Prudence Plummer

Cognitive-Motor Interference During Functional Mobility After Stroke: State of the Science and Implications for Future Research

Cognitive-motor interference (CMI) is evident when simultaneous performance of a cognitive task and a motor task results in deterioration in performance in one or both of the tasks, relative to performance of each task separately. The purpose of this review is to present a framework for categorizing patterns of CMI and to examine the specific patterns of CMI evident in published studies comparing single-task and dual-task performance of cognitive and motor tasks during gait and balance activities after stroke. We also examine the literature for associations between patterns of CMI and a history of falls, as well as evidence for the effects of rehabilitation on CMI after stroke. Overall, this review suggests that during gait activities with an added cognitive task, people with stroke are likely to demonstrate significant decrements in motor performance only (cognitive-related motor interference), or decrements in both motor and cognitive performance (mutual interference). In contrast, patterns of CMI were variable among studies examining balance activities. Comparing people poststroke with and without a history of falls, patterns and magnitude of CMI were similar for fallers and nonfallers. Longitudinal studies suggest that conventional rehabilitation has minimal effects on CMI during gait or balance activities. However, early-phase pilot studies suggest that dual-task interventions may reduce CMI during gait performance in community-dwelling stroke survivors. It is our hope that this innovative and critical examination of the existing literature will highlight the limitations in current experimental designs and inform improvements in the design and reporting of dual-task studies in stroke.

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

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

Texting and walking: Effect of environmental setting and task prioritization on dual-task interference in healthy young adults

Recent studies have shown that young adults significantly reduce their gait speed and weave more when texting while walking. Previous research has not examined the simultaneous dual-task effects on texting performance, therefore, the attention prioritization strategy used by young adults while texting and walking is not currently known. Moreover, it is not known whether laboratory-based studies accurately reflect texting and walking performance in the real world. This study compared dual-task interference during texting and walking between laboratory and real-world settings, and examined the ability of young adults to flexibly prioritize their attention between the two tasks in each environment. Texting and walking were assessed in single-task and three dual-task conditions (no-priority, gait-priority, texting-priority) in the lab and a University Student Center, in 32 healthy young adults. Dual-task effects on gait speed, texting speed, and texting accuracy were significant, but did not significantly differ between the two environments. Young adults were able to flexibly prioritize their attention between texting and walking, according to specific instruction, and this ability was not influenced by environmental setting. In the absence of instructions, young adults prioritized the texting task in the low-distraction environment, but displayed more equal focus between tasks in the real world. The finding that young adults do not significantly modify their texting and walking behavior in high-distraction environments lends weight to growing concerns about cell phone use and pedestrian safety.

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

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

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

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

Reliability and validity of the protokinetics movement analysis software in measuring center of pressure during walking

Our purpose was to determine the validity and test-retest reliability of the Protokinetics Movement Analysis Software (PKMAS) in measuring center of pressure (COP) during walking as compared to a force plate gold standard. Twenty-five healthy participants (14 females, 11 males; age 20.0±1.5years) completed 2 testing sessions approximately 5days apart (mean=5.5±1.1 days). In each session, participants completed 16 total trials across a 6m walkway: 8 trials walking on a ProtoKinetics Zeno Walkway using PKMAS and 8 trials walking over 2 force plates arranged in an offset tandem pattern. COP path length (cm) and speed (cm/s) were calculated from data averaged across the 8 trials on a given device for a given foot. Intraclass correlation coefficients (ICC 2, k) were computed to determine between session reliability. Pearson correlation coefficients (r) and Bland-Altman plots were produced between the PKMAS and force plate outcomes for session 1 to determine validity. The PKMAS demonstrated excellent reliability (ICC 2, k≥0.962) for all COP measures. Pearson correlation coefficients between PKMAS and force plates were ≥0.75 for all outcome variables. Bland-Altman plots and 95% levels of agreement revealed a bias where the PKMAS appeared to underestimate COP path length and speed by approximately 4cm and 6cm/s, respectively. After correcting for bias, our findings suggest the PKMAS is a reliable tool to measure COP in healthy people during gait. Using the PKMAS with the ProtoKinetics Zeno Walkway may allow for more efficient investigation of dynamic balance variables during functional movement tasks.

Reaction Time and Joint Kinematics During Functional Movement in Recently Concussed Individuals

OBJECTIVE To compare movement reaction time and joint kinematics between athletes with recent concussion and matched control recreational athletes during 3 functional tasks. DESIGN Cross-sectional. SETTING Laboratory. PARTICIPANTS College-aged recreational athletes (N=30) comprising 2 groups (15 participants each): (1) recent concussion group (median time since concussion, 126d; range, 28-432d) and (2) age- and sex-matched control group with no recent concussions. INTERVENTIONS We investigated movement reaction time and joint kinematics during 3 tasks: (1) jump landing, (2) anticipated cut, and (3) unanticipated cut. MAIN OUTCOME MEASURES Reaction time and reaction time cost (jump landing reaction time-cut reaction time/jump landing reaction time×100%), along with trunk, hip, and knee joint angles in the sagittal and frontal planes at initial ground contact. RESULTS There were no reaction time between-group differences, but the control group displayed improved reaction time cost (10.7%) during anticipated cutting compared with the concussed group (0.8%; P=.030). The control group displayed less trunk flexion than the concussed group during the nondominant anticipated cut (5.1° difference; P=.022). There were no other kinematic between-group differences (P≥.079). CONCLUSIONS We observed subtle reaction time and kinematic differences between individuals with recent concussion and those without concussion more than a month after return to activity after concussion. The clinical interpretation of these findings remains unclear, but may have future implications for postconcussion management and rehabilitation.

Visual scanning behavior during distracted walking in healthy young adults

BACKGROUND An epidemic of pedestrian accidents when walking while texting suggests that people are less aware of their surroundings during distracted walking, and highlights the importance of visual scanning for pedestrian safety. Quantitative examination of visual scanning during distracted walking is still lacking. RESEARCH QUESTION Is visual scanning behavior altered by distracted walking in healthy young adults? METHODS We compared visual scanning behavior in 20 young adults during usual (single-task) walking, walking while performing a letter-fluency task, and walking while texting. Visual scanning behavior was measured by fixation count and dwell time percentage in specific areas of interest. Dual-task effects on gait speed, letter fluency, texting speed and accuracy, and situational awareness were also examined. RESULT Visual scanning behavior differed between the three walking conditions. During dual-task letter fluency, participants had significantly more non-walking path fixations than either of the other two conditions (i.e., more frequent, broader visual scanning). Conversely, during dual-task texting, gaze was focused predominantly on the phone, with little visual scanning of the walking path and surrounding environment. When walking without texting or talking, gaze was directed equally to far walking path and surrounding environment. SIGNIFICANCE Texting while walking is associated with a considerable reduction in overt visual attention to the walking path and surrounding areas. Whether this translates to reduced conscious awareness of environmental stimuli remains unclear. Performing a verbal task while walking was associated with more frequent, wider visual scanning behavior, which may be specific to the nature of the verbal task in this study.

Age and falls history effects on antagonist leg muscle coactivation during walking with balance perturbations

Background: Inspired by a reliance on visual feedback for movement control in older age, optical flow perturbations provide a unique opportunity to study the neuromuscular mechanisms involved in walking balance control, including aging and falls history effects on the response to environmental balance challenges. Specifically, antagonist leg muscle coactivation, which increases with age during walking, is considered a neuromuscular defense against age‐associated deficits in balance control. The purpose of this study was to investigate the effects of age and falls history on antagonist leg muscle coactivation during walking with and without optical flow perturbations of different amplitudes. Methods: Eleven young adults [mean (standard deviation) age: 24.8 (4.8) years], eleven older non‐fallers [75.3 (5.4) years] and eleven older fallers [age: 78 (7.6) years] participated in this study. Participants completed 2‐minute walking trials while watching a speed‐matched virtual hallway that, in some conditions, included mediolateral optical flow perturbations designed to elicit the visual perception of imbalance. Findings: We first found that lower leg antagonist muscle coactivation during normal walking increased with age, independent of falls history. We also found that older but not young adults increased antagonist leg muscle coactivation in the presence of optical flow perturbations, with more pervasive effects in older adults with a history of falls. Interpretation: Our findings allude to a greater susceptibility to optical flow perturbations in older fallers during walking, which points to a higher potential for risk of instability in more complex and dynamic everyday environments. These findings may also have broader impacts related to the design of innovative training paradigms and neuromuscular targets for falls prevention.

Higher-dose, higher-repetition upper limb motor rehabilitation program after stroke is not superior to dose-matched or usual-dose customary occupational therapy [synopsis]

of: Winstein CJ, Wolf SL, Dromerick AW, Lane CJ, elson MA, Lewthwaite R, et al, for the Interdisciplinary Compreensive Arm Rehabilitation Evaluation (ICARE) Investigative Team. ffect of a task-oriented rehabilitation program on upper extremty recovery following motor stroke. The ICARE randomized clinical rial. JAMA. 2016;315:571-581. Question: Does intensive, high-repetition, task-oriented trainng during outpatient rehabilitation improve upper extremity otor function after stroke compared to dose-equivalent usual ccupational therapy or conventional (low-dose) occupational herapy. Design: Phase 3, parallel 3-group, assessor-blinded, ranomised, controlled trial with stratification by motor severity nd time from stroke onset. Setting: Seven sites (predominantly npatient rehabilitation). Participants: Individuals who were an verage of 46 days post stroke (SD 22) with moderate upper limb otor impairment. Key exclusion criteria were severe cognitive nd sensory impairments. Randomisation of 361 patients allocated 19 to the Accelerated Skill Acquisition Program, 120 to receive ose-equivalent usual and customary occupational therapy care, nd 122 to receive observation only (low-dose) customary occuational therapy. Interventions: The Accelerated Skill Acquisition rogram, which was delivered three times per week for 1 hour per ession for 10 weeks, was an intensive, task-specific intervention n which purposeful movement was emphasised; constraint of the ess affected hand was optional. Dose-equivalent usual and cusomary occupational therapy care received usual and customary are at the same dose as the Accelerated Skill Acquisition Program ntervention. The observation only (low-dose) customary occupaional therapy was a usual-care group, where the dose was not difference: 19 seconds) and the proportion of participants who increased by at least 25 points on the hand subscale of the Stroke Impact Scale. Results: Eighty-four percent of patients (n = 306) completed the study with no significant difference in attrition between groups. The mean between-group differences in the logtransformed Wolf Motor Function Test time score at 12 months were not statistically significant: the Accelerated Skill Acquisition Program versus dose-equivalent usual and customary occupational therapy care was 0.14 log-transformed seconds (95% CI –0.05 to 0.33); the Accelerated Skill Acquisition Program versus observation only (low-dose) customary occupational therapy was –0.01 (95% CI –0.22 to 0.21); the dose-equivalent usual and customary occupational therapy care versus Accelerated Skill Acquisition Program was –0.14 (95% CI –0.32 to 0.05). These between-group mean differences corresponded to small changes in absolute values, ranging from 0.5 to 2.0 seconds. Across all participants, the mean improvement in Wolf Motor Function Test time over 12 months was 6.8 seconds (95% CI 5.3 to 8.3). The proportion of patients in each group with hand function scale improvement (≥ 25 points) was 73%, 72% and 69%, respectively, with no between-group differences. Conclusion: Providing a structured and intensive (27 hours) upper limb motor rehabilitation program was not superior to usual occupational therapy (either dose-equivalent or low dose, 11 hours). Moreover, mean improvements did not exceed clinically meaningful thresholds in upper limb motor function.