. Participants will be randomised in blocks of four to one of the following four arms: (1) combined exercise (aerobic and resistance)+cognitive training (NEUROPEAK); (2) combined exercise+control cognitive training (web searching); (3) control exercise (balance and toning)+cognitive training; and (4) control exercise+control cognitive training. SYNERGIC@Home will be implemented through video conferencing. Baseline and post-intervention assessments at 4-month and 10-month follow-up will include measures of cognition, frailty, mobility, sleep, diet and psychological health. Primary feasibility outcome is adherence to the interventions. Primary analytic outcome is the relationship between pre-allocation preference for a given intervention and subsequent adherence to the allocated intervention. A series of secondary analytic outcomes examining the potential effect of the individual and combined interventions on cognitive, mobility and general well-being will be measured at baseline and follow-up.

ETHICS AND DISSEMINATION

Ethics approval was granted by the relevant research ethics boards. Findings of the study will be presented to stakeholders and published in peer-reviewed journals and at provincial, national and international conferences.

TRIAL REGISTRATION NUMBER

NCT04997681, Pre-results.

Baseline capacities and motivation in executive control training of healthy older adults

OBJECTIVES

Normal aging involves progressive prefrontal declines and impairments in executive control. This study aimed to examine the efficacy of an executive-control training focusing on working memory and inhibition, in healthy older adults, and to explore the role of individual differences in baseline capacities and motivation in explaining training gains.

METHODS

Forty-four healthy older adults were randomly assigned to an experimental (training executive control) or active control group (training processing speed). Participants completed six online training sessions distributed across two weeks. Transfer effects to working memory (Operation Span test), response inhibition (Stop-Signal test), processing speed (Pattern Comparison) and reasoning (Raven's Advanced Progressive Matrices and Cattell Culture Fair test) were evaluated. Furthermore, we explored individual differences in baseline capacities and assessed motivation during and after the intervention.

RESULTS

The experimental group, but not the active control, showed significant transfer to response inhibition. Moreover, a general compensation effect was found: older adults with lower baseline capacities achieved higher levels of training improvement. Motivation was not related to training performance.

CONCLUSION

Our results encourage the use of executive control training to improve cognitive functions, reveal the importance of individual differences in training-related gains, and provide further support for cognitive plasticity during healthy aging.

Physical Exercise Training Effect and Mediation Through Cardiorespiratory Fitness on Dual-Task Performances Differ in Younger-Old and Older-Old Adults

OBJECTIVE

It has often been reported that dual-task (DT) performance declines with age. Physical exercise can help improve cognition, but these improvements could depend on cognitive functions and age groups. Moreover, the mechanisms supporting this enhancement are not fully elucidated. This study investigated the impacts of physical exercise on single- and dual-task performance in younger-old (<70) and older-old (70+) adults. The study also assessed whether the training effect on cognition was mediated by improvement in cardiorespiratory fitness.

METHODS

One hundred forty-three participants (65-89 years) took part in a physical exercise intervention for 3 months or were assigned to a control group. All participants completed a DT paradigm and an estimated measure of cardiorespiratory fitness. Regression models were used to test the training effect on these outcomes, and mediation analyses were used to determine whether the training-related cognitive changes were mediated by changes in cardiorespiratory fitness.

RESULTS

In 70+, training predicted improved processing speed (βc = -.33) and cardiorespiratory fitness (βa = .26) and the effect of training on processing speed was fully mediated by change in cardiorespiratory fitness (βab = -.12). In <70, training predicted improvement in task-set cost (βc = -.26) and change in cardiorespiratory fitness (βa = .30) but improvement in task-set cost was not entirely mediated by change in cardiorespiratory fitness.

DISCUSSION

Results are discussed in terms of the mechanisms supporting DT performance improvement following physical exercise training in older adults.

Structuralist Mental Representation of Dual-action Demands: Mechanisms of Improved Dual-task Performance after Practice in Older Adults

Aim: The present study was designed to investigate how behavioral (dual-action) demands in dual tasks are mentally represented in older adults and how these representations might contribute to the practice-related improvement of dual-task performance. Three different theoretical representation accounts were empirically tested: a structuralist account, a holistic account, and a contextual change account. The first account assumes that component tasks remain structurally intact when combined with another task while the second account assumes that dual-action requirements in dual tasks are represented holistically and entirely distinct from its component (single-action) requirements. The final account assumes that a change in context (e.g., from single to dual requirement) might generally impede response retrieval, similar to repeating a response when the task context switches. Methods: To address this issue of dual-action representations in older adults, we assessed trial-by-trial effects in a single/dual switch paradigm (involving a randomized mix of single- and dual-task trials within blocks). In detail, we re-analyzed a large set of practice data involving seven sessions, in which an auditory-vocal task was combined with a visual-manual task.  Results: At the end of practice, the current results were largely consistent with the structuralist account.  Conclusions: We conclude that dual-action requirements in the present dual-task setting are mentally represented in a predominantly structuralist fashion at the end of practice in older adults. The results are discussed in the context of other theories on practice-related mechanisms of improved dual-task performance in this age group.

Normative Data for a Tablet-Based Dual-Task Assessment in Healthy Older Adults

OBJECTIVE

The objective of this study is to provide normative data for a tablet-based dual-task assessment in older adults without cognitive deficits.

METHOD

In total, 264 participants aged between 60 and 90 years, French and English-speaking, were asked to perform two discrimination tasks, alone and concurrently. The participants had to answer as fast as possible to one or two images appearing in the center of the tablet by pressing to the corresponding buttons. Normative data are provided for reaction time (RT), coefficient of variation, and accuracy. Analyses of variance were performed by trial types (single-pure, single-mixed, dual-mixed), and linear regressions assessed the relationship between performance and sociodemographic characteristics.

RESULTS

The participants were highly educated and a large proportion of them were women (73.9%). The accuracy on the task was very high across all blocks. RT data revealed both a task-set cost and a dual-task cost between the blocks. Age was associated with slower RT and with higher coefficient of variability. Men were significantly slower on dual-mixed trials, but their coefficient of variability was lower on single-pure trials. Education was not associated with performance.

CONCLUSIONS

This study provides normative data for a tablet-based dual-task assessment in older adults without cognitive impairment, which was lacking. All participants completed the task with good accuracy in less than 15 minutes and thus, the task is transferable to clinical and research settings.

Synergistic Effects of Cognitive Training and Physical Exercise on Dual-Task Performance in Older Adults

BACKGROUND

Studies report benefits of physical exercise and cognitive training to enhance cognition in older adults. However, most studies did not compare these interventions to appropriate active controls. Moreover, physical exercise and cognitive training seem to involve different mechanisms of brain plasticity, suggesting a potential synergistic effect on cognition.

OBJECTIVE

This study investigated the synergistic effect of cognitive training and aerobic/resistance physical exercise on dual-task performance in older adults. Intervention effects were compared to active controls for both the cognitive and the exercise domain.

METHOD

Eighty-seven older adults completed one of 4 different combinations of interventions, in which computer lessons was active control for cognitive training and stretching/toning exercise control for aerobic/resistance training: (a) cognitive dual-task training and aerobic/resistance training (COG+/AER+), (b) computer lessons and aerobic/resistance training (COG-/AER+), (c) cognitive dual-task training and stretching/toning exercises (COG+/AER-), and (d) computer lessons and stretching/toning exercises (COG-/AER-). The primary outcome was performance in an untrained transfer dual task. Stepwise backward removal regression analyses were used to predict pre- versus post-test changes in groups that have completed the dual-task training, aerobic/resistance or both interventions.

RESULTS

Participation in AER+ did not predict improvement in any dual-task outcomes. Participation in COG+ predicted reduction in dual-task cost and participation in COG+/AER+ predicted reduction in task-set cost.

DISCUSSION

Results suggest that the combination of cognitive and physical training protocols exerted a synergistic effect on task-set cost which reflects the cost of maintaining multiple response alternatives, whereas cognitive training specifically improved dual-task cost, which reflects the ability of synchronizing concurrent tasks.

Non-drug therapies for cognitive impairment

The review considers basic methods for non-drug correction of cognitive disorders, as well as a combined approach, including the use of drugs and cognitive-motor training in the rehabilitation of patients with impaired cognitive functions. The authors present their own data on the efficiency of non-drug therapies in patients with Alzheimer’s disease.

Cognitive Involvement in Balance, Gait and Dual-Tasking in Aging: A Focused Review From a Neuroscience of Aging Perspective

A substantial corpus of evidence suggests that the cognitive involvement in postural control and gait increases with aging. A large portion of such studies were based on dual-task experimental designs, which typically use the simultaneous performance of a motor task (e.g., static or dynamic balancing, walking) and a continuous cognitive task (e.g., mental arithmetic, tone detection). This focused review takes a cognitive neuroscience of aging perspective in interpreting cognitive motor dual-task findings. Specifically, we consider the importance of identifying the neural circuits that are engaged by the cognitive task in relation to those that are engaged during motor task performance. Following the principle of neural overlap, dual-task interference should be greatest when the cognitive and motor tasks engage the same neural circuits. Moreover, the literature on brain aging in general, and models of dedifferentiation and compensation, in particular, suggest that in cognitive motor dual-task performance, the cognitive task engages different neural substrates in young as compared to older adults. Also considered is the concept of multisensory aging, and the degree to which the age-related decline of other systems (e.g., vision, hearing) contribute to cognitive load. Finally, we discuss recent work on focused cognitive training, exercise and multimodal training of older adults and their effects on postural and gait outcomes. In keeping with the principle of neural overlap, the available cognitive training research suggests that targeting processes such as dividing attention and inhibition lead to improved balance and gait in older adults. However, more studies are needed that include functional neuroimaging during actual, upright performance of gait and balance tasks, in order to directly test the principle of neural overlap, and to better optimize the design of intervention studies to improve gait and posture.

Limited Benefits of Heterogeneous Dual-Task Training on Transfer Effects in Older Adults

Objectives

It has often been reported that cognitive training has limited transfer effects. The present study addresses training context variability as a factor that could increase transfer effects, as well as the manifestation through time of transfer effects.

Method

Fifty-eight older adults were assigned to an active placebo or two dual-task training conditions, one in which the training context varies between sessions (heterogeneous training) and the other in a fixed training context (homogeneous training). Transfer was assessed with near and far-modality transfer tasks.

Results

Results show that heterogeneous and homogeneous training led to larger near-modality transfer effects than an active placebo (computer lessons). Transfer effects were roughly comparable in both training groups, but heterogeneous training led to a steeper improvement of the dual-task coordination learning curve within training sessions. Also, results indicated that dual-task cost did not improve in the active placebo group from the pre- to the post-training sessions.

Discussion

Heterogeneous training showed modest advantages over homogeneous training. Results also suggest that transfer effects on dual-task cost induced by training take place early on in the post-training session. These findings provide valuable insights on benefits arising from variability in the training protocol for maximizing transfer effects.

Transferability of Dual-Task Coordination Skills after Practice with Changing Component Tasks

Recent research has demonstrated that dual-task performance with two simultaneously presented tasks can be substantially improved as a result of practice. Among other mechanisms, theories of dual-task practice-relate this improvement to the acquisition of task coordination skills. These skills are assumed (1) to result from dual-task practice, but not from single-task practice, and (2) to be independent from the specific stimulus and response mappings during the practice situation and, therefore, transferable to new dual task situations. The present study is the first that provides an elaborated test of these assumptions in a context with well-controllable practice and transfer situations. To this end, we compared the effects of dual-task and single-task practice with a visual and an auditory sensory-motor component task on the dual-task performance in a subsequent transfer session. Importantly, stimulus and stimulus-response mapping conditions in the two component tasks changed repeatedly during practice sessions, which prevents that automatized stimulus-response associations may be transferred from practice to transfer. Dual-task performance was found to be improved after practice with the dual tasks in contrast to the single-task practice. These findings are consistent with the assumption that coordination skills had been acquired, which can be transferred to other dual-task situations independently on the specific stimulus and response mapping conditions of the practiced component tasks.

Mechanisms of Practice-Related Reductions of Dual-Task Interference with Simple Tasks: Data and Theory

In dual-task situations, interference between two simultaneous tasks impairs performance. With practice, however, this impairment can be reduced. To identify mechanisms leading to a practice-related improvement in sensorimotor dual tasks, the present review applied the following general hypothesis: Sources that impair dual-task performance at the beginning of practice are associated with mechanisms for the reduction of dual-task impairment at the end of practice. The following types of processes provide sources for the occurrence of this impairment: (a) capacity-limited processes within the component tasks, such as response-selection or motor response stages, and (b) cognitive control processes independent of these tasks and thus operating outside of component-task performance. Dual-task practice studies show that, under very specific conditions, capacity-limited processes within the component tasks are automatized with practice, reducing the interference between two simultaneous tasks. Further, there is evidence that response-selection stages are shortened with practice. Thus, capacity limitations at these stages are sources for dual-task costs at the beginning of practice and are overcome with practice. However, there is no evidence demonstrating the existence of practice-related mechanisms associated with capacity-limited motor-response stages. Further, during practice, there is an acquisition of executive control skills for an improved allocation of limited attention resources to two tasks as well as some evidence supporting the assumption of improved task coordination. These latter mechanisms are associated with sources of dual-task interference operating outside of component task performance at the beginning of practice and also contribute to the reduction of dual-task interference at its end.

Does Combined Physical and Cognitive Training Improve Dual-Task Balance and Gait Outcomes in Sedentary Older Adults?

Everyday activities like walking and talking can put an older adult at risk for a fall if they have difficulty dividing their attention between motor and cognitive tasks. Training studies have demonstrated that both cognitive and physical training regimens can improve motor and cognitive task performance. Few studies have examined the benefits of combined training (cognitive and physical) and whether or not this type of combined training would transfer to walking or balancing dual-tasks. This study examines the dual-task benefits of combined training in a sample of sedentary older adults. Seventy-two older adults (≥60 years) were randomly assigned to one of four training groups: Aerobic + Cognitive training (CT), Aerobic + Computer lessons (CL), Stretch + CT and Stretch + CL. It was expected that the Aerobic + CT group would demonstrate the largest benefits and that the active placebo control (Stretch + CL) would show the least benefits after training. Walking and standing balance were paired with an auditory n-back with two levels of difficulty (0- and 1-back). Dual-task walking and balance were assessed with: walk speed (m/s), cognitive accuracy (% correct) and several mediolateral sway measures for pre- to post-test improvements. All groups demonstrated improvements in walk speed from pre- (M = 1.33 m/s) to post-test (M = 1.42 m/s, p < 0.001) and in accuracy from pre- (M = 97.57%) to post-test (M = 98.57%, p = 0.005).They also increased their walk speed in the more difficult 1-back (M = 1.38 m/s) in comparison to the 0-back (M = 1.36 m/s, p < 0.001) but reduced their accuracy in the 1-back (M = 96.39%) in comparison to the 0-back (M = 99.92%, p < 0.001). Three out of the five mediolateral sway variables (Peak, SD, RMS) demonstrated significant reductions in sway from pre to post test (p-values < 0.05). With the exception of a group difference between Aerobic + CT and Stretch + CT in accuracy, there were no significant group differences after training. Results suggest that there can be dual-task benefits from training but that in this sedentary sample Aerobic + CT training was not more beneficial than other types of combined training.

Effects of combined physical and cognitive training on fitness and neuropsychological outcomes in healthy older adults

PURPOSE

Physical exercise and cognitive training have been shown to enhance cognition among older adults. However, few studies have looked at the potential synergetic effects of combining physical and cognitive training in a single study. Prior trials on combined training have led to interesting yet equivocal results. The aim of this study was to examine the effects of combined physical and cognitive interventions on physical fitness and neuropsychological performance in healthy older adults.

METHODS

Seventy-six participants were randomly assigned to one of four training combinations using a 2×2 factorial design. The physical intervention was a mixed aerobic and resistance training program, and the cognitive intervention was a dual-task (DT) training program. Stretching and toning exercises and computer lessons were used as active control conditions. Physical and cognitive measures were collected pre- and postintervention.

RESULTS

All groups showed equivalent improvements in measures of functional mobility. The aerobic-strength condition led to larger effect size in lower body strength, independently of cognitive training. All groups showed improved speed of processing and inhibition abilities, but only participants who took part in the DT training, independently of physical training, showed increased task-switching abilities. The level of functional mobility after intervention was significantly associated with task-switching abilities.

CONCLUSION

Combined training did not yield synergetic effects. However, DT training did lead to transfer effects on executive performance in neuropsychological tests. Both aerobic-resistance training and stretching-toning exercises can improve functional mobility in older adults.

White matter integrity as a marker for cognitive plasticity in aging

Age-related differences in white matter (WM) integrity are substantial, but it is unknown whether between-subject variability in WM integrity influences the capacity for cognitive improvement. We investigated the effects of memory training related to active and passive control conditions in older adults and tested whether WM integrity at baseline was predictive of training benefits. We hypothesized that (1) memory improvement would be restricted to the training group, (2) widespread areas would show greater mean diffusivity (MD) and lower fractional anisotropy in older adults relative to young adults, and (3) within these areas, variability in WM microstructure in the older group would be predictive of training gains. The results showed that only the group receiving training improved their memory. Significant age differences in MD and fractional anisotropy were found in widespread areas. Within these areas, voxelwise analyses showed a negative relationship between MD and memory improvement in 3 clusters, indicating that WM integrity could serve as a marker for the ability to adapt in response to cognitive challenges in aging.

Training-induced changes in subsequent-memory effects: No major differences among children, younger adults, and older adults

The neural correlates of encoding mode, or the state of forming new memory episodes, have been found to change with age and mnemonic training. However, it is unclear whether neural correlates of encoding success, termed subsequent-memory (SM) effects, also differ by age and mnemonic skill. In a multi-session training study, we investigated whether SM effects are altered by instruction and training in a mnemonic skill, and whether such alterations differ among children, younger adults, and older adults. Before and after strategy training, fMRI data were collected while participants were memorizing word pairs. In all age groups, participants receiving training showed greater performance gains than control group participants. Analysis of task-relevant regions showed training-induced reductions in SM effects in left frontal regions. Reductions in SM effects largely generalized across age and primarily reflected greater training-induced activation increases for omissions than for remembered items, indicating that training resulted in more consistent use of the mnemonic strategy. The present results reveal no major age differences in SM effects in children, younger adults, and older adults.

Training of Working Memory Impacts Neural Processing of Vocal Pitch Regulation

Working memory training can improve the performance of tasks that were not trained. Whether auditory-motor integration for voice control can benefit from working memory training, however, remains unclear. The present event-related potential (ERP) study examined the impact of working memory training on the auditory-motor processing of vocal pitch. Trained participants underwent adaptive working memory training using a digit span backwards paradigm, while control participants did not receive any training. Before and after training, both trained and control participants were exposed to frequency-altered auditory feedback while producing vocalizations. After training, trained participants exhibited significantly decreased N1 amplitudes and increased P2 amplitudes in response to pitch errors in voice auditory feedback. In addition, there was a significant positive correlation between the degree of improvement in working memory capacity and the post-pre difference in P2 amplitudes. Training-related changes in the vocal compensation, however, were not observed. There was no systematic change in either vocal or cortical responses for control participants. These findings provide evidence that working memory training impacts the cortical processing of feedback errors in vocal pitch regulation. This enhanced cortical processing may be the result of increased neural efficiency in the detection of pitch errors between the intended and actual feedback.

Evidence for the acquisition of dual-task coordination skills in older adults

Practicing two simultaneously presented tasks in dual-task situations results in improved dual-task performance, in both younger and older adults. Recent findings with younger adults demonstrated that this improvement is attributable in part to improved task coordination skills acquired through practice. However, it is unclear whether practice also improves older adults' skills at dual-task coordination. To clarify this, the present study examined the acquisition of task coordination skills, reflecting one specific mechanism of practice-dependent improvement in dual-task performance for this particular age group. This examination was based on two assumptions, namely, that (1) these skills are acquired during practice of the tasks presented simultaneously (dual-task situations), but not during the separate practice of the two tasks (single-task situations), and (2), rather than being dependent on the specific properties of practiced tasks, these skills are transferable to new dual-task situations. In the context of dual-task situations with well-structured reaction-time tasks, the results indeed revealed improved dual-task performance following dual-task practice, as compared to single-task practice, in both the practiced dual-task and new dual-task (transfer) situations. These findings are consistent with the notion that, similar to younger adults, acquired task coordination skills represent one practice-related mechanism that contributes to improved dual-task performance in the age group of older adults.

Does initial performance variability predict dual-task optimization with practice in younger and older adults?

BACKGROUND/STUDY CONTEXT: The variability associated with reaction time (RT) is sometimes considered as a proxy for inefficient neural processing, particularly in old age and complex situations relying upon executive control functions. Here, it is examined whether the amount of variability exhibited early in practice can predict the amount of improvement with later practice in dual-task performance, and whether the predictive power of variability varies between younger and older adults.

METHODS

To investigate the relationship between variability and practice-related improvement, RT mean and variability data are used, obtained from an experiment in which younger and older adults performed two tasks in single-task and dual-task conditions across seven practice sessions. These RT and variability data were related to the single-task and dual-task practice benefits. These benefits were computed as follows: dual-task/single-task RTs at the beginning of practice minus dual-task/single-task RTs at the end of practice.

RESULTS

In both age groups, dual-task processing was speeded up with practice and variability associated with the means was reduced. Most important, independent of mean RTs, variability allowed predicting dual-task practice benefit in both age groups under specific conditions.

CONCLUSION

These findings suggest that the relationship between performance variability and executive control functions under some specific conditions. Implications of these results for models of practiced dual tasks are discussed.

Cognitive plasticity in older adults: effects of cognitive training and physical exercise

Cognitive training, physical activity, and exercise have often been reported to improve cognitive performance in older adults. This paper reviews some seminal and recent studies using these approaches to improve cognition and physical functioning in healthy older adults and in patients suffering from non-neurological chronic medical conditions. Results from cognitive training studies suggest that despite performance improvement in trained tasks, transfer effects appeared very limited. Surprisingly though, computerized dual-task training has been shown to improve balance and postural control in tests of physical functioning, suggesting that broad transfer can sometimes be observed. Physical exercise intervention studies generally found significant and large improvements in physical capacity, in some cognitive domains, and in quality of life. The benefits seem to be equivalent between frail and nonfrail participants. Overall, results reviewed here support the notion that cognitive plasticity for attentional control, as induced by cognitive training or physical activity and exercise, is preserved in late adulthood. Moreover, results of studies with patients at risk of cognitive decline also suggest that cognitive training and exercise interventions are promising nonpharmaceutical tools to help improve cognition in older at-risk individuals.

A randomized controlled trial of brain training with non-action video games in older adults: results of the 3-month follow-up

This randomized controlled study (ClinicalTrials.gov NCT02007616) investigated the maintenance of training effects of 20 1-hr non-action video game training sessions with selected games from a commercial package on several age-declining cognitive functions and subjective wellbeing after a 3-month no-contact period. Two groups of cognitively normal older adults participated in both the post-training (posttest) and the present follow-up study, the experimental group who received training and the control group who attended several meetings with the research team during the study but did not receive training. Groups were similar at baseline on demographics, vocabulary, global cognition, and depression status. Significant improvements in the trained group, and no variation in the control group had been previously found at posttest, in processing speed, attention and visual recognition memory, as well as in two dimensions of subjective wellbeing. In the current study, improvement from baseline to 3 months follow-up was found only in wellbeing (Affection and Assertivity dimensions) in the trained group whereas there was no change in the control group. Previous significant improvements in processing speed, attention and spatial memory become non-significant after the 3-month interval. Training older adults with non-action video games enhanced aspects of cognition just after training but this effect disappeared after a 3-month no-contact follow-up period. Cognitive plasticity can be induced in older adults by training, but to maintain the benefits periodic boosting sessions would be necessary.

Brain training with non-action video games enhances aspects of cognition in older adults: a randomized controlled trial

Age-related cognitive and brain declines can result in functional deterioration in many cognitive domains, dependency, and dementia. A major goal of aging research is to investigate methods that help to maintain brain health, cognition, independent living and wellbeing in older adults. This randomized controlled study investigated the effects of 20 1-h non-action video game training sessions with games selected from a commercially available package (Lumosity) on a series of age-declined cognitive functions and subjective wellbeing. Two groups of healthy older adults participated in the study, the experimental group who received the training and the control group who attended three meetings with the research team along the study. Groups were similar at baseline on demographics, vocabulary, global cognition, and depression status. All participants were assessed individually before and after the intervention, or a similar period of time, using neuropsychological tests and laboratory tasks to investigate possible transfer effects. The results showed significant improvements in the trained group, and no variation in the control group, in processing speed (choice reaction time), attention (reduction of distraction and increase of alertness), immediate and delayed visual recognition memory, as well as a trend to improve in Affection and Assertivity, two dimensions of the Wellbeing Scale. Visuospatial working memory (WM) and executive control (shifting strategy) did not improve. Overall, the current results support the idea that training healthy older adults with non-action video games will enhance some cognitive abilities but not others.

Plasticity of brain and cognition in older adults

Aging is typically related to changes in brain and cognition, but the aging process is heterogeneous and differs between individuals. Recent research has started investigating the influence of cognitive and physical training on cognitive performance, functional brain activity, and brain structure in old age. The functional relevance of neural changes and the interactions among these changes following interventions is still a matter of debate. Here we selectively review research on structural and functional brain correlates of training-induced performance changes in healthy older adults and present exemplary longitudinal intervention studies sorted by the type of training applied (i.e., strategy-based training, process-specific training, and physical exercise). Although many training studies have been conducted recently, within each task domain, the number of studies that used comparable methods and techniques to assess behavioral and neural changes is limited. We suggest that future studies should include a multimodal approach to enhance the understanding of the relation between different levels of brain changes in aging and those changes that result from training. Investigating inter-individual differences in intervention-induced behavioral and neuronal changes would provide more information about who would benefit from a specific intervention and why. In addition, a more systematic examination of the time course of training-related structural and functional changes would improve the current level of knowledge about how learning is implemented in the brain and facilitate our understanding of contradictory results.

Neuroplasticity-based computerized cognitive remediation for treatment-resistant geriatric depression

Executive dysfunction (ED) in geriatric depression (GD) is common, predicts poor clinical outcomes and often persists despite remission of symptoms. Here we develop a neuroplasticity-based computerized cognitive remediation treatment (CCR-GD) to target ED in GD. Our assumption is that remediation of these deficits may modulate the underlying brain network abnormalities shared by executive dysfunction and depression. We compare CCR-GD to a gold standard treatment (escitalopram: 20mgs/12 weeks) in 11 treatment resistant older adults with major depression; and 33 matched historical controls. We find that 91% of participants complete CCR-GD. CCR-GD is equally as effective at reducing depressive symptoms as escitalopram but does so in 4 weeks instead of 12. In addition CCR-GD improves measures of executive function more than the escitalopram. We conclude that CCR-GD may be equally effective as escitalopram in treating GD. In addition, CCR-GD participants showed greater improvement in executive functions than historical controls treated with escitalopram.

Catechol-O-methyltransferase (COMT) genotype affects age-related changes in plasticity in working memory: a pilot study

Objectives. Recent work suggests that a genetic variation associated with increased dopamine metabolism in the prefrontal cortex (catechol-O-methyltransferase Val158Met; COMT) amplifies age-related changes in working memory performance. Research on younger adults indicates that the influence of dopamine-related genetic polymorphisms on working memory performance increases when testing the cognitive limits through training. To date, this has not been studied in older adults. Method. Here we investigate the effect of COMT genotype on plasticity in working memory in a sample of 14 younger (aged 24–30 years) and 25 older (aged 60–75 years) healthy adults. Participants underwent adaptive training in the n-back working memory task over 12 sessions under increasing difficulty conditions. Results. Both younger and older adults exhibited sizeable behavioral plasticity through training (P < .001), which was larger in younger as compared to older adults (P < .001). Age-related differences were qualified by an interaction with COMT genotype (P < .001), and this interaction was due to decreased behavioral plasticity in older adults carrying the Val/Val genotype, while there was no effect of genotype in younger adults. Discussion. Our findings indicate that age-related changes in plasticity in working memory are critically affected by genetic variation in prefrontal dopamine metabolism.

Cognitive reserve in young and old healthy subjects: differences and similarities in a testing-the-limits paradigm with DSST

Cognitive reserve (CR) is understood as capacity to cope with challenging conditions, e.g. after brain injury or in states of brain dysfunction, or age-related cognitive decline. CR in elderly subjects has attracted much research interest, but differences between healthy older and younger subjects have not been addressed in detail hitherto. Usually, one-time standard individual assessments are used to characterise CR. Here we observe CR as individual improvement in cognitive performance (gain) in a complex testing-the-limits paradigm, the digit symbol substitution test (DSST), with 10 repeated measurements, in 140 younger (20–30 yrs) and 140 older (57–74 yrs) healthy subjects. In addition, we assessed attention, memory and executive function, and mood and personality traits as potential influence factors for CR. We found that both, younger and older subjects showed significant gains, which were significantly correlated with speed of information processing, verbal short-term memory and visual problem solving in the older group only. Gender, personality traits and mood did not significantly influence gains in either group. Surprisingly about half of the older subjects performed at the level of the younger group, suggesting that interindividual differences in CR are possibly age-independent. We propose that these findings may also be understood as indication that one-time standard individual measurements do not allow assessment of CR, and that the use of DSST in a testing-the-limits paradigm is a valuable assessment method for CR in young and elderly subjects.

Online Attention Training for Older Adults

Evidence suggests that cognitive training interventions can improve older adults' cognitive performance. Successful training programs are adaptable and train multiple cognitive domains to target individual strengths and weaknesses. Computerized training programs are useful because they allow older adults to easily access training. This pilot study used an online attention training program, ATTENTION WORKOUT™, to enhance three aspects of attention- coordination, allocation, and selective focus -in community-dwelling older adults randomized to either an abbreviated (n=13) or an extended (n=17) practice training program over a 6-week period. Participants in the extended practice group significantly improved on selective focus reading distraction tasks with unrelated words (U=39.5; Z=-2.34; p=.02) and blanks (U=26.5; Z=-3.05; p=.002) as well as a matching attributes task (U=49.5; Z=-2.33; p=.02). The extended practice group significantly improved on three tasks of coordinating attention - radio-tuning (U=30; Z=-2.73; p=.01), circuit-breaker resetting (U=46; Z=-2.24; p=.03), and the combination of the two tasks (U=15; Z=-3.51; p<.0001) - as well as a memory generalization task (U=20; Z=-3.27; p=.001). A post-test satisfaction survey found both groups enjoyed the program, but the abbreviated practice group felt the tasks were more difficult. These findings suggest online attention training programs, like ATTENTION WORKOUT, can improve attention-related skills in community-dwelling older adults.

Executive process training in young and old adults

There is a growing body of research on the modifiability of executive functions in different stages of life. Previous studies demonstrate robust training effects but limited transfer in younger and particularly in older adults. The aim of the present study was to investigate whether a theoretically derived intervention for executive functioning, addressing several basic processes (updating, shifting, and inhibition), can induce transfer effects in early and late adulthood. Fifty-nine healthy adults, 29 young and 30 older adults, were randomly assigned to either training or no-contact control groups. The training groups received 15 sessions of executive process training for about 45 min/session during 5 weeks. A test battery including a criterion task and near, intermediate, and far transfer tasks was administered before and after training. Results showed pronounced age-equivalent gains on the criterion task. Near transfer was seen to non-trained updating and inhibition tasks for the young and older trained participants. However, only the young adults showed intermediate transfer to two complex working memory tasks. No far transfer effects were seen for either age group. These findings provide additional evidence for age-related constraints in the ability to generalize acquired executive skills, and specifically show that training of multiple executive processes is not sufficient to foster transfer beyond the very near in older adults.

Age-related decline in divided-attention: from theoretical lab research to practical real-life situations

The purpose of this advanced review is to provide readers with an up-to-date synopsis of age-related changes in divided-attention abilities. An interdisciplinary approach is taken, supplying readers with evidence from very structured laboratory studies and findings from more ecological research studies that target real-life divided-attention situations (i.e., walking and talking). The review goes beyond the reported age-related declines in divided-attention abilities and offers the reader an overview of current cognitive (dual-task) training findings which suggest that these declines can be diminished with training. The contents of this review and the future directions proposed demonstrate that divided-attention research and its recent application to aging and mobility has become a major and fast growing scientific field of investigation. WIREs Cogn Sci 2013, 4:623-640. doi: 10.1002/wcs.1252 CONFLICT OF INTEREST: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the WIREs website.

Walking Stroop carpet: an innovative dual-task concept for detecting cognitive impairment

Background

Several studies have reported the potential value of the dual-task concept during locomotion in clinical evaluation because cognitive decline is strongly associated with gait abnormalities. However, current dual-task tests appear to be insufficient for early diagnosis of cognitive impairment.

Methods

Forty-nine subjects (young, old, with or without mild cognitive impairment) underwent cognitive evaluation (Mini-Mental State Examination, Frontal Assessment Battery, five-word test, Stroop, clock-drawing) and single-task locomotor evaluation on an electronic walkway. They were then dual-task-tested on the Walking Stroop carpet, which is an adaptation of the Stroop color–word task for locomotion. A cluster analysis, followed by an analysis of variance, was performed to assess gait parameters.

Results

Cluster analysis of gait parameters on the Walking Stroop carpet revealed an interaction between cognitive and functional abilities because it made it possible to distinguish dysexecutive cognitive fragility or decline with a sensitivity of 89% and a specificity of 94%. Locomotor abilities differed according to the group and dual-task conditions. Healthy subjects performed less well on dual-tasking under reading conditions than when they were asked to distinguish colors, whereas dysexecutive subjects had worse motor performances when they were required to dual task.

Conclusion

The Walking Stroop carpet is a dual-task test that enables early detection of cognitive fragility that has not been revealed by traditional neuropsychological tests or single-task walking analysis.

Neuroplasticity-based computerized cognitive remediation for geriatric depression

OBJECTIVE

This article describes a novel treatment model designed to target specific neurocognitive deficits in geriatric depression with neuroplasticity-based computerized cognitive remediation (NBCCR).

METHOD

The recent National Institute of Mental Health (NIMH) report "From Discovery to Cure" calls for studies focusing on mechanisms of treatment response with the goal of arriving at new interventions for those who do not respond to existing treatments. We describe the process that led to the identification of specific executive deficits and their underlying neurobiology, as well as the rationale for targeting these symptoms as a part of a strategy intended to improve both executive dysfunction and depression. We then propose a strategy for further research in this emerging area.

RESULTS AND CONCLUSIONS

Despite significant developments, conventional antidepressant treatments leave many older adults still depressed and suffering. Psychotherapy may be effective in some depressed elders, although a recent review concluded that none of the available treatment studies meets stringent criteria for efficacy in the acute treatment of geriatric depression. Appropriately developed and targeted NBCCR, has the potential to serve as a novel treatment intervention for geriatric depression. Pathophysiological changes associated with executive dysfunction may be an appropriate target for NBCCR. Examining both behavioral changes and indices of structural integrity and functional change of networks related to cognitive and emotional regulation may lead to a novel treatment and elucidate the role of specific cerebral networks in geriatric depression.

Age differences in intra-individual variability in simple and choice reaction time: systematic review and meta-analysis

BACKGROUND

Intra-individual variability in reaction time (RT IIV) is considered to be an index of central nervous system functioning. Such variability is elevated in neurodegenerative diseases or following traumatic brain injury. It has also been suggested to increase with age in healthy ageing.

OBJECTIVES

To investigate and quantify age differences in RT IIV in healthy ageing; to examine the effect of different tasks and procedures; to compare raw and mean-adjusted measures of RT IIV.

DATA SOURCES

Four electronic databases: PsycINFO, Medline, Web of Science and EMBASE, and hand searching of reference lists of relevant studies.

STUDY ELIGIBILITY

English language journal articles, books or book chapters, containing quantitative empirical data on simple and/or choice RT IIV. Samples had to include younger (under 60 years) and older (60 years and above) human adults.

STUDY APPRAISAL AND SYNTHESIS

Studies were evaluated in terms of sample representativeness and data treatment. Relevant data were extracted, using a specially-designed form, from the published report or obtained directly from the study authors. Age-group differences in raw and RT-mean-adjusted measures of simple and choice RT IIV were quantified using random effects meta-analyses.

RESULTS

Older adults (60+ years) had greater RT IIV than younger (20-39) and middle-aged (40-59) adults. Age effects were larger in choice RT tasks than in simple RT tasks. For all measures of RT IIV, effect sizes were larger for the comparisons between older and younger adults than between older and middle-aged adults, indicating that the age-related increases in RT IIV are not limited to old age. Effect sizes were also larger for raw than for RT-mean-adjusted RT IIV measures.

CONCLUSIONS

RT IIV is greater among older adults. Some (but not all) of the age-related increases in RT IIV are accounted for by the increased RT means.

Structural integrity of the corpus callosum predicts long-term transfer of fluid intelligence-related training gains in normal aging

Although cognitive training usually improves cognitive test performance, the capability to transfer these training gains into respective or functionally related cognitive domains varies significantly. Since most studies demonstrate rather limited transfer effects in older adults, aging might be an important factor in transfer capability differences. This study investigated the transfer capability of logical reasoning training gains to a measure of Fluid Intelligence (Gf) in relation to age, general intelligence, and brain structural integrity as measured by diffusion tensor imaging. In a group of 41 highly educated healthy elderly, 71% demonstrated successful transfer immediately after a 4-week training session (i.e. short-term transfer). In a subgroup of 22% of subjects transfer maintained over a 3-month follow-up period (i.e. long-term transfer). While short-term transfer was not related to structural integrity, long-term transfer was associated with increased structural integrity in corpus and genu of the corpus callosum. Since callosal structural integrity was also related to age (in the present and foregoing studies), previously observed associations between age and transfer might be moderated by the structural integrity. Surprisingly, age was not directly associated with transfer in this study which could be explained by the multi-dependency of the structural integrity (modulating factors beside age, e.g. genetics). In this highly educated sample, general intelligence was not related to transfer suggesting that high intelligence is not sufficient for transfer in normal aging. Further studies are needed to reveal the interaction of transfer, age, and structural integrity and delineate mechanisms of age-dependent transfer capabilities.

An investigation of response and stimulus modality transfer effects after dual-task training in younger and older

It has been shown that dual-task training leads to significant improvement in dual-task performance in younger and older adults. However, the extent to which training benefits to untrained tasks requires further investigation. The present study assessed (a) whether dual-task training leads to cross-modality transfer in untrained tasks using new stimuli and/or motor responses modalities, (b) whether transfer effects are related to improved ability to prepare and maintain multiple task-set and/or enhanced response coordination, (c) whether there are age-related differences in transfer effects. Twenty-three younger and 23 older adults were randomly assigned to dual-task training or control conditions. All participants were assessed before and after training on three dual-task transfer conditions; (1) stimulus modality transfer (2) response modality transfer (3) stimulus and response modalities transfer task. Training group showed larger improvement than the control group in the three transfer dual-task conditions, which suggests that training leads to more than specific learning of stimuli/response associations. Attentional costs analyses showed that training led to improved dual-task cost, only in conditions that involved new stimuli or response modalities, but not both. Moreover, training did not lead to a reduced task-set cost in the transfer conditions, which suggests some limitations in transfer effects that can be expected. Overall, the present study supports the notion that cognitive plasticity for attentional control is preserved in late adulthood.

Working-memory training in younger and older adults: training gains, transfer, and maintenance

Working memory (WM), a key determinant of many higher-order cognitive functions, declines in old age. Current research attempts to develop process-specific WM training procedures, which may lead to general cognitive improvement. Adaptivity of the training as well as the comparison of training gains to performance changes of an active control group are key factors in evaluating the effectiveness of a specific training program. In the present study, 55 younger adults (20–30 years of age) and 45 older adults (60–70 years of age) received 5 weeks of computerized training on various spatial and verbal WM tasks. Half of the sample received adaptive training (i.e., individually adjusted task difficulty), whereas the other half-worked on the same task material but on a low task difficulty level (active controls). Performance was assessed using criterion, near-transfer, and far-transfer tasks before training, after 5 weeks of intervention, as well as after a 3-month follow-up interval. Results indicate that (a) adaptive training generally led to larger training gains than low-level practice, (b) training and transfer gains were somewhat greater for younger than for older adults in some tasks, but comparable across age groups in other tasks, (c) far-transfer was observed to a test on sustained attention and for a self-rating scale on cognitive functioning in daily life for both young and old, and (d) training gains and transfer effects were maintained across the 3-month follow-up interval across age.

Testing the limits of optimizing dual-task performance in younger and older adults

Impaired dual-task performance in younger and older adults can be improved with practice. Optimal conditions even allow for a (near) elimination of this impairment in younger adults. However, it is unknown whether such (near) elimination is the limit of performance improvements in older adults. The present study tests this limit in older adults under conditions of (a) a high amount of dual-task training and (b) training with simplified component tasks in dual-task situations. The data showed that a high amount of dual-task training in older adults provided no evidence for an improvement of dual-task performance to the optimal dual-task performance level achieved by younger adults. However, training with simplified component tasks in dual-task situations exclusively in older adults provided a similar level of optimal dual-task performance in both age groups. Therefore through applying a testing the limits approach, we demonstrated that older adults improved dual-task performance to the same level as younger adults at the end of training under very specific conditions.