Effects of explicit prioritization on dual task walking in patients with Parkinson's disease

Attentional management of cognitive-motor interference in adults during walking: Insights from an EEG study

Dual-task paradigms, which involve performing cognitive and motor tasks simultaneously, are commonly used to study how attentional resources are allocated and managed under varying task demands. This study aimed to investigate cognitive-motor interferences (CMI) under different levels of cognitive and motor task difficulty without instruction on task prioritization. 17 healthy young adults performed an auditory oddball task with increasing cognitive and motor (walking vs. sitting) difficulty. Cognitive and motor performances, along with P3 (P3a and P3b) brainwave components, were analysed. Increasing cognitive difficulty resulted in more errors and increased P3a amplitude, reflecting enhanced attentional demand, while P3b remained unaffected. This suggests a threshold effect on attentional resources. Motor complexity lengthened P3a and P3b latencies without affecting amplitude, indicating delayed attentional resource recruitment. Additionally, walking with the most difficult cognitive task increased cognitive error, suggesting attentional resource limits. With increased motor and cognitive complexity, CMI emerged, leading to cognitive error increase and improved gait stability without amplitude changes in P3a and P3b. Two hypotheses were proposed: motor prioritization and motor facilitation. Our study suggests managing attentional resources to balance cognitive and motor tasks rather than linearly increasing task complexity. Viewing dual tasks as a new, integrated task is proposed, supported by previous neural network integration studies. Thus, understanding how the brain organizes tasks in response to constraints is crucial for comprehending complex task execution.

Effect of Explicit Prioritization on Dual Tasks During Standing and Walking in People With Neurologic and Neurocognitive Disorders: A Systematic Review and Meta-analysis

OBJECTIVES

To examine the effectiveness of explicit task (ie, equal, motor or cognitive) prioritization during dual tasking (DT) in adults with neurologic and neurocognitive disorders (stroke, Parkinson disease [PD], multiple sclerosis, dementia, Alzheimer disease, and mild cognitive impairment).

DATA SOURCE

A systematic search in 4 databases (PubMed, Web of Science, Embase, and Cochrane Central) yielded 1138 unique studies published up to 2023.

STUDY SELECTION

Forty-one experimental studies were selected that assessed the effect of explicit prioritization instructions on both motor and cognitive performance during dual-tasks related to standing and walking in selected populations. Primary outcome measures were walking speed and response accuracy. Availability of data allowed us to perform a meta-analysis on 27 of the 41 articles by using inverse variance with a random effects model.

DATA EXTRACTION

The data including design, subject characteristics, motor and cognitive tasks, prioritization, motor and cognitive outcomes, instructions, and key findings were extracted. Two assessors rated the selected studies for risk of bias and quality using the Quality Assessment Tools of the National Institutes of Health.

DATA SYNTHESIS

This study examined 1535 adults who were asked to perform motor-cognitive DT in standing or walking, including 381 adults with stroke, 526 with PD, 617 with multiple sclerosis, 10 with dementia, 9 with Alzheimer disease, and 8 with mild cognitive impairment. During all prioritization instructions, participants slowed down during DT (standardized mean difference (SMD)equal=0.43; SMDmotor=0.78; SMDcognitive=0.69, P<.03) while maintaining similar response accuracy (SMDequal=0.12; SMDmotor=0.23; SMDcognitive=-.01, P>.05). However, considerable between-group heterogeneity was observed resulting in different motor and cognitive responses between pathologies.

CONCLUSION

Motor prioritization was achieved in adults with PD and stroke, unlike adults with neurocognitive disorders who were negatively affected by any type DT prioritizing. The reported within-group heterogeneity revealed that effects of explicit task prioritization are dependent on motor and cognitive task complexity, and the type of instructions. Recommendations are provided to ensure accurate use of instructions during DT paradigms.

The contribution of cognitive reserve in explaining the dual-task walking performance in iNPH patients: comparison with other cognitive, functional, and socio-demographic variables

BACKGROUND

Idiopathic normal pressure hydrocephalus (iNPH) is a prevalent neurological disorder, but its diagnosis remains challenging. Dual-task (DT) walking performance is a reliable indicator of iNPH but less is known about the role of cognitive reserve (CR) in predicting DT walking performance.

AIMS

The objective of this study was to evaluate the contribution of CR on DT walking in healthy controls (HC) and in iNPH patients (iNPH-P).

METHODS

68 iNPH-P (77.2 +/- 6.7 years old) and 28 HC (74.5 +/- 5.7 years old) were evaluated on their single-task walking (Vsimple) and on 4 DT walking (walking and counting or counting backwards, naming animals, naming words beginning with the letter P) (Vcount, VcountB, Vanimals and Vletter respectively). The contribution of CR on the different DT walking speeds was compared between HC and iNPH-P. In iNPH-P, the contribution of CR on the walking speeds was compared with regard to other cognitive, functional, and socio-demographic variables.

RESULTS

Simple linear regression demonstrated a moderate influence of CR on single and DT walking speed in iNPH-P (β > 0.3, p < .001) but not in HC where the relation was not significant. In iNPH-P, results showed that CR played a major role in explaining each of the single and DT walking speeds with NPH-scale.

CONCLUSION

As CR could be improved through the life cycle, these results support the idea of developing and supporting physical activity programs that will enrich social, physical, and cognitive resources to protect against age-related functional decline, especially in iNPH-P patients where the age-related deficits are greater.

EFFECTS OF TREADMILL GAIT TRAINING ON BALANCE IN PARKINSON'S PATIENTS AFTER DEEP BRAIN STIMULATION

Objective

After deep brain stimulation (DBS), patients with Parkinson's disease (PD) typically still present significant gait and postural stability problems, and thus additional interventions are needed. In this way, our purpose was evaluate the comparative effectiveness of treadmill training, with and without body weight support, on balance outcomes among patients with PD after DBS.

Methods

Eleven patients with PD that were using bilateral subthalamic nucleus DBS were evaluated using Time Up and Go test (TUG); Berg Balance Scale (BBS) and Static Posturography. In phase 1, all subjects participated in 8-weeks of treadmill training in conjunction with conventional physiotherapy. After six weeks (wash-out), each patient then participated in a subsequent 8-weeks of treadmill training with partial body weight support.

Results

After the phase 1, there were improvements on the cognitive TUG performance (Before: 15.7 ± 1,8 sec; After: 13.7 ± 3.1 sec; p < 0.01) and an increase of anteroposterior and medio-lateral body oscillation with eyes closed. After the phase 2, there were improvements in conventional (Before: 12.3 ± 2.0 sec; After: 10.7 ± 1.7 sec; p < 0.01) and cognitive (Before: 14.6 ± 3.5 sec; After: 12.5 ± 1.6 sec; p < 0.05) TUG performances. There were no significant changes in the Berg Balance Scale following either training protocol.

Conclusion

Both trainings improved static and dynamic balance and had similar results; however, supported treadmill training seemed to be a potentially superior option, as patients tended to feel safer. Level of Evidence II, therapeutic studies - investigation of treatment outcomes.

Comparing the effects of dual-task training and single-task training on walking, balance and cognitive functions in individuals with Parkinson's disease: A systematic review

BACKGROUND

This systematic review aimed to examine whether dual-task (DT) training was superior to single-task (ST) training in improving DT walking, balance and cognitive functions for individuals with Parkinson's disease (PD).

METHODS

Literature search was performed in the following electronic databases: PubMed, the Cochrane Library, Web of Science, and Metstr covering inception to May 10, 2023. And in order to facilitate comparison across trials, we calculated the effect size (Hedges' g) of gait, balance, cognitive, and other parameters under both ST and DT conditions, using the mean change score and standard deviation (SD) of change score of the experimental and control groups. Randomized controlled trials that examined the effects of DT motor and cognitive training in individuals with Parkinson's disease were included for this systematic review.

RESULTS

A total of 214 participants recruited from six articles (actually five trials) were involved in this review. In terms of walking ability, only double support time and stride time variability showed significant between-group difference (Hedges' g = 0.34, 0.18, respectively). Compared to ST training group, DT training group had a more improvement effect in laboratory balance measurement (Hedges' g = 0.18, 1.25), but no significant improvement in clinical balance measurement. No significant between-group differences were observed, thus its training effect on cognitive function was inconclusive.

CONCLUSIONS

The DT training failed to achieve promising results better than ST training in improving DT walking and balance functions for individuals with PD. Any firm conclusion cannot be drawn at present, due to the limited number of eligible publications. Larger sample size and high-quality studies are needed to investigate the effectiveness of DT training in individuals with PD.

Neural Oscillations and Functional Significances for Prioritizing Dual-Task Walking in Parkinson's Disease

Background

Task prioritization involves allocating brain resources in a dual-task scenario, but the mechanistic details of how prioritization strategies affect dual-task walking performance for Parkinson's disease (PD) are little understood.

Objective

We investigated the performance benefits and corresponding neural signatures for people with PD during dual-task walking, using gait-prioritization (GP) and manual-prioritization (MP) strategies.

Methods

Participants (N = 34) were asked to hold two inter-locking rings while walking and to prioritize either taking big steps (GP strategy) or separating the two rings (MP strategy). Gait parameters and ring-touch time were measured, and scalp electroencephalograph was performed.

Results

Compared with the MP strategy, the GP strategy yielded faster walking speed and longer step length, whereas ring-touch time did not significantly differ between the two strategies. The MP strategy led to higher alpha (8-12 Hz) power in the posterior cortex and beta (13-35 Hz) power in the left frontal-temporal area, but the GP strategy was associated with stronger network connectivity in the beta band. Changes in walking speed and step length because of prioritization negatively correlated with changes in alpha power. Prioritization-related changes in ring-touch time correlated negatively with changes in beta power but positively with changes in beta network connectivity.

Conclusions

A GP strategy in dual-task walking for PD can enhance walking speed and step length without compromising performance in a secondary manual task. This strategy augments attentional focus and facilitates compensatory reinforcement of inter-regional information exchange.

Cognitive-motor dual-task interference in Alzheimer's disease, Parkinson's disease, and prodromal neurodegeneration: A scoping review

BACKGROUND

Cognitive-motor interference (CMI) is a common deficit in Alzheimer's (AD) disease and Parkinson's disease (PD) and may have utility in identification of prodromal neurodegeneration. There is lack of consensus regarding measurement of CMI resulting from dual task paradigms.

RESEARCH QUESTION

How are individuals with AD, PD, and prodromal neurodegeneration impacted by CMI as measured by dual-task (DT) performance?

METHODS

A systematic literature search was performed in six datasets using the PRISMA guidelines. Studies were included if they had samples of participants with AD, PD, or prodromal neurodegeneration and reported at least one measure of cognitive-motor DT performance.

RESULTS

4741 articles were screened and 95 included as part of this scoping review. Articles were divided into three non-mutually exclusive groups based on diagnoses, with 26 articles in AD, 56 articles in PD, and 29 articles in prodromal neurodegeneration, and results presented accordingly.

SIGNIFICANCE

Individuals with AD and PD are both impacted by CMI, though the impact is likely different for each disease. We found a robust body of evidence regarding the utility of measures of DT performance in the detection of subtle deficits in prodromal AD and some signals of utility in prodromal PD. There are several key methodological challenges related to DT paradigms for the measurement of CMI in neurodegeneration. Overall, DT paradigms show good potential as a clinical method to probe specific brain regions, networks, and function; however, task selection and effect measurement should be carefully considered.

The predictive relationships between advanced dynamic balance and physical activity/quality of life in Parkinson's disease

Gait and balance problems commonly occur in Parkinson's disease (PD). However, balance tasks with only one performance objective (e.g., sit-to-stand) may not be sufficient, compared to dual motor tasks (e.g., carrying a tray while walking), to be applied to the assessments and interventions which are designed to promote PD patients' balance functioning, physical activity (PA) and health-related quality of life (HQoL). The aim of this study, therefore, was to determine whether advanced dynamic balance, measured by a demanding motor-motor dual task, is a significant predictor of PA/HQoL in older adults with and without PD. Participants with (n = 22) and without (n = 23) PD were assessed using the Berg Balance Scale (BBS), the single leg hop and stick series task (SLHS), the Physical Activity Scale for the Elderly (PASE), and the Parkinson's Disease Questionnaire-39 (PDQ39). We calculated the R² change, namely the incremental validity, between the multiple regression models before and after adding the scores on the BBS/SLHS. While controlling for biological and socioeconomic covariates, competence in the SLHS task provided moderate and large levels of incremental validity to PA (ΔR² = 0.08, Cohen's f² = 0.25, p = .035) and HQoL (ΔR² = 0.13, Cohen's f² = 0.65, p < .001), respectively. In particular for participants with PD, the SLHS explained significantly more variance in HQoL in relation to psychosocial functioning (ΔR² = 0.25, Cohen's f² = 0.42, p = .028) compared to the BBS (p = .296). Assessing advanced dynamic balance by means of a highly demanding dual-task paradigm was not only strongly associated with PA but also covered a wider spectrum of HQoL components. This approach is recommended for use in evaluations and interventions carried out in clinical and research settings in order to promote healthy living.

The Executive-Function-Related Cognitive-Motor Dual Task Walking Performance and Task Prioritizing Effect on People with Parkinson's Disease

To safely walk in a community environment requires dual cognitive-walking ambulation ability for people with Parkinson's disease (PD). A past study showed inconsistent results on cognitive-walking performance for PD patients, possibly due to the various cognitive tasks used and task priority assignment. This study designed cognitive-walking tests that used executive-related cognitive tasks to evaluate patients with early-stage Parkinson's disease who did not have obvious cognitive deficits. The effect of assigning task prioritization was also evaluated. Sixteen individuals with PD (PD group) and 16 individuals without PD (control group) underwent single cognitive tests, single walking tests, dual walking tests, and prioritizing task tests. Three types of cognitive, spatial memory, Stroops, and calculation tasks were employed. The cognitive performance was evaluated by response time, accuracy, and speed-accuracy trade off composite score. The walking performance was evaluated by the temporal spatial gait characteristics and variation in gait. The results showed that the walking performance of the PD group was significantly worse than the control group in both single and dual walking conditions. The group difference in cognitive performance was shown in composite score under the dual calculation walking task but not under the single task. While assigning priority to walking, no group difference in walking was observed but the response accuracy rate of PD groups declined. This study concluded that the dual task walking test could sharpen the cognitive deficits for early-stage PD patients. The task priority assignment might not be recommended while testing gait deficits since it decreased the ability to discriminate group differences.

Fronto-parietal cortex activation during walking in patients with Parkinson's disease adopting different postural strategies

Background

Cortical activation patterns in patients with Parkinson's disease (PD) may be influenced by postural strategies, but the underlying neural mechanisms remain unclear. Our aim is to examine the role of the fronto-parietal lobes in patients with PD adopting different postural strategies and the effect of dual task (DT) on fronto-parietal activation.

Methods

Two groups of patients with PD adopting either the posture first strategy (PD-PF) or the posture second strategy (PD-PS) were examined respectively when in the “OFF” state while single-walking task (SW) and DT. Frontal and parietal lobe activity was assessed by functional near infrared spectroscopy (fNIRS) and measuring gait parameters. Linear mixed models were used for analyses.

Results

Patients with PD who adopted PS had greater cortical activation than those who adopted PF, and there was no difference between PF and PS in the behavioral parameters. For oxyhemoglobin levels, the task condition (SW vs. DT) had a main effect in fronto-parietal lobes. Postural strategy (PD-PF vs. PD-PS) a main effect in the left prefrontal cortex (LPFC), left parietal lobe (LPL), and right parietal lobe (RPL) regions. In the task of walking with and without the cognitive task, patients with PD adopting PS had higher activation in the LPL than those adopting PF. In DT, only PD patients who adopted PS had elevated oxyhemoglobin levels in the LPFC, right prefrontal cortex (RPFC), and LPL compared with the SW, whereas patients with PD who adopted PF showed no differences in any region.

Conclusion

Different patterns of fronto-parietal activation exist between PD-PF and PD-PS. This may be because PD-PS require greater cortical functional compensation than those adopting PF.

Abnormal neural oscillations during gait and dual-task in Parkinson’s disease

Gait dysfunctions are debilitating motor symptoms of Parkinson’s disease (PD) and may result in frequent falling with health complications. The contribution of the motor-cognitive network to gait disturbance can be studied more thoroughly by challenging motor-cognitive dual-task gait performances. Gait is a complex motor task that requires an appropriate contribution from motor and cognitive networks, reflected in frequency modulations among several cortical and subcortical networks. Electrophysiological recordings by scalp electroencephalography and implanted deep brain stimulation (DBS) electrodes have unveiled modulations of specific oscillatory patterns in the cortical-subcortical circuits in PD. In this review, we summarize oscillatory contributions of the cortical, basal ganglia, mesencephalic locomotor, and cerebellar regions during gait and dual-task activities in PD. We detail the involvement of the cognitive network in dual-task settings and compare how abnormal oscillations in the specific frequency bands in the cortical and subcortical regions correlate with gait deficits in PD, particularly freezing of gait (FOG). We suggest that altered neural oscillations in different frequencies can cause derangements in broader brain networks, so neuromodulation and pharmacological therapies should be considered to normalize those network oscillations to improve challenged gait and dual-task motor functions in PD. Specifically, the theta and beta bands in premotor cortical areas, subthalamic nucleus, as well as alpha band activity in the brainstem prepontine nucleus, modulate under clinically effective levodopa and DBS therapies, improving gait and dual-task performance in PD with FOG, compared to PD without FOG and age-matched healthy control groups.

A Novel Way of Measuring Dual-Task Interference: The Reliability and Construct Validity of the Dual-Task Effect Battery in Neurodegenerative Disease

BACKGROUND

Decreased automaticity is common among individuals with neurodegenerative disease and is often assessed using dual-task (DT) paradigms. However, the best methods for assessing performance changes related to DT demands remain inconclusive.

OBJECTIVE

To investigate the reliability and validity of a novel battery of DT measures (DT Effect-Battery (DTE-B)) encompassing three domains: task-specific interference, task prioritization, and automaticity.

METHODS

Data for this retrospective cross-sectional study included 125 participants with Parkinson's disease (PD), 127 participants with Alzheimer's disease (AD), and 84 healthy older adults. Reliability analyses were conducted using a subset of each population. DTE-B measures were calculated from single and DT performance on the Timed Up and Go test and a serial subtraction task. Construct validity was evaluated via associations within the DTE-B and with theoretically supported measures as well as known-groups validity analyses.

RESULTS

Good to excellent reliability was found for DTE-B measures of task interference (motor and cognitive DT effects) (ICCs≥.658) and automaticity (combined DT effect (cDTE)) (ICCs≥.938). Evidence for convergent validity was found with associations within the hypothesized constructs. Known-groups validity analyses revealed differences in the DTE-B among the healthy group and PD and AD groups (ps≤.001), excepting task prioritization (ps≥.061).

CONCLUSIONS

This study provides evidence to support the DTE-B as a reliable measure of multiple constructs pertinent to DT performance. The cDTE demonstrated evidence to support its validity as a measure of automaticity. Further investigation of the utility of the DTE-B in both PD and AD, as well as other populations, is warranted.

Effects of task prioritization on a postural-motor task in early-stage Parkinson's disease: EEG connectivity and clinical implication

Appropriate attentional resource allocation could minimize exaggerated dual-task interference due to basal ganglia dysfunction in Parkinson's disease (PD). Here, we assessed the electroencephalography (EEG) functional connectivity to investigate how task prioritization affected posture-motor dual-tasks in PD. Sixteen early-stage PD patients and 16 healthy controls maintained balance in narrow stance alone (single-posture task) or while separating two interlocking rings (postural dual-task). The participants applied a posture-focus or supraposture-focus strategy in the postural dual-task. Postural sway dynamics, ring-touching time, and scalp EEG were analyzed. Both groups exhibited smaller postural sway size, postural determinism, and ring-touching time with the supraposture-focus versus posture-focus strategy. PD patients exhibited higher mean inter-regional connectivity strength than control subjects in both single and dual-task postural conditions. To cope with dual-task interference, PD patients increased inter-regional connectivity (especially with the posture-focus strategy), while control subjects reduced inter-regional connectivity. The difference in mean connectivity strength between the dual-task condition with supraposture-focus and single-posture condition was negatively correlated to the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part III total scores and hand-related sub-scores. Our findings suggest differential task prioritization effects on dual-task performance and cortical reorganization between early-stage PD and healthy individuals. Early-stage PD patients are advocated to use a supraposture-focus strategy during a postural dual-task. In addition, with a supraposture-focus strategy, PD patients with mild motor severity could increase compensatory inter-regional connectivity to cope with dual-task interference.

Mobile Phone Use during Gait: The Role of Perceived Prioritization and Executive Control

(1) Background: Mobile phone use during gait is associated with adverse health outcomes, namely increased risk of pedestrian injury. Healthy individuals can voluntarily prioritize concurrent task performance, but the factors underlying the impact of phone use during walking remain largely unknown. Thus, the objective of this work was to evaluate the relationship between subjective (perceived) prioritization, cognitive flexibility and dual-task performance when using a mobile phone during walking. (2) Methods: Thirty young participants walked for one minute with and without reading or texting on a mobile phone, as well as reading or texting while sitting. Walking performance (kinematics) was recorded, as well as phone use (text comprehension, text read/written), mental workload, perceived prioritization (visual analog scale), and cognitive flexibility (trail-making test). (3) Results: Texting while walking was associated with larger decreases in gait speed, larger gait variability, higher mental workload, and lower text comprehension compared to reading. Perceived prioritization was associated with walking dual-task costs (DTCs) (r = 0.39–0.42, p < 0.04) when texting, and better cognitive flexibility was associated with lower gait DTCs when texting (r = 0.55, p = 0.002) but not reading. (4) Conclusions: The context-dependent link between perceived prioritization, cognitive flexibility, and walking DTCs promotes our understanding of the factors underlying texting-while-walking performance. This could identify individuals who are more prone to dual-task interference in this increasingly common and dangerous task.

Dual-Task Effects During a Motor-Cognitive Task in Parkinson's Disease: Patterns of Prioritization and the Influence of Cognitive Status

People with Parkinson’s disease (PD) experience greater difficulties during dual task (DT) walking compared to healthy controls, but factors explaining the variance in DT costs remain largely unknown. Additionally, as cognitive impairments are common in PD it is important to understand whether cognitive status influences the strategies used during DT paradigms. The study aimed to (1) explore DT costs on gait and cognition during DT walking, (2) investigate factors associated with DT costs, and (3) to investigate to what extent patterns of DT costs and prioritization differed according to cognitive status. A total of 93 people with Parkinson’s disease were examined when walking in single and DT conditions. Information regarding demographics, PD severity, mobility, and cognitive and affective symptoms was collected, and an extensive neuropsychological test battery was used to classify whether participants had mild cognitive impairment (PD MCI) or not (PD non-MCI). Dual task costs were observed across all gait domains except asymmetry. Cognitive status was associated with DT costs on both gait and cognition. Nonmotor experiences of daily living were further associated with DT cost on cognition, and TUG-cog associated with DT cost on gait. People with PD MCI had larger DT costs on gait than PD non-MCI. Strategies differed according to cognitive status, whereby PD MCI used a posture-second strategy, and PD non-MCI used a posture-first strategy. Once verified in future studies, these results can inform clinicians and researchers when tailoring DT training paradigms to the specific characteristics of people with PD.

The impact of smartphone use on gait in young adults: Cognitive load vs posture of texting

Many researches have reported that the use of smartphones has a negative impact on gait variability and speed of pedestrians by dispersion of cognition, but the influence of factors other than cognitive function on gait is still unclear. The purpose of this study was to investigate the impact of smartphone use on spatiotemporal gait parameters in healthy young people while walking. 42 healthy young adults were recruited and instructed to walk in four conditions (walking without using a smartphone, typing on a smartphone with both hands, typing on a smartphone with one hand, and texting posture with non-task). All spatiotemporal gait parameters were measured using the GAITRite walkway. Compared to walking without using a smartphone, the subjects walked with a slower cadence and velocity and changed stride length and gait cycle and spent more time in contact with the ground when using a smartphone (p < 0.05). In addition, even if a texting posture was taken without performing a task, a similar change was observed when using a smartphone (p < 0.05). This study found that a cautious gait pattern occurred due to smartphone use, and that a change in gait appeared just by taking a posture without using smartphone.

Dopaminergic therapy and prefrontal activation during walking in individuals with Parkinson's disease: does the levodopa overdose hypothesis extend to gait?

The "levodopa-overdose hypothesis" posits that dopaminergic replacement therapy (1) increases performance on tasks that depend on the nigrostriatal-pathway (e.g., motor-control circuits), yet (2) decreases performance on tasks that depend upon the mesocorticolimbic-pathway (e.g., prefrontal cortex, PFC). Previous work in Parkinson's disease (PD) investigated this model while focusing on cognitive function. Here, we evaluated whether this model applies to gait in patients with PD and freezing of gait (FOG). Forty participants were examined in both the OFF anti-Parkinsonian medication state (hypo-dopaminergic) and ON state (hyper-dopaminergic) while walking with and without the concurrent performance of a serial subtraction task. Wireless functional near-infrared spectroscopy measured PFC activation during walking. Consistent with the "overdose-hypothesis", performance on the subtraction task decreased (p = 0.027) after dopamine intake. Moreover, the effect of walking condition on PFC activation depended on the dopaminergic state (i.e., interaction effect p = 0.001). Gait significantly improved after levodopa administration (p < 0.001). Nonetheless, PFC activation was higher (p = 0.013) in this state than in the OFF state during usual-walking. This increase in PFC activation in the ON state suggests that dopamine treatment interfered with PFC functioning. Otherwise, PFC activation, putatively a reflection of cognitive compensation, should have decreased. Moreover, in contrast to the OFF state, in the ON state, PFC activation failed to increase (p = 0.313) during dual-tasking, perhaps due to a "ceiling effect". These findings extend the "levodopa-overdose hypothesis" and suggest that it also applies to gait in PD patients. While dopaminergic therapy improves certain aspects of motor performance, optimal treatment should consider the "double-edged sword" of levodopa.

Backward Protective Stepping During Dual-Task Scenarios in People With Parkinson's Disease: A Pilot Study

Introduction. Reactive movements in response to a loss of balance are altered in people with Parkinson's disease (PD) and are critical for fall prevention. Further, falls are more common while attention is divided. Although divided attention has been shown to impact postural responses in healthy older adults, the impact of dividing attention on reactive balance, and the natural prioritization across postural and cognitive tasks in people with PD is largely unknown. Objectives. To characterize (1) the impact of a secondary cognitive task on reactive postural control and (2) the prioritization across stepping and cognitive tasks in people with PD. Methods. Sixteen people with PD and 14 age-matched controls underwent step-inducing, support-surface perturbations from stance, with and without an auditory Stroop secondary cognitive task. Cognitive, neuromuscular, and protective stepping performance were calculated for single and dual task scenarios. Results. In PD and control participants, cognitive reaction times (P = .001) and muscle onset latency (P = .007), but not protective step outcomes (P > .12 for all) were worse during dual tasking compared with single-task scenarios. Both PD and control groups prioritized the protective stepping task over the cognitive task. Overall, people with PD exhibited worse first-step margin of stability (a measure of protective step performance) than controls (P = .044). Conclusion. This study provides preliminary evidence that people with PD, like age-matched controls, exhibit cognitive and neuromuscular, but not protective step, dual-task interference. The lack of dual-task interference on step performance indicates a postural prioritization for PD and healthy older adults during dual-task protective stepping.

Turn Characteristics During Gait Differ With and Without a Cognitive Demand Among College Athletes

CONTEXT

Sports often involve complex movement patterns, such as turning. Although cognitive load effects on gait patterns are well known, little is known on how it affects biomechanics of turning gait among athletes. Such information could help evaluate how concussion affects turning gait required for daily living and sports.

OBJECTIVE

To determine the effect of a dual task on biomechanics of turning while walking among college athletes.

DESIGN

Cross-sectional study.

SETTING

University laboratory.

PARTICIPANTS

Fifty-three participants performed 5 trials of a 20-m walk under single- and dual-task conditions at self-selected speed with a 180° turn at 10-m mark. The cognitive load included subtraction, spelling words backward, or reciting the months backward.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Turn duration, turning velocity, number of steps, SD of turn duration and velocity, and coefficient of variation of turn duration and velocity.

RESULTS

Participants turned significantly slower (155.99 [3.71] cm/s vs 183.52 [4.17] cm/s; P < .001) and took longer time to complete the turn (2.63 [0.05] s vs 2.33 [0.04] s; P < .001) while dual tasking, albeit taking similar number of steps to complete the turn. Participants also showed more variability in turning time under the dual-task condition (SD of turn duration = 0.39 vs 0.31 s; P = .004).

CONCLUSIONS

Overall, college athletes turned slower and showed more variability during turning gait while performing a concurrent cognitive dual-task turning compared with single-task turning. The slower velocity increased variability may be representative of specific strategy of turning gait while dual tasking, which may be a result of the split attention to perform the cognitive task. The current study provides descriptive values of absolute and variability turning gait parameters for sports medicine personnel to use while they perform their concussion assessments on their college athletes.

The association between dual-task walking and counting responses and cognitive function and disability after severe head injury: A preliminary study

Adverse outcomes after severe head injury (SHI) can be difficult to detect in primary care and other settings where there is not specialist expertise for interpretation. Walking and counting dual-task (DT) measures are strongly associated with cognitive impairment and dementia and this preliminary study investigates whether performance on DT walking and counting tasks are associated with cognitive function and disability in 125 participants who sustained a SHI on average 26 years before. Single Task (ST) walking (speed over 6 metres) and ST counting (Serial 3s) and DT performance of concurrent walking and Serial 3s were compared with neuropsychological, wellbeing and disability tests for strength of association. The strongest correlations were between ST Correct Cognitive Responses (CCRs) and MMSE (rho = 0.435), DT CCRs and Short-term Memory Binding Tests (STMBT) binding accuracy (rho = 0,409) and DT CCRs and STROOP (rho = 0.420), but associations were less strong with disability. Developing this test, as a cost-efficient screening tool for triage to onward referral for neuropsychological assessment, holds promise, but requires further research.

Multimodal Training Reduces Fall Frequency as Physical Activity Increases in Individuals With Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) results in a global decrease in information processing, ultimately resulting in dysfunction executing motor-cognitive tasks. Motor-cognitive impairments contribute to postural instability, often leading to falls and decreased physical activity. The aim of this study was to determine the effects of a multimodal training (MMT) versus single-modal (SMT) training on motor symptoms, fall frequency, and physical activity in patients with PD classified as fallers.

METHODS

Individuals with PD were randomized into SMT (n = 11) or MMT (n = 10) and completed training 3 times per week for 8 weeks. The SMT completed gait and cognitive training separately, whereas MMT completed gait and cognitive training simultaneously during each 45-minute session. Physical activity, 30-day fall frequency, and PD motor symptoms were assessed at baseline, posttreatment, and during a 4-week follow-up.

RESULTS

Both groups exhibited significant (P < .05) improvements in clinical ratings of motor function, as symptoms improved by 8% and 15% for SMT and MMT, respectively. Physical activity significantly increased (P < .05) for both groups from baseline (mean steps 4942 [4415]) to posttreatment (mean steps 5914 [5425]). The MMT resulted in a significant 60% reduction in falls.

CONCLUSIONS

Although SMT and MMT approaches are both effective in improving physical activity and motor symptoms of PD, only MMT reduced fall frequency after the intervention.

Cognitive-motor interference in post-stroke individuals and healthy adults under different cognitive load and task prioritization conditions

[Purpose] We aimed to compare the effects of cognitive load and task prioritization on dual task strategies in patients with stroke and healthy adults in order to clarify the characteristics of cognitive-motor interference. [Participants and Methods] In total, 26 patients with stroke and 26 age-matched healthy adults (controls) performed the Timed Up and Go Test while performing a serial subtraction task from random numbers between 90 and 100. Dual task was measured under four conditions in which two difficulty levels of "3 subtraction" and "7 subtraction" were multiplied by two prioritizing tasks that involved "paying equal attention to both walking and subtraction tasks" (no priority) and "paying attention while mainly focusing on subtraction tasks" (cognitive priority). [Results] Increasing cognitive load and prioritizing cognitive tasks affected motor performance in terms of the amount of time and number of steps required to complete the Timed Up and Go Test in both the patients and controls. However, cognitive load and task prioritization did not affect cognitive performance. [Conclusion] When cognitive load increases and instructions are given to prioritize increases in cognitive load, patients with stroke use the "posture first" strategy to stabilize their gait as effectively as healthy adults do.

A meta-analysis: Parkinson's disease and dual-task walking

A growing body of literature has reported the effects of dual tasks on gait performance in people with Parkinson's disease (PD). The purpose of this meta-analysis was to synthesize the existing literature and quantify the overall influence of dual tasks on gait performance in PD. A thorough literature search was conducted, and 19 studies met the stringent inclusion criteria. Two moderator variable analyses examined the dual-task effect by: (a) mean single-task gait speed for each study (≥1.1 m/s or < 1.1 m/s), and (b) the type of dual task (arithmetic, language, memory, and motor). Three main findings were revealed by a random effects model analysis. First, a strong negative effect of dual tasks on walking performance (SMD = -0.68) confirmed that gait performance is adversely affected by dual tasks in people with PD. Second, the significant negative effect of dual tasks is present regardless of the mean level of single-task gait speed in a study. Third, dual-task walking speed deteriorates regardless of the type of dual task. Together, these results confirm that dual tasks severely affect walking performances in people with PD.

Cognitive-motor interference during goal-directed upper-limb movements

Research and clinical practice have focused on effects of a cognitive dual‐task on highly automated motor tasks such as walking or maintaining balance. Despite potential importance for daily life performance, there are only a few small studies on dual‐task effects on upper‐limb motor control. We therefore developed a protocol for assessing cognitive‐motor interference (CMI) during upper‐limb motor control and used it to evaluate dual‐task effects in 57 healthy individuals and two highly prevalent neurological disorders associated with deficits of cognitive and motor processing (57 patients with Parkinson's disease [PD], 57 stroke patients). Performance was evaluated in cognitive and motor domains under single‐ and dual‐task conditions. Patterns of CMI were explored to evaluate overall attentional capacity and attention allocation. As expected, patients with neurological deficits showed different patterns of CMI compared to healthy individuals, depending on diagnosis (PD or stroke) and severity of cognitive and/or motor symptoms. Healthy individuals experienced CMI especially under challenging conditions of the motor task. CMI was greater in PD patients, presumably due to insufficient attentional capacity in relation to increased cognitive involvement in motor control. Although no general increase of CMI was observed in stroke patients, correlation analyses suggested that especially patients with severe motor dysfunction experienced CMI. Clinical ratings of cognitive and motor function were weakly associated with CMI, suggesting that CMI reflects a different construct than these unidimensional clinical tests. It remains to be investigated whether CMI is an indicator of difficulties with day‐to‐day activities.

Thinking While Moving or Moving While Thinking - Concepts of Motor-Cognitive Training for Cognitive Performance Enhancement

The demographic change in industrial countries, with increasingly sedentary lifestyles, has a negative impact on mental health. Normal and pathological aging leads to cognitive deficits. This development poses major challenges on national health systems. Therefore, it is necessary to develop efficient cognitive enhancement strategies. The combination of regular physical exercise with cognitive stimulation seems especially suited to increase an individual's cognitive reserve, i.e., his/her resistance to degenerative processes of the brain. Here, we outline insufficiently explored fields in exercise-cognition research and provide a classification approach for different motor-cognitive training regimens. We suggest to classify motor-cognitive training in two categories, (I) sequential motor-cognitive training (the motor and cognitive training are conducted time separated) and (II) simultaneous motor-cognitive training (motor and cognitive training are conducted sequentially). In addition, simultaneous motor-cognitive training may be distinguished based on the specific characteristics of the cognitive task. If successfully solving the cognitive task is not a relevant prerequisite to complete the motor-cognitive task, we would consider this type of training as (IIa) motor-cognitive training with additional cognitive task. In contrast, in ecologically more valid (IIb) motor cognitive training with incorporated cognitive task, the cognitive tasks are a relevant prerequisite to solve the motor-cognitive task. We speculate that incorporating cognitive tasks into motor tasks, rather than separate training of mental and physical functions, is the most promising approach to efficiently enhance cognitive reserve. Further research investigating the influence of motor(-cognitive) exercises with different quantitative and qualitative characteristics on cognitive performance is urgently needed.

Postural sway in patients with early Parkinson's disease performing cognitive tasks while standing

OBJECTIVES

We investigated postural sway in patients with early Parkinson's disease (PD) to test the hypothesis that the postural control system was affected already at an early stage of PD. Moreover, we identified cases of dysfunction of stereopsis in PD patients.

METHODS

We examined 23 patients with early PD and 23 healthy, sex- and age-matched control subjects. Postural sway was measured with an accelerometer at the center of mass at the lower spine. Subjects were asked to stand quietly for 30 s under two usual conditions (eyes open and eyes closed) and two dual tasks conditions (eyes open with dual task, eyes closed with dual task). Stereopsis was assessed using the Titmus fly test.

RESULTS

In the usual conditions, no differences were found between the control group and PD group. With increasing task difficulty, PD patients showed an increase of RMS values of sway acceleration, compared to control subjects. These differences reached significance during cognitive task performance. PD patients showed larger JERK values with increasing difficulty of the sway task which also reached significance during cognitive task performance. Relative to controls, PD patients showed decreased stereopsis function. But, there were no statistically significant correlations between log seconds of arc of the Titmus test and JERK, even during cognitive task performance.

CONCLUSION

Our results indicate that patients with early PD have subtle signs of postural instability when their attention is diverted or reduced. In addition, deficits of stereopsis may be common in early PD patients. St Abbreviations: ACC: Accelerometers; ANOVA: Analysis of variance; AP: Antero-posterior; COP: Center of pressure; EC: Eyes closed; ECDT: eyes closed with dual task; EO: Eyes open; EODT: Eyes open with dual task; GDS: Geriatric depression scale; JERK: Jerkiness of sway; ML: Medio-lateral; MMSE: Mini mental state examination; MoCA: Montreal cognitive assessment; PD: Parkinson's disease; PDAbS: PD Patients with abnormal stereopsis; PDNrS: PD Patients with normal stereopsis; PIGD: Postural instability and gait disorder; RMS: Root mean square; UPDRS: Unified Parkinson's disease rating scale.

Improving Dual-Task Control With a Posture-Second Strategy in Early-Stage Parkinson Disease

OBJECTIVE

To examine the task prioritization effects on postural-suprapostural dual-task performance in patients with early-stage Parkinson disease (PD) without clinically observed postural symptoms.

DESIGN

Cross-sectional study. Participants performed a force-matching task while standing on a mobile platform, and were instructed to focus their attention on either the postural task (posture-first strategy) or the force-matching task (posture-second strategy).

SETTING

University research laboratory.

PARTICIPANTS

Individuals (N=16) with early-stage PD who had no clinically observed postural symptoms.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Dual-task change (DTC; percent change between single-task and dual-task performance) of posture error, posture approximate entropy (ApEn), force error, and reaction time (RT). Positive DTC values indicate higher postural error, posture ApEn, force error, and force RT during dual-task conditions compared with single-task conditions.

RESULTS

Compared with the posture-first strategy, the posture-second strategy was associated with smaller DTC of posture error and force error, and greater DTC of posture ApEn. In contrast, greater DTC of force RT was observed under the posture-second strategy.

CONCLUSIONS

Contrary to typical recommendations, our results suggest that the posture-second strategy may be an effective dual-task strategy in patients with early-stage PD who have no clinically observed postural symptoms in order to reduce the negative effect of dual tasking on performance and facilitate postural automaticity.

Can Dual Task Walking Improve in Parkinson's Disease After External Focus of Attention Exercise? A Single Blind Randomized Controlled Trial

BACKGROUND

It may be possible to use attention-based exercise to decrease demands associated with walking in Parkinson's disease (PD), and thus improve dual task walking ability. For example, an external focus of attention (focusing on the effect of an action on the environment) may recruit automatic control processes degenerated in PD, whereas an internal focus (limb movement) may recruit conscious (nonautomatic) control processes. Thus, we aimed to investigate how externally and internally focused exercise influences dual task walking and symptom severity in PD.

METHODS

Forty-seven participants with PD were randomized to either an Externally (n = 24) or Internally (n = 23) focused group and completed 33 one-hour attention-based exercise sessions over 11 weeks. In addition, 16 participants were part of a control group. Before, after, and 8 weeks following the program (pre/post/washout), gait patterns were measured during single and dual task walking (digit-monitoring task, ie, walking while counting numbers announced by an audio-track), and symptom severity (UPDRS-III) was assessed ON and OFF dopamine replacement. Pairwise comparisons (95% confidence intervals [CIs]) and repeated-measures analyses of variance were conducted.

RESULTS

Pre to post: Dual task step time decreased in the external group (Δ = 0.02 seconds, CI 0.01-0.04). Dual task step length (Δ = 2.3 cm, CI 0.86-3.75) and velocity (Δ = 4.5 cm/s, CI 0.59-8.48) decreased (became worse) in the internal group. UPDRS-III scores (ON and OFF) decreased (improved) in only the External group. Pre to washout: Dual task step time ( P = .005) and percentage in double support ( P = .014) significantly decreased (improved) in both exercise groups, although only the internal group increased error on the secondary counting task (ie, more errors monitoring numbers). UPDRS-III scores in both exercise groups significantly decreased ( P = .001).

CONCLUSIONS

Since dual task walking improvements were found immediately, and 8 weeks after the cessation of an externally focused exercise program, we conclude that externally focused exercise may improve on functioning of automatic control networks in PD. Internally focused exercise hindered dual tasking ability. Overall, externally focused exercise led to greater rehabilitation benefits in dual tasking and motor symptoms compared with internally focused exercise.

Dual-task walking over a compliant foam surface: A comparison of people with transfemoral amputation and controls

People with lower limb amputation are unable to reliably sense ground characteristics due to compromised sensory inputs from the missing limb. As a result, they may rely on compensatory strategies, such as use of cognitive resources, when walking over complex surfaces. This study examined interactions between cognition and walking over a compliant surface in 14 people with transfemoral amputation (TFA) and 14 controls using a dual-task paradigm. Walking was assessed with quantitative motion analysis in both single-task (walking alone) and dual-task (walking while performing a cognitive task) conditions over a compliant foam surface. Outcomes were walking speed, step width, step time asymmetry, step time variability, and the speed and accuracy of cognitive task performance. For each outcome, effects of task (single-task, dual-task) and group (TFA, control) were examined with repeated-measures analysis of variance. No significant group-by-task interactions were observed for cognitive task performance. A significant group-by-task interaction for step time asymmetry indicated that participants with TFA increased temporal asymmetry in dual-task relative to single-task conditions, while control participants maintained symmetrical gait. The addition of a concurrent cognitive task did not differentially affect other aspects of gait between groups. Significant main effects of group for all walking outcomes indicated that participants with TFA walked slower, with wider, more asymmetric, and more variable steps than controls. Results suggest that gait quality degrades in challenging dual-task conditions for people with TFA, but not controls, consistent with the idea that people with TFA may use increased cognitive resources to control walking in complex environments.

Cognitive-motor interference in multiple sclerosis: What happens when the gait speed is fixed?

During the last decade, numerous studies have confirmed a coupling between walking performance and cognition in people with multiple sclerosis (PwMS). Our aim was to provide new insights into a walking-cognitive dual-task (DT) in PwMS. We tested the DT phenomenon by controlling the walking speed using an instrumented treadmill. Thirty PwMS (20 women) with a mean age 40.1 (SD=12.0) participated in the study. Twenty-one healthy subjects served as controls. Each subject completed a sequence of tests: a) Normal walking (ST) - the participant walked on the instrumented treadmill at a comfortable walking speed for 1min; b) Cognitive evaluation (ST) - subjects performed two cognitive tests while seated; c) DT cognitive tests performed while walking on the treadmill at the identical speed performed during normal walking. Outcome measures were spatio-temporal parameters of gait (mean and variability), the Word List Generation Test (WLG) and the Serial-3 Subtraction Test. MS participants significantly decreased their cadence while increasing their stride length during the DT condition compared to the ST condition. Non-significant differences were observed for the WLG and Serial-3 Subtraction Cognitive Tests between the ST condition and the DT condition in both the MS and healthy groups. In terms of gait variability parameters, MS subjects demonstrated a 2 to 3-fold greater gait variability compared to the healthy controls. Non-significant differences in gait variability parameters were observed between the ST and DT conditions in both the MS and control groups. This study provides new insights into the DT phenomenon in the MS population.

Polestriding Intervention Improves Gait and Axial Symptoms in Mild to Moderate Parkinson Disease

OBJECTIVE

To evaluate the effects of 12-week polestriding intervention on gait and disease severity in people with mild to moderate Parkinson disease (PD).

DESIGN

A-B-A withdrawal study design.

SETTING

Outpatient movement disorder center and community facility.

PARTICIPANTS

Individuals (N=17; 9 women [53%] and 8 men [47%]; mean age, 63.7±4.9y; range, 53-72y) with mild to moderate PD according to United Kingdom brain bank criteria with Hoehn & Yahr score ranging from 2.5 to 3.0 with a stable medication regimen and ability to tolerate "off" medication state.

INTERVENTIONS

Twelve-week polestriding intervention with 12-week follow-up.

MAIN OUTCOME MEASURES

Gait was evaluated using several quantitative temporal, spatial, and variability measures. In addition, disease severity was assessed using clinical scales such as Unified Parkinson's Disease Rating Scale (UPDRS), Hoehn & Yahr scale, and Parkinson's Disease Questionnaire-39.

RESULTS

Step and stride lengths, gait speed, and step-time variability were improved significantly (P<.05) because of 12-week polestriding intervention. Also, the UPDRS motor score, the UPDRS axial score, and the scores of UPDRS subscales on walking and balance improved significantly after the intervention.

CONCLUSIONS

Because increased step-time variability and decreased step and stride lengths are associated with PD severity and an increased risk of falls in PD, the observed improvements suggest that regular practice of polestriding may reduce the risk of falls and improve mobility in people with PD.

Observing prioritization effects on cognition and gait: The effect of increased cognitive load on cognitively healthy older adults' dual-task performance

Previous studies exploring the effects of attention-prioritization on cognitively healthy older adults' gait and cognitive dual task (DT) performance have shown DT cost in gait outcomes but inconsistent effects on cognitive performance, which may reflect task difficulty (the cognitive load). This study aimed to identify whether changing the cognitive load during a walking and counting DT improved the challenge/sensitivity of the cognitive task to observe prioritization effects on concurrent gait and cognitive performance outcomes. Seventy-two cognitively healthy older adults (Mean=73years) walked 15m, counted backwards in 3s and 7s as single tasks (ST), and concurrently walked and counted backwards as DTs. Attention-prioritization was examined in Prioritizing Walking (PW) and Prioritizing Counting (PC) DT conditions. Dual-task performance costs (DTC) were calculated for number of correct cognitive responses (CCR) in the counting tasks, and step-time variability and velocity in the gait task. All DT conditions showed a benefit (DTB) for cognitive outcomes with trade-off cost to gait. In the Serial 3s task, the cognitive DTBs increased in PC over the PW condition (p<0.05), with a greater cost to walking velocity (p<0.05). DT effects were more pronounced in the Serial 7s with a lower cognitive DTB when PC than when PW, (p<0.05) with no trade-off increase in cost to gait outcomes (p<0.05). The findings suggest that increased cognitive load during a gait and cognitive DT produces more pronounced gait measures of attention-prioritization in cognitively healthy older adults. A cognitive load effect was also observed in the cognitive outcomes, with unexpected results.

Residual standard deviation: Validation of a new measure of dual-task cost in below-knee prosthesis users

We developed and evaluated properties of a new measure of variability in stride length and cadence, termed residual standard deviation (RSD). To calculate RSD, stride length and cadence are regressed against velocity to derive the best fit line from which the variability (SD) of the distance between the actual and predicted data points is calculated. We examined construct, concurrent, and discriminative validity of RSD using dual-task paradigm in 14 below-knee prosthesis users and 13 age- and education-matched controls. Subjects walked first over an electronic walkway while performing separately a serial subtraction and backwards spelling task, and then at self-selected slow, normal, and fast speeds used to derive the best fit line for stride length and cadence against velocity. Construct validity was demonstrated by significantly greater increase in RSD during dual-task gait in prosthesis users than controls (group-by-condition interaction, stride length p=0.0006, cadence p=0.009). Concurrent validity was established against coefficient of variation (CV) by moderate-to-high correlations (r=0.50-0.87) between dual-task cost RSD and dual-task cost CV for both stride length and cadence in prosthesis users and controls. Discriminative validity was documented by the ability of dual-task cost calculated from RSD to effectively differentiate prosthesis users from controls (area under the receiver operating characteristic curve, stride length 0.863, p=0.001, cadence 0.808, p=0.007), which was better than the ability of dual-task cost CV (0.692, 0.648, respectively, not significant). These results validate RSD as a new measure of variability in below-knee prosthesis users. Future studies should include larger cohorts and other populations to ascertain its generalizability.

Temporal and spatial gait parameters in children with Cri du Chat Syndrome under single and dual task conditions

AIM

To describe temporal and spatial gait characteristics in individuals with Cri du Chat syndrome (CdCS) and to explore the effects of performing concurrent manual tasks while walking.

METHODS

The gait parameters of 14 participants with CdCS (mean age 10.3, range 3-20 years) and 14 age-matched controls (mean age 10.1, range 3-20 years) were collected using the GAITRite^® instrumented walkway. All participants first walked without any concurrent tasks and then performed 2 motor dual task walking conditions (pitcher and tray).

RESULTS

Individuals with CdCS took more frequent, smaller steps than controls, but, on average, had a comparable gait speed. In addition, there was a significant task by group interaction. Participants decreased gait speed, decreased cadence, decreased step length, and increased% time in double limb support under dual task conditions compared to single task conditions. However, the age-matched controls altered their gait for both manual tasks, and the participants with CdCS only altered their gait for the tray task.

INTERPRETATION

Although individuals with CdCS ambulate with a comparable gait speed to age-matched controls under single task conditions, they did not significantly alter their gait when carrying a pitcher with a cup of water inside, like controls. It is not clear whether or not individuals with CdCS had difficulty attending to task demands or had difficulty modifying their gait.

The Effect of External and Internal Focus of Attention on Gait Variability in Older Adults

Internal focus of attention on a movement or focusing on an external target are both strategies that can affect motor performance. The authors explored whether manipulating subjects' focus of attention while walking would alter gait variability, a measure reflecting consistency of gait and associated with the risk of falling in older adults. Twenty community-living older adults participated in the study and were tested while focusing their attention on (a) gait consistency (internal focus) or (b) metronome beats (external focus). In both conditions gait variability increased (i.e., worsened p < .05) or did not change. No benefit was found in instructing subjects to focus on gait consistency or metronome beats. Such instructions may actually have distracted and interfered with the execution of gait.

Effects of aging on the relationship between cognitive demand and step variability during dual-task walking

A U-shaped relationship between cognitive demand and gait control may exist in dual-task situations, reflecting opposing effects of external focus of attention and attentional resource competition. The purpose of the study was twofold: to examine whether gait control, as evaluated from step-to-step variability, is related to cognitive task difficulty in a U-shaped manner and to determine whether age modifies this relationship. Young and older adults walked on a treadmill without attentional requirement and while performing a dichotic listening task under three attention conditions: non-forced (NF), forced-right (FR), and forced-left (FL). The conditions increased in their attentional demand and requirement for inhibitory control. Gait control was evaluated by the variability of step parameters related to balance control (step width) and rhythmic stepping pattern (step length and step time). A U-shaped relationship was found for step width variability in both young and older adults and for step time variability in older adults only. Cognitive performance during dual tasking was maintained in both young and older adults. The U-shaped relationship, which presumably results from a trade-off between an external focus of attention and competition for attentional resources, implies that higher-level cognitive processes are involved in walking in young and older adults. Specifically, while these processes are initially involved only in the control of (lateral) balance during gait, they become necessary for the control of (fore-aft) rhythmic stepping pattern in older adults, suggesting that attentional resources turn out to be needed in all facets of walking with aging. Finally, despite the cognitive resources required by walking, both young and older adults spontaneously adopted a "posture second" strategy, prioritizing the cognitive task over the gait task.

Secondary task performance during challenging walking tasks and freezing episodes in Parkinson's disease

Parkinson's disease (PD) patients likely use attentional strategies to compensate for their gait deficits, which increases the cognitive challenge of walking. The interplay between cognitive functions and gait can be investigated by evaluating the subject's attendance to a secondary task during walking. We hypothesized that the ability to attend to a secondary task decreases during challenging walking conditions in PD, particularly during freezing of gait (FOG)-episodes. Twenty-nine PD patients and 14 age-matched controls performed a simple reaction task that involved squeezing a ball as fast as possible in response to an auditory stimulus. Participants performed this reaction task during four conditions: (1) walking at preferred speed; (2) walking with short steps at preferred speed; (3) walking with short steps, as rapidly as possible; (4) making rapid full turns. We used surface electromyography to determine reaction times, and a pressure sensor located within the ball to determine movement onset. Reaction times of PD patients were slower (on average by 42 ms) compared to controls, regardless of the walking task. In both groups, reaction times were significantly longer during the turning condition compared to all other conditions. FOG-episodes were most often seen during the turning condition. In PD patients, reaction times were significantly longer during FOG-episodes compared to trials without FOG. Our results suggest that turning requires more attentional resources than other walking tasks. The observation of delayed reaction times during FOG-episodes compared to trials without FOG suggests that freezers use additional resources to overcome their FOG-episodes.

Freezing of Gait in Parkinson's Disease: An Overload Problem?

Freezing of gait (FOG) is arguably the most severe symptom associated with Parkinson's disease (PD), and often occurs while performing dual tasks or approaching narrowed and cluttered spaces. While it is well known that visual cues alleviate FOG, it is not clear if this effect may be the result of cognitive or sensorimotor mechanisms. Nevertheless, the role of vision may be a critical link that might allow us to disentangle this question. Gaze behaviour has yet to be carefully investigated while freezers approach narrow spaces, thus the overall objective of this study was to explore the interaction between cognitive and sensory-perceptual influences on FOG. In experiment #1, if cognitive load is the underlying factor leading to FOG, then one might expect that a dual-task would elicit FOG episodes even in the presence of visual cues, since the load on attention would interfere with utilization of visual cues. Alternatively, if visual cues alleviate gait despite performance of a dual-task, then it may be more probable that sensory mechanisms are at play. In compliment to this, the aim of experiment#2 was to further challenge the sensory systems, by removing vision of the lower-limbs and thereby forcing participants to rely on other forms of sensory feedback rather than vision while walking toward the narrow space. Spatiotemporal aspects of gait, percentage of gaze fixation frequency and duration, as well as skin conductance levels were measured in freezers and non-freezers across both experiments. Results from experiment#1 indicated that although freezers and non-freezers both walked with worse gait while performing the dual-task, in freezers, gait was relieved by visual cues regardless of whether the cognitive demands of the dual-task were present. At baseline and while dual-tasking, freezers demonstrated a gaze behaviour that neglected the doorway and instead focused primarily on the pathway, a strategy that non-freezers adopted only when performing the dual-task. Interestingly, with the combination of visual cues and dual-task, freezers increased the frequency and duration of fixations toward the doorway, compared to non-freezers. These results suggest that although increasing demand on attention does significantly deteriorate gait in freezers, an increase in cognitive demand is not exclusively responsible for freezing (since visual cues were able to overcome any interference elicited by the dual-task). When vision of the lower limbs was removed in experiment#2, only the freezers' gait was affected. However, when visual cues were present, freezers' gait improved regardless of the dual-task. This gait behaviour was accompanied by greater amount of time spent looking at the visual cues irrespective of the dual-task. Since removing vision of the lower-limbs hindered gait even under low attentional demand, restricted sensory feedback may be an important factor to the mechanisms underlying FOG.

A System for Real-Time Feedback to Improve Gait and Posture in Parkinson's Disease

For people with Parkinson's disease (PD), gait and postural impairments can significantly affect their ability to perform activities of daily living. Presentation of appropriate cues has been shown to improve gait in PD. Based on this, a treadmill-based system and experimental paradigm were developed to determine if people with PD can utilize real-time feedback (RTFB) of step length or back angle (uprightness) to improve gait and posture. Eleven subjects (mean age 67 ± 8 years) with mild-to-moderate PD (Hoehn and Yahr stage I-III) were evaluated regarding their ability to successfully utilize RTFB of back angle or step length during quiet standing and treadmill walking tasks during a single session in their medication-on state. Changes in back angle and step length due to feedback were compared using Friedman nonparametric tests with Wilcoxon Signed-Rank tests for post-hoc comparisons. Improvements in uprightness were observed as an increase in back angle during quiet standing (p = 0.005) and during treadmill walking (p = 0.005) with back angle feedback when compared to corresponding tasks without feedback. Improvements in gait were also observed as an increase in step length (p = 0.005) during step length feedback compared to tasks without feedback. These results indicate that people with mild-to-moderate PD can utilize RTFB to improve upright posture and gait. Future work will investigate the long-term effects of this RTFB paradigm and the development of systems for clinical or home-based use.

Brain activity during walking: A systematic review

BACKGROUND

This systematic review provides an overview of the literature deducing information about brain activation during (1) imagined walking using MRI/fMRI or (2) during real walking using measurement systems as fNIRS, EEG and PET.

METHODS

Three independent reviewers undertook an electronic database research browsing six databases. The search request consisted of three search fields. The first field comprised common methods to evaluate brain activity. The second search field comprised synonyms for brain responses to movements. The third search field comprised synonyms for walking.

RESULTS

48 of an initial yield of 1832 papers were reviewed. We found differences in cortical activity regarding young vs. old individuals, physically fit vs. physically unfit cohorts, healthy people vs. patients with neurological diseases, and between simple and complex walking tasks.

CONCLUSIONS

We summarize that the dimension of brain activity in different brain areas during walking is highly sensitive to task complexity, age and pathologies supporting previous assumptions underpinning the significance of cortical control. Many compensation mechanisms reflect the brain's plasticity which ensures stable walking.

Dual task performance: a comparison between healthy elderly individuals and those with Parkinson’s disease

Introduction The dual tasks (DT) is learned during the whole life and a prerequisite in functional performance in different activities of daily living. Healthy elderly have reduced ability to perform motor activities and cognitive tasks simultaneously, compared to young adults. Parkinson’s disease (PD) is the second most common neurodegenerative disease in the elderly and classic motor symptoms coexist with prejudice in cognitive domains. Objective To compare balance, gait and performance in dual tasks of individuals with Parkinson’s disease and healthy elderly. Material and method Transversal study consisted of 21 individuals with PD, classified between 1.5 to 3 in Hoehn and Yahr scale and 21 healthy individuals. To evaluate the performance on simple tasks and dual tasks the participants were submitted to five simple tasks (motor) and each was associated with a cognitive task, featuring a DT. To balance and gait evaluation was used the following instruments: Berg Balance Scale, Tinetti Scale and Dynamic Gait Index. Results In respect to gait and performance in dual tasks, there was a statistically significant difference with the worst performance for the group of individuals with PD. Conclusion It was found that the group of elderly people with PD has lower performance in the execution of concurrent tasks when compared with healthy elderly, so the DT can be introduced in rehabilitation programs to improve the performance of these patients.

Effects of dual-task training on balance and executive functions in Parkinson's disease: A pilot study

The aim of this study was to analyze the efficacy of cognitive-motor dual-task training compared with single-task training on balance and executive functions in individuals with Parkinson's disease. Fifteen subjects, aged between 39 and 75 years old, were randomly assigned to the dual-task training group (n = 8) and single-task training group (n = 7). The training was run twice a week for 6 weeks. The single-task group received balance training and the dual-task group performed cognitive tasks simultaneously with the balance training. There were no significant differences between the two groups at baseline. After the intervention, the results for mediolateral sway with eyes closed were significantly better for the dual-task group and anteroposterior sway with eyes closed was significantly better for the single-task group. The results suggest superior outcomes for the dual-task training compared to the single-task training for static postural control, except in anteroposterior sway with eyes closed.

Cognitive contributions to gait and falls: evidence and implications

Dementia and gait impairments often coexist in older adults and patients with neurodegenerative disease. Both conditions represent independent risk factors for falls. The relationship between cognitive function and gait has recently received increasing attention. Gait is no longer considered merely automated motor activity but rather an activity that requires executive function and attention as well as judgment of external and internal cues. In this review, we intend to: (1) summarize and synthesize the experimental, neuropsychological, and neuroimaging evidence that supports the role played by cognition in the control of gait; and (2) briefly discuss the implications deriving from the interplay between cognition and gait. In recent years, the dual task paradigm has been widely used as an experimental method to explore the interplay between gait and cognition. Several neuropsychological investigations have also demonstrated that walking relies on the use of several cognitive domains, including executive-attentional function, visuospatial abilities, and even memory resources. A number of morphological and functional neuroimaging studies have offered additional evidence supporting the relationship between gait and cognitive resources. Based on the findings from 3 lines of studies, it appears that a growing body of evidence indicates a pivotal role of cognition in gait control and fall prevention. The interplay between higher-order neural function and gait has a number of clinical implications, ranging from integrated assessment tools to possible innovative lines of interventions, including cognitive therapy for falls prevention on one hand and walking program for reducing dementia risk on the other.

Performance variance on walking while talking tasks: theory, findings, and clinical implications

Dual tasks that involve walking and cognitive interference tests are commonly used in mobility assessments and interventions. However, factors that explain variance in dual-task performance costs are poorly understood. We, therefore, examined the moderating effects of two putative constructs, postural reserve and hazard estimate, on performance on a walking while talking paradigm. Participants were 285 non-demented older adults (mean age = 76.9 years; %female = 54.4). Postural reserve was operationalized as the presence or absence of clinical gait abnormalities. An empirical factor, based on measures of executive functions, served as a marker for hazard estimate. The moderation effects of postural reserve and hazard estimate on dual-task costs were examined via two-way interactions in a joint linear mixed effect model. Significant dual-task costs were observed for gait speed (95% CI = 30.814 to 39.121) and cognitive accuracy (95% CI = 6.568 to 13.607). High hazard estimate had a protective effect against decline in gait speed (95% CI = -8.372 to -0.151) and cognitive accuracy (95% CI = -8.372 to -0.680). Poor postural reserve was associated with reduced decline in gait speed (95% CI = -9.611 to -0.702) but did not moderate the decline in cognitive accuracy (95% CI = -3.016 to 4.559). Assessing postural reserve and hazard estimate can help improve mobility risk assessment procedures and interventions for individuals with cognitive and movement disorders.