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

Comparing laboratory and online settings: equivalence in training and transfer effects for training task-order coordination processes

Introduction

The literature on dual-task training suggests reductions in task-coordination costs with extensive practice, yet such regimens are resource-intensive. This study investigates the feasibility of online assessments for cognitive training studies by comparing training and transfer effects on task-order coordination (TOC) skills in laboratory versus online settings.

Methods

We conducted a 5-day training regimen including pre-and post-test. Sixty-two participants completed training either in our laboratory or online via Pavlovia. They were assigned to one of two training order conditions, either practicing two visual-manual tasks in a dual-task situation with fixed task order or with random task order. Performance metrics included reaction time (RT) and error rates for trained and untrained tasks to assess TOC costs before and after the training. Data from both setting conditions (laboratory vs. online) were compared.

Results

Firstly, data of both settings revealed training-order specific training and transfer effects for TOC costs on RT level. Random task order training improved TOC for trained and untrained tasks, whereas fixed order training did not. Secondly, cross-setting analyses, both frequentists and Bayesian, confirmed these effects and revealed no reliable impact of setting on outcomes.

Discussion

This research carries two significant implications. Our findings demonstrate the acquisition of task-order coordination skills, extending prior research on improving task-coordination in dual-task situations. Additionally, the robust effects for such improvements were independent of specific tasks and setting (whether investigated online or in the laboratory), supporting the use of online testing in cognitive training regimens for resource savings without compromising quality.

Do Motor-Cognitive and Motor-Motor Dual-Task Training Differently Affect Dual-Task Interference in Individuals With Intellectual Disability?

This study explored the effect of different dual-task (DT) training programs on DT interference in adults with intellectual disability. Center-of-pressure (CoP) mean velocity in single-task (ST) and cognitive-DT conditions and the Timed Up-and-Go Test (TUGT) during ST, cognitive-DT, and motor-DT conditions were assessed before and after intervention in a cognitive-motor training group, a motor-motor training group, and a control group. Before training, CoP mean velocity and TUGT time increased (p < .001) in DT compared with the ST condition. After training, the CoP mean velocity values remained unchanged (p = .07) in DT compared with the ST condition among the cognitive-motor training group. Furthermore, compared with the ST condition, no increase (p = 1) was reported in the TUGT time during the cognitive-DT condition for the cognitive-motor training group and during the motor-DT for the motor-motor training group (p = .12). The effect of DT training on DT interference depends on the training modality.

The effect of dual-task training on postural and cognitive performances in adolescents with down syndrome

BACKGROUND

The dual task training (DTT) has been shown to improve postural and cognitive performances in many populations. Therefore, it seems of interest to explore the effect of such training modality in individuals with Down syndrome (DS) presenting both cognitive and postural deficits.

AIMS

This study explored the effect of a DTT compared to a single task training (STT) on postural and cognitive performances in adolescents with DS.

METHODS AND PROCEDURES

The center of pressure velocity (CoPVm) and the cognitive performance in the selective word recall test were recorded under single task (ST) and DT conditions before and after 8 weeks in the STT group (STTG), the DTTG and the control group (CG).

OUTCOMES AND RESULTS

Before training, CoPVm values increased and cognitive performances decreased (p < 0.001) during the DT compared to ST conditions in all groups. After training, CoPVm decreased (p < 0.001) in the DTTG and the STTG under the ST conditions. However, under DT conditions, these values decreased (p < 0.001) only in the DTTG. The cognitive performance increased (p < 0.001) only in the DTTG in both ST and DT conditions.

CONCLUSION

The DTT is strongly recommended to improve both postural and cognitive performances in individuals with DS notably in DT conditions.

Stimulating prefrontal cortex facilitates training transfer by increasing representational overlap

A recent hypothesis characterizes difficulties in multitasking as being the price humans pay for our ability to generalize learning across tasks. The mitigation of these costs through training has been associated with reduced overlap of constituent task representations within frontal, parietal, and subcortical regions. Transcranial direct current stimulation, which can modulate functional brain activity, has shown promise in generalizing performance gains when combined with multitasking training. However, the relationship between combined transcranial direct current stimulation and training protocols with task-associated representational overlap in the brain remains unexplored. Here, we paired prefrontal cortex transcranial direct current stimulation with multitasking training in 178 individuals and collected functional magnetic resonance imaging data pre- and post-training. We found that 1 mA transcranial direct current stimulation applied to the prefrontal cortex paired with multitasking training enhanced training transfer to spatial attention, as assessed via a visual search task. Using machine learning to assess the overlap of neural activity related to the training task in task-relevant brain regions, we found that visual search gains were predicted by changes in classification accuracy in frontal, parietal, and cerebellar regions for participants that received left prefrontal cortex stimulation. These findings demonstrate that prefrontal cortex transcranial direct current stimulation may interact with training-related changes to task representations, facilitating the generalization of learning.

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.

Practice effects on dual-task order coordination and its sequential adjustment

When the performance of two tasks overlaps in time, performance impairments in one or both tasks are common. Various theoretical explanations for how component tasks are controlled in dual-task situations have been advanced. However, less attention has been paid to the issue of how two temporally overlapping tasks are appropriately coordinated in terms of their order. The current study focuses on two specific aspects of this task-order coordination: (1) the potential effects of practice on task-order coordination performance and (2) its relationships with cognitive meta-control mechanisms that adjust this coordination. These aspects were investigated in a visual-auditory dual-task combination with randomly changing task orders across trials after four sessions of dual-task practice (N = 24) and single-task practice (N = 24). The results demonstrated that task-order coordination improves during dual-task practice, and in contrast to the effects of single-task practice. Practice, on the other hand, did not show substantial evidence of an effect on the adjustment of task-order coordination. This practice-related dissociation is consistent with the assumption that (1) task-order coordination and (2) its sequential adjustment are separable sets of processes.

Dynamics of task preparation processes revealed by effect course analysis on response times and error rates

Cuing or executing a task impacts processing pathways for task-relevant information. While there is ample evidence that processing associated with task execution changes with practice, such evidence regarding cue-induced task preparation is scarce. Here we explored practice-related changes of processing pathways by task cuing in order to assess the plasticity of task preparation. We first developed and validated a new method for the study of practice-related changes, the effect course analysis. The effect course analysis is a model-free, non-parametric method designed to reveal effect changes within an experimental session on a continuous time scale. Then we applied this method to a new study in which cued task sets were supposed to remain activated during assessment of task-relevant pathways, as potential task execution was postponed at the end of the trial. The results showed that, with little practice, task cuing amplified task-relevant pathways, whereas this effect vanished with practice, suggesting that practice prompts fundamental changes of how task cues are used for task preparation. Hence, if one cannot be certain that cognitive processing is stationary, investigating the time course of experimental effects appears to be crucial to determine how cognitive processing is influenced by practice.

Effectiveness and cost of integrated cognitive and balance training for balance and falls in cerebellar ataxia: a blinded two-arm parallel group RCT

Background

In patients with cerebellar ataxia (CA), dual-tasking deteriorates the performance of one or both tasks.

Objective

Evaluate the effects of 4 weeks of cognitive-coupled intensive balance training (CIBT) on dual-task cost, dynamic balance, disease severity, number of falls, quality of life, cognition and cost among patients with CA.

Methods

This RCT compared CIBT (Group 1) to single-task training (Group 2) among 32 patients with CA. The intervention included either dual-task (CIBT) or single-task training for 4 weeks followed by 6 months of unsupervised home exercises. Dual-task timed up-and-go test (D-TUG) assessed dual-task cost of the physical and cognitive tasks. Assessment time points included baseline 1 (Week 0:T1), baseline 2 (Week 6:T2), post-intervention (Week 10:T3), and follow-up (Week 34:T4).

Results

Compared to single-task training CIBT improved the dual-task cost of physical task [MD -8.36 95% CI (-14.47 to -2.36, p < 0.01), dual-tasking ability [-6.93 (-13.16 to -0.70); p = 0.03] assessed using D-TUG, balance assessed using the scale for the assessment and rating of ataxia (SARAbal) [-2.03 (-4.04 to -0.19); p = 0.04], visual scores of the SOT (SOT-VIS) [-18.53 (-25.81 to -11.24, p ≤ 0.01] and maximal excursion [13.84 (4.65 to 23.03; p ≤ 0.01] of the Limits of Stability (LOS) in the forward direction and reaction time in both forward [-1.11 (-1.42 to -0.78); p < 0.01] and right [-0.18 (0.05 to 0.31); p < 0.01] directions following 4 weeks of training. CIBT did not have any additional benefits in reducing the number of falls, or improving disease severity, quality of life and cognition. The mean cost of intervention and healthcare costs for 7 months was HKD 33,380 for CIBT group and HKD 38,571 for single-task training group.

Conclusion

We found some evidence to support the use of CIBT for improving the dual-tasking ability, dual-task cost of physical task and dynamic balance in CA. Future large fully-powered studies are needed to confirm this claim.

Clinical trial registration

https://clinicaltrials.gov/study/NCT04648501, identifier [Ref: NCT04648501].

Mutual interplay between cognitive offloading and secondary task performance

Various modern tools, such as smartphones, allow for cognitive offloading (i.e., the externalization of cognitive processes). In this study, we examined the use and consequences of cognitive offloading in demanding situations in which people perform multiple tasks concurrently-mimicking the requirements of daily life. In a preregistered study, we adapted the dual-task paradigm so that one of the tasks allowed for cognitive offloading. As a primary task, our participants (N = 172) performed the pattern copy task-a highly demanding working memory task that allows for offloading at various degrees. In this task, we manipulated the temporal costs of offloading. Concurrently, half of the participants responded to a secondary N-back task. As our main research question, we investigated the impact of offloading behavior on secondary task performance. We observed that more pronounced offloading in the condition without temporal costs was accompanied by a more accurate performance in the N-back task. Furthermore, the necessity to respond to the N-back task increased offloading behavior. These results suggest an interplay between offloading and secondary task performance: in demanding situations, individuals increasingly use cognitive offloading, which releases internal resources that can then be devoted to improving performance in other, concurrent tasks.

Aerobic physical exercise versus dual-task cognitive walking in cognitive rehabilitation of people with stroke: a randomized clinical trial

Introduction

Stroke is a neurological deficit caused by an acute focal injury to the central nervous system due to vascular injury that can result in loss of neurological function, lasting brain damage, long-term disability and, in some cases, death. The literature reports that aerobic physical exercise, as well as dual-task cognitive walking, are used for the cognitive recovery of people with stroke. We aimed to assess whether aerobic physical exercise influences post-stroke cognitive recovery, namely performance on selective and sustained attention. We tested the hypothesis that post-stroke aerobic physical exercise leads to more significant gains than post-stroke dual-task cognitive walking.

Methods

We used a Randomized Clinical Trial, single-blind, parallel group, to verify the existence of differences between two groups. A total of 34 patients with subacute to chronic stroke were divided into two groups to train three times a week for 12 weeks: the aerobic physical exercise (PE) group engaged in 20 min on a treadmill, 20 min on a stationary bicycle and 5 min on a desk bike pedal exerciser per session; the dual-task (DT) gait exercise group walked for 45 min while simultaneously performing cognitive tasks per session. All participants were assessed on cognitive functioning with the Mini-Mental State Examination (MMSE) and d2 Test of Attention before acute interventions and post interventions. We have also applied a Visual Analog Scale to monitor the participants' perceived difficulty, pre-, post-acute, and post-chronic interventions. Participants also responded to a Borg Scale of perceived exertion following the acute and the final session of chronic training.

Results

A mixed model ANOVA revealed a significant interaction effect with a large effect size for most of the cognitive variables under study. The variables associated with the d2 Test of Attention showed significant differences between the groups, mainly from T0 to T2. Also for MMSE, an ANOVA revealed a significant interaction effect with significant improvements from T0 to T2. Our results strongly suggest that aerobic physical exercise is more beneficial than dual-task cognitive-gait exercise since in the PE group, cognitive attention scores increase, and cognitive impairment and perception of exertion decrease, compared to the DT group.

Conclusion

These findings support that PE provides more significant benefits for patients post-stroke when compared to DT.

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.

Scoping review of dual-task interference in individuals with intellectual disability

Dual-task paradigms can provide insights on the structures and mechanisms underlying information processing and hold diagnostic, prognostic, and rehabilitative value for populations with cognitive deficits such as in individuals with intellectual disability (ID). In this paradigm, two tasks are performed separately (single-task context) and concurrently (dual-task context). The change in performance from single- to dual-task context represents dual-task interference. Findings from dual-task studies have been largely inconsistent on whether individuals with ID present with dual-task-specific deficits. The current review aimed to map the published literature on dual-task methods and pattern of dual-task interference in individuals with ID. A scoping review based on Arksey and O'Malley's five-stage methodological framework was performed. Seventeen electronic databases and registries were searched to identify relevant studies, including gray literature. Charted data from included studies were analyzed quantitatively and qualitatively. PRISMA guidelines informed the reporting of this review. Twenty-two studies involving 1,102 participants (656 with ID and 446 without ID) met the review's inclusion criteria. Participants in the included studies were heterogeneous in sex, age (range 3-59 years), etiology and ID severity. Included studies characterized their ID-sample in different ways, most commonly using intelligence quotient (IQ) scores. Other measures of intellectual function (e.g., mental age, ID severity, verbal and/or visuospatial ability scores) were also used, either solely or in combination with IQ. Methods of dual-task testing varied across studies, particularly in relation to dual-task combinations, equation of single-task performance between groups, measurement and reporting of dual-task performance for each single-task, and task priority instructions. Thematic content of the included studies were: (1) structural interference to dual-tasking; (2) etiology-based differences in dual-tasking; (3) gait and balance dual-task performance; (4) testing executive function using dual-task paradigms; and (5) training effect on dual-task performance. Although the evidence consistently supported the intact dual-tasking ability of individuals with ID, the pattern of dual-task interference was inconsistent. Likewise, the evidence was inconclusive regarding dual-task deficit specific to individuals with ID because of heterogeneity in dual-task study designs among included studies.

Treadmill Walking Maintains Dual-task Gait Performance and Reduces Frontopolar Cortex Activation in Healthy Adults

Studies examining dual-task gait (DTG) have used varying conditions such as overground or treadmill walking, however it is not known whether brain activation patterns differ during these conditions. Therefore, this study compared oxyhaemoglobin (O2Hb) responses of the prefrontal cortex (PFC) during overground and treadmill walking. A total of 30 participants (14M/16F) were recruited in a randomized crossover study comparing overground and treadmill walking under single- and dual-task (STG and DTG) conditions. The DTG consisted of performing walking and cognitive (serial subtraction by 7's) tasks concurrently. A portable 24-channel functional near-infrared spectroscopy system was placed over the PFC, corresponding the left and right dorsolateral PFC and frontopolar cortices (DLPFC and FPC) during overground and treadmill STG and DTG. Results showed a reduction in gait speed during DTG compared to STG on overground but not treadmill walking, while cognitive performance was maintained during DTG on both overground and treadmill walking. A reduction in O2Hb was seen in the FPC during DTG compared to a cognitive task only, and on the treadmill compared to overground walking. Increased activation was seen in the left and right DLPFC during DTG but did not differ between treadmill and overground walking. Our results support the concept of improved gait efficiency during treadmill walking, indicated by the lack of change in STG and DTG performance and concomitant with a reduction in FPC activation. These findings suggest different neural strategies underpinning treadmill and overground walking, which should be considered when designing gait assessment and rehabilitation interventions.

Dual-Task Training Effects on the Cognitive-Motor Interference in Individuals with Intellectual Disability

This study explored the effect of dual task (DT) training compared to single task (ST) training on postural and cognitive performances in DT conditions in individuals with intellectual disability (ID). Postural sways and cognitive performances were measured separately and simultaneously before and after 8 weeks in the ST training group (STTG), the DT training group (DTTG) and the control group (CG) that did not received any training. Before training, postural sways and cognitive performances were higher in the DT condition compared to ST one in all groups. After training, postural sways were higher in the DT condition compared to the ST only in the STTG and the CG. The cognitive performance increased after training only in the DTTG.

Knowledge generalization and the costs of multitasking

Humans are able to rapidly perform novel tasks, but show pervasive performance costs when attempting to do two things at once. Traditionally, empirical and theoretical investigations into the sources of such multitasking interference have largely focused on multitasking in isolation to other cognitive functions, characterizing the conditions that give rise to performance decrements. Here we instead ask whether multitasking costs are linked to the system's capacity for knowledge generalization, as is required to perform novel tasks. We show how interrogation of the neurophysiological circuitry underlying these two facets of cognition yields further insights for both. Specifically, we demonstrate how a system that rapidly generalizes knowledge may induce multitasking costs owing to sharing of task contingencies between contexts in neural representations encoded in frontoparietal and striatal brain regions. We discuss neurophysiological insights suggesting that prolonged learning segregates such representations by refining the brain's model of task-relevant contingencies, thereby reducing information sharing between contexts and improving multitasking performance while reducing flexibility and generalization. These proposed neural mechanisms explain why the brain shows rapid task understanding, multitasking limitations and practice effects. In short, multitasking limits are the price we pay for behavioural flexibility.

Effects of dual task training on dual task gait performance and cognitive function in individuals with Parkinson's disease: A meta-analysis and meta-regression

OBJECTIVE

To explore the effects of dual task (DT) training on DT gait performance and cognitive function in individuals with Parkinson's disease (PD) and to examine factors that might influence the effects of DT training.

DATA SOURCES

PubMed, Wiley Online Library, Cochrane Library, CINAHL, and Medline were searched for articles published from January 2006 to December 2021.

STUDY SELECTION

Randomized controlled trials comparing DT training with usual care or general exercise were included.

DATA EXTRACTION

The outcomes studied were DT gait parameters including speed, step and stride length, cadence, step and stride time variability, dual task cost on gait speed, and Trail Making Tests (TMT) presented as standardized mean differences. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) was used to evaluate the quality of evidence.

DATA SYNTHESIS

Ten randomized controlled trials with 466 participants were included in the meta-analysis. The included studies presented, in general, with a low to high risk of bias. Meta-analyses used a random-effects model for all analysis. The meta-analysis showed the DT training effects on DT gait speed (SMD=0.825, p=0.012), DT step and stride length (SMD=0.400, p=0.015), TMT-A (SMD=0.533, p=0.010) and TMT-B (SMD=0.516, p=0.012) compared to the control group. Only the effect on TMT-A was maintained at the follow-up assessment. The results of meta-regression showed that participants with slower initial single task gait speed improved more after DT training on DT step and stride length.

CONCLUSIONS

The DT training improved more in DT gait speed with moderate-quality evidence as compared with usual care or conventional physical training in individuals with PD. The beneficial effects of DT training on DT step and stride length, attention and executive function were also demonstrated in this meta-analysis. Furthermore, the improvement in the DT walking step and stride length was related to the participant's initial single task gait speed.

Dual-task interference as a function of varying motor and cognitive demands

Multitasking is a critical feature of our daily lives. Using a dual-task paradigm, this experiment explored adults’ abilities to simultaneously engage in everyday motor and cognitive activities, counting while walking, under conditions varying the difficulty of each of these tasks. Motor difficulty was manipulated by having participants walk forward versus backward, and cognitive difficulty was manipulated by having participants count forward versus backward, employing either a serial 2 s or serial 3 s task. All of these manipulations were performed in single-task conditions (walk only, count only) and dual-task conditions (walk and count simultaneously). Both motor performance variables (cycle time, stride length, walking velocity) and cognitive variables (counting fluency, counting accuracy) were assessed in these conditions. Analyses of single-task conditions revealed that both motor and cognitive manipulations predictably influenced performance. Analyses of dual-task performance revealed influences of motor and cognitive factors on both motor and cognitive performance. Most centrally, dual-task costs (normalized difference between single- and dual-task conditions) for motor variables revealed that such costs occurred primarily for temporal or spatiotemporal gait parameters (cycle time, walking velocity) and were driven by cognitive manipulations. Dual-task cost analyses for cognitive measures revealed negative dual-task costs, or dual-task benefits, for cognitive performance. Finally, the effects of dual-task manipulations were correlated for motor and cognitive measures, indicating dual-task performance as a significant individual difference variable. These findings are discussed with reference to theories of attentional allocation, as well as the possible role of auditory–motor entrainment in dual-task conditions.

Mix-and-Match or Mismatch? Exploring the Perspectives of Older Adults About Zumba Dance and Its Potential Utilization for Dual-Task Training

Despite the popularity of Zumba dancing, research is scarce about its impact on older adults. Meanwhile, the integration of cognitive tasks with physical exercises, also known as dual tasking, is an evolving strategy to facilitate activities for older adults. This study investigated the perceptions of persons aged ≥55 years on Zumba and its potential to be incorporated into a dual-task program. We conducted a descriptive-qualitative study involving 44 Filipino older adults. Using content analysis, four themes were identified: moving toward match or mismatch, balancing benefits with burdens, dual tasking as innovative yet potentially challenging, and overcoming barriers with enablers. Although Zumba was perceived as an inclusive and beneficial activity, individual and contextual limitations could hinder its suitability. Moreover, dual tasking in Zumba was considered an innovative approach, although challenges should be addressed to promote its feasibility. Several strategies could enable the design and implementation of age-appropriate Zumba and dual-tasking programs for older adults.

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.

Expanding dual-task research by a triple-task

Multitasking research in the laboratory is dominated by extremely simplistic dual-task paradigms. Although dual-tasks allow for some variations, they do not compare well to more complex everyday task settings. This study expands a classical dual-task paradigm by adding a third task. The dual-tasks and the triple-task always consisted of the same three single tasks. The aim was to investigate the effects of the combinations of the three single-tasks and in which manner response times and costs increased. Stimulus-response pairings were varied either once within participants (E1) or between participants (E2). Our results showed that the increase in response time from dual-tasks to triple-tasks was only 43% of the increase from single-tasks to dual-tasks suggesting a non-linear cost of adding tasks. Moreover, response times in each subtask were higher in triple-task situations compared to single-task or dual-task situations. This is in contrast to classical dual-tasks, in which typically only one of the two responses is delayed. Cognitively, for costs in triple-tasks, unlike in dual-tasks, task coordination seems to play a larger role compared to the classically suggested relationships between stimulus and response in terms of their modality- and ideomotor-compatibility which we will discuss. Overall, the study demonstrates that current multitasking research is limited in its generalizability by focusing only on dual-tasks and would benefit from research with more complex task settings.

Anterograde interference emerges along a gradient as a function of task similarity: A behavioural study

Anterograde interference emerges when two opposite (B → A) or identical tasks (A → A) are learned in close temporal succession, suggesting that interference cannot be fully accounted for by competing memories. Informed by neurobiological evidence, this work tested the hypothesis that interference depends upon the degree of overlap between the neural networks involved in the learning of two tasks. In a fully within‐subject and counterbalanced design, participants (n = 24) took part in two learning sessions where the putative overlap between learning‐specific neural networks was behaviourally manipulated across four conditions by modifying reach direction and the effector used during gradual visuomotor adaptation. The results showed that anterograde interference emerged regardless of memory competition—that is, to a similar extent in the B → A and A → A conditions—and along a gradient as a function of the tasks' similarity. Specifically, learning under similar reaching conditions generated more anterograde interference than learning under dissimilar reaching conditions, suggesting that putatively overlapping neural networks are required to generate interference. Overall, these results indicate that competing memories are not the sole contributor to anterograde interference and suggest that overlapping neural networks between two learning sessions are required to trigger interference. One discussed possibility is that initial learning modifies the properties of its neural networks to constrain further plasticity induction and learning capabilities, therefore causing anterograde interference in a network‐dependent manner. One implication is that learning‐specific neural networks must be maximally dissociated to minimize the interfering influences of previous learning on subsequent learning.

Deciding while moving: Cognitive interference biases value-based decisions

When people act, they repeatedly have to make value-based decisions about the further course of actions. For example, when driving on the highway, they must decide whether to overtake other cars by changing lanes to arrive at their destination quicker; concurrently, they are required to stay on their momentary lane by controlling the steering wheel. Embodied choice models predict that concurrent action execution modulates value-based decisions. Here, we examined whether value-based decisions are influenced by a change of action costs and/or cognitive interference between concurrent actions and decision making. In a novel, computerized multilane tracking task paradigm, participants (N = 50) controlled a cursor moving on one of three horizontal lanes. During tracking (concurrent action), participants had to switch to other lanes to avoid obstacles or collect rewards (value-based decisions). The action costs associated with a lane switch depended on the cursor position relative to the currently tracked lane, and this relationship varied between conditions. Results showed that value-based lane switching decisions were biased by the cursor state. While this influence was partly attributed to minimizing action costs, a considerable part of the influence could be attributed to cognitive interference. Our findings provide further evidence for embodied choice models, showing that both cognitive interference as well as action costs bias value-based decisions.

Influence of Single Bouts of Aerobic Exercise on Dual-Tasking Performance in Healthy Adults

Dual-tasking performance (DTP) is critical for most real-life activities. Interventions to improve DTP would be clinically valuable. This study investigated effects of single-bouts of two different aerobic exercises on the performance of Extended cognitive Timed-Up and Go (ETUGcog), a dual-task test involving concurrent performance of a physical (ETUG) and cognitive (counting backwards serial 7 s) task. Twenty-two adults performed single bouts of high-intensity interval training (HIIT) and moderate-intensity exercise (MIE), separately. ETUGcog was performed before, immediately following, and 24 hours after each exercise. Number and rates of correct serial 7 s were significantly higher 24 hours after HIIT, with no difference in times to complete ETUGcog. No such effects were found for MIE. Single bouts of HIIT could provide delayed improvements in DTP.

Rationalizing constraints on the capacity for cognitive control

Humans are remarkably limited in: (i) how many control-dependent tasks they can execute simultaneously, and (ii) how intensely they can focus on a single task. These limitations are universal assumptions of most theories of cognition. Yet, a rationale for why humans are subject to these constraints remains elusive. This feature review draws on recent insights from psychology, neuroscience, and machine learning, to suggest that constraints on cognitive control may result from a rational adaptation to fundamental, computational dilemmas in neural architectures. The reviewed literature implies that limitations in multitasking may result from a trade-off between learning efficacy and processing efficiency and that limitations in the intensity of commitment to a single task may reflect a trade-off between cognitive stability and flexibility.

Tandem gait test performance in healthy, physically active adults: Clinical implications for concussion evaluation

OBJECTIVES

To identify factors affecting performance on the tandem gait test in healthy, physically active adults.

DESIGN

Cross-sectional.

METHODS

Participants completed the tandem gait test according to Sport Concussion Assessment Tool 3 (SCAT3) guidelines. Dependent variables included time for best trial (initial 3m, turn, final 3m and total) and whether the trial was "pass" or "fail". Independent variables included sex, concussion history, foot length, height and total number of trials.

RESULTS

55% (35/64) of participants passed the first trial of the tandem gait test; 19% (12/64) had a best time <14s. Sex and concussion history did not affect performance (p>0.05). There were no differences in turn times for those with and without a history of concussion (t=0.26, p=0.80). The number of trials was not significantly correlated with best time (þ=-0.04, p=0.74). There were low (þ=-0.31) to negligible (þ<0.30) correlations between foot length, height and all portions of the test. There was more variability in times for the turn (COV=27%) than during the straight portions (COV=18%).

CONCLUSIONS

Current recommendations for the tandem gait test led to a high false-positive rate in healthy, physically active adults. Sex, concussion history, number of trials and foot length had little to no influence on scores on the test. Turning times were more variable than times on the straight portions of the test. Clinicians may use these results as a guideline when interpreting performance on the tandem gait test in healthy physically active adults.

Dual-memory retrieval efficiency after practice: effects of strategy manipulations

The study investigated practice effects, instruction manipulations, and the associated cognitive architecture of dual-memory retrieval from a single cue. In two experiments, we tested predictions about the presence of learned parallelism in dual-memory retrieval within the framework of the set-cue bottleneck model. Both experiments included three experimental laboratory sessions and involved computerized assessments of dual-memory retrieval performance with strategy instruction manipulations. In Experiment 1, subjects were assigned to three distinct dual-task practice instruction groups: (1) a neutral instruction group without a specific direction on how to solve the task (i.e., neutral instruction), (2) an instruction to synchronize the responses (i.e., synchronize instruction), and (3) an instruction to use a sequential response style (i.e., immediate instruction). Results indicate that strategy instructions are able to effectively influence dual retrieval during practice. Mainly, the instruction to synchronize responses led to the presence of learned retrieval parallelism. Experiment 2 provided an assessment of the cognitive processing architecture of dual-memory retrieval. The results provide support for the presence of a structural bottleneck that cannot be eliminated by extensive practice and instruction manipulations. Further results are discussed with respect to the set-cue bottleneck model.

Effects of task probability on prioritized processing: Modulating the efficiency of parallel response selection

Four experiments investigated the extent to which a limited pool of resources can be shared between different tasks performed simultaneously when it is efficient to do so. The experiments used a prioritized processing paradigm, in which stimuli for both a primary task and a background task were presented in each trial. If the primary-task stimulus required a response in a trial, participants made only that response. If the primary-task stimulus did not require a response, participants responded to the background task. The main manipulation was the relative probability that a response would be required to the primary versus background task. In some blocks, the majority of trials required responses to the primary task (Experiments 1 and 2: 80%; Experiments 3 and 4: 60%), whereas in other blocks the majority required responses to the background task. Background-task responses were substantially faster in blocks where they were more likely to be required, consistent with the idea that more capacity was allocated to them in these blocks. Backward compatibility effects on primary-task responses and stimulus-onset asynchrony effects on background-task responses provided further evidence of greater capacity allocation to the background task when there was a higher probability of responding to it. The results support the view that two tasks can be processed in parallel, with resources divided between them, when it is efficient to do so.

Cognitive Capacity Limits Are Remediated by Practice-Induced Plasticity between the Putamen and Pre-Supplementary Motor Area

Humans show striking limitations in information processing when multitasking yet can modify these limits with practice. Such limitations have been linked to a frontal-parietal network, but recent models of decision-making implicate a striatal-cortical network. We adjudicated these accounts by investigating the circuitry underpinning multitasking in 100 human individuals and the plasticity caused by practice. We observed that multitasking costs, and their practice-induced remediation, are best explained by modulations in information transfer between the striatum and the cortical areas that represent stimulus-response mappings. Specifically, our results support the view that multitasking stems at least in part from taxation in information sharing between the putamen and pre-supplementary motor area (pre-SMA). Moreover, we propose that modulations to information transfer between these two regions leads to practice-induced improvements in multitasking.

THE EFFECTS OF MULTIPLE MODALITIES OF COGNITIVE LOADING ON DYNAMIC POSTURAL CONTROL IN INDIVIDUALS WITH CHRONIC ANKLE INSTABILITY

BACKGROUND

Evidence of neuroplasticity after joint injury has suggested that individuals with chronic ankle instability (CAI) may have degraded movement when facing cognitive demand. To date, research into these effects have been limited to static balance models, and typically only incorporate a single type of cognitive demands.

RESEARCH QUESTION

We aimed to determine the effects of multiple modalities of cognitive load (quantitative, verbal-memory, visuospatial) on dynamic postural control strategies in a sample of patients with CAI compared to uninjured controls.

METHODS

Thirty-two participants (16 CAI, 16 healthy) performed a series of 20 hops-to-stabilization while either under no cognitive load (CON), or while performing Benton's judgment of line orientation (JLO), the symbol digit modalities test (SDM), or a serial seven task (SVN). Dynamic postural stability indices and mean muscle activation from the lower leg muscles were extracted and assessed via analysis of variance.

RESULTS

Healthy subjects demonstrated better vertical and dynamic postural stability indices under JLO (P ≤ 0.017) and SVN (P ≤ 0.010) conditions compared to CON. Postural stability was unaffected in CAI (P > 0.050). Peroneus longus and lateral gastrocnemius activation was lowest in SVN across all subjects (P ≤ 0.033). Lateral gastrocnemius activation was greatest in SDM (P ≤ 0.033).

SIGNIFICANCE

These results suggest improvements in postural stability under cognitive demand in healthy individuals that did not occur in CAI, suggesting less movement optimization. Quantitative tasks appear to impede stabilizing muscle activation in the leg, while verbal-memory tasks result in a more protective landing strategy.

The Effects of Cognitive Loading on Motor Behavior in Injured Individuals: A Systematic Review

BACKGROUND

Research suggests that individuals with musculoskeletal injury may have difficulty negotiating physical tasks when they are combined with cognitive loads.

OBJECTIVE

Our objective was to conduct a systematic review to understand the effects of increased cognitive demand on movement patterns among individuals with musculoskeletal injuries.

METHODS

A comprehensive search of PubMed, MEDLINE, the Cumulative Index for Nursing and Allied Health Literature (CINAHL), and SPORTDiscus was conducted to find research reports that included a population that had previously experienced an ankle, knee, or low back injury, included an uninjured control group, and assessed a dual-task paradigm.

RESULTS

Forty-five full-text research reports were assessed, of which 28 studies (six ankle injury, nine knee injury, and 13 low back pain studies) were included in the review. Included studies were assessed for methodological quality and the study design extracted for analysis including the participants, cognitive and physical tasks performed, as well as outcome measures (e.g., three-dimensional kinematics, center of pressure, etc.). All studies included were cross-sectional or case-control with methodological quality scores of 17.8 ± 2.2 out of a possible 22. Twenty-five of the 28 studies found changes in motor performance with dual-task conditions compared with single tasks. Furthermore, 54% of studies reported a significant group by task interaction effect, reporting at least one alteration in injured groups' motor performance under dual-task conditions when compared with an uninjured group.

CONCLUSION

The results of this systematic review indicate that motor performance is further impaired by placing a cognitive load on individuals in populations with musculoskeletal injury. More demanding tasks such as gait appear to be more affected in injured individuals than simple balance tasks. Future investigators may want to consider the difficulty of the tasks included as well as the impact of dual-task paradigms on rehabilitation programs.

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.

Electrophysiological examination of response-related interference while dual-tasking: is it motoric or attentional?

The possibility that interference between motor responses contributes to dual-task costs has long been neglected, yet is supported by several recent studies. There are two competing hypotheses regarding this response-related interference. The motor-bottleneck hypothesis asserts that the motor stage of Task 1 triggers a refractory period that delays the motor stage of Task 2. The response-monitoring hypothesis asserts that monitoring of the Task-1 motor response delays the response-selection stage of Task 2. Both hypotheses predict lengthening of Task-2 response time (RT2) when Task 1 requires motor processing relative to when it does not. However, they assume different loci for the response-related bottleneck, and therefore make different predictions regarding (a) the interaction between Task-1 motor requirement and the Task-2 difficulty effect as measured by RT2 and (b) the premotoric durations and motoric durations of Task 2 as measured by lateralized readiness potentials (LRPs). To test these predictions, we conducted two experiments manipulating the Task-1 motor requirement (Go vs. NoGo) and Task-2 response-selection difficulty, as well as the stimulus-onset asynchrony (SOA). Task-1 motor processing significantly lengthened RT2, suggesting response-related interference. Importantly, the Task-1 motor response reduced the Task-2 difficulty effect at the short SOA, indicating postponement of the Task-2 motor stage, consistent with the motor-bottleneck hypothesis. Further consistent with the motor-bottleneck hypothesis, the Task-2 LRP indicated a consistent premotoric duration of Task 2 regardless of Task-1 motor requirement. These results are difficult to reconcile with the response-monitoring hypotheses, which places the response-related bottleneck before the response-selection stage of Task 2. The results also have important implications regarding use of locus-of-slack logic in PRP studies.

Dual-task training on cognition and resistance training improved both balance and working memory in older people

Objectives: With increasing age, declines in executive functions and basic motor skills such as posture control, muscle strength, and balance performance have been observed. However, no intervention has focused on enhancing both executive functions and balance performance concomitantly. Accordingly, the aim of the present study is to investigate whether and to what extent two different dual-task interventions improved both working memory and balancing. Specifically, we examined whether either a motor-cognitive dual task training (mCdtt) or a motor-motor dual-task training (mMdtt) impacted more favorably on working memory and on balance performance among a sample of older adults.Methods: A total of 60 older males (mean age: 68.31 years; SD = 3.83) were randomly assigned either to the mCdtt, the mMdtt or to control condition. Balance performance and working memory performance were tested at baseline, four weeks later at study completion, and again 12 weeks later at follow-up.Results: Balance and working memory improved from baseline to post-intervention and to follow-up (significant Time effect), but more so in the mCdtt compared to the mMdtt condition (significant Time × Group interaction). Further, compared to the mMdtt condition, higher scores were observed in the mCdtt condition (significant Group effect).Conclusion: Dual-task interventions improved both balance performance and working memory, but more so if cognitive performance was specifically trained along with resistance training.

The effect of using a cycling workstation on mouse dexterity

This study investigated the effect of using a cycling workstation on mouse dexterity, including if and how this changed with practice. Thirty-four healthy adults were allocated to a sitting group (n = 17) or cycling group (n = 17). All participants completed standardised computer tasks on 6 occasions: baseline and final—all participants were seated; practice 1 to 4—sitting group participants were seated, cycling group participants pedalled on an under desk cycle. Three computer tasks were employed: (1) Tracking (continuous task)—participants used the mouse pointer to track a dot in a figure of 8 pattern at 3 different speeds without a guide then with a guide (2) Aiming (discrete task)—participants moved the mouse pointer to a dot which repeatedly disappeared then reappeared again in different locations, creating the outline of a pentagram (3) Steering (continuous task)—participants steered the mouse pointer around two different pathways. Accuracy was measured during the Tracking and Steering tasks as the root mean square error and penalised path accuracy respectively. Speed was measured during the Aiming task as the movement time. Data was analysed using frequentist and Bayes Factor analyses. During the continuous tasks (Tracking and Steering), accuracy was impaired among participants using the cycling workstation, both compared to their accuracy when seated and to the accuracy of participants in the sitting group. In contrast, no deficits in speed were noted among participants using the cycling work station during the discrete task (Aiming). No learning effects were observed among either group for any tasks. These findings suggest using a cycling workstation may impair the accuracy but not speed of mouse use, regardless of task practice. Overall this supports the implementation of cycling workstations in typical office settings, but suggests cycling workstations may impair productivity among workers performing high precision mouse tasks.

Smartphone use and study behavior: A Korean and Australian comparison

Smartphone use amongst university students is widespread and a common practice while studying. However, this usage can lead to academic performance costs. This study examined the relationship between smartphone use during study, problematic smartphone use and academic performance in Korean and Australian university students. 119 Korean and 270 Australian students aged between 18 and 26 years completed a survey comprised of a smartphone usage questionnaire, smartphone addiction scale and self-report of their current GPA score. Average smartphone use and problematic smartphone use were found to be significantly higher for Korean compared to Australian students. A positive relationship was found between smartphone use and problematic smartphone use. For Australian students, a negative relationship was found between smartphone use and GPA. Results indicate that smartphone use and smartphone addiction proneness are currently higher for Korean students compared to Australian students. Furthermore, the more time a student spends using their smartphone, the more at risk they are for problematic smartphone use and possible academic performance costs.

Single and dual tandem gait assessment post concussion: What performance time is clinically relevant across adult ages and what can influence results?

AIM

The three-metre tandem gait test (TG) is used to assess postural control during locomotion following sports concussion. However, values used to determine a pass/fail result are currently based on young athletic populations. Times for test completion may be influenced by several intrinsic or extrinsic factors. The aim of this study was to collate healthy individual single, dual task as well as dual task cost - motor TG times for a non-elite athlete population, across several age groups, and to investigate several potential influencing factors.

METHODS

Healthy individuals aged 18-55+, who had never experienced a concussion completed single and dual task TG following the SCAT5 protocol. A separate group (n = 20, age, foot length and body mass index matched) performed the tests with alternate instructions.

RESULTS

Mean best TG time for all participants were: single task 21.03 (±5.26s), dual task 29.59 (±9.84s) and DTC-motor 8.57 (±7.5s:41.7%). Age and foot length but not specificity of verbal instructions were related to TG times. Significantly slower single and dual task times were identified for the 55 + age group when compared to the three youngest groups (p < 0.01). No difference was seen for DTC-motor time or % between age groups (p > 0.05).

CONCLUSION

Healthy individual data collected exceeded previously reported average times. Faster times were evident in younger participants and those with longer foot length. Results from this study can be used as a reliable guideline to inform clinical decisions around the pass/fail result of TGT across age ranges in non-elite athlete populations post-concussion.

Does integrated cognitive and balance (dual-task) training improve balance and reduce falls risk in individuals with cerebellar ataxia?

Frequent falls in people with cerebellar ataxia (CA) is a significant problem Therefore, an intervention that could improve balance and reduce the number of falls is of paramount importance from the patients' perspective. Combining cognitive training with physical training to improve balance is a new approach for reducing the risk of falls in patient populations who are at risk for falls. To determine if adding structured cognitive demands to conventional balance and coordination training we designed the Cognitive-coupled Intensive Balance Training (CIBT) program. We found that the more intensive and focused CIBT intervention reduced dual-task cost, improved balance, and reduced the number of falls in a sample of individuals with CA. We hypothesize that (1) CIBT will improve balance and reduce falls; and (2) CIBT will be a cost-effective treatment option for improving balance and reduce falls. To test these hypotheses, we propose conducting a randomized controlled trial (RCT) with economic evaluation . This paper reports the findings of our study testing the feasibility of the CIBT program, rationale for testing our hypothesis and an overview of our future study design to test the effectiveness and cost-effectiveness of the CIBT program.

Cross-modal transfer after auditory task-switching training

Task-switching training was shown to improve performance not only for the trained tasks (i.e., reduced performance costs resulting from the task switches), but also for structurally similar (near transfer) or even dissimilar tasks (far transfer). However, it is still unclear whether the improvement is specific to the trained input modality or whether cognitive control occurs at an amodal processing level enabling transfer of set-shifting abilities to different input modalities. In this study, training and transfer was assessed for an auditory task-switching paradigm in which spoken words from different semantic categories were presented dichotically requiring participants to switch between two auditory categorization tasks. Cross-modal transfer of task-switching training was assessed in terms of the performance costs in a visual task-switching situation using tasks that were structurally similar to the trained tasks. The 4-day training significantly reduced the costs resulting from mixing the two auditory tasks, as compared to both an active (auditory single-task training) and a passive control group (no training). More importantly, the auditory task-switching training was also found to reduce the mixing costs for untrained visual tasks, indicating cross-modal transfer. This finding suggests that the improvement resulting from task-switching training is not specific to the trained stimulus modality, but it seems to be driven by a cognitive control mechanism operating at an amodal processing level. The training did not reveal any far-transfer effects to working memory, inhibition, or fluid intelligence, suggesting that the modality-independent enhancement of set-shifting does not generalize to other cognitive control functions.

Common Cognitive Control Processes Underlying Performance in Task-Switching and Dual-Task Contexts

In the present study, participants performed highly comparable task-switching and dual-task paradigms, and the paradigm-specific performance costs were analysed in the context of the commonly postulated core components of cognitive control (i.e., working memory updating, inhibition, and shifting). In the task-switching paradigm, we found switch costs (i.e., switch trials vs. repetition trials) and mixing costs (i.e., repetition trials in mixed-task blocks vs. single-task trials). In the dual-task paradigm, we observed a psychological refractory period (PRP) effect (i.e., Task 2 [T2] performance after short stimulus-onset asynchrony [SOA] vs. long SOA), dual-task costs (i.e., T2 dual-task performance with a long SOA in trials with a task repetition between Task 1 [T1] and T2 vs. single-task performance), and switch costs in T2 (i.e., dual-task performance in trials with a switch between T1 and T2 vs. dual-task performance in trials with a repetition between T1 and T2). A within-subjects comparison of the performance costs showed a correlation between mixing costs and dual-task costs, possibly indicating shared underlying cognitive control processes in terms of working memory updating. Surprisingly, there was also a correlation between switch costs and the PRP effect, presumably suggesting that cognitive control, as opposed to passive queuing of response selection processes, contributes to the PRP effect.