Practice-related optimization and transfer of executive functions: a general review and a specific realization of their mechanisms in dual tasks

Cognitive control and meta-control in dual-task coordination

When two tasks are presented simultaneously or in close succession, such as in the overlapping task paradigm of the psychological refractory period, dual-task performance on those tasks is usually impaired compared with separate single-task performance. Numerous theories explain these emerging dual-task costs in terms of the existence of capacity limitations in the constituent component tasks. The current paper proposes active dual-task coordination processes that work on the scheduling of these capacity-limited processes. Further, there are recent findings that point to a meta-cognitive control level in addition to these active coordination processes. This additional level's responsibility is to adjust the dual-task coordination of capacity-limited stages (i.e., coordination adjustment). I review evidence focusing on the existence of dual-task coordination processes and processes of coordination adjustment. The remainder of the paper elaborates on preliminary findings and points to the separability of these sets of processes, which is a key assumption of the framework of dual-task coordination adjustment.

Can frequent long stimulus onset ansynchronies (SOAs) foster the representation of two separated task-sets in dual-tasking?

Recent findings suggest that in dual-tasking the elements of the two tasks are associated across tasks and are stored in a conjoint memory episode, meaning that the tasks are not represented as isolated task-sets. In the current study, we tested whether frequent long stimulus onset ansynchronies (SOAs) can foster the representation of two separated task-sets thereby reducing or even hindering participants to generate conjoint memory episodes-compared to an integrated task-set representation induced by frequent short SOAs. Alternatively, it is conceivable that conjoint memory episodes are an inevitable consequence of presenting two tasks within a single trial. In two dual-task experiments, we tested between consecutive trials whether repeating the stimulus-response bindings of both tasks would lead to faster responses than repeating only one of the two tasks' stimulus-response bindings. The dual-task consisted of a visual-manual search task (VST) and an auditory-manual discrimination task (ADT). Overall, the results suggest that, after processing two tasks within a single trial, generating a conjoint memory episode seems to be a default process, regardless of SOA frequency. However, the respective SOA frequency affected the participants' strategy to group the processing of the two tasks or not, thereby modulating the impact of the reactivated memory episode on task performance.

Uncorking the limitation-improving dual tasking using transcranial electrical stimulation and task training in the elderly: a systematic review

Introduction

With aging, dual task (DT) ability declines and is more cognitively demanding than single tasks. Rapidly declining DT performance is regarded as a predictor of neurodegenerative disease. Task training and non-invasive transcranial electrical stimulation (tES) are methods applied to optimize the DT ability of the elderly.

Methods

A systematic search was carried out in the PUBMED, TDCS (transcranial direct current stimulation) databases, as well as Web of Science, and a qualitative analysis was conducted in 56 included studies. Aiming to summarize the results of studies that implemented tES, task training, or the combination for improving DT ability and related performance changes in healthy elderly and geriatric patients. For different approaches, the training procedures, parameters, as well as outcomes were discussed.

Results

Task training, particularly cognitive-motor DT training, has more notable effects on improving DT performance in the elderly when compared to the neuromodulation method.

Discussion

Anodal transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (L-DLPFC), or its combination with task training could be promising tools. However, additional evidence is required from aged healthy people and patients, as well as further exploration of electrode montage.

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.

Dual-Task and Single-Task Practice Does Not Influence the Attentional Demands of Movement Sequence Representations

This study examined the attentional demands of movement sequence representations at different temporal points after single- or dual-task practice. The visual-spatial representation encodes the movement based on visual-spatial coordinates such as the target locations. The motor representation encodes the movement in motor coordinates including joint angles and muscle activation patterns. Participants were randomly assigned to a single-task or dual-task practice group. Following acquisition, participants performed two retention tests and inter-manual transfer tests, both under dual-task and single-task. The transfer tests consisted of a mirror and non-mirror test and examined motor and visual-spatial representation development. The main finding is that attentional demands of the sequence representations were not affected by the practice condition. However, movement initiation requires more attention than the end of the movement in both representations.

Neural underpinnings of response inhibition in substance use disorders: weak meta-analytic evidence for a widely used construct

RATIONALE

Substance use disorders (SUDs) rank among the most severely debilitating psychiatric conditions. Among others, decreased response inhibition capacities could make it more difficult for patients to abstain from drug use and maintain abstinence. However, meta-analyses on the neural basis of response inhibition in SUDs yielded conflicting results.

OBJECTIVE

In this study, we revisited the neuroimaging research field and summarized the existing fMRI literature on overt response inhibition (Go/NoGo and stop-signal paradigms) across different SUDs.

METHODS

We performed a systematic literature review and an activation likelihood estimation (ALE) meta-analysis to investigate the actual convergence of functional deviations observed in SUD samples. Results were further supplied by consecutive robustness measures and a post-hoc random-effects meta-analysis of behavioural data.

RESULTS

We identified k = 21 eligible studies for our analysis. The ALE analysis indicated a significant cluster of convergence with its statistical peak in the right anterior insula. Consecutive analyses, however, indicated this result was not robust and susceptible towards publication bias. Additionally, a post-hoc random effects meta-analysis of the behavioural parameters of Go/NoGo and stop-signal paradigms reported by the included studies revealed no significant differences in task performance comparing SUD samples and controls.

CONCLUSION

We discuss that the role of task-based response inhibition may require some refinement as an overarching marker for SUD pathology. Finally, we give a few prospects for future research that should be further explored in this context.

The slow rate of working memory consolidation from vision is a structural limit

The speed with which information from vision is transformed into working memory (WM) representations that resist interference from ongoing perception and cognition is the subject of conflicting results. Using distinct paradigms, researchers have arrived at estimates of the consolidation time course ranging from 25 ms to 1 s - a range of more than an order of magnitude. However, comparisons of consolidation duration across very different estimation paradigms rely on the implicit assumption that WM consolidation speed is a stable, structural constraint of the WM system. The extremely large variation in WM consolidation speed estimates across measurement approaches motivated the current work's goal of determining whether consolidation speed truly is a stable structural constraint of WM encoding, or instead might be under strategic control as suggested by some accounts. By manipulating the relative task priority of WM encoding and a subsequent sensorimotor decision in a dual-task paradigm, the current experiments demonstrate that the long duration of WM consolidation does not change as a result of task-specific strategies. These results allow comparison of WM consolidation across estimation approaches, are consistent with recent multi-phase WM consolidation models, and are consistent with consolidation duration being an inflexible structural limit.

Modulation of the executive control network by anodal tDCS over the left dorsolateral prefrontal cortex improves task shielding in dual tasking

Task shielding is an important executive control demand in dual-task performance enabling the segregation of stimulus-response translation processes in each task to minimize between-task interference. Although neuroimaging studies have shown activity in left dorsolateral prefrontal cortex (dlPFC) during various multitasking performances, the specific role of dlPFC in task shielding, and whether non-invasive brain stimulation (NIBS) may facilitate task shielding remains unclear. We therefore applied a single-blind, crossover sham-controlled design in which 34 participants performed a dual-task experiment with either anodal transcranial direct current stimulation (atDCS, 1 mA, 20 min) or sham tDCS (1 mA, 30 s) over left dlPFC. Task shielding was assessed by the backward-crosstalk effect, indicating the extent of between-task interference in dual tasks. Between-task interference was largest at high temporal overlap between tasks, i.e., at short stimulus onset asynchrony (SOA). Most importantly, in these conditions of highest multitasking demands, atDCS compared to sham stimulation significantly reduced between-task interference in error rates. These findings extend previous neuroimaging evidence and support modulation of successful task shielding through a conventional tDCS setup with anodal electrode over the left dlPFC. Moreover, our results demonstrate that NIBS can improve shielding of the prioritized task processing, especially in conditions of highest vulnerability to between-task interference.

Individual differences in everyday multitasking behavior and its relation to cognition and personality

Our ability to multitask-focus on multiple tasks simultaneously-is one of the most critical functions of our cognitive system. This capability has shown to have relations to cognition and personality in empirical studies, which have received much attention recently. This review article integrates the available findings to examine how individual differences in multitasking behavior are linked with different cognitive constructs and personality traits to conceptualize what multitasking behavior represents. In this review, we highlight the methodological differences and theoretical conceptions. Cognitive constructs including executive functions (i.e., shifting, updating, and inhibition), working memory, relational integration, divided attention, reasoning, and prospective memory were investigated. Concerning personality, the traits of polychronicity, impulsivity, and the five-factor model were considered. A total of 43 studies met the inclusion criteria and entered the review. The research synthesis directs us to propose two new conceptual models to explain multitasking behavior as a psychometric construct. The first model demonstrates that individual differences in multitasking behavior can be explained by cognitive abilities. The second model proposes that personality traits constitute a moderating effect on the relation between multitasking behavior and cognition. Finally, we provide possible future directions for the line of research.

A meta-analysis of polychronicity: Applying modern perspectives of multitasking and person-environment fit

We apply modern theory on multitasking and person-environment fit to holistically explain the relations of polychronicity as well as provide justifications for disparate results found in prior studies, such as undetected differences regarding task-switching and dual-tasking. We then conduct a meta-analysis of polychronicity's relations. We show that the nomological net surrounding polychronicity matches our proposed fit perspective. We likewise demonstrate that differences in task-switching and dual-tasking indeed influence the observed results of polychronicity, and the growing complexity of businesses may have caused the association of polychronicity and job performance to strengthen over time. Our discussion highlights that polychronicity plays an important role in personal well-being and employee performance, which can be understood by our person-environment fit perspective.

Plain Language Summary

We apply modern theory on multitasking and person-environment fit to holistically explain the relations of polychronicity as well as provide justifications for disparate results found in prior studies, such as undetected differences regarding task-switching and dual-tasking. We then conduct a meta-analysis of polychronicity's relations. We show that the nomological net surrounding polychronicity matches our proposed fit perspective. We likewise demonstrate that differences in task-switching and dual-tasking indeed influence the observed results of polychronicity, and the growing complexity of businesses may have caused the association of polychronicity and job performance to strengthen over time. Our discussion highlights that polychronicity plays an important role in personal well-being and employee performance, which can be understood by our person-environment fit perspective.

Dual-task interference in simulated car driving: The psychological refractory period effect when not only the second, but also the first task is ecologically relevant

The psychological refractory period (PRP) effect denotes the finding that shortening the temporal interval between two tasks leads to increased reaction time in the second task. Earlier work in driving simulators confirmed the emergence of a PRP effect even if the second task (T2) was ecologically relevant, such as in a car-braking task. Here we evaluate the PRP effect if the first task (T1) is ecologically relevant as well. In a driving simulator, participants had to warn pedestrians against crossing the street (T1), and had to brake when the lead car braked (T2). As the temporal interval between tasks decreased, reaction time in T2 increased, confirming once more the emergence of a PRP effect. The PRP effect in our study was larger than in previous studies where T1 was artificial rather than ecologically relevant. This suggests that an ecologically relevant T1 is processed more elaborately, resulting in stronger interference with T2.

A Comparison of the Effects of Short-Term Physical and Combined Multi-Modal Training on Cognitive Functions

Physical training has beneficial effects not only on physical fitness, but also on cognitive functions. The most effective way to improve cognitive functions via physical training as well as the degree to which training effects transfer to untrained cognitive functions is still unclear, however. Here, we investigated the effects of adaptive and multi-modal short-term training interventions on cognitive training gains and transfer effects. Over a period of 12 weeks, 102 employees of a car manufacturing company (age range 20 to 61 years) received trainer-guided exercises, consisting of either two adaptive training interventions, physical (strength) training and multi-modal (motor-cognitive) training, or non-adaptive strength training (active control group). For the multi-modal intervention, the "Agility Board" was employed, a novel, multi-modal training device. Pre- and post-training, psychometric tests were conducted to measure cognitive abilities, such as perceptual speed, attention, short-term memory, working memory, inhibition, and mental rotation. In addition, motor-cognitive performance was assessed. Compared with the active control group, both training groups showed enhanced performance at posttest. While multi-modal training yielded performance improvements only in trained tasks, physical training was associated with improvements in untrained working memory updating and immediate recall tasks, suggesting transfer effects to short-term and working memory functioning. In summary, the results demonstrate the importance of adaptive difficulty settings for short-term physical training interventions, at least for the enhancement of working memory.

Inter-Individual Differences in Executive Functions Predict Multitasking Performance - Implications for the Central Attentional Bottleneck

Human multitasking suffers from a central attentional bottleneck preventing parallel performance of central mental operations, leading to profound deferments in task performance. While previous research assumed that the deferment is caused by a mere waiting time (refractory period), we show that the bottleneck requires executive functions (EF; active scheduling account) accounting for a profound part of the deferment. Three participant groups with EF impairments (dyslexics, highly neurotics, deprived smokers) showed worse multitasking performance than respective control groups. Three further groups with EF improvements (video-gamers, bilinguals, coffee consumers) showed improved multitasking. Finally, three groups performed a dual-task and different measures of EF (reading span, rotation span, symmetry span) and showed significant correlations between multitasking performance and working memory capacity. Demands on EF during multitasking may cause more errors, mental fatigue and stress, with parts of the population being considerably more prone to this.

Investigation of reward effects in overlapping dual-task situations

In dual-task (DT) situations, performance in reaction time and error rates decrease compared with single-task situations. These performance decrements are usually explained with the serial processing at the response selection stage constituting a bottleneck. Evidence for this assumption stems from the observation that response times for the second task (task 2; RT 2) increase with decreasing stimulus-onset asynchrony (SOA). In this study, we investigated the effect of reward on bottleneck processing in DTs. In Experiment 1, we addressed two questions. First, does reward provided for task 2 performance affect task 2 performance, or does it affect task 1 performance? To conclude whether reward affected task 2 or task 1 performance, we relied on the psychological refractory period paradigm (PRP) as a chronometric tool. Second, we asked for the locus of the reward effect within the DT stream. We demonstrated shorter RTs in task 1 in a rewarded compared with an un-rewarded condition indicating reward affected task 1 processing. Furthermore, this reward effect is propagated onto task 2 at short SOA suggesting that the locus of the reward effect can be pinpointed before or at the bottleneck of task 1. In Experiment 2, we tested for the locus of the effect propagation onto task 2. To this end, we implemented an additional difficulty manipulation of the response selection of task 2 and found that the reward effect is propagated from task 1 onto the response selection stage of task 2.

On the reliability of behavioral measures of cognitive control: retest reliability of task-inhibition effect, task-preparation effect, Stroop-like interference, and conflict adaptation effect

This study examined the reliability (retest and split-half) of four common behavioral measures of cognitive control. In Experiment 1 (N = 96), we examined N – 2 task repetition costs as a marker of task-level inhibition, and the cue-stimulus interval (CSI) effect as a marker of time-based task preparation. In Experiment 2 (N = 48), we examined a Stroop-like face-name interference effect as a measure of distractor interference control, and the sequential congruency effect (“conflict adaptation effect”) as a measure of conflict-triggered adaptation of cognitive control. In both experiments, the measures were assessed in two sessions on the same day, separated by a 10 min-long unrelated filler task. We observed substantial experimental effects with medium to large effect sizes. At the same time, split-half reliabilities were moderate, and retest reliabilities were poor, for most measures, except for the CSI effect. Retest reliability of the Stroop-like effect was improved when considering only trials preceded by congruent trials. Together, the data suggest that these cognitive control measures are well suited for assessing group-level effects of cognitive control. Yet, except for the CSI effect, these measures do not seem suitable for reliably assessing interindividual differences in the strength of cognitive control, and therefore are not suited for correlational approaches. We discuss possible reasons for the discrepancy between robustness at the group level and reliability at the level of interindividual differences.

Predicting Physical Activity Behavior by Automatic and Reflective Self-Regulatory Processes

In this study, we examined the interaction of automatic (i.e., automatic affective evaluations) and reflective [i.e., reflective intention and executive functions (EFs)] processes on physical activity (PA) behavior based on dual-process theories. We expected main effects as well as significant interaction effects between automatic associations, intention, and EFs on behavior. In particular, a well-controlled implicit-association-test (IAT) was applied to assess automatic affective evaluation. A prospective study with two points of measurement (N=212 students) was conducted. At t1, age, sex, PA behavior (control variables), automatic associations, EFs (shifting, updating, inhibition), and PA intention (predictors and moderators) were assessed with standardized questionnaires and tests. At t2 (4weeks later), PA behavior (dependent variable) was measured with a standardized questionnaire. A hierarchical multiple linear regression analysis including two- and three-way interactions between IAT results, intention, and EFs on PA behavior was conducted. Results showed that the interactions Intention x Shifting and IAT x Intention x Inhibition were significant. Moderation analyses revealed that participants with higher intentions and lower inhibition values (improved inhibition abilities) showed a negative association between IAT and PA, while those with lower intentions and lower inhibition values showed a positive association between IAT and PA, which was documented in a significant slope difference test between these two groups. Thus, both automatic and reflective processes contribute and interact in predicting PA. As well as fostering more positive affective evaluations towards PA, interventions to strengthen PA intentions and to improve EFs could help to increase PA behavior.

Media Multitasking: A Bibliometric Approach and Literature Review

Media multitasking became increasingly popular over the past decade. As this behavior is intensely taxing cognitive resources, it has raised interest and concerns among academics in a variety of fields. Consequently, in recent years, research on how, when, and why people media multitask has strongly emerged, and the consequences of the behavior for a great variety of outcomes (such as working memory, task performance, or socioemotional outcomes) have been explored. While efforts are made to summarize the findings of media multitasking research until date, these meta, and literature studies focused on specific research subdomains. Therefore, the current study adopted a quantitative method to map all studies in the broad field of media multitasking research. The bibliometric and thematic content analyses helped us identifying five major research topics and trends in the overall media multitasking domain. While media multitasking research started by studying its prevalence, appearance, and predictors, early research within the domain was also interested in the impact of this media consumption behavior on individuals' cognitive control and academic performance. Later on in 2007, scholars investigated the implications of media multitasking on the processing of media- and persuasive content, while its impact on socioemotional well-being received attention ever since 2009. Our analyses indicate that research within the field of media multitasking knows a dominant focus on adolescents, television watching, and cognitive depletion. Based on these findings, the paper concludes by discussing directions for future research.

Structuralist mental representation of dual-action demands: Evidence for compositional coding from dual tasks with low cross-task dimensional overlap

The present study asks how behavioral (dual-action) demands in dual tasks are mentally represented and whether changes in representation might govern practice-related dual-task performance improvements. Three different representation accounts were empirically tested based on the idea that dual-action demands required in a dual-task trial might be represented in different ways. According to a compositional (Structuralist) account, component tasks remain structurally intact when combined with another task. In contrast, a holistic (Gestalt) account posits that dual-action requirements in dual tasks are represented holistically and entirely distinct from its component action requirements. Finally, a contextual change account assumes that a change in context (e.g., from single- to dual-action requirement) generally impedes response retrieval, similar to repeating a response while the task context switches. To address this issue, we analyzed trial-by-trial effects in a single/dual switch paradigm (SDS paradigm, involving a randomized mix of single- and dual-task trials within blocks). Specifically, we analyzed performance in an extensive dual-task training setting (involving training sessions across several days) combining an auditory-vocal task and a visual-manual task. The results indicated that, throughout practice, nearly all relevant comparisons of performance between complete switch trials (e.g., between the two single tasks) and partial repetition trials (e.g., from dual to single task) revealed partial repetition benefits, that is, for both the auditory-vocal and the visual-manual task, and for both single- and dual-task performance analyses. Therefore, dual-action requirements in the present dual-task setting are mentally represented in a compositional, Structuralist fashion, probably due to low between-task dimensional overlap.

Learning of across- and within-task contingencies modulates partial-repetition costs in dual-tasking

Dual-task costs might result from confusions on the task-set level as both tasks are not represented as distinct task-sets, but rather being integrated into a single task-set. This suggests that events in the two tasks are stored and retrieved together as an integrated memory episode. In a series of three experiments, we tested for such integrated task processing and whether it can be modulated by regularities between the stimuli of the two tasks (across-task contingencies) or by sequential regularities within one of the tasks (within-task contingencies). Building on the experimental approach of feature binding in action control, we tested whether the participants in a dual-tasking experiment will show partial-repetition costs: they should be slower when only the stimulus in one of the two tasks is repeated from Trial n - 1 to Trial n than when the stimuli in both tasks repeat. In all three experiments, the participants processed a visual-manual and an auditory-vocal tone-discrimination task which were always presented concurrently. In Experiment 1, we show that retrieval of Trial n - 1 episodes is stable across practice if the stimulus material is drawn randomly. Across-task contingencies (Experiment 2) and sequential regularities within a task (Experiment 3) can compete with n - 1-based retrieval leading to a reduction of partial-repetition costs with practice. Overall the results suggest that participants do not separate the processing of the two tasks, yet, within-task contingencies might reduce integrated task processing.

Music Modulates Cognitive Flexibility? An Investigation of the Benefits of Musical Training on Markers of Cognitive Flexibility

Cognitive flexibility enables the rapid change in goals humans want to attain in everyday life as well as in professional contexts, e.g., as musicians. In the laboratory, cognitive flexibility is usually assessed using the task-switching paradigm. In this paradigm participants are given at least two classification tasks and are asked to switch between them based on valid cues or memorized task sequences. The mechanisms enabling cognitive flexibility are investigated through two empirical markers, namely switch costs and n-2 repetition costs. In this study, we assessed both effects in a pre-instructed task-sequence paradigm. Our aim was to assess the transfer of musical training to non-musical stimuli and tasks. To this end, we collected the data of 49 participants that differed in musical training assessed using the Goldsmiths Musical Sophistication Index. We found switch costs that were not significantly influenced by the degree of musical training. N-2 repetition costs were small for all levels of musical training and not significant. Musical training did not influence performance to a remarkable degree and did not affect markers of mechanisms underlying cognitive flexibility, adding to the discrepancies of findings on the impact of musical training in non-music-specific tasks.

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.

The Acute and Chronic Effects of Dual-Task on the Motor and Cognitive Performances in Athletes: A Systematic Review

Athletes must distribute their attention to many relevant cues during a match. Therefore, athletes’ ability to deal with dual-tasks may be different from the non-athlete population, demanding a deeper investigation within the sports domain. This study aimed to systematically review the acute and chronic effects of dual-tasks in motor and cognitive performances in athletes from different modalities. The search for articles followed all the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The keywords used were: “dual-task” OR “double task” OR “multi-task” OR “divided attention” OR “secondary task” OR “second task” AND “working memory” OR “visual” OR “decision making” OR “gaze behavior” OR “attention” AND “sports” OR “athletes” OR “players”. The Scopus, Pubmed, and Web of Science databases were screened for studies comparing single and dual-tasks, in which the participants were athletes competing at any level, and in which at least one of the following variables were investigated: working memory, decision-making, visual search behavior, perception, anticipation, attention, or motor tasks. Articles were screened using pre-defined selection criteria, and methodological quality was assessed by two researchers independently. Following the eligibility criteria, we included 18 articles in the review: 13 on the acute effects, and five on the chronic effects. This review showed that the acute effect of dual-tasks impairs the motor and cognitive performances of athletes (dual-task cost). However, training with dual-tasks (chronic effect) improved working memory skills and attentional control. We conclude that dual-tasks acutely and chronically impacts motor and cognitive performance.

Dual n-back working memory training evinces superior transfer effects compared to the method of loci

Working memory (WM) training is a prevalent intervention for multiple cognitive deficits, however, the transfer effects to other cognitive tasks from gains in WM induced by different training techniques still remains controversial. Therefore, the current study recruited three groups of young adults to investigate the memory training transference, with N-back group (NBG) (n = 50) training on dual n-back task, Memory Palace group (MPG) (n = 50) on method of loci, and a blank control group (BCG) (n = 48) receiving no training. Our results showed that both training groups separately improved WM capacity on respective trained task. For untrained tasks, both training groups enhanced performance on digit-span task, while on change detection task, significant improvement was only observed in NBG. In conclusion, while both techniques can be used as effective training methods to improve WM, the dual n-back task training method, perhaps has a more prominent transfer effect than that of method of loci.

Additional Functional Performance Gains After 24-Week Unstable Strength Training With Cognitive Training in Community-Dwelling Healthy Older Adults: A Randomized Trial

The authors investigated the effects of unstable strength training (UST) without or with cognitive training (C+UST) on functional performance in community-dwelling older adults. A total of 50 participants were randomly assigned (1:1) to either 24 weeks of thrice-weekly UST (n = 25) or C+UST (n = 25). All participants performed moderate-intensity strength exercises using unstable surfaces, and C+UST participants simultaneously received cognitive training in addition to UST. Primary outcomes included measures of functional performance: single- and dual-task timed up and go tests. Secondary outcomes included dynamic balance, mobility, handgrip strength, flexibility, quality of life, and concern about falling. The authors observed similar improvements on functional performance through the interventions. The C+UST group experienced additional gains at completion (single-task timed up and go: -0.90 s, 95% confidence interval [-2.38, -0.03]; dual-task timed up and go: -4.80 s, 95% confidence interval [-8.65, -0.95]) compared with the UST group. Moreover, significant differences were observed in mobility (sitting-rising test: -1.34, 95% confidence interval [-2.00, -0.20]) at 24 weeks. Both exercise modes improved single-task functional performance, while adding cognitive-training-optimized dual-task functional performance gains.

Parallel and serial task processing in the PRP paradigm: a drift-diffusion model approach

Even after a long time of research on dual-tasking, the question whether the two tasks are always processed serially (response selection bottleneck models, RSB) or also in parallel (capacity-sharing models) is still going on. The first models postulate that the central processing stages of two tasks cannot overlap, producing a central processing bottleneck in Task 2. The second class of models posits that cognitive resources are shared between the central processing stages of two tasks, allowing for parallel processing. In a series of three experiments, we aimed at inducing parallel vs. serial processing by manipulating the relative frequency of short vs. long SOAs (Experiments 1 and 2) and including no-go trials in Task 2 (Experiment 3). Beyond the conventional response time (RT) analyses, we employed drift–diffusion model analyses to differentiate between parallel and serial processing. Even though our findings were rather consistent across the three experiments, they neither support unambiguously the assumptions derived from the RSB model nor those derived from capacity-sharing models. SOA frequency might lead to an adaptation to frequent time patterns. Overall, our diffusion model results and mean RTs seem to be better explained by participant’s time expectancies.

Influences of age, mental workload, and flight experience on cognitive performance and prefrontal activity in private pilots: a fNIRS study

The effects of aging on cognitive performance must be better understood, especially to protect older individuals who are engaged in risky activities (e.g. aviation). Current literature on executive functions suggests that brain compensatory mechanisms may counter cognitive deterioration due to aging, at least up to certain task load levels. The present study assesses this hypothesis in private pilots engaged in two executive tasks from the standardized CANTAB battery, namely Spatial Working Memory (SWM) and  One Touch Stockings of Cambridge (OTS). Sixty-one pilots from three age groups (young, middle-aged, older) performed these two tasks from low to very high difficulty levels, beyond those reported in previous aging studies. A fNIRS headband measured changes in oxyhemoglobin (HbO2) in the prefrontal cortex. Results confirmed an overall effect of the difficulty level in the three age groups, with a decline in task performance and an increase in prefrontal HbO2 signal. Performance of older relative to younger pilots was impaired in both tasks, with the greatest impairment observed for the highest-load Spatial Working Memory task. Consistent with this behavioral deficit in older pilots, a plateau of prefrontal activity was observed at this highest-load level, suggesting that a ceiling in neural resources was reached. When behavioral performance was either equivalent between age groups or only slightly impaired in the older group, there were not any age-related differences in prefrontal activity. Finally, older pilots with extensive flying experience tend to show better preserved spatial working memory performance when compared to mildly-experienced of the same age group. The present findings are discussed in the frames of HAROLD and CRUNCH theoretical models of cognitive and neural aging, evoking the possibility that piloting expertise may contribute to preserve executive functions throughout adulthood.

Structure of executive functions in young and in older persons

INTRODUCTION

Using factor analysis, several studies reported that higher-order cognitive control involves separable executive functions. However, the number and definition of the purported functions differed between studies. One possible explanation for this discrepancy is that executive functions don't exhibit a clear factorial structure, i.e., there is no clear dichotomy between executive function tests which are well-correlated (representing a common factor) and those which are poorly correlated (representing distinct factors). We scrutinize this explanation separately in data from young and from older persons.

METHODS & RESULTS

Young and older volunteers completed cognitive tests of the purported executive functions shifting, updating, inhibition and dual-tasking (two tests per function). Confirmatory and exploratory factor analyses yielded, for either age group, factorial structures that were within the range reported in literature. More importantly, when correlations between tests were sorted in ascending order, and were then fitted them by piecewise linear regression with a breakpoint, there was no evidence for a distinct breakpoint between low and high correlations in either age group. Correlations between tests were significantly higher in older compared to young participants, and the pattern of test pairs with high and with low correlations differed between age groups.

DISCUSSION

The absence of a breakpoint indicates that executive function tests don't segregate into well-correlated and poorly correlated pairs, and therefore are not well suited for factor analyses. We suggest that executive functions are better described as a partly overlapping rather than a factorial structure. The increase of correlations in older participants supports the existence of age-related dedifferentiation, and the dissimilarity of correlations in the two age groups supports the existence of age-related reorganization.

Time-Interval Emphasis in an Aeronautical Dual-Task Context: A Countermeasure to Task Absorption

OBJECTIVE

We tested a training method intended to prevent unsafe aeronautical behavior (i.e., too much time spent gazing inside the cockpit) induced by the modern cockpit, by teaching individuals to perform a task complementing the see-and-avoid mandatory safety task within a limited time interval.

BACKGROUND

Aeronautical activities led crews to perform several tasks simultaneously in an ergonomic environment under constant change. See and avoid remains one of the main safety tasks during visual flight. However, modern cockpits induce absorption and impair performance of this safety task. Many laboratory studies showed the relevance of training methods for managing dual-task situations and estimating time intervals.

METHOD

A specific virtual environment was developed to expose participants to a dual-task situation in which time-interval emphasis was provided in real time. Two types of emphasis training were tested: a permissive one that allowed participants to pursue the inside-cockpit task beyond the time limit and a nonpermissive one that did not.

RESULTS

The best time-interval acquisition, with retention up to 24 hr later, was observed in the nonpermissive condition, but task performances immediately after the training sessions were equivalent across conditions.

CONCLUSION

Time-emphasis training appears to be an efficient means of promoting absorption resistance while preserving task performance. Transferability of time-interval estimation skills has yet to be tested.

APPLICATION

Most areas of application for absorption resistance (aviation, shipping, rail, road, etc.) could benefit from this type of training to manage multitask situations.

Is the head-fake effect in basketball robust against practice? Analyses of trial-by-trial adaptations, frequency distributions, and mixture effects to evaluate effects of practice

Reactions to the pass of a basketball player performing a head fake are typically slower than reactions to a basketball player who passes without a head fake (i.e., head-fake effect). The present study shows that extensive practice reduces the head-fake effect in basketball. Additional analyses were conducted to explore the mechanism behind the reduced head-fake effect. First, we analyzed whether or not participants developed some control over the processing of irrelevant gaze direction, as indicated by specific trial-to-trial adaptations (i.e., congruency sequence effect). Second, we fitted the individual frequency distributions of RTs to ex-Gaussian distributions, to evaluate if practice specifically affects the Gaussian part of the distribution or the exponential part of the distribution. Third, we modeled individual RT distributions as the so-called mixture effects to examine whether the way irrelevant gaze direction impacts performance (either occasionally but massively or continuously but moderately) changes with practice. The analyses revealed that the effect of practice could not be explained with an increasing congruency-sequence effect. Also, it could not be found in the ex-Gaussian distributional analyses. The assumption that residual failure to inhibit the processing of the gaze direction in contrast to continuous failures to do so might favor mixed effects over uniform effects at later courses of practice could not be validated. The reduced head-fake effect thus is argued to source in participants' general increasing ability to inhibit the processing of the task-irrelevant gaze direction information and/or in a priority shift of gaze processing to a processing of the pass direction.

The effect of Tai Chi training on the dual-tasking performance of stroke survivors: a randomized controlled trial

Objective:

To compare the effect of Tai Chi training with conventional exercise on dual-tasking performance among stroke survivors.

Design:

An assessor-blinded, randomized controlled trial.

Subjects:

Community-dwelling stroke survivors.

Setting:

Community centers and university.

Interventions:

Subjects in the Tai Chi group and the conventional exercise group were trained with the corresponding exercises for 12 weeks (1 hour/session, 2/week). No training was given to the controls.

Main measures:

An auditory Stroop test, a turning-while-walking test, and a dual-tasking condition that combined the two tests were conducted at baseline, after the intervention, and one month later.

Results:

Forty-seven subjects were randomized into Tai Chi group ( n = 15), conventional exercise group ( n = 17), or control group ( n = 15). There was no significant difference in the outcome measures among the three groups after the intervention and at the one month follow-up assessment. Within-group comparisons showed improvements in dual-tasking performance after Tai Chi training and further improvement during the follow-up period (composite score on the auditory Stroop test: pre-assessment: 73.1 ± 27.6, post-assessment: 89.9 ± 23.4, follow-up assessment: 91.7 ± 26.9; completion time of the turning-while-walking test: pre-assessment: 17.7 ± 6.9 seconds, post-assessment: 15.6 ± 5.2 seconds, follow-up assessment: 14.9 ± 4.9 seconds).

Conclusion:

Tai Chi training does not have superior effect on dual-tasking performance compared with conventional exercise among stroke survivors. Further studies with larger sample size, longer training, and follow-up periods are needed.

Can Driving-Simulator Training Enhance Visual Attention, Cognition, and Physical Functioning in Older Adults?

Virtual reality offers a good possibility for the implementation of real-life tasks in a laboratory-based training or testing scenario. Thus, a computerized training in a driving simulator offers an ecological valid training approach. Visual attention had an influence on driving performance, so we used the reverse approach to test the influence of a driving training on visual attention and executive functions. Thirty-seven healthy older participants (mean age: 71.46 ± 4.09; gender: 17 men and 20 women) took part in our controlled experimental study. We examined transfer effects from a four-week driving training (three times per week) on visual attention, executive function, and motor skill. Effects were analyzed using an analysis of variance with repeated measurements. Therefore, main factors were group and time to show training-related benefits of our intervention. Results revealed improvements for the intervention group in divided visual attention; however, there were benefits neither in the other cognitive domains nor in the additional motor task. Thus, there are no broad training-induced transfer effects from such an ecologically valid training regime. This lack of findings could be addressed to insufficient training intensities or a participant-induced bias following the cancelled randomization process.

Dynamic, continuous multitasking training leads to task-specific improvements but does not transfer across action selection tasks

The ability to perform multiple tasks concurrently is an ever-increasing requirement in our information-rich world. Despite this, multitasking typically compromises performance due to the processing limitations associated with cognitive control and decision-making. While intensive dual-task training is known to improve multitasking performance, only limited evidence suggests that training-related performance benefits can transfer to untrained tasks that share overlapping processes. In the real world, however, coordinating and selecting several responses within close temporal proximity will often occur in high-interference environments. Over the last decade, there have been notable reports that training on video action games that require dynamic multitasking in a demanding environment can lead to transfer effects on aspects of cognition such as attention and working memory. Here, we asked whether continuous and dynamic multitasking training extends benefits to tasks that are theoretically related to the trained tasks. To examine this issue, we asked a group of participants to train on a combined continuous visuomotor tracking task and a perceptual discrimination task for six sessions, while an active control group practiced the component tasks in isolation. A battery of tests measuring response selection, response inhibition, and spatial attention was administered before and immediately after training to investigate transfer. Multitasking training resulted in substantial, task-specific gains in dual-task ability, but there was no evidence that these benefits generalized to other action control tasks. The findings suggest that training on a combined visuomotor tracking and discrimination task results in task-specific benefits but provides no additional value for untrained action selection tasks.

An fMRI paradigm based on Williams inhibition test to study the neural substrates of attention and inhibitory control

The purpose of this study is to present an fMRI paradigm, based on the Williams inhibition test (WIT), to study attentional and inhibitory control and their neuroanatomical substrates. We present an index of the validity of the proposed paradigm and test whether the experimental task discriminates the behavioral performances of healthy participants from those of individuals with acquired brain injury. Stroop and Simon tests present similarities with WIT, but this latter is more demanding. We analyze the BOLD signal in 10 healthy participants performing the WIT. The dorsolateral prefrontal cortex, the inferior prefrontal cortex, the anterior cingulate cortex, and the posterior cingulate cortex were defined for specified region of interest analysis. We additionally compare behavioral data (hits, errors, reaction times) of the healthy participants with those of eight acquired brain injury patients. Data were analyzed with GLM-based random effects and Mann-Whitney tests. Results show the involvement of the defined regions and indicate that the WIT is sensitive to brain lesions. This WIT-based block design paradigm can be used as a research methodology for behavioral and neuroimaging studies of the attentional and inhibitory components of executive functions.

Short-term language switching training tunes the neural correlates of cognitive control in bilingual language production

The present study investigated how language switching experience would modulate the neural correlates of cognitive control involved in bilingual language production. A group of unbalanced Chinese-English bilinguals undertook an 8-day cued picture naming training during which they named pictures in either of their languages based on visually presented cues. Participants' brain activation was scanned before and after the training in the same task. Behavioral results revealed a significant training effect such that switch costs were reduced after training. fMRI results showed that after training, activation of brain areas associated with cognitive control including the anterior cingulated cortex and the caudate was reduced. Besides, the activation reduction in the left dorsal anterior cingulated cortex positively correlated with the reduction in switch costs in response time and this training effect could be transferred to untrained stimuli. These findings suggest that neural correlates of cognitive control, especially that of the conflict monitoring process, in bilingual language production could be modulated by short-term language switching training. Hum Brain Mapp 38:5859-5870, 2017. © 2017 Wiley Periodicals, Inc.

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.

Neural interactions mediating conflict control and its training-induced plasticity

Cognitive control is of great plasticity. Training programs targeted on improving it have been suggested to yield neural changes in the brain. However, until recently, the relationship between training-induced brain changes and improvements in cognitive control is still an open issue. Besides, although the literature has attributed the operation of cognitive control to interactions between large-scale networks, the neural pathways directly associated with it remain unclear. The current study aimed to examine these issues by focusing on conflict processing. In particular, we employed a training program with a randomized controlled design. The main findings were as follows: 1) In behavior, the training group showed reduced conflict effect after training, relative to the control group; 2) In the pretest stage, the behavioral conflict effect was negatively correlated with a number of neural pathways, including the connectivity from the cingulo-opercular network (CON) to the cerebellum and to sub-regions of the dorsal visual network; 3) increase in the connectivity strength of several network interactions, such as the connectivity from the CON to the cerebellum and to the primary visual network, was associated with behavioral gains; 4) there were also nonlinear correlations between behavioral and neural changes. These findings highlighted a critical role of the modulation of CON on other networks in mediating conflict processing and its plasticity, and raised the significance of investigating nonlinear relationship in the field of cognitive training.

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.