Dual-task Interference Research Articles

Measuring treatment effects on dual-task performance: a framework for research and clinical practice.

The relevance of dual-task walking to everyday ambulation is widely acknowledged, and numerous studies have demonstrated that dual-task interference can significantly impact recovery of functional walking in people with neurological disorders. The magnitude and direction of dual-task interference is influenced by the interaction between the two tasks, including how individuals spontaneously prioritize their attention. Therefore, to accurately interpret and characterize dual-task interference and identify changes over time, it is imperative to evaluate single and dual-task performance in both tasks, as well as the tasks relative to each other. Yet, reciprocal dual-task effects (DTE) are frequently ignored. The purpose of this perspective paper is to present a framework for measuring treatment effects on dual-task interference, specifically taking into account the interactions between the two tasks and how this can provide information on whether overall dual-task capacity has improved or a different attentional strategy has been adopted. In discussing the clinical implications of using this framework, we provide specific examples of using this method and provide some explicit recommendations for research and clinical practice.

Walking stability during cell phone use in healthy adults

The number of falls and/or accidental injuries associated with cellular phone use during walking is growing rapidly. Understanding the effects of concurrent cell phone use on human gait may help develop safety guidelines for pedestrians. It was shown previously that older adults had more pronounced dual-task interferences than younger adults when concurrent cognitive task required visual information processing. Thus, cell phone use might have greater impact on walking stability in older than in younger adults. This study examined gait stability and variability during a cell phone dialing task (phone) and two classic cognitive tasks, the Paced Auditory Serial Addition Test (PASAT) and Symbol Digit Modalities Test (SDMT). Nine older and seven younger healthy adults walked on a treadmill at four different conditions: walking only, PASAT, phone, and SDMT. We computed short-term local divergence exponent (LDE) of the trunk motion (local stability), dynamic margins of stability (MOS), step spatiotemporal measures, and kinematic variability. Older and younger adults had similar values of short-term LDE during all conditions, indicating that local stability was not affected by the dual-task. Compared to walking only, older and younger adults walked with significantly greater average mediolateral MOS during phone and SDMT conditions but significantly less ankle angle variability during all dual-tasks and less knee angle variability during PASAT. The current findings demonstrate that healthy adults may try to control foot placement and joint kinematics during cell phone use or another cognitive task with a visual component to ensure sufficient dynamic margins of stability and maintain local stability.

Instructions and skill level influence reliability of dual-task performance in young adults

The purpose of this study was to assess the trial-to-trial repeatability of dual-task performance and establish the minimal detectable change (MDC95) of gait-related dual-task interference. Thirty-one healthy young adults (22.5, SD 2.1 years) performed texting and walking tasks in isolation (single-task) and in combination (dual-task). The dual-task was repeated with three different instructional sets regarding how attention should be prioritized (no-priority, gait-priority, texting-priority) in two different environments (low-distraction, high-distraction). Participants performed two trials for each condition. Trial-to-trial repeatability of gait speed, texting speed, texting accuracy, and the relative dual-task effects (DTE) on each was examined using intraclass correlation coefficients and standard error of measurement. MDC95 scores were also computed for each performance measure. Among young adults, reliability of gait speed in a challenging dual-task situation is excellent, even in a high-distraction environment. In the absence of specific task prioritization instructions, changes in dual-task gait speed greater than 0.15m/s or 11.9% DTE represent real change. Reliability of the more novel, non-gait task has poor to good reliability. Dual-task effects are more reliable when participants are given specific instructions about how to prioritize their attention. The findings also suggest that reliability of dual-task performance in a novel or challenging task is greater when individuals are more skilled at the task. Implications for clinical assessment of dual-task performance are discussed.

A conflict monitoring account of the control mechanisms involved in dual-tasking

The present study investigates the cognitive mechanism underlying the control of interference during dual-task coordination. Partially inspired by the conflict monitoring hypothesis, we test the assumption that dual-task interference is resolved by a top-down adaptation mechanism that is responsible for behavioural adjustments in the prioritisation of the coordinated tasks. In a series of two experiments, we measured conflict adaptation to the so-called Gratton effect—the decrease in dual-task interference following incompatible trials. In Experiment 1 the primary task was a low demand choice discrimination task, whereas in Experiment 2 the primary task was an updating task that imposes a continuous load on working memory. The secondary task was a tone discrimination task. Both experiments consistently showed that the response conflict of previous trial triggers top-down behavioural adjustments that reduce interference. We conclude that dual-task interference shows strong similarities to Stroop-like types of cognitive interference, namely in the way that suboptimal performance is dealt with by the cognitive system.

A dual-task paradigm for behavioral and neurobiological studies in nonhuman primates

BackgroundThe dual-task paradigm is a procedure in which subjects are asked to perform two behavioral tasks concurrently, each of which involves a distinct goal with a unique stimulus–response association. Due to the heavy demand on subject's cognitive abilities, human studies using this paradigm have provided detailed insights regarding how the components of cognitive systems are functionally organized and implemented. Although dual-task paradigms are widely used in human studies, they are seldom used in nonhuman animal studies. New methodWe propose a novel dual-task paradigm for monkeys that requires the simultaneous performance of two cognitively demanding component tasks, each of which uses an independent effector for behavioral responses (hand and eyes). We provide a detailed description of an optimal training protocol for this paradigm, which has been lacking in the existing literature. ResultsAn analysis of behavioral performance showed that the proposed dual-task paradigm (1) was quickly learned by monkeys (less than 40 sessions) with step-by-step training protocols, (2) produced specific behavioral effects, known as dual-task interference in human studies, and (3) achieved rigid and independent control of the effectors for behavioral responses throughout the trial. Comparison with existing methodsThe proposed dual-task paradigm has a scalable task structure, in that each of the two component tasks can be easily replaced by other tasks, while preserving the overall structure of the paradigm. ConclusionsThis paradigm should be useful for investigating executive control that underlies dual-task performance at both the behavioral and neuronal levels.

Attentional switches and dual-task interference.

In four experiments, we studied the time course of interference between detection of an oddball orientation target (OT) in an 8-item circular search display, and identification of a letter target (LT) in a central stream of distractor letters. Dual-task performance for different temporal lags between targets was compared to single-task performance. When the LT preceded the OT, dual-task performance levels were reduced at short inter-target intervals of 0 and 166 ms; when the OT preceded the LT, the dual-task interference was unexpectedly stronger and lasted for up to 500 ms. Resource competition due to temporally overlapping target processing cannot account for this result, because the feature search task is easier than the letter identification task, and therefore would have generated less interference when presented first. Two alternative explanations were explored. First, by manipulating the spatial inter-target distance, we investigated to what degree there is a penalty associated with directing the attentional window from a large object (the search display) to a smaller object (the central letter stream). Second, by varying the duration of the OT and subsequent mask, we studied whether the interference was caused by the difficulty of disengaging attention from the search display. Results support this second explanation and thus indicate that switching attention to the letter stream is hampered by the continuing presence of (masked) search display items. This result shows that attentional effects may play a major role in dual-task execution and can easily obscure interference due to other factors such as resource competition.

Effects of Physical Exercise Interventions on Gait-Related Dual-Task Interference in Older Adults: A Systematic Review and Meta-Analysis

Dual-task interference during walking can substantially limit mobility and increase the risk of falls among community-dwelling older adults. Previous systematic reviews examining intervention effects on dual-task gait and mobility have not assessed relative dual-task costs (DTC) or investigated whether there are differences in treatment-related changes based on the type of dual task or the type of control group. The purpose of this systematic review was to examine the effects of physical exercise interventions on dual-task performance during walking in older adults. A meta-analysis of randomized controlled trials (RCTs) compared treatment effects between physical exercise intervention and control groups on single- and dual-task gait speed and relative DTC on gait speed. A systematic search of the literature was conducted using the electronic databases PubMed, CINAHL, EMBASE, Web of Science, and PsycINFO searched up to September 19, 2014. Randomized, nonrandomized, and uncontrolled studies published in English and involving older adults were selected. Studies had to include a physical exercise intervention protocol and measure gait parameters during continuous, unobstructed walking in single- and dual-task conditions before and after the intervention. Of 614 abstracts, 21 studies met the inclusion criteria and were included in the systematic review. Fourteen RCTs were included in the meta-analysis. The mean difference between the intervention and control groups significantly favored the intervention for single-task gait speed (mean difference: 0.06 m/s, 95% CI: 0.03, 0.10, p < 0.001), dual-task gait speed (mean difference: 0.11 m/s, 95% CI 0.07, 0.15, p < 0.001), and DTC on gait speed (mean difference: 5.23%, 95% CI 1.40, 9.05, p = 0.007). Evidence from subgroup comparisons showed no difference in treatment-related changes between cognitive-motor and motor-motor dual tasks, or when interventions were compared to active or inactive controls. In summary, physical exercise interventions can improve dual-task walking in older adults primarily by increasing the speed at which individuals walk in dual-task conditions. Currently, evidence concerning whether physical exercise interventions reduce DTC or alter the self-selected dual-task strategy during unobstructed walking is greatly lacking, mainly due to the failure of studies to measure and report reciprocal dual-task effects on the non-gait task.

Working memory storage is intrinsically domain specific.

A longstanding debate in working memory (WM) is whether information is maintained in a central, capacity-limited storage system or whether there are domain-specific stores for different modalities. This question is typically addressed by determining whether concurrent storage of 2 different memory arrays produces interference. Prior studies using this approach have shown at least some cost to maintaining 2 memory arrays that differed in perceptual modalities. However, it is not clear whether these WM costs resulted from competition for a central, capacity-limited store or from other potential sources of dual-task interference, such as task preparation and coordination, overlap in representational content (e.g., object vs. space based), or cognitive strategies (e.g., verbalization, chunking of the stimulus material in a higher order structure). In the present study we assess dual-task costs during the concurrent performance of a visuospatial WM task and an auditory object WM task when such sources of interference are minimized. The results show that performance of these 2 WM tasks are independent from each another, even at high WM load. Only when we introduced a common representational format (spatial information) to both WM tasks did dual-task performance begin to suffer. These results are inconsistent with the notion of a domain-independent storage system, and suggest instead that WM is constrained by multiple domain-specific stores and central executive processes. Evidently, there is nothing intrinsic about the functional architecture of the human mind that prevents it from storing 2 distinct representations in WM, as long as these representations do not overlap in any functional domain.

Auditory temporal preparation induced by rhythmic cues during concurrent auditory working memory tasks.

The present study investigated whether participants can develop temporal preparation driven by auditory isochronous rhythms when concurrently performing an auditory working memory (WM) task. In Experiment 1, participants had to respond to an auditory target presented after a regular or an irregular sequence of auditory stimuli while concurrently performing a Sternberg-type WM task. Results showed that participants responded faster after regular compared with irregular rhythms and that this effect was not affected by WM load; however, the lack of a significant main effect of WM load made it difficult to draw any conclusion regarding the influence of the dual-task manipulation in Experiment 1. In order to enhance dual-task interference, Experiment 2 combined the auditory rhythm procedure with an auditory N-Back task, which required WM updating (monitoring and coding of the information) and was presumably more demanding than the mere rehearsal of the WM task used in Experiment 1. Results now clearly showed dual-task interference effects (slower reaction times [RTs] in the high- vs. the low-load condition). However, such interference did not affect temporal preparation induced by rhythms, with faster RTs after regular than after irregular sequences in the high-load and low-load conditions. These results revealed that secondary tasks demanding memory updating, relative to tasks just demanding rehearsal, produced larger interference effects on overall RTs in the auditory rhythm task. Nevertheless, rhythm regularity exerted a strong temporal preparation effect that survived the interference of the WM task even when both tasks competed for processing resources within the auditory modality.

Building a framework for a dual task taxonomy.

The study of dual task interference has gained increasing attention in the literature for the past 35 years, with six MEDLINE citations in 1979 growing to 351 citations indexed in 2014 and a peak of 454 cited papers in 2013. Increasingly, researchers are examining dual task cost in individuals with pathology, including those with neurodegenerative diseases. While the influence of these papers has extended from the laboratory to the clinic, the field has evolved without clear definitions of commonly used terms and with extreme variations in experimental procedures. As a result, it is difficult to examine the interference literature as a single body of work. In this paper we present a new taxonomy for classifying cognitive-motor and motor-motor interference within the study of dual task behaviors that connects traditional concepts of learning and principles of motor control with current issues of multitasking analysis. As a first step in the process we provide an operational definition of dual task, distinguishing it from a complex single task. We present this new taxonomy, inclusive of both cognitive and motor modalities, as a working model; one that we hope will generate discussion and create a framework from which one can view previous studies and develop questions of interest.

Auditory and motor contributions to the timing of melodies under cognitive load.

Current theoretical models and empirical research suggest that sensorimotor control and feedback processes may guide time perception and production. In the current study, we investigated the role of motor control and auditory feedback in an interval-production task performed under heightened cognitive load. We hypothesized that general associative learning mechanisms enable the calibration of time against patterns of dynamic change in motor control processes and auditory feedback information. In Experiment 1, we applied a dual-task interference paradigm consisting of a finger-tapping (continuation) task in combination with a working memory task. Participants (nonmusicians) had to either perform or avoid arm movements between successive key presses (continuous vs. discrete). Auditory feedback from a key press (a piano tone) filled either the complete duration of the target interval or only a small part (long vs. short). Results suggested that both continuous movement control and long piano feedback tones contributed to regular timing production. In Experiment 2, we gradually adjusted the duration of the long auditory feedback tones throughout the duration of a trial. The results showed that a gradual shortening of tones throughout time increased the rate at which participants performed tone onsets. Overall, our findings suggest that the human perceptual-motor system may be important in guiding temporal behavior under cognitive load.

Ideomotor-compatible tasks partially escape dual-task interference in both young and elderly adults.

Under most circumstances, it is not possible to carry out central processing for 2 tasks at the same time; effectively there is a bottleneck. Nevertheless, in 2 experiments it is demonstrated here that both younger and older adults are able to partially bypass the bottleneck in a psychological refractory period procedure, even without extensive training, when the 2nd of the 2 tasks is a saccade or a body tilt in the direction of rotation of a visual stimulus. Consistent with earlier research, the findings showed that younger adults can bypass when the second task has ideomotor-compatible stimuli and responses. Most strikingly, they demonstrated that bypass can also occur in older adults. Overall, the findings are inconsistent with any categorical claim that younger adults can bypass the dual-task bottleneck whereas older adults cannot. The construct of ideomotor-compatible tasks may comprise 2 quite different classes of experimental procedures.

Asymmetric Dual-Task Interference of Auditory Message in Change Detection in Older Adults

Asymmetric Dual-Task Interference of Auditory Message in Change Detection in Older Adults

Evidence linking FMR1 mRNA and attentional demands of stepping and postural control in women with the premutation

Recent studies in young adult females with the fragile X mental retardation 1 (FMR1) gene premutation (PM) have shown subtle but significant impairments in executive control and postural stability. Less is known about the influence of age and FMR1 gene expression on executive control and postural stability in females with the PM. Here, we examined the attentional demands of reactive stepping using a well-validated measure of choice stepping reaction time under dual-task interference. We explored the interrelationships between step initiation times during a concurrent verbal fluency task and specific impairments in executive control previously reported in females with the PM. Our results showed increased dual-task interference on step initiation times and variability in female PM compared with control subjects. In addition, we observed greater choice stepping reaction time dual-task costs above the breakpoint of 81 CGG repeats relative to below this CGG range. Dual-task interference on both reaction time and movement time were significantly predicted by low working memory capacity in female PM carriers. Importantly, we revealed that FMR1 messenger RNA level is the most significant predictor accounting for dual-task stepping variability in both reaction time and movement time in PM females. These findings for the first time provide evidence linking elevated FMR1 messenger RNA levels that have been previously associated with FMR1 RNA toxicity and deficits in cerebellar motor and cognitive networks in a subgroup of at-risk PM women.

Effects of task difficulty during dual-task circle tracing in Huntington's disease.

Huntington's disease (HD) is associated with impairments in dual-task performance. Despite that, only a few studies have investigated dual-tasking in HD. We examined dual-task performance in 15 participants in the early stages of HD and 15 healthy controls. Participants performed direct circle tracing (able to view arm) and indirect circle tracing (arm obscured) either on their own (single tasks) or paired with serial subtraction by twos or threes (dual tasks). Overall, our results suggested that HD participants were significantly slower and less accurate than controls. Both groups were slower and less accurate when performing indirect circle tracing compared with direct circle tracing. HD participants experienced greater dual-task interference in terms of accuracy when performing direct circle tracing compared with indirect circle tracing. Despite that, controls were more inclined to speed-accuracy trade-offs compared with HD participants. Importantly, unlike controls, HD participants were not disproportionately faster when performing direct circle tracing as a single task compared with the dual-task conditions. Our results suggest that simple tasks place greater attentional demands on HD participants compared with controls. These findings support that impaired automaticity may be responsible for some of the attentional deficits manifested in HD.

EEG measures reveal dual-task interference in postural performance in young adults.

The study used a dual-task (DT) postural paradigm (two tasks performed at once) that included electroencephalography (EEG) to examine cortical interference when a visual working memory (VWM) task was paired with a postural task. The change detection task was used, as it requires storage of information without updating or manipulation and predicts VWM capacity. Ground reaction forces (GRFs) (horizontal and vertical), EMG, and EEG elements, time locked to support surface perturbations, were used to infer the active neural processes underlying the automatic control of balance in 14 young adults. A significant reduction was seen between single task (ST) and DT conditions in VWM capacity (F(1,13) = 6.175, p < 0.05, r = 06) and event-related potential (ERP) N1 component amplitude over the L motor (p < 0.001) and R sensory (p < 0.05) cortical areas. In addition, a significant increase in the COP trajectory peak (pkcopx) was seen in the DT versus ST condition. Modulation of VWM capacity as well as ERP amplitude and pkcopx in DT conditions provided evidence of an interference pattern, suggesting that the two modalities shared a similar set of attentional resources. The results provide direct evidence of the competition for central processing attentional resources between the two modalities, through the reduction in amplitude of the ERP evoked by the postural perturbation.

Cognitive and Manual Dual-Task Effects on Phases of the Timed Up and Go in Aging

To characterize the dual task interference from manual and cognitive tasks on different phases (straight walking, turns and transitions) of the Timed Up and Go (TUG) test of functional mobility in healthy young and older adults.

Relationships Between Cognitive Function and Gait-Related Dual-Task Interference After Stroke

Previous studies have reported that decreased cognitive ability has been consistently associated with significant declines in performance of one or both tasks under a dual-task walking condition. This study examined the relationship between specific cognitive abilities and the dual-task costs (DTCs) of spatio-temporal gait parameters in stroke patients. The spatio-temporal gait parameters were measured among 30 stroke patients while walking with and without a cognitive task (Stroop Word-Color Task) at the study participant’s preferred walking speed. Cognitive abilities were measured using Computerized Neuropsychological Testing. Pearson’s correlation coefficients (r) were calculated to quantify the associations between the neuropsychological measures and the DTCs in the spatio-temporal gait parameters. Moderate to strong correlations were found between the Auditory Continuous Performance test (ACPT) and the DTCs of the Single Support Time of Non-paretic (r=.37), the Trail Making A (TMA) test and the DTCs of Velocity (r=.71), TMA test and the DTCs of the Step Length of Paretic (r=.37), TMA test and the DTCs of the Step Length Non-paretic (r=.36), the Trail Making B (TMB) test and the DTCs of Velocity (r=.70), the Stroop Word-Color test and the DTCs of Velocity (r -.40), Visual-span Backward (V-span B) test and the DTCs of Velocity (r=-.41), V-span B test and the DTCs of the Double Support Time of Non-paretic (r=.38), Digit-span Forward test and the DTCs of the Step Time of Non-paretic (r=-.39), and Digit-span Backward test and the DTCs of the Single Support Time of Paretic (r=.36). Especially TMA test and TMB test were found to be more strongly correlated to the DTCs of gait velocity than the other correlations. Understanding these cognitive features will provide guidance for identifying dual- task walking ability.

Dual-task interference and brain structural connectivity in people with Parkinson's disease who freeze

BackgroundFreezing of gait in people with Parkinson's disease (PD) is likely related to attentional control (ie, ability to divide and switch attention). However, the neural pathophysiology of altered attentional control...

Age difference in dual-task interference effects on procedural learning in children

The current study aimed to investigate the role played by explicit mechanisms during procedural learning in two age groups of children (7 and 10years) using a dual-task paradigm. To do this, we explored the effect of an interference task during the early and late phases of a mirror tracing learning task. The results showed a differential impact of the secondary task on the two age groups, but only during the first learning phase; the performance of 10-year-olds was affected by the second task, whereas in 7-year-olds no performance difference was found between the single- and dual-task conditions. Overall, our study suggests that there are differences in the amount of effortful processing in which 7- and 10-year-olds engage at the beginning of the learning process; procedural learning in young children is mainly implicit, as attested by its lesser sensitivity to an interference task, whereas high-level explicit mechanisms seem to contribute to the procedural performance of 10-year-olds. However, these explicit mechanisms, even if they have an effect on performance, might not have an impact on the learning curve given that no difference in rate of acquisition was found between age groups. These findings are discussed in the light of classical conceptions of procedural learning.