Age-related differences in working memory and force control under dual-task conditions

The aim of this study was to investigate the relationship between force control and cognitive performance under dual-task conditions in younger (18-22 years) and older adults (65-77 years). Cognitive (n-back test) and motor performance (force-tracking) was measured independently and simultaneously. Results indicated overall age-related differences for the n-back and the force-tracking task. Age-related differences increased during dual-task conditions. While younger adults exhibited no decrease in cognitive or motor performance during dual-task conditions, older adults showed a decrease in motor and cognitive performance. Additionally, when older adults made an error in the cognitive task they tended to show greater variability in the force-tracking task. These results suggest that cognitive motor deficits are responsible for older adults' performance decrements under dual-task conditions.     

Dual-task costs of texting while walking forward and backward are greater for older adults than younger adults

Cognitive-motor dual-tasking involves concurrent performance of two tasks with distinct cognitive and motor demands and is associated with increased fall risk. In this hypothesis-driven study, younger (18–30 years, n = 24) and older (60–75 years, n = 26) adults completed six walking tasks in triplicate. Participants walked forward and backward along a GAITRite mat, in isolation or while performing a verbal fluency task. Verbal fluency tasks involved verbally listing or typing on a smartphone as many words as possible within a given category (e.g., clothes). Using repeated measures MANOVA models, we examined how age, method of fluency task (verbal or texting), and direction of walking altered dual-task performance. Given that tasks like texting and backward walking require greater cognitive resources than verbal and forward walking tasks, respectively, we hypothesized older adults would show higher dual-task costs (DTCs) than younger adults across different task types and walking directions, with degree of impairment more apparent in texting dual-task trials compared to verbal dual-task trials. We also hypothesized that both age groups would have greater DTCs while walking backward than while walking forward, regardless of task.Independent of age group, velocity and stride length were reduced for texting compared to the verbal task during both forward and backward walking; cadence and velocity were reduced while walking forward compared to walking backward for the texting task; and stride length was reduced for forward walking compared to backward walking during the verbal task. Younger adults performed better than older adults on all tasks with the most pronounced differences seen in velocity and stride length during forward-texting and backward-texting. Interaction effects for velocity and stride length while walking forward indicated younger adults performed better than older adults for the texting task but similarly during the verbal task. An interaction for cadence during the verbal task indicated younger adults performed better than older adults while walking backward but similarly while walking forward.In summary, older adults experienced greater gait decrement for all dual-task conditions. The greater declines in velocity and stride length in combination with cadence being stable suggest reductions in velocity during texting were due to shorter strides rather than a reduced rate of stepping. Contrary to our hypotheses, we found greater DTCs while walking forward rather than backward, which may be due to reduced gait performance during single-task backward walking; thus, further decrements with dual-tasking are unlikely. These findings underscore the need for further research investigating fall risk potential associated with texting and walking among aging populations and how interventions targeting stride length during dual-task circumstances may improve performance.     

Age- and practice-related influences on dual-task costs and compensation mechanisms under optimal conditions of dual-task performance

Impaired dual-task performance in younger and older adults can be improved with practice. Optimal conditions even allow for a (near) elimination of this impairment in younger adults. However, practice effects under these conditions in older adults are unknown. Further, it is open, how changed task scheduling and/ or the acquisition of task coordination skills affect the temporal overlap of two tasks in different age groups; this overlap indicate the involvement of these practice-related mechanisms to compensate for impaired dual-task performance. In a dual-task situation of Schumacher et al. (2001 , Psychological Science, 12, 230) including optimal conditions for dual-task performance, both younger and older adults were able to achieve an improvement in dual-task performance with 8 practice sessions to the same degree. The temporal task overlap changed similarly in both age groups during these sessions demonstrating a similar degree of the involvement of compensation mechanisms in younger and older adults. At the end of practice, however, we showed that older adults do not achieve the same optimized dual-task performance level of younger adults.     

Walking While Memorizing: Age-Related Differences in Compensatory Behavior

This study investigated predictions of the life-span theory of selection, optimization, and compensation, focusing on different patterns of task priority during dual-task performance in younger and older adults. Cognitive (memorizing) and sensorimotor (walking a narrow track) performance were measured singly, concurrently, and when task difficulty was manipulated. Use of external aids was measured to provide another index of task priority. Before dual-task testing, participants received extensive training with each component task and external aid. Age differences in dual-task costs were greater in memory performance than in walking, suggesting that older adults prioritized walking over memory. Further, when given a choice of compensatory external aids to use, older adults optimized walking, whereas younger adults optimized memory performance. The results have broad implications for systemic theories of cognitive and sensorimotor aging, and the costs and benefits of assistive devices and environmental support for older populations.     

Age and Cognitive Stress Influences Motor Skill Acquisition,Consolidation, and Dual-Task Effect in Humans

This study examined motor skill learning using a weight-bearing and cognitive-motor dual-task that incorporated unexpected perturbations and measurements of cognitive function. Forty young and 24 older adults performed a single-limb weight bearing task with novel speed, resistance, and cognitive dual task conditions to assess motor skill acquisition, retention and transfer. Subjects performed a cognitive dual task: summing letters in one color/orientation (simple) or two colors/orientations (complex). Increased cognitive load diminished the rate of skill acquisition, decreased transfer to new conditions, and increased error rate during an unexpected perturbation; however, young adults had a dual-task benefit from cognitive load. Executive function predicted 80% of the variability in dual-task performance. Although initial learning of a weight-bearing cognitive-motor dual-task was poor, longer term goals of improved dual-task effect and retention emerged.     

Effects of age on listening and postural control during realistic multi-tasking conditions

Successful performance of balance-related activities requires the effective integration of sensory, cognitive, and motor processes that can be affected by age-related changes. Of these age-related sensory changes, the effects of declines in hearing on balance have not been well-studied despite the fact that hearing loss has now been acknowledged as a significant risk factor for falls. The goal of this study was to evaluate age-related differences in a “standing while listening” task within increasingly challenging conditions resembling those that are often encountered in realistic, everyday situations.This study used a dual-task paradigm in an immersive Virtual Reality street scene setting in which postural load (firm, compliant), listening load (number of talkers), and visual load (eyes open/closed) were manipulated. A multi-talker divided attention listening task was used. Postural performance was assessed using center of pressure (COP) path length, while listening performance was assessed using spoken word recognition accuracy.Results demonstrated that age-related differences were observed in postural performance when postural demands were the highest and in listening performance when listening demands were the highest. Proportional dual-task costs were more pronounced for postural task performance compared to listening task performance and were more pronounced for older compared to younger adults. Postural dual-task costs increased as a function of increasing listening loads. Removal of visual information improved listening task performance across both groups and reduced the dual-task costs to listening in older adults when listening demands were highest (resulting in dual-task benefits).Taken together, the findings support previously documented age-related declines in postural control and auditory processing, demonstrate that increasing listening demands may result in poorer balance, particularly in older adults, and provide additional insights into the interactive effects of age-related declines when sensory, motor, and cognitive challenges are incremented factorially.     

“The threat is in the head,not in the legs”: Activating negative age stereotypes generates extra cognitive load during walking

ObjectiveActivating negative age stereotypes has been consistently shown to impair cognitive performance in older adults, but not motor performance, especially on mobility tasks. We tested the hypothesis that older adults may still experience stereotype threat, even if mobility performance is not affected. To do so, we examined whether inducing negative stereotypes may increase cognitive load during a walking task.MethodThis question was investigated in a dual-task paradigm: older adults performed simultaneously a walking task and a Stroop task, in stereotype and control conditions.ResultsResults showed that the stereotype induction did not affect walking parameters but decreased performance on the Stroop task, indicating that this induction increased cognitive load during walking.DiscussionThese results suggest that negative age stereotypes may be damaging even if walking parameters are not affected, by altering older adults' attention to their walking environment. We conclude by highlighting theoretical and practical implications.     

Age differences between children and young adults in the dynamics of dual-task prioritization: body (balance) versus mind (memory)

Task prioritization can lead to trade-off patterns in dual-task situations. The authors compared dual-task performances in 9- and 11-year-old children and young adults performing a cognitive task and a motor task concurrently. The motor task required balancing on an ankle-disc board. Two cognitive tasks measured working memory and episodic memory at difficulty levels individually adjusted during the course of extensive training. Adults showed performance decrements in both task domains under dual-task conditions. In contrast, children showed decrements only in the cognitive tasks but actually swayed less under dual-task than under single-task conditions and continued to reduce their body sway even when instructed to focus on the cognitive task. The authors argue that children perform closer to their stability boundaries in the balance task and therefore prioritize protection of their balance under dual-task conditions.     

Domain-general contributions to social reasoning: theory of mind and deontic reasoning re-explored

Using older adults and dual-task interference, we examined performance on two social reasoning tasks: theory of mind (ToM) tasks and versions of the deontic selection task involving social contracts and hazardous conditions. In line with performance accounts of social reasoning, evidence from both aging and the dual-task method suggested that domain-general resources contribute to performance of these tasks. Specifically, older adults were impaired relative to younger adults on all types of social reasoning tasks tested; performance varied as a function of the demands these tasks placed on domain-general resources. Moreover, in younger adults, simultaneous performance of a working memory task interfered with younger adults' performance on both types of social reasoning tasks; here too, the magnitude of the interference effect varied with the processing demands of each task. Limits placed on social reasoning by executive functions contribute a great deal to performance, even in old age and in healthy younger adults under conditions of divided attention. The role of potentially non-modular and modular contributions to social reasoning is discussed.     

Training effects on dual-task performance: are there age-related differences in plasticity of attentional control?

A number of studies have suggested that attentional control skills required to perform 2 tasks concurrently become impaired with age (A. A. Hartley, 1992; J. M. McDowd & R. J. Shaw, 2000). A. A. Hartley (2001) recently observed that the age-related differences in dual-task performance were larger when the 2 tasks required similar motor responses. The present study examined the extent to which age-related deficits in dual-task performance or time sharing--in particular, dual-task performance of 2 discrimination tasks with similar motor requirements--can be moderated by training. The results indicate that, even when the 2 tasks required similar motor responses, both older and younger adults could learn to perform the tasks faster and more accurately. Moreover, the improvement in performance generalized to new task combinations involving new stimuli. Therefore, it appears that training can substantially improve dual-task processing skills in older adults.     

Do working-memory executive components mediate the effects of age on strategy selection or on strategy execution? Insights from arithmetic problem solving

Younger and older adults performed an inequality verification task (7+6 < 15, Yes/No?) in a control condition and in a dual-task condition where they simultaneously performed an executive-component task. Arithmetic-problem characteristics were manipulated in order to test strategy selection (i.e., choice of appropriate strategies in order to improve performance) and strategy execution (i.e., performance of the cognitive processes involved in each strategy). Results revealed that strategy selection changes with age: Older adults mainly selected one type of strategies in contrast to younger adults who used several types of strategies. These age-related changes were similar in the control and dual-task conditions. Strategy execution also changed with age, as shown by larger age-related differences on hardest problems. These age-related changes were larger in the dual-task condition, compared to the control condition. This impact of executive components as mediator of age-related changes depended on general age-related slowing. We discuss these findings in order to further understand the effects of age on arithmetic performance.     

Age Differences in Multiple Outcome Measures of Time-Based Prospective Memory

ABSTRACT

This study examined time-based prospective memory performance in relation to age, monitoring strategy, response accuracy, and dual-task demands. Young, middle-aged and older adults (N?=?115) completed a prospective memory task, in which they indicated the passing of time every 5 min while listening to a short story (low task demands) or completing a series of cognitive tasks (high task demands). Young and older adults showed similar patterns of monitoring behavior, with low rates of clock checking during the early phase of each 5-min interval, followed by linearly accelerating monitoring functions. However, to obtain the same level of prospective memory performance older adults needed more frequent clock checks than young adults. Furthermore, older adults' compensatory monitoring strategy was associated with an additional cost in primary task performance. Finally, increased primary task demands shifted age differences in prospective memory from monitoring frequency to response accuracy. These findings suggest that goal-directed behavior requires efficient task coordination and resource allocation, and that age-related differences in time-based prospective memory should be evaluated by using multiple outcome measures.     

Influence of cognitive and motor tasks using smartphone during gait: EMG and gait performance analysis – Dual-task study

Previous studies reported changes in spatiotemporal gait parameters during dual-task performance while walking using a smartphone compared to walking without a smartphone. However, studies that assess muscle activity while walking and simultaneously performing smartphone tasks are scarce. So, this study aimed to assess the effects of motor and cognitive tasks using a smartphone while simultaneously performing gait on muscle activity and gait spatiotemporal parameters in healthy young adults. Thirty young adults (22.83 ± 3.92 years) performed five tasks: walking without a smartphone (single-task, ST); typing on a smartphone keyboard in a sitting position (secondary motor single-task); performing a cognitive task on a smartphone in a sitting position (cognitive single-task); walking while typing on a smartphone keyboard (motor dual-task, mot-DT) and walking while performing a cognitive task on a smartphone (cognitive dual-task, cog-DT). Gait speed, stride length, stride width and cycle time were collected using an optical motion capture system coupled with two force plates. Muscle activity was recorded using surface electromyographic signals from bilateral biceps femoris, rectus femoris, tibialis anterior, gastrocnemius medialis, gastrocnemius lateralis, gluteus maximus and lumbar erector spinae. Results showed a decrease in stride length and gait speed from the single-task to cog-DT and mot-DT (p < 0.05). On the other hand, muscle activity increased in most muscles analyzed from single- to dual-task conditions (p < 0.05). In conclusion, performing a cognitive or motor task using a smartphone while walking promote a decline in spatiotemporal gait parameters performance and change muscle activity pattern compared to normal walking.     

Walking and talking: dual-task effects on street crossing behavior in older adults

The ability to perform multiple tasks simultaneously has become increasingly important as technologies such as cell phones and portable music players have become more common. In the current study, we examined dual-task costs in older and younger adults using a simulated street crossing task constructed in an immersive virtual environment with an integrated treadmill so that participants could walk as they would in the real world. Participants were asked to cross simulated streets of varying difficulty while either undistracted, listening to music, or conversing on a cell phone. Older adults were more vulnerable to dual-task impairments than younger adults when the crossing task was difficult; dual-task costs were largely absent in the younger adult group. Performance costs in older adults were primarily reflected in timeout rates. When conversing on a cell phone, older adults were less likely to complete their crossing compared with when listening to music or undistracted. Analysis of time spent next to the street prior to each crossing, where participants were presumably analyzing traffic patterns and making decisions regarding when to cross, revealed that older adults took longer than younger adults to initiate their crossing, and that this difference was exacerbated during cell phone conversation, suggesting impairments in cognitive planning processes. Our data suggest that multitasking costs may be particularly dangerous for older adults even during everyday activities such as crossing the street.     

Exploring collaborative problem solving in adulthood

Collaborative problem solving occurs in situations in which two or more individuals cooperate in appraising, representing, and solving a variety of cognitive tasks. Collaborative groups are the context for much everyday cognitive activity in adulthood. Collaboration has been explored as a means through which older adults may maintain high levels of performance, perhaps compensating for individual-level cognitive and neurological decline. This study explored the effects of collaboration (group size) and adult age on solving both fixed- and unrestricted-alternatives 20 Questions tasks. Younger (M=24.3 years) and older (M=67.9 years) adults were randomly assigned to one of three homogeneous group size conditions: individuals, dyads, and tetrads. Results indicated some dissociation between individual-level performance (poorer for older adults) and collaborative performance (better for older adults). For the fixed-alternatives task, older adults produced more of the relatively inefficient hypothesis-scanning questions than did younger adults. In contrast, older collaborative groups produced more of the efficient constraint-seeking questions than hhpothesis-scanning questions, and an amount equivalent to that of younger adults. Overall performance for the difficult unrestricted-alternatives task was less efficient for both younger and older adults. The roles of task type, group characteristics, and adult age are discussed.     

Effects of dual task difficulty in motor and cognitive performance: Differences between adults and adolescents

In the present study our aim was to compare dual-task performance in thirteen adolescents and fifteen young adults while concurrently performing a cognitive and a motor task. The postural control variables were obtained under three different conditions: i) bipedal stance, ii) tandem stance and iii) unipedal stance. The cognitive task consisted of a backward digit span test in which the participants were asked to memorize a sequence of numbers and then repeat the number in reverse order at three different difficulty levels (i.e. with 3, 4 and 5 digits). The difficulty of the cognitive task was seen to have different effects on adolescents and young adults. Adolescents seem to prioritize postural control during high difficulty postural conditions while a cross-domain competition model appeared in easy postural conditions.     

Unimpaired performance during cognitive and visual manipulations in persons with anterior cruciate ligament reconstruction compared to healthy adults

Emerging research has proposed an increased reliance on visual processing and cognitive faculties in persons following anterior cruciate ligament reconstruction (ACLR). ACLR individuals display increased activation of visual and cognitive processing brain areas during task execution and exhibit dramatic performance decrements when vision is removed or cognitive difficulty is increased. Despite these intriguing findings, no previous studies have comprehensively assessed performance-related outcomes during tasks that challenge the cognitive and visual systems in ACLR individuals. The following hypotheses were proposed: 1) ACLR individuals will perform better on cognitive tests that required visual scanning; 2) ACLR individuals will utilize visual biofeedback when available during a proprioceptive task but experience decrements in performance when visual biofeedback is removed; and 3) during a cognitive-motor dual-task, the motor task will be more attentionally demanding for ACLR individuals compared to controls, whereas cognitive dual-task effects will be similar between groups. Twenty-one individuals with ACLR and 21 matched healthy adults performed a series of cognitive tests (Stroop, Trail Making Test, and NIH EXAMINER Battery), as well as a single-task angle-matching paradigm with and without visual biofeedback and a dual-task angle-matching paradigm with varying levels of visual and cognitive difficulty. ACLR individuals performed similarly on cognitive tasks, regardless of visual scanning requirements, demonstrated similar proprioceptive performance, evident via similar drift during the single-task conditions, and exhibited similar dual-task effects when the angle-matching paradigm was performed concurrently with a cognitive test compared to healthy adults. Despite a growing literature suggesting alterations to visual and cognitive system utilization in ACLR individuals, the current investigation found a subset of ACLR individuals do not exhibit this performance.     

When and how did you go wrong? Characterizing mild functional difficulties in older adults during an everyday task

ABSTRACT

Mild functional difficulties associated with cognitive aging may be reliably measured by coding “micro-errors” during everyday tasks, like meal preparation. Micro-errors made by 25 older adult and 48 younger adults were coded on four dimensions to evaluate the influence of: 1) poor error monitoring; 2) goal decay; 3) competition for response selection when switching to a new subtask; and 4) interference from distractor objects. Micro-errors made by young adults under a dual task load also were analyzed to determine the influence of overall performance level. Older adults’ micro-errors were observed when switching to a new subtask and to unrelated distractors. Slowed error monitoring and goal decay also influenced micro-errors in older adults, but not significantly more so than younger adults under the dual task. Interventions to reduce interference from distractors and to increase attention at critical choice points during tasks may optimize everyday functioning and preclude decline in older adults.     

Community-dwelling older adults with mild cognitive impairments show subtle visual attention costs when descending stairs

BackgroundOlder adults are at greater risk of falls while descending stairs. Cognitive deficits can further influence one's ability and mild cognitive impairments (MCI) specifically affect visual attention and dual tasking behavior. The present study aimed at comparing the attentional costs at different points during the approach to and descent of a staircase between older adults with and without MCI.MethodsEleven older adults with MCI and twenty-three healthy older individuals without cognitive impairments were recruited. Neuropsychological tests were carried out. In addition, participants approached and descended a 5-step staircase while a simultaneous visual Stroop dual-task was randomly introduced during the approach, transition or steady state descent phases across trials. Three-dimensional kinematics and accuracy on the Stroop task were analyzed and dual task costs were calculated.ResultsThe MCI group showed deficits for visuo-spatial attention, memory and multi-tasking abilities, as well as balance and decreased confidence for falls efficacy, but not for daily activity scores. Despite such changes, this group of community-dwelling individuals with MCI presented a functional capacity to descend stairs even during divided visual attention. However, there were subtle, but significant, group differences for movement fluidity and performance on the simultaneous cognitive task, particularly during the approach and transition to descent phases. The MCI group also tended to descend slower while using the handrails more than healthy older adults.ConclusionThe present cohort of community-dwelling older adults with MCI were functional, but appeared to prioritize locomotor demands over the simultaneous cognitive task in a possible “posture first” strategy to descend stairs. The present findings should be considered for developing more ecologically based clinical assessments of mobility deficits following cognitive impairments, with the approach and transition phases during stair descent as key points of focus.     

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

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.