Transcranial direct current stimulation of dorsolateral prefrontal cortex improves dual-task gait performance in patients with Parkinson’s disease: A double blind,sham-controlled study

BackgroundDespite advances in pharmacological treatments and surgical processes, the problem of impaired dual-tasking persists in people with Parkinson’s disease (PD). Recently, transcranial direct current stimulation (tDCS) applied to the dorsolateral prefrontal cortex (DLPFC) has shown the potential to improve dual-task walking.Research QuestionCan combining left DLPFC stimulation using tDCS with dual-task performance reduce the cost of dual-tasking in individuals with PD?MethodsWe conducted a sham-controlled, cross-over, and double-blind study to investigate the effect of combining tDCS with the dual-task walk and its sustained effects among people with PD. Twenty participants with PD completed two sessions (anodal or sham tDCS) with at least a 1-week gap. Stimulation involved transferring 2 mA current through the left DLPFC for 30 min. Single- and dual-task gait was assessed before, during, immediately after, 15, and 30 min after stimulation ceased. Phoneme verbal fluency task was given as the cognitive distractor during dual task.Results and ConclusionThe results of this study show that in the dual-task condition, participants walked faster at fifteen minutes (p = 0.017) and thirty minutes (p < 0.01) after anodal tDCS ceased compared to sham. Similarly, participants generated a higher number of words per minute at fifteen minutes (p = 0.017), and thirty minutes (p < 0.01) after anodal tDCS ceased compared to sham. Furthermore, the dual-task cost (DTC) associated with gait speed was significantly lower (p = 0.022) at fifteen minutes after anodal tDCS compared to sham tDCS. However, no significant effect of tDCS was observed on gait and cognitive performance under the single-task condition. In conclusion, left DLPFC stimulation can improve dual-tasking in participants with PD and the peaking of the tDCS effect was observed at fifteen minutes after stimulation ceased.     

High-frequency repetitive transcranial magnetic stimulation enhanced treadmill training effects on gait performance in individuals with chronic stroke: A double-blinded randomized controlled pilot trial

BackgroundRepetitive transcranial magnetic stimulation (rTMS) combined with treadmill training has been suggested to modulate corticomotor activity and improve gait performance in people with Parkinson’s disease.Research questionIt is unclear whether this combination therapy has a similar effect in people with stroke. The current study aimed to investigate whether high-frequency rTMS enhances the effects of subsequent treadmill training in individuals with chronic stroke.MethodsFourteen participants meeting the selection criteria were randomly assigned to either the experimental (n = 8) or control (n = 6) group. The experimental group received 5 Hz rTMS prior to treadmill training three times per week for 3 weeks. The control group received sham rTMS before treadmill training. Walking speed, gait symmetry, corticomotor excitability, motor function of the lower extremities, and muscle activity during walking were measured before intervention, after intervention, and at 1-month follow-up.ResultsThe walking speed, spatial asymmetry of gait, and motor function of the lower extremities improved significantly in the experimental group, and these improvements exhibited significant differences in between-group comparisons. However, there was no significant difference in corticomotor excitability or brain asymmetry ratio after the intervention in each group.SignificanceThe current results revealed that applying 5 Hz high-frequency rTMS over the leg motor cortex in the affected hemisphere enhanced the effects of subsequent treadmill training on gait speed and spatial asymmetry in individuals with chronic stroke. Improvement in gait speed persisted for at least 1 month in individuals with chronic stroke.     

Attentional prioritization in dual-task walking: Effects of stroke,environment, and instructed focus

BackgroundThe impact of high distraction, real-world environments on dual-task interference and flexibility of attentional prioritization during dual-task walking in people with stroke is unknown.Research questionHow does a real-world environment affect dual-task performance and flexible task prioritization during dual-task walking in adults with and without stroke?MethodsAdults with stroke (n = 29) as well as age-, gender-, and education-matched adults without stroke (n = 23) participated. Single and dual-task walking were examined in two different environments (lab hallway, hospital lobby). Two different dual-task combinations were assessed (Stroop-gait, speech-gait). Each dual-task was performed first without explicit instruction about task prioritization (no-priority) and then with gait-priority instruction and Stroop/speech-priority instruction in randomized order.ResultsPeople with stroke had significantly slower dual-task gait speed (Stroop only) in the lobby than the lab, but the effect was not clinically meaningful. Stroop reaction time for all participants was also slower in the lobby than the lab. All participants slowed their walking speed while generating spontaneous speech, but this effect was not influenced by environment. The dual-task attention allocation strategy was generally inflexible to instructed prioritization in adults with and without stroke in both environments, however, the volitional attention allocation strategy differed for the two dual-task conditions such that speech was prioritized in the speech-gait dual-task and gait appeared to be prioritized in the Stroop-gait dual-task.SignificanceAlthough dual-tasking slows walking speed and verbal responses to auditory stimuli in people with stroke, the effects are not considerably impacted by a more complex, distracting environment. Adults with and without stroke may have difficulty overriding the preferred attention allocation strategy during dual-task walking, especially for habitual dual-tasks such as walking while speaking. It may also be that the cognitive control strategy governing task prioritization is influenced by degree of cognitive engagement.     

Dual-task treadmill walking at self-paced versus fixed speeds

BackgroundInvestigating cognitive-motor interference on the treadmill allows for better examination of motor adaptation to the dual-task challenges through the information of continuous strides. However, one of the major critiques for conducting dual-task investigation on a treadmill is the use of a constant, fixed walking speed, constraining the natural fluctuations of the speed of human walking, which could be addressed by using the self-paced feature of a feedback-controlled treadmill.Research questionDo people use different adaptation and task prioritization strategies during the dual-task treadmill walking at self-paced versus fixed speeds?MethodsEighteen healthy younger participants walked on an instrumented treadmill (1) under two speed conditions: self-paced and fixed-speed, and (2) with and without each of the four different cognitive tasks. Dynamic margins of stability (MOS), step spatiotemporal measures, kinematic variability, and local dynamic stability were computed for each trial.ResultsParticipants had significantly more local instability during self-paced than fixed-speed treadmill walking. The often-reported response of reducing stride time variability during dual-task, fixed-speed walking was not observed during dual-task, self-paced walking. In addition, there were significantly greater dual-task interference effects on stride time variability and local dynamic stability as well as the Paced Auditory Serial Addition Test performance during self-paced walking. Reduced variability in the lower-extremity joint angles, trunk motion and position, and MOS measures were observed both in dual-task, self-paced and fixed-speed walking.SignificanceHealthy younger adults had different task prioritization and greater dual-task effects on gait stability and cognitive performance during self-paced versus fixed-speed walking. However, similar adaptation strategies, in terms of gait adjustments, were used for the two walking conditions. The results suggest that self-paced treadmill walking is more challenging than the fixed-speed walking and can serve as a better alternative to the overground walking than the fixed-speed walking for the dual-task investigation.     

Factors associated with texting and walking performance in children with ADHD: The role of age,environment, and symptom severity

BackgroundChildren with ADHD show deficits in executive function, as well as motor symptoms such as difficulties in gross and fine motor skills and gait stability. Texting while walking is becoming increasingly common and is a significant health risk among people of all ages.Research questionThe objective of this work was to compare texting and walking performance between children with ADHD and controls and between two environments (indoors and outdoors), and evaluate the role of age and symptom severity in dual-task performance.MethodsNineteen children with ADHD and 30 healthy children walked across an indoors corridor and an outdoors street, with and without texting on a mobile phone. Walking and texting performance were measured using inertial measurement units and a custom-made mobile app.ResultsNo between-group differences were found in texting or walking performance. Walking and texting were similar across environments. In both groups, older children had smaller dual-task performance deficits for both gait and texting speed. Children with ADHD who had more severe symptoms of hyperactivity had larger dual task costs for gait speed outdoors (r = 0.69, p = 0.002), and those with more motor symptoms typed faster under dual-task conditions indoors (r = 0.6, p = 0.007) but were less accurate (r = − 0.60, p = 0.009).SignificanceChildren with ADHD do not demonstrate deficits in dual-task performance of a texting and walking task indoors or outdoors. The relationship of age, hyperactivity and motor symptoms with texting and walking performance supports a more personalized approach for examination of dual-task performance in children with ADHD.     

The effect of a dual task on gait speed in community dwelling older adults: A systematic review and meta-analysis

Background and purposeReduced walking speed in older adults is associated with adverse health outcomes. This review aims to examine the effect of a cognitive dual-task on the gait speed of community-dwelling older adults with no significant pathology affecting gait.Data sources and study selectionElectronic database searches were performed in, Web of Science, PubMed, SCOPUS, Embase and psychINFO. Eligibility and methodological quality was assessed by two independent reviewers. The effect size on gait speed was measured as the raw mean difference (95% confidence interval) between single and dual-task performance. Pooled estimates of the overall effect were computed using a random effects method and forest plots generated.Data extraction and data synthesis22 studies (27 data sets) with a population of 3728 were reviewed and pooled for meta-analysis. The mean walking speed of participants included in all studies was >1.0 m/s and all studies reported the effect of a cognitive dual-task on gait speed. Sub-analysis examined the effect of type of cognitive task (mental-tracking vs. verbal-fluency). Mean single-task gait speed was 1.21 (0.13) m/s, the addition of a dual-task reduced speed by 0.19 m/s to 1.02 (0.16) m/s (p < 0.00001), both mental-tracking and verbal-fluency tasks resulted in significant reduction in gait speed.Limitations and conclusionThe cross-sectional design of the studies made quality assessment difficult. Despite efforts, high heterogeneity remained, possibly due to participant characteristics and testing protocols. This meta-analysis shows that in community-dwelling older adults, the addition of a dual-task significantly reduces gait speed and may indicate the value of including dual-task walking as part of the standard clinical assessment of older people.     

Comparable walking gait performance during executive and non-executive cognitive dual-tasks in chronic stroke: A pilot study

BackgroundFalls are a serious problem among stroke survivors due to subsequent injuries, recovery setbacks, dependence, and mortality. A growing body of dual-task (DT) studies suggests a role of executive functions in gait control and falls, particularly in subacute stroke. However, few studies have compared distinct executive and non-executive tasks, nor their effects on chronic stroke gait. Research question: The purpose of this cross-sectional study was to compare the effects of distinct working memory (2-back) and inhibition (Stroop) tasks on walking gait performance in chronic stroke survivors.MethodsA pilot sample of chronic stroke survivors (n = 11, 8 males, mean age = 70.91, 6-12months post-stroke event) and age-matched healthy controls (n = 13, 4 male; mean age = 68.46) were tested. Gait performance (speed, stride time, stride time variability, stride length and stride length variability) was measured using 2 wireless inertial measurement sensors under 4 walking conditions: 1) preferred walking (single-task: ST), 2) walking with a 2-back DT, 3) walking with a Stroop DT, and 4) walking with a non-executive motor response DT. The secondary tasks were also carried out in both ST (seated) and DT conditions, to examine bidirectional effects.ResultsWhile the stroke survivor sample had a slower gait speed across conditions and tasks, there were no significant differences between the groups [F(1, 22) = 1.13, p =.299, η²p = .049] on the spatial or temporal gait characteristics recorded: gait performance was maintained during executive and non-executive DTs. In addition, we did not find a significant effect of group on cognitive task performance (all p > .052). However, we observed a cost in accuracy on the 2-back DT for both groups, suggesting resource overlap and greater cognitive load (all t > 19.72, all p < .001).SignificanceOur gait data contradict previous studies evidencing impaired gait post-stroke, suggesting functional recovery in this chronic stroke sample.     

Dual-task prioritization during overground and treadmill walking in healthy adults

BackgroundThe dual-task effect on walking performance is different during treadmill and overground walking, though the cause of this difference is unknown. This study examined the effects of task prioritization on overground and treadmill dual-task walking.MethodTwenty-two adults walked overground and on a treadmill under three dual-task conditions: prioritization of walking performance, prioritization of cognitive performance (serial subtraction in sevens), or no prioritization.ResultsCompared to single-task walking, stride velocity was reduced and stride time variability was increased during dual-task overground walking. During treadmill walking, there was no dual-task effect on walking performance, but cognitive task performance was improved. Prioritization of the cognitive task reduced the dual-task effect on stride velocity during overground walking only, whilst prioritization of the walking task reduced cognitive task performance in both walking modalities.SignificanceThese results corroborate recent findings that the dual-task effects on treadmill walking are not equivalent to those on overground walking. Healthy adults appear to prioritize cognitive task performance during treadmill dual-task walking without detrimental effects to gait. During overground walking however, allocation of attention to the secondary task reduces gait performance. These results indicate that treadmill based dual-task paradigms should not be used to infer factors which influence the cognitive control of overground walking.     

Association between fall risk and assessments of single-task and dual-task walking among community-dwelling individuals with chronic stroke: A prospective cohort study

BackgroundFalling and fall-related injuries are common among community-dwelling individuals with chronic stroke. Falls often occur during dual-task walking scenarios. Accurate fall prediction is critical for formulating effective fall prevention strategies.Research questionsCan dual-task walking tests and corresponding single-task tests predict falls among individuals with chronic stroke? Are dual-task walking tests involving visuospatial cognition more effective in predicting falls than those involving other cognitive domains?MethodsNinety-three individuals with stroke (age: 62.4 ± 6.7 years; stroke duration: 5.6 ± 4.5 years) participated in this prospective cohort study. Two mobility tasks (level-ground walking and obstacle-crossing) were performed with and without two cognitive tasks (auditory clock test and auditory Stroop test). Demographic information and clinical measures of depression, motor function, walking speed and balance were collected. Monthly telephone interviews were conducted to collect data on fall incidence, related circumstances and injuries incurred during a 12-month follow-up period. Multivariate logistic regression analysis was performed to identify predictive factors associated with future risk of falls.ResultsThirty-six participants (39%) reported one or more falls during the follow-up period. The regression model including reaction time during the auditory clock task performance while negotiating obstacles correctly classified the fall status of 80% of the participants (72% future fallers and 84% non-fallers). Performance did not differ between fallers and non-fallers on any other measures tested.SignificanceDual-task assessment combining an auditory clock task with an obstacle-crossing task has potential clinical utility for identifying future fall risk among people with chronic stroke.     

Cortical activation during gait adaptability in people with Parkinson’s disease

BackgroundPeople with Parkinson’s disease (PD) have difficulties adapting their gait. While underlying neural mechanisms involving the prefrontal cortex (PFC) have been studied across various complex walking tasks, less is known about the premotor cortex (PMC) and supplementary motor area (SMA), key cortical regions for motor planning. This study compared frontal cortical regions activation patterns using functional near-infrared spectroscopy (fNIRS), between people with PD and healthy controls (HC) during gait adaptability tasks.MethodsForty-nine people with PD (mean (SD) age: 69.5 (7.9) years) and 21 HC (69.0 (5.9) years) completed a simple walk and three randomly presented gait adaptability tasks: (i) stepping on targets, (ii) avoiding obstacles and (iii) negotiating both targets and obstacles. Cortical activity in the dorsolateral PFC (DLPFC), SMA and PMC were recorded using fNIRS. Step length, velocity and accuracy and cortical activity were contrasted between the groups and walking conditions.ResultsCompared with the HC, the PD group exhibited greater PMC activation and walked significantly slower and took shorter steps in all conditions. A statistically significant group by condition interaction indicated an increase in DLPFC cortical activation in the HC participants when undertaking the obstacle avoidance task compared with the simple walk but no increase in cortical activation in the PD group when undergoing this more challenging gait task.ConclusionsOur findings suggest people with PD have little or no DLPFC, SMA and PMC capacity beyond what they need for simple walking and in consequence need to slow their gait velocity to meet the demands of target stepping and obstacle avoidance tasks. Such behavioral and neural patterns appear consistent with concepts of compensatory over-activation and capacity limitation.     

A machine learning approach for the identification of kinematic biomarkers of chronic neck pain during single- and dual-task gait

BackgroundChanges in gait characteristics have been reported in people with chronic neck pain (CNP).Research questionCan we classify people with and without CNP by training machine learning models with Inertial Measurement Units (IMU)-based gait kinematic data?MethodsEighteen asymptomatic individuals and 21 participants with CNP were recruited for the study and performed two gait trajectories, (1) linear walking with their head straight (single-task) and (2) linear walking with continuous head-rotation (dual-task). Kinematic data were recorded from three IMU sensors attached to the forehead, upper thoracic spine (T1), and lower thoracic spine (T12). Temporal and spectral features were extracted to generate the dataset for both single- and dual-task gait. To evaluate the most significant features and simultaneously reduce the dataset size, the Neighbourhood Component Analysis (NCA) method was utilized. Three supervised models were applied, including K-Nearest Neighbour, Support Vector Machine, and Linear Discriminant Analysis to test the performance of the most important temporal and spectral features.ResultsThe performance of all classifiers increased after the implementation of NCA. The best performance was achieved by NCA-Support Vector Machine with an accuracy of 86.85%, specificity of 83.30%, and sensitivity of 92.85% during the dual-task gait using only nine features.SignificanceThe results present a data-driven approach and machine learning-based methods to identify test conditions and features from high-dimensional data obtained during gait for the classification of people with and without CNP.     

Effect of dual-tasking on walking and cognitive demands in adults with Alzheimer’s dementia experienced in using a 4-wheeled walker

BackgroundLearning to walk with a 4-wheeled walker increases cognitive demands in people with Alzheimer’s dementia (AD). However, it is expected that experience will offset the increased cognitive demand. Current research has not yet evaluated gait in people with AD experienced in using a 4-wheeled walker under complex gait situations.Research questionWhat is the effect of dual-task testing on the spatial-temporal gait parameters and cognitive performance of people with AD experienced with a 4-wheeled walker?MethodsTwenty-three adults with mild to moderate AD (87.4 ± 6.2 years, 48 % female) and at least 6 months of walker use experience participated. Three walking configurations: 1) straight path (SP), 2) Groningen Meander Walking Test (GMWT), and 3) Figure of 8 path (F8) were tested under two walking conditions: 1) single-task (walking with aid) and 2) dual-task (walking with aid and completing a cognitive task). Tri-axial accelerometers collected velocity, cadence and stride time variability (STV). Gait and cognitive task cost were the percentage difference between single-task and dual-task conditions. Two-way repeated measures ANOVAs were used to answer the study question.ResultsA significant interaction between walking configuration and condition was found for velocity (p = 0.002, ω² = 0.36), cadence (p = 0.04, ω² = 0.15) and STV (p < 0.001, ω² = 0.53). Velocity and cadence decreased and STV increased with increasing walking configuration complexity and upon dual-tasking. Dual-task gait and cognitive task cost deteriorated in all walking configurations, but gait was prioritized in the GMWT and F8 configurations.Despite familiarity, experienced walker users with AD exhibit impaired gait when walking in complex situations which increases falls risk. Upon dual-task, individuals with AD self-prioritized a posture-first strategy in complex configurations.SignificanceDual-task testing in experienced users results in slower walking, fewer steps and increased STV, which increases falls risk in people with mild to moderate AD and becomes most pronounced in complex environments.     

The effects of dual tasks on gait in children with cerebral palsy

AimTo assess the gait and cognitive performances of children with cerebral palsy (CP) during dual tasks (DT) in comparison to typically developing (TD) children.MethodThis prospective, observational, case-control study included 18 children with CP (7 girls, 11 boys; median age 12 [10:13] years and 19 controls (9 girls, 10 boys; median age 12 [10:13y6mo] years). Performances were recorded during a simple walking task, 5 DT (walking + cognitive tasks with increasing cognitive load), and 5 simple cognitive tasks (while sitting). Gait parameters were computed using an optoelectronic system during walking tasks. Six parameters were selected for analysis by a principal component analysis. Cognitive performance was measured for each cognitive task. The dual-task cost (DTC) was calculated for each DT.ResultsGait performance decreased in both groups as DT cognitive load increased (e.g., walking speed normalized by leg length, in simple task: 1.25 [1.15:1.46] s⁻¹ for CP, 1.53 [1.38:1.62] s⁻¹ for TD; DT with highest load: 0.64 [0.53:0.80] s⁻¹ for CP, 0.95 [0.75:1.08] s⁻¹ for TD). The CP group performed significantly worse than TD group in every task (including the simple task), but DTC were similar in both groups. A task effect was found for the majority of the gait parameters.InterpretationThe reduced gait performance induced by DT may generate underestimated difficulties for children with CP in daily-life situations, where DT are common. This should be considered in clinical assessments.     

Motor adaptation to cognitive challenges and walking perturbations in healthy young adults

BackgroundCognitive-walking interference is manifested when simultaneously performing a cognitive task while walking. However, majority of the dual-task walking paradigms incorporated relatively short testing trials and were focused on posing a cognitive challenge by adding a secondary cognitive task but not introducing walking perturbations.Research questionHow do healthy young adults adapt to concurrent cognitive challenges and walking perturbations in terms of task prioritization and adaptation strategies to control walking stability?MethodsEighteen healthy young participants walked with and without (1) continuous treadmill platform sways (Perturbed and Unperturbed walking), and (2) performing one of the cognitive tasks: visual and auditory Stroop tasks, Clock task, Paced Auditory Serial Addition Test (PASAT), and walk only. Primary outcome measures included cognitive task performance, mediolateral dynamic margins of stability (MOS_ML), M-L local dynamic stability, stride time variability and the dual-task interference (DTI) on these measures.ResultsGait adjustments made during Perturbed walking did not improve walking stability but instead, showing more local instability and greater gait variability (all p < 0.001) than Unperturbed walking. Participants increased average MOS_ML during Clock and PASAT compared to Walk Only for both Perturbed and Unperturbed walking (THSD, p < 0.05). Participants had significantly less DTI on stride time variability during Unperturbed walking than during Perturbed walking (p < 0.001). Participants also had significantly greater DTI on PASAT performance during Perturbed than during Unperturbed walking (THSD, p < 0.05)SignificanceParticipants prioritized the walking task under a more challenging walking condition although the adjustments made during Perturbed walking were not sufficient to maintain a similar level of walking stability as Unperturbed walking. Adjustments to the cognitive-walking challenges were differed by the type of cognitive tasks. The current findings suggest that cognitive tasks involving both working memory and information processing or visuospatial recognition or attention have greater impact on gait especially during the perturbed walking condition.     

The Effect Of Visual Dual-Tasking Interference On Walking In Healthy Young Adults

BackgroundVisual dual-task skills are essential for stable ambulation in everyday life such as walking while reading text. Gait analysis in a virtual environment can provide insight into altered walking performance while visual dual-tasking.Research questionHow visual dual-tasking including cognitive load of reading text and altered optical flow influences walking speed and stability in healthy adults? Also, is there a relationship between the mediolateral centre of mass(CoM) displacement and mediolateral trunk movement?MethodsNineteen able-bodied young adults performed self-selected walking on a treadmill in a virtual environment under the following three conditions; single-task walking, walking while viewing scrolling lines, and walking while reading text scrolling on the screen. Three-dimensional motion analysis was used to measure the effect of dual-tasking on gait velocity, step length, mediolateral CoM displacement, and mediolateral thorax inclination.ResultsThe effect of visual dual-tasking showed significantly increased walking speed and longer step length compared to single-tasking. The cognitive load of reading text while walking had a significant impact on reduced step length variability and greater mediolateral CoM displacement. This was related to the mediolateral thorax inclination.SignificanceA visual dual-task influences gait through altered optical flow and a cognitive load effect. Altered optical flow increased walking speed whilst the visual attention to read text affected foot placement and upright trunk posture, together with greater mediolateral CoM displacement. Thus, dual-tasking of reading text in a virtual environment substantially affected walking stability in healthy young people. This paradigm is therefore useful for assessment of walking stability in daily life and in the clinical setting.     

Gait balance control after fatigue: Effects of age and cognitive demand

BackgroundFatigue is a commonly mentioned symptom in older adults, and walking under the influence of fatigue frequently occurs in daily activities. Studies have reported individual effects from fatigue or cognitive demand on gait performance. However, the information on how fatigue and cognitive demand interact to affect gait balance control is still lacking.Research QuestionHow does fatigue affect walking balance control in young and older adults with and without performing a concurrent cognitive task?MethodsWe collected and analyzed motion data from 17 young and 17 older adults, who performed over-ground walking with and without a concurrent working memory test, before and after been fatigued by performing repetitive sit-to-stand movements. Three-way ANOVAs were used for statistical analysis with Age (young and older adults), Fatigue (pre- and post-fatigue), and Task (single-task and dual-task) as factors.ResultsFrom pre- to post-fatigue, an increased gait velocity was observed during dual-task walking regardless of age (p = .02). Only young adults demonstrated a significant increase in mediolateral center of mass displacement (M-L CoM) at post-fatigue (p = .019). Accuracies of the working memory test were not affected by Age, Task, or Fatigue.SignificanceOur findings revealed that gait balance control, as measured by the M-L CoM, deteriorated post-fatigue in young adults. Older adults maintained their mediolateral body sway from pre-fatigue to post-fatigue. Fatigue effects were not further exacerbated during dual-task walking, and similar cognitive performance was maintained as performance fatigability increased.     

Changes in dorsolateral prefrontal connectivity after rTMS in treatment-resistant depression: a brain perfusion SPECT study

Purpose

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive and safe alternative to electroconvulsive therapy for treatment-resistant depression (TRD). After rTMS, changes in brain SPECT perfusion have been remotely identified within medial temporal limbic areas, while no local effects have been found within the left dorsolateral prefrontal cortex (DLPFC)—i.e. under the coil. Functional changes in connectivity may underlie these remote effects. Interestingly, functional connectivity has been recently investigated using perfusion SPECT, and abnormalities identified in TRD patients. The aim of the present study is to evaluate perfusion and connectivity SPECT changes in TRD patients after rTMS of the left DLPFC. We hypothesize that changes in DLPFC networks may explain remote hypoperfusions found after rTMS.

Methods

Fifty-eight TRD patients underwent a brain SPECT before and after high-frequency rTMS of the left DLPFC. Whole-brain voxel-based changes in perfusion were evaluated with SPM8, and inter-regional correlation analysis performed to study left DLPFC functional connectivity (p?<?0.005, corrected for cluster volume).

Results

After rTMS, patients were significantly improved on Beck Depression Inventory score (p?<?0.0001). Considering a 50% reduction threshold, 27 patients were identified as responders (47%). After rTMS, perfusion changes were not found locally within the left DLPFC, but remotely within the bilateral temporal lobes, including limbic areas. Inter-regional correlation SPECT analysis brings out a decrease of connectivity between the left DLPFC and both the cingulate/medial frontal cortex and bilateral medial temporal limbic areas, in relation with the clinical response.

Conclusions

rTMS of DLPFC in TRD patients leads to remote temporal hypoperfusions in relation with changes in functional connectivity between the DLPFC and the default mode network, especially including medial temporal limbic areas.

     

Paretic propulsion as a measure of walking performance and functional motor recovery post-stroke: A review

BackgroundAlthough walking speed is the most common measure of gait performance post-stroke, improved walking speed following rehabilitation does not always indicate the recovery of paretic limb function. Over the last decade, the measure paretic propulsion (Pp, defined as the propulsive impulse generated by the paretic leg divided by the sum of the propulsive impulses of both legs) has been established as a measure of paretic limb output and recently targeted in post-stroke rehabilitation paradigms. However, the literature lacks a detailed synthesis of how paretic propulsion, walking speed, and other biomechanical and neuromuscular measures collectively relate to post-stroke walking performance and motor recovery.ObjectiveThe aim of this review was to assess factors associated with the ability to generate Pp and identify rehabilitation targets aimed at improving Pp and paretic limb function.MethodsRelevant literature was collected in which paretic propulsion was used to quantify and assess propulsion symmetry and function in hemiparetic gait.ResultsParetic leg extension during terminal stance is strongly associated with Pp. Both paretic leg extension and propulsion are related to step length asymmetry, revealing an interaction between spatiotemporal, kinematic and kinetic metrics that underlies hemiparetic walking performance. The importance of plantarflexor function in producing propulsion is highlighted by the association of an independent plantarflexor excitation module with increased Pp. Furthermore, the literature suggests that although current rehabilitation techniques can improve Pp, these improvements depend on the patient’s baseline plantarflexor function.SignificancePp provides a quantitative measure of propulsion symmetry and should be a primary target of post-stroke gait rehabilitation. The current literature suggests rehabilitation techniques that target both plantarflexor function and leg extension may restore paretic limb function and improve gait asymmetries in individuals post stroke.     

A comparison of two walking while talking paradigms in aging

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