Dopamine improves defective cortical and muscular connectivity during bilateral control of gait in Parkinson's disease.

Parkinson's Disease (PD)-typical declines in gait coordination are possibly explained by weakness in bilateral cortical and muscular connectivity. Here, we seek to determine whether this weakness and consequent decline in gait coordination is affected by dopamine levels. To this end, we compare cortico-cortical, cortico-muscular, and intermuscular connectivity and gait outcomes between body sides in people with PD under ON and OFF medication states, and in older adults. In our study, participants walked back and forth along a 12 m corridor. Gait events (heel strikes and toe-offs) and electrical cortical and muscular activities were measured and used to compute cortico-cortical, cortico-muscular, and intermuscular connectivity (i.e., coherences in the alpha, beta, and gamma bands), as well as features characterizing gait performance (e.g., the step-timing coordination, length, and speed). We observe that people with PD, mainly during the OFF medication, walk with reduced step-timing coordination. Additionally, our results suggest that dopamine intake in PD increases the overall cortico-muscular connectivity during the stance and swing phases of gait. We thus conclude that dopamine corrects defective feedback caused by impaired sensory-information processing and sensory-motor integration, thus increasing cortico-muscular coherences in the alpha bands and improving gait.

Transcranial direct current stimulation suggests not improving postural control during adapted tandem position in people with Parkinson's disease: A pilot study.

BACKGROUND: Balance impairments in people with Parkinson's disease (PD) demonstrated mainly in challenging postural tasks, such as increased body oscillation may be attributed to the deficits in the brain structures functionality involved in postural control (e.g., motor cortex, midbrain, and brainstem). Although promising results, the effect of transcranial direct current stimulation (tDCS) on postural control in people with PD is unclear, especially in objective measures such as the center of pressure (CoP) parameters. Thus, we analyzed the effects of a single session of tDCS on the CoP parameters during the adapted tandem position in people with PD. METHODS: Nineteen people with PD participated in this crossover, randomized, and double-blind study. Anodal tDCS was applied over the primary motor cortex in two conditions of stimulation (2 mA/active and sham) on two different days for 20 min immediately before the postural control evaluation. Participants remained standing in an adapted tandem position for the postural control assessment for 30 s (three trials). CoP parameters were acquired by a force plate. RESULTS: No significant differences were demonstrated between stimulation conditions (p-value range = 0.15-0.89). CONCLUSIONS: Our results suggested that a single session of tDCS with 2 mA does not improve the postural control of people with PD during adapted tandem.

Facilitating Access to Current, Evidence-Based Health Information for Non-English Speakers.

Scientific communication is crucial for the development of societies and the advancement of knowledge. However, many countries, and, consequently, their researchers, clinicians and community members, lack access to this information due to the information being disseminated in English rather than their native language. In this viewpoint, we aim to discuss the impacts of this problem and also outline recommendations for facilitating non-English speakers' access to current, evidence-based health information, thus extending the impact of science beyond academia. First, the authors discuss the barriers to accessing scientific health information for non-English speakers and highlight the negative impact of imposing English as a predominant language in academia. Next, the authors discuss the impacts of reduced access to clinical information for non-English speakers and how this reduced access impacts clinicians, clients, and health systems. Finally, the authors provide recommendations for enhancing access to scientific communication worldwide.

Being physically active minimizes the effects of leg muscle fatigue on obstacle negotiation in people with Parkinson's disease.

It is challenging for people with Parkinson's disease (PwPD) to adjust their gait to perturbations, including fatigue. Obstacle negotiation increases the risk of tripping and falling in PD. Being physically active can improve gait control and the ability to negotiate obstacles while walking under fatigue state. We thus determined the effects of Parkinson's disease, fatigue, and level of physical activity on gait during the approach to and crossing an obstacle during gait. Forty participants were stratified to people with Parkinson's disease active and inactive, and control individuals active and inactive. Participants walked on an 8 m walkway and stepped over an obstacle placed at the middle (4 m). They performed three trials before and after repeated sit-to-stand (rSTS)-induced fatigue state. Maximum voluntary force was assessed before and after rSTS. We measured the length, width, duration, and velocity of the approach (stride before obstacle) and crossing (step over the obstacle) phases and the leading and trailing placements and clearance during crossing phase. Fatigue trait was determined by multidimensional fatigue inventory. Before rSTS, people with Parkinson's disease inactive vs. other subgroups approached the obstacle using 18-28% shorter, wider and slower steps and crossed the obstacle slower (all p < 0.04). After rSTS, people with Parkinson's disease inactive increased (23-34%) stride length and velocity and decreased (-21%) the step width (p < 0.01). People with Parkinson's disease approached the obstacle similarly to control individuals. Physical activity minimizes Parkinson's disease-typical gait impairments during obstacle negotiation and affords a protective effect against fatigue-effects on obstacle negotiation.

Effect of different types of exercises on psychological and cognitive features in people with Parkinson's disease: A randomized controlled trial.

BACKGROUND: Parkinson's disease (PD) is a neurodegenerative and progressive disease marked by the presence of motor and non-motor symptoms, as psychological and cognitive impairment. Physical exercises have been prescribed as complementary therapy for PD, and the type of intervention and duration of the intervention should be taken into account. OBJECTIVE: We aimed to compare the effect of different exercise modalities (functional mobility, multimodal and cognitive) and length (4 and 8 months) on psychological and cognition in people with PD. This study followed the CONSORT extension for non-pharmacological trials. METHODS: In this randomized controlled trial, we assessed 107 participants between 2011 and 2013. At the end of 3 years, participants with PD (mild to moderate stages) who achieved the criteria were assessed considering 3 different groups of exercise: Multimodal (n=38), Functional Mobility (n=33) and Mental/Leisure (n=36). All 3 interventions were performed for 32 weeks, twice a week, with 60min for each session (64 sessions in total). Psychological and cognitive function were assessed at baseline and after 4 and 8 months. RESULTS: The Functional Mobility and Mental/Leisure training had a potential effect on maintaining cognitive function (executive function, attention and work memory). The Multimodal training did not show a benefit for cognitive features and was not even able to delay the progressive decline in cognitive functions; however, this modality had a positive effect on physical stress after 8 months of exercise. CONCLUSIONS: An intervention that requires high complexity and specific activities, such as locomotor and cognitive exercise, provides a maintenance effect against the degeneration in cognition associated with the progression of PD and thus can delay the progressive decline in cognitive function in PD.

Effects of experimentally induced fatigue on healthy older adults' gait: A systematic review.

INTRODUCTION: While fatigue is ubiquitous in old age and visibly interferes with mobility, studies have not yet examined the effects of self-reported fatigue on healthy older adults' gait. As a model that simulates this daily phenomenon, we systematically reviewed eleven studies that compared the effects of experimentally induced muscle and mental performance fatigability on gait kinematics, variability, kinetics, and muscle activity in healthy older adults. METHODS: We searched for studies in databases (PubMed and Web of Science) using Fatigue, Gait, and Clinical conditions as the main terms and extracted the data only from studies that experimentally induced fatigue by sustained muscle or mental activities in healthy older adults. RESULTS: Eleven studies were included. After muscle performance fatigability, six of nine studies observed increases in stride length, width, gait velocity (Effect Size [ES] range: 0.30 to 1.22), inter-stride trunk acceleration variability (ES: 2.06), and ankle muscle coactivation during gait (ES: 0.59, n = 1 study). After sustained mental activity, the coefficient of variation of stride outcomes increased (ES: 0.59 to 0.67, n = 1 study) during dual-task but not single-task walking. CONCLUSION: Muscle performance fatigability affects spatial and temporal features of gait and, mainly, inter-stride trunk acceleration variability. In contrast, sustained mental activity tends only to affect step variability during dual tasking. A critical and immediate step for future studies is to determine the effects of self-reported fatigue on gait biomechanics and variability in healthy older adults to verify the viability of experimentally induced fatigue as a model for the study of gait adaptability in old age.

Minimal effects of age and prolonged physical and mental exercise on healthy adults' gait.

BACKGROUND: Gait adaptability in old age can be examined by responses to various perturbations. Fatigability due to mental or muscle exercises can perturb internal cognitive and muscle resources, necessitating adaptations in gait. RESEARCH QUESTION: What are the effects of age and mental and muscle fatigability on stride outcomes and gait variability? METHODS: Twelve older (66-75yrs) and twelve young (20-25 yrs) adults walked at 1.2 m/s before and after two fatigue conditions in two separate sessions. Fatigue conditions were induced by repetitive sit-to-stand task (RSTS) and by 30-min of mental tasks and randomized between days (about a week apart). We calculated the average and coefficient of variation of stride length, width, single support, swing time and cadence, and the detrended fluctuations analysis (DFA) based on 120 strides time intervals. We also calculated multi-scale sample entropy (MSE) and the maximal Lyapunov exponent (λmax) of mediolateral (ML) and anteroposterior (AP) of the Center of Pressure (CoP) trajectories. RESULTS: In both age groups, RSTS modestly affected stride length, single support time, cadence, and CV of stride length (p ≤ 0.05), while the mental task did not affect gait. After fatigability, λmax - ML increased (p ≤ 0.05), independent of fatigue condition. All observed effects were small (η²: 0.001 to 0.02). SIGNIFICANCE: Muscle and mental fatigability had minimal effects on gait in young and healthy older adults possibly because treadmill walking makes gait uniform. It is still possible that age-dependent muscle activation underlies the uniform gait on the treadmill. Age- and fatigability effects might be more overt during real life compared with treadmill walking, creating a more effective model for examining gait and age adaptability to fatigability perturbations.

Author Correction: Variability of crossing phase in older people with Parkinson's disease is dependent of obstacle height.

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Postural control after unexpected external perturbation: Effects of Parkinson's disease subtype.

Different clinical subtypes of Parkinson's disease (PD) have long been recognized. Recent studies have focused on two PD subtypes: Postural Instability and Gait Difficulty (PIGD) and Tremor Dominant (TD). PIGD patients have greater difficulties in postural control in relation to TD. However, knowledge about the differences in reactive adjustment mechanisms following a perturbation in TD and PIGD is limited. This study aimed to compare reactive postural adjustments under unexpected external perturbation in TD, PIGD, and control group (CG) subjects. Forty-five individuals (15 TD, 15 PIGD, and 15 CG) participated in this study. Postural perturbation was applied by the posterior displacement of the support surface in an unexpected condition. The velocity (15 cm/s) and displacement (5 cm/s) of perturbation were the same for all participants. Center of pressure (CoP) and center of mass (CoM) were analyzed for two reactive windows after the perturbation (0-200 ms and 200-700 ms). The Bonferroni post hoc test indicated a higher range of CoP in the PIGD when compared to the CG (p = 0.021). The PIGD demonstrated greater time to recover the stable posture compared to the TD (p = 0.017) and CG (p = 0.003). Furthermore, the TD showed higher AP-acceleration peak of CoM when compared to the PIGD (p = 0.048) and CG (p = 0.013), and greater AP-acceleration range of CoM in relation to the CG (p = 0.022). These findings suggest that PD patients present worse reactive postural control after perturbation compared to healthy older individuals. CoP and CoM parameters are sensitive to understand and detect the differences in reactive postural mechanisms in PD subtypes.

Variability of crossing phase in older people with Parkinson's disease is dependent of obstacle height.

Our aim was investigating variability in spatiotemporal parameters and kinetics of obstacle avoidance steps of different height obstacles in people with Parkinson's disease (PD) and healthy older people. Twenty-eight participants have included (15 PD - stage disease: 2.1 ± 0.4 pts) and 13 healthy older people (control group). Each subject performed 10 trials of the following tasks: low obstacle, intermediate obstacle and high obstacle. The presentation order was randomized by block for each condition and participant. The spatiotemporal parameters was collected by GAITRite. An optoelectronic system (Optotrak Northern Digital Inc.) with 100 Hz of frequency was used to collect obstacle parameters. The kinect parameters (propulsion impulse and braking impulse) were acquire through two force plates (AccuGait), with a frequency of acquisition 200 Hz. Intersteps variability was calculated throughout mean values, standard deviation and coefficient of variation of two obstacle avoidance steps for each trial. PD group presented greater variability than control group on vertical and horizontal distances to the obstacle. Obstacle height did not change kinect's parameters for both groups. The combination of task complexity (obstacle height) and disease impairments (gait alteration, loss of balance, etc) contributing for greater variability of Parkinson's group. Besides, low obstacle and high obstacle seem to exacerbate variability of distance between obstacle and foot.