Simple Dual Task Research Articles

Effects of divided attention on movement-related cortical potential in community-dwelling elderly adults: A preliminary study

Dual-tasking is defined as performing two or more tasks concurrently. This study aimed to investigate the effect of divided attention on movement-related cortical potential (MRCP) during dual-task performance in 11 community-dwelling elderly individuals while the load of the secondary task was altered. MRCP was recorded during a single task (ST), simple dual task (S-DT), and complex dual task (C-DT) as no-, low-, and high-load divided attention tasks, respectively. The ST involved self-paced tapping with an extended right index finger. In the S-DT and C-DT, the subjects simultaneously performed the ST and a visual number counting task with different levels of load. The coefficient of variation of movement frequency was significantly more variable in the C-DT than in the ST. The MRCP amplitude from electroencephalography electrode C3, contralateral to the moving hand, was significantly higher in the C-DT than in the ST. Higher attention diversion led to a significant reduction in MRCP amplitude in the participants. These results suggest that attention division in dual-task situations plays an important role in movement preparation and execution. We propose that MRCP can serve as a marker for screening the ability of older individuals to perform dual-tasks.

Gait impairments on single and dual tasks in cerebral amyloid angiopathy

AbstractBackgroundCerebral Amyloid Angiopathy (CAA) is a small vessel disease wherein amyloid beta protein is deposited in the vessels of the cerebral cortex and leptomeninges. Little is known about CAA and gait impairment, even though gait is known to be affected by Alzheimer’s disease (AD). We hypothesized that gait would be impaired in CAA compared to normal controls (NC), and that more complex mental tasks would elicit further impairments in AD compared to CAA.MethodParticipants were NC (n=44), non‐demented CAA (n=31), and mild AD‐dementia (n=16). The ProtoKinetics Walkway was used to capture footfalls over a 6 m walk during a single task (walking only) and two dual tasks of differing complexity (counting backwards by ones [simple task] and naming animals [complex task]). For gait velocity, the dual task cost was calculated as the percent change during dual task compared to preferred pace walking. Analysis of covariance was used to test group differences, controlling for age, sex, and height.ResultCAA participants were older and more likely to be men (Table 1). Gait parameters during preferred pace walk, dual task with counting backwards, and dual task with animal naming are shown in Tables 2‐4. Across all three tasks, both CAA and AD performed poorer than NC on mean Stride Length, Stride Length variability, mean Stride Time, mean Velocity, and mean Cadence. However, mean Stride Width, and Stride Width variability did not differ. There were no differences between CAA and AD (Tables 2‐4). On measures of Velocity, the dual task cost for going from single task to counting backwards (simple dual task) was greater in AD than NC but not in CAA than NC (Table 5). The dual task cost for going from single task to naming animals (complex dual task) was greater in AD than CAA and NC.ConclusionGait is impaired in CAA to a similar extent as in AD, however dual task cost was higher for AD possibly because of greater cognitive impairment. Future research should investigate causes of gait impairments in CAA, including the effects of hemorrhagic and ischemic lesions such as white matter hyperintensities.

Measuring the Cognitive Workload During Dual-Task Walking in Young Adults: A Combination of Neurophysiological and Subjective Measures.

Background: Walking while performing a secondary task (dual-task (DT) walking) increases cognitive workload in young adults. To date, few studies have used neurophysiological measures in combination to subjective measures to assess cognitive workload during a walking task. This combined approach can provide more insights into the amount of cognitive resources in relation with the perceived mental effort involving in a walking task.Research Question: The objective was to examine cognitive workload in young adults during walking conditions varying in complexity.Methods: Twenty-five young adults (mean = 24.4 ± 5.4) performed four conditions: (1) usual walking, (2) simple DT walking, (3) complex DT walking and (4) standing while subtracting. During the walking task, mean speed, cadence, stride time, stride length, and their respective coefficient of variation (CV) were recorded. Cognitive workload will be measured through changes in oxy- and deoxy-hemoglobin (ΔHbO2 and ΔHbR) during walking in the dorsolateral prefrontal cortex (DLPFC) and perceived mental demand score from NASA-TLX questionnaire.Results: In young adults, ΔHbO2 in the DLPFC increased from usual walking to both DT walking conditions and standing while subtracting condition. ΔHbO2 did not differ between the simple and complex DT and between the complex DT and standing while subtracting condition. Perceived mental demand gradually increased with walking task complexity. As expected, all mean values of gait parameters were altered according to task complexity. CV of speed, cadence and stride time were significantly higher during DT walking conditions than during usual walking whereas CV of stride length was only higher during complex DT walking than during usual walking.Significance: Young adults had greater cognitive workload in the two DT walking conditions compared to usual walking. However, only the mental demand score from NASA-TLX questionnaire discriminated simple from complex DT walking. Subjective measure provides complementary information to objective one on changes in cognitive workload during challenging walking tasks in young adults. These results may be useful to improve our understanding of cognitive workload during walking.

The effects of dual tasking on gait synchronization during over-ground side-by-side walking

Recent studies have shown that gait synchronization during natural walking is not merely anecdotal, but it is a repeatable phenomenon that is quantifiable and is apparently related to available sensory feedback modalities. However, the mechanisms underlying this phase-locking of gait have only recently begun to be investigated. For example, it is not known what role, if any, attention plays. We employed a dual tasking paradigm in order to investigate the role attention plays in gait synchronization. Sixteen pairs of subjects walked under six conditions that manipulated the available sensory feedback and the degree of difficulty of the dual task, i.e., the attention. Movement was quantified using a trunk-mounted tri-axial accelerometer. A gait synchronization index (GSI) was calculated in order to quantify the degree of synchronization of the gait pattern. A simple dual task resulted in an increased level of synchronization, whereas a more complex dual task lead to a reduction in synchronization. Handholding increased synchronization, compared to the same attention condition without handholding. These results indicate that in order for two walkers to synchronize, some level of attention is apparently required, such that a relatively complex dual task utilizes enough attentional resources to reduce the occurrence of synchronization.

Rivastigmine for gait stability in patients with Parkinson's disease (ReSPonD): a randomised, double-blind, placebo-controlled, phase 2 trial

Falls are a frequent and serious complication of Parkinson's disease and are related partly to an underlying cholinergic deficit that contributes to gait and cognitive dysfunction in these patients. Gait dysfunction can lead to an increased variability of gait from one step to another, raising the likelihood of falls. In the ReSPonD trial we aimed to assess whether ameliorating this cholinergic deficit with the acetylcholinesterase inhibitor rivastigmine would reduce gait variability. We did this randomised, double-blind, placebo-controlled, phase 2 trial at the North Bristol NHS Trust Hospital, Bristol, UK, in patients with Parkinson's disease recruited from community and hospital settings in the UK. We included patients who had fallen at least once in the year before enrolment, were able to walk 18 m without an aid, had no previous exposure to an acetylcholinesterase inhibitor, and did not have dementia. Our clinical trials unit randomly assigned (1:1) patients to oral rivastigmine or placebo capsules (both taken twice a day) using a computer-generated randomisation sequence and web-based allocation. Rivastigmine was uptitrated from 3 mg per day to the target dose of 12 mg per day over 12 weeks. Both the trial team and patients were masked to treatment allocation. Masking was achieved with matched placebo capsules and a dummy uptitration schedule. The primary endpoint was difference in step time variability between the two groups at 32 weeks, adjusted for baseline age, cognition, step time variability, and number of falls in the previous year. We measured step time variability with a triaxial accelerometer during an 18 m walking task in three conditions: normal walking, simple dual task with phonemic verbal fluency (walking while naming words beginning with a single letter), and complex dual task switching with phonemic verbal fluency (walking while naming words, alternating between two letters of the alphabet). Analysis was by modified intention to treat; we excluded from the primary analysis patients who withdrew, died, or did not attend the 32 week assessment. This trial is registered with ISRCTN, number 19880883. Between Oct 4, 2012 and March 28, 2013, we enrolled 130 patients and randomly assigned 65 to the rivastigmine group and 65 to the placebo group. At week 32, compared with patients assigned to placebo (59 assessed), those assigned to rivastigmine (55 assessed) had improved step time variability for normal walking (ratio of geometric means 0.72, 95% CI 0.58-0.88; p=0.002) and the simple dual task (0.79; 0.62-0.99; p=0.045). Improvements in step time variability for the complex dual task did not differ between groups (0.81, 0.60-1.09; p=0.17). Gastrointestinal side-effects were more common in the rivastigmine group than in the placebo group (p<0.0001); 20 (31%) patients in the rivastigmine group versus three (5%) in the placebo group had nausea and 15 (17%) versus three (5%) had vomiting. Rivastigmine can improve gait stability and might reduce the frequency of falls. A phase 3 study is needed to confirm these findings and show cost-effectiveness of rivastigmine treatment. Parkinson's UK.

Associations between Tactile Sensory Threshold and Postural Performance and Effects of Healthy Aging and Subthreshold Vibrotactile Stimulation on Postural Outcomes in a Simple Dual Task.

Specific activities that require concurrent processing of postural and cognitive tasks may increase the risk for falls in older adults. We investigated whether peripheral receptor sensitivity was associated with postural performance in a dual-task and whether an intervention in form of subthreshold vibration could affect performance. Ten younger (age: 20–35 years) and ten older adults (70–85 years) performed repeated auditory-verbal 1-back tasks while standing quietly on a force platform. Foot sole vibration was randomly added during several trials. Several postural control and performance measures were assessed and statistically analyzed (significance set to α-levels of .05). There were moderate correlations between peripheral sensitivity and several postural performance and control measures (r = .45 to .59). Several postural performance measures differed significantly between older and younger adults (p < 0.05); addition of vibration did not affect outcome measures. Aging affects healthy older adults' performance in dual-tasks, and peripheral sensitivity may be a contributor to the observed differences. A vibration intervention may only be useful when there are more severe impairments of the sensorimotor system. Hence, future research regarding the efficacy of sensorimotor interventions in the form of vibrotactile stimulation should focus on older adults whose balance is significantly affected.

Validity of Simple Gait-Related Dual-Task Tests in Predicting Falls in Community-Dwelling Older Adults

ObjectiveTo investigate the predictive validity of simple gait-related dual-task (DT) tests in predicting falls in community-dwelling older adults. DesignA validation cohort study with 6 months' follow-up. SettingGeneral community. ParticipantsIndependently ambulant community-dwelling adults (N=66) aged ≥65 years, with normal cognitive function. Sixty-two completed the follow-up. No participants required frames for walking. InterventionsNot applicable. Main Outcome MeasuresOccurrence of falls in the follow-up period and performance on primary and secondary tasks of 8 DT tests and 1 triple-task (TT) test. ResultsA random forest classification analysis identified the top 5 predictors of a fall as (1) absolute difference in time between the Timed Up & Go (TUG) as a single task (ST) and while carrying a cup; (2) time required to complete the walking task in the TT test; (3 and 4) walking and avoiding a moving obstacle as an ST and while carrying a cup; and (5) performing the TUG while carrying a cup. Separate bivariate logistic regression analyses showed that performance on these tasks was significantly associated with falling (P<.01). Despite the random forest analysis being a more robust approach than multivariate logistic regression, it was not clinically useful for predicting falls. ConclusionsThis study identified the most important outcome measures in predicting falls using simple DT tests. The results showed that measures of change in performance were not useful in a multivariate model when compared with an “allocated all to falls” rule.

The test–retest reliability of gait-related dual task performance in community-dwelling fallers and non-fallers

Gait-related dual task tests have been used to assess differences between fallers and non-fallers, without a thorough assessment of reliability. This study investigated the test–retest reliability of eight gait-related dual and one triple task tests in forty-four community-dwelling older adults (twenty with and twenty-four without a history of falls). The reliability of single, dual and change in performance (percentage change) from single to dual task conditions was assessed. The results showed that single and dual task walking time had fair to excellent reliability (ICC=0.53–0.92) across tasks. The percentage change in walking time (dual-task decrement) showed only poor to good reliability (ICC=−0.11 to 0.75). Cognitive task performance speed and accuracy showed poor to good reliability in single and dual task conditions (ICC=−0.16 to 0.83). The difference between the two conditions in speed and accuracy showed poor to fair reliability (ICC=−0.40 to 0.51). A secondary motor task (carrying a cup of water) ranged from slightly to moderately reliable in dual task conditions and when change in performance was measured (kappa=0.18–0.57). This study showed that simple dual task tests are reliable in the single and dual conditions but measures of change in performance, which are recommended for dual task assessment, are less reliable and is something which needs to be considered in future research. Of the nine examined, only one test, the walking while talking test, showed good reliability on primary and secondary tasks.

Characterization of postural control deficit in whiplash patients by means of linear and nonlinear analyses – A pilot study

The ability to maintain balance is diminished in patients suffering from a whiplash injury. The aim of this study was to characterize the variability of postural control in patients with chronic whiplash injury. For this purpose, we analyzed static postural recordings from 11 whiplash patients and sex- and age-matched asymptomatic healthy volunteers. Static postural recordings were performed randomly with eyes open, eyes closed, and eyes open and speaking (dual task). Spatial–temporal changes of the center of pressure displacement were analyzed to assess the amplitude and structure of postural variability by computing, respectively, the standard deviation/coefficient of variation and sample entropy/fractal dimension of the time series. The amplitude of variability of the center of pressure was larger among whiplash patients compared with controls ( P < 0.001) while fractal dimension was lower ( P < 0.001). The sample entropy increased during both eyes closed and a simple dual task compared with eyes open ( P < 0.05). The analysis of postural control dynamics revealed increased amplitude of postural variability and decreased signal dimensionality related to the deficit in postural stability found in whiplash patients. Linear and nonlinear analyses can thus be helpful for the quantification of postural control in normal and pathological conditions.

Deficits in interval timing measured by the dual‐task paradigm among children and adolescents with attention‐deficit/hyperactivity disorder

The underlying mechanism of time perception deficit in long time intervals in attention-deficit/hyperactivity disorder (ADHD) is still unclear. This study used the time reproduction dual task to explore the role of the attentional resource in time perception deficits among children and adolescents with ADHD. Participants included 168 children and adolescents with DSM-IV ADHD and 90 control children and adolescents without ADHD, aged 10 to 17 years, in Taipei. The DSM-IV diagnoses of ADHD and other psychiatric comorbid conditions were made by clinical assessments and confirmed by the psychiatric interviews of both parents and participants using the Chinese Kiddie Epidemiologic version of the Schedule for Affective Disorders and Schizophrenia. The participants were also assessed by using the Wechsler Intelligence Scale for Children-3(rd) edition (WISC-III), and time reproduction tasks (the single task and the simple and difficult versions of the dual tasks) at 5-second, 12-second, and 17-second intervals. The linear mixed model was used for data analysis. Children and adolescents with ADHD had less precise time reproduction than the controls in all three tasks except the 5-second interval of the single task. There were significant interactions between group and interval (12-second vs. 5-second, p = .030; 17-second vs. 5-second, p < .001), and between group and task (simple dual task vs. single task, p = .016; difficult dual task vs. single task, p < .001) after controlling for FSIQ, comorbidity, sex, age, use of methylphenidate, and the performance of the non-temporal tasks in dual tasks, if relevant. Significantly increased estimation errors in ADHD with increased task difficulties suggest that impaired timing processing in children and adolescents with ADHD during long time intervals may be accounted for by the limited attentional capacity rather than a primary problem in timing per se. This finding does not apply to rapid time intervals, in which cerebellar circuitry is important.

A Simple Dual-Task Study of Laterality, Sex-Differences and Handedness

Nine-hundred and eight-one right-handed and 55 left-handed subjects were required to tap with a pen for 10 secs between targets 6 cm apart whilst either saying nothing, reciting a tongue-twister or saying la-la. The numbers of dots produced in 10 secs in each condition were analysed. The right-handed group demonstrated the usually found degradation in their right-hand performance whilst reciting the meaningful words, but showed a lesser effect when saying la-la. Their left-handed performance was essentially unaffected. Absolutely no evidence for the presence of a sex difference in lateralization of language was found. The much smaller sample of left-handed subjects presented a complex picture of no significant effects, whether they were the sole left-handers in their family, or had other left-handed close relations.