Greater Dual-task Costs Research Articles

Impaired dual-task gait in Parkinson's disease is associated with brain morphology changes.

In Parkinson's disease (PD), impaired gait and cognition affect daily activities, particularly in the more advanced stages of the disease. This study investigated the relationship between gait parameters, cognitive performance, and brain morphology in patients with early untreated PD. 64 drug-naive PD patients and 47 healthy controls (HC) participated in the study. Single- and dual-task gait (counting task) were examined using an expanded Timed Up & Go Test measured on a GaitRite walkway. Measurements included gait speed, stride length, and cadence. A brain morphometry analysis was performed on T1-weighted magnetic resonance (MR) images. In PD patients compared to HC, gait analysis revealed reduced speed (p < 0.001) and stride length (p < 0.001) in single-task gait, as well as greater dual-task cost (DTC) for speed (p = 0.007), stride length (p = 0.014) and cadence (p = 0.029). Based on the DTC measures in HC, PD patients were further divided into two subgroups with normal DTC (PD-nDTC) and abnormally increased DTC (PD-iDTC). For PD-nDTC, voxel-based morphometric correlation analysis revealed a positive correlation between a cluster in the left primary motor cortex and stride-length DTC (r = 0.57, p = 0.027). For PD-iDTC, a negative correlation was found between a cluster in the right lingual gyrus and the DTC for gait cadence (r=-0.35, pFWE = 0.018). No significant correlations were found in HC. The associations found between brain morphometry and gait performance with a concurrent cognitive task may represent the substrate for gait and cognitive impairment occurring since the early stages of PD.

Brain activity during dual-task standing in older adults

BackgroundIn older adults, the extent to which performing a cognitive task when standing diminishes postural control is predictive of future falls and cognitive decline. The neurophysiology of such “dual-tasking” and its effect on postural control (i.e., dual-task cost) in older adults are poorly understood. The purpose of this study was to use electroencephalography (EEG) to examine the effects of dual-tasking when standing on brain activity in older adults. We hypothesized that compared to single-task “quiet” standing, dual-task standing would decrease alpha power, which has been linked to decreased motor inhibition, as well as increase the ratio of theta to beta power, which has been linked to increased attentional control.MethodsThirty older adults without overt disease completed four separate visits. Postural sway together with EEG (32-channels) were recorded during trials of standing with and without a concurrent verbalized serial subtraction dual-task. Postural control was measured by average sway area, velocity, and path length. EEG metrics included absolute alpha-, theta-, and beta-band powers as well as theta/beta power ratio, within six demarcated regions-of-interest: the left and right anterior, central, and posterior regions of the brain.ResultsMost EEG metrics demonstrated moderate-to-high between-day test–retest reliability (intra-class correlation coefficients > 0.70). Compared with quiet standing, dual-tasking decreased alpha-band power particularly in the central regions bilaterally (p = 0.002) and increased theta/beta power ratio in the anterior regions bilaterally (p < 0.001). A greater increase in theta/beta ratio from quiet standing to dual-tasking in numerous demarcated brain regions correlated with greater dual-task cost (i.e., absolute increase, indicative of worse performance) to postural sway metrics (r = 0.45–0.56, p < 0.01). Lastly, participants who exhibited greater alpha power during dual-tasking in the anterior-right (r = 0.52, p < 0.01) and central-right (r = 0.48, p < 0.01) regions had greater postural sway velocity during dual-tasking.ConclusionIn healthy older adults, alpha power and theta/beta power ratio change with dual-task standing. The change in theta/beta power ratio in particular may be related to the ability to regulate standing postural control when simultaneously performing unrelated, attention-demanding cognitive tasks. Modulation of brain oscillatory activity might therefore be a novel target to minimize dual-task cost in older adults.

The Cortical Dynamics of Dual-Task Standing in Older Adults

In older adults, the extent to which performing a cognitive task when standing diminishes postural control is predictive of future falls and cognitive decline. The cortical control of such “dual-tasking,” however, remains poorly understood. Electroencephalogram (EEG) studies have demonstrated that the level of attention and cognitive inhibitory activity during cognitive task performance can be quantified by changes in brain activity in specific frequency bands; namely, an increase in theta/beta ratio and a decrease in alpha-band power, respectively. We hypothesized that in older adults, dual-tasking would increase theta/beta ratio and decrease alpha-band power, and, that greater alpha-band power during quiet standing would predict worse dual-task performance. To test this hypothesis, we recorded postural sway and EEG (32-channels) in 30 older adults without overt disease as they completed trials of standing, with and without verbalized serial subtractions, on four separate visits. Postural sway speed, as well as absolute theta/beta power ratio and alpha-band power, were calculated. The theta/beta power ratio and alpha-band power demonstrated high test-retest reliability during quiet and dual-task standing across visits (intra-class correlation coefficients >0.70). Compared with quiet standing, dual-tasking increased theta/beta power ratio (p<0.0001) and decreased alpha-band power (p=0.002). Participants who exhibited greater alpha-band power during quiet standing demonstrated a greater dual-task cost (i.e., percent increase, indicative of worse performance) to postural sway speed (r=0.3, p=0.01). These results suggest that in older adults, dual-tasking while standing increases EEG-derived metrics related to attention, and, that greater cognitive inhibitory activity during quiet standing is associated with worse dual-task standing performance.

Effects of Age on Dual Task Walking Performance as Measured Using a Smartphone Application in Middle-Aged Adults

After the age of 65, one’s ability to walk while performing an additional cognitive task (i.e., dual-tasking) is predictive of both future falls and cognitive decline. However, while it is well-known that older adults exhibit diminished dual-task performance, the time course of age-related dual-task decline has not been established. We thus conducted an analysis of data collected within the ongoing Barcelona Brain Health Initiative, a prospective population-based study characterizing the determinants of brain health maintenance in middle-aged adults. Cognitively-unimpaired participants (n=655) aged 40-65 years without neuro-psychiatric disease completed laboratory-based trials of walking normally (single-task) and walking while performing a verbalized serial subtraction task (dual-task). A smartphone-based gait assessment application was used to capture data and derive both the mean stride time (ST) and stride time variability (STV, defined as the coefficient of variation about the mean stride time) of each trial. The dual-task costs (DTC) to each gait metric were obtained by calculating the percent change from single- to dual-task conditions. We categorized participants into five groups according to age (e.g. Group 1: 40-45 years; Group 5: 60-65 years). Age group did not have an effect on single-task gait outcomes (p>0.51). However, the oldest age group, as compared to each of the other groups, exhibited greater DTC to both ST and STV (p<0.03). These results indicate that dual-task walking performance in particular may begin to diminish in late middle age even in the absence of detectable cognitive issues, DTC may offer a sensitive metric to age-related change in cognitive function.

Unraveling the Cognitive-Motor Interaction in Individuals With Amnestic Mild Cognitive Impairment.

This study aimed to determine whether increasing the contribution of executive functions worsens dual-task performance in individuals with amnestic mild cognitive impairment (aMCI). Fourteen individuals with aMCI (mean [SD]: 74 [4] years) and 19 control adults (71 [5] years) recalled a list of letters in the order of presentation (SPAN-O) or in alphabetic order (SPAN-A) while ascending or descending a 3-step staircase. Dual-task cost (DTC) represented the average decrement of motor and cognitive performances during dual tasks, with greater DTC indicating worse performance. SPAN-A (P < 0.001) and stair descent (P = 0.023) increased the DTC in both groups compared with SPAN-O and stair ascent. Furthermore, individuals with aMCI had a greater DTC (93.4 [41.2]%) than the control group (48.3 [27.9]%) for SPAN-A (P < 0.001). Dual-task cost was also greater in descent (76.6 [42.1]%) than ascent (64.0 [34.5]%) in individuals with aMCI (P = 0.024) but not in the control group (P = 0.99). Significant negative partial correlations (β < -0.39; P < 0.05) were found between Montreal Cognitive Assessment score and DTC, while controlling for age and physical function. A greater DTC in individuals with aMCI when the cognitive task requires working memory (SPAN-A) or during complex locomotor task (descent) suggests that aMCI impedes the capacity to perform 2 tasks simultaneously when higher-order cognitive processes are challenged. Furthermore, a greater DTC in our dual-task situations appears to reflect cognitive decline, as assessed by the Montreal Cognitive Assessment score. Overall, this study indicates that increasing the contribution of executive functions worsens the cognitive-motor interaction in individuals with aMCI.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1 available at: http://links.lww.com/JNPT/A375).

The influence of cognitive tasks on sensory organization test performance

IntroductionMany static postural tasks requiring vestibular contributions are completed while dual- tasking. ObjectiveWe investigated the influence of dual-tasks on sensory integration for postural control and cognitive performance during the sensory organization test and examined the relationship between cognitive function and dual-task cost during the sensory organization test. MethodsTwenty adults completed single and dual-task versions of the six conditions of the sensory organization test were completed during two visits separated by one week. A subset of 13 participants completed three National Institute of Health (NIH)-toolbox cognitive tests including the Flanker inhibitory control and attention test, dimensional change card sort test and pattern comparison processing speed test. Wilcoxon signed rank tests were used to compare postural sway during single and dual-task sensory organization test. Friedman’s test, with pairwise comparison post-hoc tests, was used to compare single task serial subtraction performance to the 6 dual-task sensory organization test conditions. Spearman’s correlation coefficients were used to assess the relationship between cognitive performance on NIH-toolbox test and postural and cognitive dual-task cost during the sensory organization test. ResultsPerforming a cognitive dual-task during the sensory organization test resulted in a significant increase in postural sway during condition 1 (Z=−3.26, p=0.001, ES=0.73), condition 3 (Z=−2.53, p=0.012, ES=0.56), and condition 6 (Z=−2.02, p=0.044, ES=0.45). Subtraction performance significantly decreased in during condition 6 (Z=−2.479, p=0.011, ES=0.55) compared to single-task. The dimensional change card sort test demonstrated moderate correlations with dual-task cost of serial subtraction performance in condition 5 (dimensional change card sort test: r=−0.62, p=0.02) and condition 6 (dimensional change card sort test: r=−0.56, p=0.04). Pattern comparison processing speed test scores were significantly correlated with dual-task cost of postural control during condition 2. ConclusionPerforming a cognitive task during the sensory organization test resulted in significantly increased postural sway during three conditions, particularly during visual environment manipulation oppose to vestibular and somatosensory manipulation. Cognitive performance decreased during the most complex sensory organization test condition. Additionally, we found participants with poorer executive function had greater dual-task cost during more complex sensory integration demands.

Task specificity impacts dual-task interference in older adults.

Task prioritization is an important factor determines the magnitude and direction of dual-task interference in older adults. Greater dual-task cost during walking may lead to falling, sometimes causing lasting effects on mobility. We investigated dual-task interference for walking and cognitive performance. Twenty healthy, older adults (71 ± 5years) completed three cognitive tasks: letter fluency, category fluency, and serial subtraction during seated and walking conditions on a self-paced treadmill for 3 min each, in addition to walking only condition. Walking speed, step length and width were measured during walking and each dual-task condition. Comparing the percentage of correct answers in cognitive tasks across single and dual-task conditions, there was a main effect of cognitive task (p = 0.021), showing higher scores during letter fluency compared to serial subtraction (p = 0.011). Step width was significantly wider during dual-task letter fluency compared to walking alone (p = 0.003), category fluency (p = 0.001), and serial subtraction (p = 0.007). During both fluency tasks, there was a cost for gait and cognition, with category showing a slightly higher cognitive cost compared to letter fluency. During letter fluency, to maintain cognitive performance, gait was sacrificed by increasing step width. During serial subtraction, there was a cost for gait, yet a benefit for cognitive performance. Differential effect of cognitive task on dual-task performance is critical to be understood in designing future research or interventions to improve dual-task performance of most activities of daily living.

Multiscale Dynamics of Spontaneous Brain Activity Is Associated With Walking Speed in Older Adults.

In older adults, compromised white matter tract integrity within the brain has been linked to impairments in mobility. We contend that poorer integrity disrupts mobility by altering the processing of sensorimotor and cognitive and attentional resources in neural networks. The richness of information processing in a given network can be quantified by calculating the complexity of resting-state functional MRI time series. We hypothesized that (i) older adults with lower brain complexity, specifically within sensorimotor, executive, and attention networks, would exhibit slower walking speed and greater dual-task costs (ie, dual-task cost) and (ii) such complexity would mediate the effect of white matter integrity on these metrics of mobility. Fifty-three older adults completed a walking assessment and a neuroimaging protocol. Brain complexity was quantified by calculating the multiscale entropy of the resting-state functional MRI signal within seven previously defined functional networks. The white matter integrity across structures of the corpus callosum was quantified using fractional anisotropy. Participants with lower resting-state complexity within the sensorimotor, executive, and attention networks walked more slowly under single- and dual-task (ie, walking while performing a serial-subtraction task) conditions (β > 0.28, p ≤ .01) and had a greater dual-task cost (β < -0.28, p < .04). Complexity in these networks mediated the influence of the corpus callosum genu on both single- (indirect effects > 0.15, 95% confidence intervals = 0.02-0.32) and dual-task walking speeds (indirect effects > 0.13, 95% confidence intervals = 0.02-0.33). These results suggest that the multiscale dynamics of resting-state brain activity correlate with mobility and mediate the effect of the microstructural integrity in the corpus callosum genu on walking speed in older adults.

Neural correlates of motor-cognitive dual-tasking in young and old adults.

When two tasks are performed simultaneously, performance often declines in one or both tasks. These so-called dual-task costs are more pronounced in old than in young adults. One proposed neurological mechanism of the dual-task costs is that old compared with young adults tend to execute single-tasks with higher brain activation. In the brain regions that are needed for both tasks, the reduced residual capacity may interfere with performance of the dual-task. This competition for shared brain regions has been called structural interference. The purpose of the study was to determine whether structural interference indeed plays a role in the age-related decrease in dual-task performance. Functional magnetic resonance imaging (fMRI) was used to investigate 23 young adults (20–29 years) and 32 old adults (66–89 years) performing a calculation (serial subtraction by seven) and balance-simulation (plantar flexion force control) task separately or simultaneously. Behavioral performance decreased during the dual-task compared with the single-tasks in both age groups, with greater dual-task costs in old compared with young adults. Brain activation was significantly higher in old than young adults during all conditions. Region of interest analyses were performed on brain regions that were active in both tasks. Structural interference was apparent in the right insula, as quantified by an age-related reduction in upregulation of brain activity from single- to dual-task. However, the magnitude of upregulation did not correlate with dual-task costs. Therefore, we conclude that the greater dual-task costs in old adults were probably not due to increased structural interference.

Lesion symptom map of cognitive–postural interference in multiple sclerosis

Objective: To investigate the disease-altered structure–function relationship underlying the cognitive–postural interference (CPI) phenomenon in multiple sclerosis (MS). Methods: We measured postural sway of 96 patients and 48 sex-/age-matched healthy controls by force platform in quiet standing (single-task (ST)) while performing the Stroop test (dual-task (DT)) to estimate the dual-task cost (DTC) of balance. In patient group, binary T2 and T1 lesion masks and their corresponding lesion volumes were obtained from magnetic resonance imaging (MRI) of brain. Normalized brain volume (NBV) was also estimated by SIENAX. Correlations between DTC and lesion location were determined by voxel-based lesion symptom mapping (VLSM) analyses. Results: Patients had greater DTC than controls (p < 0.001). Among whole brain MRI metrics, only T1 lesion volume correlated with DTC (r = −0.27; p < 0.01). However, VLSM analysis did not reveal any association with DTC using T1 lesion masks. By contrast, we found clusters of T2 lesions in distinct anatomical regions (anterior and superior corona radiata, bilaterally) to be correlated with DTC (p < 0.01 false discovery rate (FDR)-corrected). A multivariable stepwise regression model confirmed findings from VLSM analysis. NBV did not contribute to fit the model. Conclusion: Our findings suggest that the CPI phenomenon in MS can be explained by disconnection along specific areas implicated in task-switching abilities and divided attention.

A comparison of two walking while talking paradigms in aging

BackgroundOur study aimed to [1] compare dual-task costs in gait and cognitive performance during two dual-task paradigms: walking while reciting alternate letters of the alphabet (WWR) and walking while counting backward by sevens (WWC); [2] examine the relationship between the gait and cognitive interference tasks when performed concurrently. ScopeGait and cognitive performance were tested in 217 non-demented older adults (mean age 76±8.8 years; 56.2% female) under single and dual-task conditions. Velocity (cm/s) was obtained using an instrumented walkway. Cognitive performance was assessed using accuracy ratio: [correct responses]/[total responses]. Linear mixed effects models revealed significant dual-task costs, with slower velocity (p<.01) and decreased accuracy ratio (p<.01) in WWR and WWC compared to their respective single task conditions. Greater dual-task costs in velocity (p<.01) were observed in WWC compared to WWR. Pearson correlations revealed significant and positive relationships between gait and cognitive performance in WWR and WWC (p<.01); increased accuracy ratio was associated with faster velocity. ConclusionsOur findings suggested that dual-task costs in gait increase as the complexity of the cognitive task increases. Furthermore, the positive association between the gait and cognitive tasks suggest that dual-task performance was not influenced by task prioritization strategies in this sample.

The division of visual attention affects the transition point from level walking to stair descent in healthy, active older adults

BackgroundStair descent is a frequent daily activity that poses great risks for injury due to falling. Very little is understood about the attentional demands of stair descent and their changes with aging. The present study compared combined locomotor and cognitive functioning during different phases of stair descent between healthy young and older individuals. MethodsSixteen young and sixteen healthy older subjects walked down a 5-step staircase, performing a simultaneous visual Stroop task (i.e., a dual task) during the approach, transition or steady-state descent phases in some trials. Three dimensional kinematics of trunk and foot motion were recorded along with the accuracy and dual task costs (DTCs) for responses to the Stroop stimuli. ResultsDual tasking influenced both gait and cognitive performance for all subjects, and older adults generally walked slower with higher foot clearances and had greater DTCs. Specific age differences were found at stair transition where older adults showed more attentional effects. ConclusionsHealthy, active older adults showed changes to attention and planning due to normal aging specifically associated with a crucial point of fall risk during stair descent.

Gait profiles as indicators of domain-specific impairments in executive control across neurodevelopmental disorders

In neurodevelopmental disorders, unique profiles of executive control and attention appear to co-occur with poor motor coordination. However, less is known about how syndrome-specific cognitive profiles interact with motor control and impact behavioural outcomes in neurodevelopmental disorders such as Williams syndrome (WS) and Down syndrome (DS). Here we aimed to examine the extent to which specific components of executive function interact with gait control when performing cognitive dual-tasks (verbal fluency, digit span) in WS and DS. Spatiotemporal gait characteristics and intra-individual variability of gait were assessed in individuals with WS who were matched on spatial ability to individuals with DS, and chronologically age (CA) matched controls. During the concurrent verbal fluency task, the WS group had greater dual-task costs on spatiotemporal gait parameters and variability than CA controls. Conversely, individuals with DS had selective gait interference during the concurrent digit span task when compared to CA controls, but only under increased demands on cognitive control where there was greater variability in step timing in DS. The interrelationships between cognitive-motor interference and behavioural measures of executive functioning appeared to differentiate between WS and DS, and emphasise the importance of task modality in unpacking the executive control profile in these neurodevelopmental disorders. These findings support the notion that associated cerebellar-cortico abnormalities may produce quite distinct profiles of executive control across cognitive and motor domains that impact on behavioural outcomes in neurodevelopmental disorders.

Postural control in hemodialysis patients

The current investigation examined whether patients undergoing hemodialysis (HD) have reduced standing postural control performance during simultaneous cognitive task performance (i.e. dual task cost (DTC)) compared to age–gender matched controls. 19 persons undergoing HD and 19 age, gender, and body mass index (BMI) matched controls participated in the investigation. All participants performed 2 trials of quiet standing balance and 2 postural trials in which they performed a cognitive task. Postural control was indexed with various measures of the center of pressure (COP) trajectory. The change in postural control with a cognitive task (e.g. dual task cost DTC) was quantified as a change in the center of COP parameters of postural control from quiet standing to the cognitive condition.The primary observations were that (1) HD patients had significantly greater postural sway than age, gender, BMI matched controls (p's<0.05); (2) HD patients had a greater DTC than the controls during quiet standing (p's<0.05). The observations highlight that HD participants have poor postural control that is further exacerbated by a simultaneous performance of a cognitive task. It is possible that this impaired postural control places HD participants at elevated fall risk. Further study is necessary to determine contributing factors to an increased DTC in this population and whether targeted interventions such as exercise can reduce DTC.

Dual-task effects of simulated lane navigation and story recall in older adults with and without memory impairment

ABSTRACT While driving is a complex task, it becomes relatively automatic over time although unfamiliar situations require increased cognitive effort. Much research has examined driving risk in cognitively impaired elders and found little effect. This study assessed whether mildly memory impaired elders made disproportionate errors in driving or story recall, under simultaneous simulated driving and story recall. Forty-six healthy (61% women; mean age = 76.4) and 15 memory impaired (66% women, mean age = 79.4) elders participated. Cognitive status was determined by neuropsychological performance. Results showed that during dual-task conditions, participants stayed in lane more, and recalled stories more poorly, than when they did the tasks separately. Follow-up analysis revealed that verbatim recall, in particular, was reduced while driving for healthy participants. While memory impaired participants performed more poorly than healthy controls on both tasks, cognitive status was not associated with greater dual-task costs when driving and story recall were combined.

Successful adaptation of gait in healthy older adults during dual-task treadmill walking

ABSTRACT Dual-task methods have been used to demonstrate increased prioritization of walking performance over cognition in healthy aging. This is expressed as greater dual-task costs in cognitive performance than in walking. However, other research shows that older adults can prioritize cognitive performance over walking when instructed to do so. We asked whether age-related cognitive prioritization would emerge by experimentally manipulating cognitive difficulty. Young and older adults performed mental arithmetic at two levels of difficulty, alone or while walking. Electromyography and footswitches were used to measure muscle activity and stride parameters. Under high cognitive load, older adults increased their stride time, stride length, and hamstring activity, while maintaining their cognitive performance. Young adults showed negligible dual-task costs in each domain. The older adults appeared to successfully adapt their stride in response to high cognitive demands. The results have implications for neural models of gait regulation, and age differences in task emphasis.

Relationships between motor function and gait-related dual-task interference after stroke: A pilot study

The purpose of this pilot study was to examine the relationships between motor performance measures and dual-task interference in gait among community-dwelling adults with stroke. Dual-task costs on gait were correlated with Fugl-Meyer lower extremity score and usual gait speed in 13 community-dwelling adults with stroke. Individuals with greater lower extremity motor impairment and slower gait speed experienced greater cognitive-motor interference in gait. Paretic single limb stance was particularly susceptible to dual-task interference. Gait speed was only vulnerable to dual-task interference in the most complex dual-task. Thus, global characteristics of gait were vulnerable in the most difficult cognitive tasks, but even easy tasks impaired discrete components of dynamic balance.

The effect of a concurrent task on the walking performance of preschool children

Forty-eight children, aged 4–6 years, walked while performing or not performing an easy or difficult concurrent motor task (carrying a tray with or without marbles on it) or cognitive task (repeating a series of digits forwards or backwards). The temporal-distance gait parameters were measured using a GAITRite electronic walkway system. Dual-task costs were calculated as the difference between the children's walking performances with and without the concurrent task. Overall, walking alone was easier than walking while performing a concurrent task. A greater dual-task cost was observed when the concurrent task was difficult compared to when it was easy. However, this effect of difficulty was found for the motor task only. The results suggest that walking demands both the central processing capacity and the domain- and modality-specific processing resources in normal 4–6-year-old children.