The electrophysiology of sequential adjustments of dual-task order coordination.

Performing two tasks simultaneously involves the coordination of their processing. This task coordination is particularly required in dual-task situations with varying task orders. When task order switches between subsequent trials, task order coordination leads to task order switch costs in comparison with order repetitions. However, it is open, whether task order coordination is exclusively controlled by the relation of the task orders of the current and the previous trials, or whether additional conditions such as task order before the previous trial leads to a behavioral and neural adjustment of task order coordination. To answer this question, we reanalyzed the data of two previously published experiments with order-cued dual-task paradigms. We did so with regard to whether task order switch costs and the EEG component order-switch positivity in the current dual-task trial would be modulated by order switches vs. repetitions in the previous trial (Trial N-1). In Experiment 1, we found a modulation of the task order switch costs in RTs and response reversals; these costs were reduced after an order switch compared with order repetitions in Trial N-1. In Experiment 2, there were no effects on the task order switch costs in the behavioral data. Nonetheless, we found the order-switch positivity to be strongly modulated by the order transition of the previous trial in both experiments. The order-switch positivity was substantially reduced if the previous trial was an order switch (compared to an order repetition) by itself. This implies that order coordination of dual tasks is adjusted in a gradual way depending on trial's history.

The contribution and interplay of implicit and explicit processes on physical activity behavior: empirical testing of the physical activity adoption and maintenance (PAAM) model.

The adoption and maintenance of physical activity (PA) is an important health behavior. This paper presents the first comprehensive empirical test of the Physical Activity Adoption and Maintenance (PAAM) model, which proposes that a combination of explicit (e.g., intention) and implicit (e.g., habit,, affect) self-regulatory processes is involved in PA adoption and maintenance. Data were collected via online questionnaires in English, German, and Italian at two measurement points four weeks apart. The study included 422 participants (Mage= 25.3, SDage= 10.1; 74.2% women) from Germany, Switzerland, Italy, Canada, and the U.S. The study results largely supported the assumptions of the PAAM model, indicating that intentions and habits significantly mediate the effects of past PA on future PA. In addition, the effect of past PA on future PA was shown to be significant through a mediation chain involving affect and habit. Although the hypothesis that trait self-regulation moderates the intention-behavior relationship was not supported, a significant moderating effect of affect on the same relationship was observed. The results suggest that interventions targeting both explicit and implicit processes may be effective in promoting PA adoption and maintenance.

Controlling response order without relying on stimulus order - evidence for flexible representations of task order.

In dual-task situations, both component tasks are typically not executed simultaneously but rather one after another. Task order is usually determined based on bottom-up information provided by stimulus presentation order, but also affected by top-down factors such as instructions and/or differentially dominant component tasks (e.g., oculomotor task prioritization). Recent research demonstrated that in the context of a randomly switching stimulus order, task order representations can be integrated with specific component task information rather than being coded in a purely abstract fashion (i.e., by containing only generic order information). This conclusion was derived from observing consistently smaller task-order switch costs for a preferred (e.g., oculomotor-manual) versus a non-preferred (e.g., manual-oculomotor) task order (i.e., order-switch cost asymmetries). Since such a representational format might have been especially promoted by the sequential stimulus presentation employed, we investigated task-order representations in situations without any bottom-up influence of stimulus order. To this end, we presented task stimuli simultaneously and cued the required task-order in advance. Experiment 1 employed abstract order transition cues that only indicated a task-order repetition (vs. switch) relative to the previous trial, while Experiment 2 used explicit cues that unambiguously indicated the task-order. Experiment 1 revealed significant task-order switch costs only for the second task (of either task order) and no order-switch cost asymmetries, indicating a rather generic representation of task order. Experiment 2 revealed task-order switch costs in both component tasks with a trend toward order-switch cost asymmetries, indicating an integration of task order representations with component task information. These findings highlight an astonishing flexibility of mental task-order representations during task-order control.

The role of working memory for task-order coordination in dual-task situations.

Dual-task (DT) situations require task-order coordination processes that schedule the processing of two temporally overlapping tasks. Theories on task-order coordination suggest that these processes rely on order representations that are actively maintained and processed in working memory (WM). Preliminary evidence for this assumption stems from DT situations with variable task order, where repeating task order relative to the preceding trials results in improved performance compared to changing task order, indicating the processing of task-order information in WM between two succeeding trials. We directly tested this assumption by varying WM load during a DT with variable task order. In Experiment 1, WM load was manipulated by varying the number of stimulus-response mappings of the component tasks. In Experiment 2A, WM load was increased by embedding an additional WM updating task in the applied DT. In both experiments, the performance benefit for trials with repeated relative to trials with changed task order was reduced under high compared to low WM load. These results confirm our assumption that the processing of the task-order information relies on WM resources. In Experiment 2B, we tested whether the results of Experiment 2A can be attributed to introducing an additional task per se rather than to increased WM load by introducing an additional task with a low WM load. Importantly, in this experiment, the processing of order information was not affected. In sum, the results of the three experiments indicate that task-order coordination relies on order information which is maintained in an accessible state in WM during DT processing.

Physical activity automaticity, intention, and trait self-control as predictors of physical activity behavior - a dual-process perspective.

Dual-process theories assume that physical activity (PA) behavior is regulated by two different processes: impulsive (i.e., automatic, fast) and reflective (i.e., effortful, slow) processes. In this study we examined main effects as well as the interaction of reflective (intention and trait self-control)and impulsive (automaticity)processes on PA behavior. A prospective study with two points of measurement (N = 118 university students) was conducted. At t1, age, sex, past PA behavior (control variables), PA intention, automaticity and trait self-control (predictors) were assessed with standardized questionnaires. At t2 (4 weeks later), PA behavior (dependent variable) was measured with a standardized questionnaire. Hierarchical multiple linear regression analysis revealed that automaticity was associated with PA behavior. The expected interaction effects Intention x Trait Self-control and Automaticity x Intention x Trait self-control on PA were significant. Moderation analyses revealed that PA intention has a significant positive association with PA behavior when trait self-control was higher compared to lower. Furthermore, automaticity has the strongest association with behavior when both intention and trait self-control where lower compared to higher. Our results underline the additive and interactive effects of impulsive and reflective processes in regulating PA behavior.

Alertness Training Increases Visual Processing Speed in Healthy Older Adults.

In this study, we investigated whether alertness training in healthy older adults increases visual processing speed (VPS) and whether functional connectivity in the cingulo-opercular network predicts training gain. Using the theory of visual attention, we derived quantitative estimates of VPS before and after training. In Study 1, 75 healthy older adults participated in alertness training, active-control training, or no training (n = 25 each). A significant Group × Session interaction indicated an increase in VPS in the alertness-training group but not in the control group, despite VPS not differing significantly between groups before training. In Study 2, 29 healthy older adults underwent resting-state functional MRI and then participated in alertness training. Pretraining functional connectivity in the cingulo-opercular network correlated with the individual training-induced change in VPS. In conclusion, results indicate that alertness training improves visual processing in older adults and that functional connectivity in the cingulo-opercular network provides a neural marker for predicting individual training gain.

Enhancement of task-switching performance with transcranial direct current stimulation over the right lateral prefrontal cortex.

Switching between two or more tasks is a key component in our modern world. Task switching, however, requires time-consuming executive control processes and thus produces performance costs when compared to task repetitions. While executive control during task switching has been associated with activation in the lateral prefrontal cortex (lPFC), only few studies so far have investigated the causal relation between lPFC activation and task-switching performance by modulating lPFC activation. In these studies, the results of lPFC modulation were not conclusive or limited to the left lPFC. In the present study, we aimed to investigate the effect of non-invasive transcranial direct current stimulation [tDCS; anodal tDCS (1 mA, 20 min) vs. cathodal tDCS (1 mA, 20 min) vs. sham tDCS (1 mA, 30 s)] over the right inferior frontal junction on task-switching performance in a well-established task-switching paradigm. In response times, we found a significant effect of tDCS Condition (atDCS, ctDCS vs. sham) on task-switching costs, indicating the modulation of task-switching performance by tDCS. In addition, we found a task-unspecific tDCS Condition effect in the first experimental session, in which participants were least familiar with the task, indicating a general enhancement of task performance in both task repetitions and task-switching trials. Taken together, our study provides evidence that the right lPFC is involved in task switching as well as in general task processing. Further studies are needed to investigate whether these findings can be translated into clinically relevant improvement in older subjects or populations with executive function impairment.

Endogenous control of task-order preparation in variable dual tasks.

Dual-task performance typically leads to performance impairments in comparison to single tasks (i.e., dual-task costs). The literature discusses the contribution to these dual-task costs due to (1) bottleneck limitations in the dual-component tasks and (2) executive control processes regulating access to this bottleneck. Previous studies investigated the characteristics of executive control processes primarily triggered by external stimulus information. In the present study, however, we investigated the existence as well as the characteristics of internally triggered and driven endogenous control processes to regulate bottleneck access. In detail, we presented dual-task blocks with varying task orders and informed participants in advance about repetitions of the same task order as well as switches between different task orders (i.e., task-order repetitions and switches were predictable). Experiment 1 demonstrated that task-order information and an increased preparation time generally increase the efficiency for endogenous task-order control and improves preparation for task-order switches. This finding is basically consistent with the assumption of the existence of endogenous control processes. Experiment 2, however, did not provide evidence that this endogenous control is related with working-memory maintenance mechanisms. Experiment 3 showed that endogenous control does not only fully complete task-order preparation but also requires exogenous, stimulus-driven components.

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

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

Investigating dual-task interference in children versus young adults with the overlapping task paradigm.

Previous studies demonstrated that dual-task impairments (i.e., dual-task costs) are higher in children than in young adults. However, these studies did not specify the mechanisms explaining higher dual-task costs and did not assess the specific task processes that particularly impair simultaneous task performance in children. We assessed sources of higher dual-task costs in children (n = 32) as compared with young adults (n = 32) by combining auditory (Task 1) and visual (Task 2) sensorimotor tasks into dual tasks of the psychological refractory period (PRP) type. Both tasks are separated by a varying stimulus onset asynchrony (SOA). In Visual Task 2, we manipulated task difficulty at the perceptual stage (contrast manipulation) and response selection stage (mapping manipulation) in order to identify age-related changes in capacity limitations during dual-task performance. The results showed that the response selection manipulation and SOA yielded additive effects in children and young adults, providing evidence for interference at response selection processes in both age groups. In contrast, the perceptual stage manipulation and SOA resulted in underadditive effects in young adults and additive effects in children. This age-related difference is consistent with the assumption that limitations in central processing are present in both age groups, whereas perceptual interference between tasks seems to be larger in children than in young 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.

Influence of a Planning Intervention on Physical Activity Behavior: the Moderating Role of Intentions and Executive Functions in a Randomized Controlled Trial.

BACKGROUND: Planning and executive functions (EFs; inhibition, updating, shifting) are self-regulatory variables that help people to become and stay physically active. The aim of this study was to examine how and for whom a planning intervention affects physical activity (PA) behavior in the short term. Therefore, the mediating role of planning and the moderating role of intentions and EFs for the planning-behavior link were examined. METHOD: In a randomized control trial with two treatment groups (planning group vs. control group) and two points of measurement (t1 and t2, 1 week apart), n = 200 students participated in both measurements. At t1, participants filled in standardized questionnaires assessing PA behavior, intention, and planning. Computer-based tests assessed the following EFs: inhibition, updating, and shifting. At t2, planning and PA behavior were measured again. Moderated mediation analyses were conducted. RESULTS: A significant increase in PA between t1 and t2 was found for the planning group compared with the control group. Furthermore, planning cognitions significantly mediated the effect of the planning group on behavior and intention, as well as the EF updating moderated the association between planning and behavior. Forming plans was particularly beneficial for participants with high intentions and lower updating performance. CONCLUSION: Planning enhances PA behavior, particularly when PA intention is high. Poor performance in updating can be compensated by planning since encouraging people to generate plans might facilitate automatic enactment of the behavior.

Modulation of dual-task control with right prefrontal transcranial direct current stimulation (tDCS).

Executive functioning of two simultaneous component tasks in dual-task situations is primarily associated with activation of the lateral prefrontal cortex (PFC), as demonstrated in functional imaging studies. However, the precise role of the lateral PFC and the causal relation between this area's activity and executive functioning in dual tasks has exclusively been demonstrated for the left lateral PFC so far. To investigate this relation for the right lateral PFC, we used anodal transcranial direct current stimulation (atDCS; 1 mA, 20 min) in contrast to sham stimulation (1 mA, 30 s) in Experiment 1 (N = 30) as well as cathodal transcranial direct current stimulation (ctDCS; 1 mA, 20 min) in contrast to sham stimulation (1 mA, 30 s) in Experiment 2 (N = 25) over the right inferior frontal junction under conditions of random task order in dual tasks; random dual tasks require decisions on task order and thus high demands on executive functioning. Across these experiments, our results showed different tDCS-related effects: while atDCS improved performance evident from reduced error rates (Experiment 1), ctDCS impaired dual-task performance and increased these rates (Experiment 2). Moreover, baseline performance correlated with tDCS-induced performance changes, indicating that baseline performance was associated with atDCS-induced improvement. Our findings suggest that dual-task performance is causally related to right lateral PFC activation under conditions that require executive functioning as well as cognitive control of task sets and task order.

The impact of free-order and sequential-order instructions on task-order regulation in dual tasks.

Dual tasks (DTs) are characterized by the requirement for additional mechanisms that coordinate the processing order of two temporally overlapping tasks. These mechanisms are indicated by two types of costs that occur when comparing DT blocks with fixed and random orders of the component tasks. On a block level, task-order control costs are reflected in increased reaction times (RTs) in random-order compared to fixed-order blocks, indicating global, monitoring-based, coordination mechanisms. On a trial level, within random-order blocks, order-switch costs are indicated by increased RTs on order switch compared to order repetition trials, reflecting memory-based mechanisms that guide task-order in DTs. To test the nature of these mechanisms in two experiments, participants performed DTs in fixed- and random-order blocks. In random-order blocks, participants were either instructed to respond to both tasks according to the order of task presentation (sequential-order instruction) or instructed to freely decide in which order to perform both tasks (free-order instruction). As a result of both experiments, we demonstrated that task-order control costs were reduced under the free-order compared to the sequential-order instruction, whereas order-switch costs were not affected by our instruction manipulation. This pattern of results suggests that the task-order control costs reflect global processes of task-order regulation such as engaging monitoring processes that are sensitive to changes in order instructions, while order-switch costs reflect rather local memory-based mechanisms that occur irrespective of any effort to coordinate task-order.

Executive Functions, Trait Self-Control, and the Intention-Behavior Gap in Physical Activity Behavior.

Many people fail to translate their physical activity intentions into behavior. This intention-behavior gap can be explained by (a) explicit trait self-control, (b) implicit executive functions, and (c) their interactions. In 118 participants, the intention-behavior gap was measured in a prospective design. Trait self-control was assessed via self-report questionnaires, whereas executive functioning was measured with test performance in inhibition, updating, and shifting at baseline. Regression analysis showed that (a) higher trait self-control predicts a smaller intention-behavior gap; (b) updating performance is related with this gap; and (c) behavior in tests on inhibition, updating, and shifting moderate the relation between the trait self-control and the intention-behavior gap. The present study showed that the complex pattern that modulates the relation between intended and realized physical activity behavior includes trait self-control, executive functions, as well as the combination of these cognitive components supporting dual-process approaches of self-control including implicit and explicit processing components.

Simultaneous interpreters vs. professional multilingual controls: Group differences in cognitive control as well as brain structure and function.

There is a vast amount of literature indicating that multiple language expertise leads to positive transfer effects onto other non-language cognitive domains possibly due to enhanced cognitive control. However, there is hardly any evidence about underlying mechanisms on how complex behavior like simultaneous interpreting benefits cognitive functioning in other non-language domains. Therefore, we investigated whether simultaneous interpreters (SIs) exhibit cognitive benefits in tasks measuring aspects of cognitive control compared to a professional multilingual control group. We furthermore investigated in how far potential cognitive benefits are related to brain structure (using voxel-based morphometry) and function (using regions-of-interest-based functional connectivity and graph-analytical measures on low-frequency BOLD signals in resting-state brain data). Concerning cognitive control, the results reveal that SIs exhibit less mixing costs in a task switching paradigm and a dual-task advantage compared to professional multilingual controls. In addition, SIs show more gray matter volume in the left frontal pole (BA 10) compared to controls. Graph theoretical analyses revealed that this region exhibits higher network values for global efficiency and degree and is functionally more strongly connected to the left inferior frontal gyrus and middle temporal gyrus in SIs compared to controls. Thus, the data provide evidence that SIs possess cognitive benefits in tasks measuring cognitive control. It is discussed in how far the central role of the left frontal pole and its stronger functional connectivity to the left inferior frontal gyrus represents a correlate of the neural mechanisms for the observed behavioral effects.

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

UNLABELLED: BACKGROUND/STUDY CONTEXT: The variability associated with reaction time (RT) is sometimes considered as a proxy for inefficient neural processing, particularly in old age and complex situations relying upon executive control functions. Here, it is examined whether the amount of variability exhibited early in practice can predict the amount of improvement with later practice in dual-task performance, and whether the predictive power of variability varies between younger and older adults. METHODS: To investigate the relationship between variability and practice-related improvement, RT mean and variability data are used, obtained from an experiment in which younger and older adults performed two tasks in single-task and dual-task conditions across seven practice sessions. These RT and variability data were related to the single-task and dual-task practice benefits. These benefits were computed as follows: dual-task/single-task RTs at the beginning of practice minus dual-task/single-task RTs at the end of practice. RESULTS: In both age groups, dual-task processing was speeded up with practice and variability associated with the means was reduced. Most important, independent of mean RTs, variability allowed predicting dual-task practice benefit in both age groups under specific conditions. CONCLUSION: These findings suggest that the relationship between performance variability and executive control functions under some specific conditions. Implications of these results for models of practiced dual tasks are discussed.

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

Improvements in performing demanding and complex task situations are typically related to the optimization of executive functions and efficient behavioral control. The present study systematizes and reviews the optimization of different executive function types: Shifting, Inhibition, Updating, and Dual tasking. In particular, we focus on optimisations of these functions with training and on transfer effects of related training skills to non-trained situations. The aim of the study's empirical part (see also Appendix) was to investigate the specific mechanisms of executive functions in the context of Dual tasking, leading to improved dual-task performance after practice. More specifically, we tested the Efficient Task Instantiation (ETI) model that includes specific assumptions regarding practice-related improvements of executive task coordination skills: Dual-task performance is improved with practice because of an efficient and conjoint instantiation of sets of relevant task information in working memory at the onset of a dual task. According to our knowledge, the ETI model is one of the first that allows illustrating the contribution of cognitive mechanisms underlying practice-related improvements in performing dual tasks and the impact of task coordination skills on this performance.

On methodological standards in training and transfer experiments.

The past two decades have seen a tremendous surge in scientific interest in the extent to which certain types of training-be it aerobic, athletic, musical, video game, or brain trainer-can result in general enhancements in cognitive function. While there are certainly active debates regarding the results in these domains, what is perhaps more pressing is the fact that key aspects of methodology remain unsettled. Here we discuss a few of these areas including expectation effects, test-retest effects, the size of the cognitive test battery, the selection of control groups, group assignment methods, difficulties in comparing results across studies, and in interpreting null results. Specifically, our goal is to highlight points of contention as well as areas where the most commonly utilized methods could be improved upon. Furthermore, because each of the sub-areas above (aerobic training through brain training) share strong similarities in goal, theoretical framework, and experimental approach, we seek to discuss these issues from a general perspective that considers each as members of the same broad "training" domain.