Age-related differences in dual task performance: a cross-sectional study on women

Aim: Simultaneous performances of motor and attention‐demanding tasks are common in activities of everyday life. The present cross‐sectional study examined the changes and age‐related differences on mobility performance with an additional cognitive or motor task, and evaluated the relative dual‐task cost (DTC) on the motor performance in young, middle‐aged and older women. Methods: A total of 30 young (mean age 25.12 ± 3.00 years), 30 middle‐aged (mean age 47.82 ± 5.06 years) and 30 older women (mean age 72.74 ± 5.95 years) were recruited. Participants carried out: (i) single task: Timed Up & Go Test; (ii) cognitive dual‐task: Timed Up & Go Test while counting backwards by three; (iii) manual dual‐task: Timed Up & Go Test while carrying a glass of water. A repeated measures anova with between‐factor as age groups and within‐factor as tasks was carried out to assess the effect of aging on the performance of mobility tasks. DTC was calculated as ([performance in single‐task − performance in dual‐task] / performance in single task) × 100%. One‐way ancova were carried out to compare the DTC among the three age groups. Results: A significant interaction between age groups and task (F4,172 = 6.716, P < 0.001, partial η2 = 0.135) was observed. Specifically, older women showed a worse mobility performance under dual‐task condition compared with young and middle‐aged groups. Furthermore, DTC differences in cognitive task were observed in older women compared with younger and middle‐aged women (F2,86 = 7.649, P < 0.001, partial η2 = 0.151), but not in manual task. Conclusion: Dual‐task conditions might affect mobility performance differently across the lifespan, and could be particularly challenging in older women

Poor Trail Making Test Performance Is Directly Associated with Altered Dual Task Prioritization in the Elderly – Baseline Results from the TREND Study

BACKGROUND: Deterioration of executive functions in the elderly has been associated with impairments in walking performance. This may be caused by limited cognitive flexibility and working memory, but could also be caused by altered prioritization of simultaneously performed tasks. To disentangle these options we investigated the associations between Trail Making Test performance--which specifically measures cognitive flexibility and working memory--and dual task costs, a measure of prioritization. METHODOLOGY AND PRINCIPAL FINDINGS: Out of the TREND study (Tuebinger evaluation of Risk factors for Early detection of Neurodegenerative Disorders), 686 neurodegeneratively healthy, non-demented elderly aged 50 to 80 years were classified according to their Trail Making Test performance (delta TMT; TMT-B minus TMT-A). The subjects performed 20 m walks with habitual and maximum speed. Dual tasking performance was tested with walking at maximum speed, in combination with checking boxes on a clipboard, and subtracting serial 7 s at maximum speeds. As expected, the poor TMT group performed worse when subtracting serial 7 s under single and dual task conditions, and they walked more slowly when simultaneously subtracting serial 7 s, compared to the good TMT performers. In the walking when subtracting serial 7 s condition but not in the other 3 conditions, dual task costs were higher in the poor TMT performers (median 20%; range -6 to 58%) compared to the good performers (17%; -16 to 43%; p<0.001). To the contrary, the proportion of the poor TMT performance group that made calculation errors under the dual tasking situation was lower than under the single task situation, but higher in the good TMT performance group (poor performers, -1.6%; good performers, +3%; p = 0.035). CONCLUSION: Under most challenging conditions, the elderly with poor TMT performance prioritize the cognitive task at the expense of walking velocity. This indicates that poor cognitive flexibility and working memory are directly associated with altered prioritization

Effects of dual task on turning ability in stroke survivors and older adults

Background: Turning is an integral component of independent mobility in which stroke survivors frequently fall. Objective: This study sought to measure the effects of competing cognitive demands on the stepping patterns of stroke survivors, compared to healthy age-match adults, during turning as a putative mechanism for falls. Methods: Walking and turning (90º) was assessed under single (walking and turning alone) and dual task (subtracting serial 3s while walking and turning) conditions using an electronic, pressure-sensitive walkway. Dependent measures were time to turn, variability in time to turn, step length, step width and single support time during three steps of the turn. Turning ability in single and dual task conditions was compared between stroke survivors (n= 17, mean ± SD: 59 ± 113 months post-stroke, 64 ± 10 years of age) and age-matched healthy counterparts (n = 15). Results: Both groups took longer, were more variable, tended to widen the second step and, crucially, increased single support time on the inside leg of the turn while turning and distracted. Conclusions. Increased single support time during turning may represent biomechanical mechanism, within stepping patterns of turning under distraction, for increased risk of falls for both stroke survivors and older adults

Cognitive loading affects motor awareness and movement kinematics but not locomotor trajectories during goal-directed walking in a virtual reality environment.

The primary purpose of this study was to investigate the effects of cognitive loading on movement kinematics and trajectory formation during goal-directed walking in a virtual reality (VR) environment. The secondary objective was to measure how participants corrected their trajectories for perturbed feedback and how participants' awareness of such perturbations changed under cognitive loading. We asked 14 healthy young adults to walk towards four different target locations in a VR environment while their movements were tracked and played back in real-time on a large projection screen. In 75% of all trials we introduced angular deviations of ±5° to ±30° between the veridical walking trajectory and the visual feedback. Participants performed a second experimental block under cognitive load (serial-7 subtraction, counter-balanced across participants). We measured walking kinematics (joint-angles, velocity profiles) and motor performance (end-point-compensation, trajectory-deviations). Motor awareness was determined by asking participants to rate the veracity of the feedback after every trial. In-line with previous findings in natural settings, participants displayed stereotypical walking trajectories in a VR environment. Our results extend these findings as they demonstrate that taxing cognitive resources did not affect trajectory formation and deviations although it interfered with the participants' movement kinematics, in particular walking velocity. Additionally, we report that motor awareness was selectively impaired by the secondary task in trials with high perceptual uncertainty. Compared with data on eye and arm movements our findings lend support to the hypothesis that the central nervous system (CNS) uses common mechanisms to govern goal-directed movements, including locomotion. We discuss our results with respect to the use of VR methods in gait control and rehabilitation

Age-related decrements in dual-task performance: comparison of different mobility and cognitive tasks. A cross sectional study

This cross-sectional study investigated the age-related differences in dual-task performance both in mobility and cognitive tasks and the additive dual-task costs in a sample of older, middle-aged and young adults. 74 older adults (M = 72.63±5.57 years), 58 middle-aged adults (M = 46.69±4.68 years) and 63 young adults (M = 25.34±3.00 years) participated in the study. Participants performed different mobility and subtraction tasks under both single- and dual-task conditions. Linear regressions, repeated-measures and one-way analyses of covariance were used, The results showed: significant effects of the age on the dual and mobility tasks (p<0.05) and differences among the age-groups in the combined dual-task costs (p<0.05); significant decreases in mobility performance under dual-task conditions in all groups (p<0.05) and a decrease in cognitive performance in the older group (p<0.05). Dual-task activity affected mobility and cognitive performance, especially in older adults who showed a higher dual-task cost, suggesting that dual-tasks activities are affected by the age and consequently also mobility and cognitive tasks are negatively influenced

Effects of tDCS of Dorsolateral Prefrontal Cortex on Dual-Task Performance Involving Manual Dexterity and Cognitive Task in Healthy Older Adults

Healthy aging limits the activities of daily living and personal independence. Furthermore, cognitive-motor interference in dual-task (e.g., walking while talking) appears to be more pronounced in the elderly. Transcranial direct current stimulation (tDCS), a form of the non-invasive brain stimulation technique, is known to modify cortical excitability and has been investigated as a tool for enhancing motor and cognitive performance in health and disease. The present study examined whether tDCS targeting the dorsolateral prefrontal cortex (DLPFC) could improve dual-task performance in healthy older adults. The effects of tDCS, among other factors, depend on stimulation polarity (anodel vs. cathodal), electrode setup (unilateral vs. bilateral) and the time of application (off-line vs. on-line). We therefore explored the effects of unilateral and simultaneous bilateral tDCS (anodel and cathodal) of left DLPFC while performing (on-line) the Grooved Pegboard Test (GPT) and Serial Seven Subtraction Test (SSST) alone or together (dual-tasking). The number of pegs and the number of correct subtractions were recorded before, during and 30 min after tDCS. The dual-task performance was measured as the percent change from single- to the dual-task condition (dual-task cost DTC). Only bilateral, anode left tDCS, induced a significant increase in subtracted numbers while dual-tasking, i.e., it reduced the DTC of manual dexterity (GPT) to a cognitive task. Significant changes 30 min after the stimulation were only present after bilateral anode right (BAR) tDCS on GPT dual-task costs. These findings suggest that anodal tDCS applied on-line interacts with a dual-task performance involving demanding cognitive and manual dexterity tasks. The results support the potential use of non-invasive brain stimulation for improvement of cognitive functioning in daily activities in older individuals

The influence of visual flow and perceptual load on locomotion speed

Visual flow is used to perceive and regulate movement speed during locomotion. We assessed the extent to which variation in flow from the ground plane, arising from static visual textures, influences locomotion speed under conditions of concurrent perceptual load. In two experiments, participants walked over a 12-m projected walkway that consisted of stripes that were oriented orthogonal to the walking direction. In the critical conditions, the frequency of the stripes increased or decreased. We observed small, but consistent effects on walking speed, so that participants were walking slower when the frequency increased compared to when the frequency decreased. This basic effect suggests that participants interpreted the change in visual flow in these conditions as at least partly due to a change in their own movement speed, and counteracted such a change by speeding up or slowing down. Critically, these effects were magnified under conditions of low perceptual load and a locus of attention near the ground plane. Our findings suggest that the contribution of vision in the control of ongoing locomotion is relatively fluid and dependent on ongoing perceptual (and perhaps more generally cognitive) task demands