The effects of subsensory electrical noise stimulation on the reactive control of balance during support surface perturbations.

Background: The ability to respond effectively to balance perturbations is crucial for fall prevention. Subsensory electrical stimulation (SES) applied to the skin leads to improved proactive balance control but there is limited evidence on the SES effect on reactive balance control.

Research Questions: To test the efficiency of SES in improving reactive balance control against unpredictable support surface perturbations and to compare the effects of SES applied to the trunk and the lower legs.

Overview of Radar-Based Gait Parameter Estimation Techniques for Fall Risk Assessment.

Current methods for fall risk assessment rely on Quantitative Gait Analysis (QGA) using costly optical tracking systems, which are often only available at specialized laboratories that may not be easily accessible to rural communities. Radar placed in a home or assisted living facility can acquire continuous ambulatory recordings over extended durations of a subject's natural gait and activity. Thus, radar-based QGA has the potential to capture day-to-day variations in gait, is time efficient and removes the burden for the subject to come to a clinic, providing a more realistic picture of older adults' mobility.

Validation of a micro-doppler radar for measuring gait modifications during multidirectional visual perturbations.

Background: Changes in spatio-temporal gait parameters and their variability during balance-challenging tasks are markers of motor performance linked to fall risk. Radio frequency (RF) sensors hold great promise towards achieving continuous remote monitoring of these parameters.

Research Questions: To establish the concurrent validity of RF-based gait metrics extracted using micro-Doppler (µD) signatures and to determine whether these metrics are sensitive to gait modifications created by multidirectional visual perturbations.

Microstates of Accelerating and Supersymmetric AdS_{4} Black Holes from the Spindle Index.

We provide a first principles derivation of the microscopic entropy of a very general class of supersymmetric, rotating, and accelerating black holes in AdS_{4}. This is achieved by analyzing the large-N limit of the spindle index and completes the construction of the first example of a holographic duality involving supersymmetric field theories defined on orbifolds with conical singularities.

Validity and reliability of inertial measurement units for gait assessment within a post stroke population.

Background: The ability to objectively measure spatiotemporal metrics within individuals post-stroke is integral to plan appropriate intervention, track recovery, and ultimately improve efficacy of rehabilitation programs. Inertial measurement units (IMUs) provide a means to systematically collect gait-specific metrics that could not otherwise be obtained from clinical outcomes. However, the use of IMUs to measure spatiotemporal parameters in stroke survivors has yet to be validated.

Entropy Functions for Accelerating Black Holes.

We introduce an entropy function for supersymmetric accelerating black holes in four-dimensional anti-de Sitter space that uplift on general Sasaki-Einstein manifolds X_{7} to solutions of M theory. This allows one to compute the black hole entropy without knowing the explicit solutions. A dual holographic microstate counting would follow from computing certain supersymmetric partition functions of Chern-Simons-matter theories compactified on a spindle.

Subsensory electrical noise stimulation applied to the lower trunk improves postural control during visual perturbations.

Background: Low levels of sensory noise applied to the skin through electrical stimulation (ES) can improve balance control through a mechanism called stochastic resonance (SR). Little is known regarding the extent subsensory ES can improve reactive control of balance after unanticipated balance perturbations and the best location where to apply the stimulation.

Research Questions: How efficient is subsensory ES in improving reactive control of balance following visual perturbations delivered in a virtual reality (VR) environment? 2) Does lower trunk stimulation have greater effects than lower legs stimulation?

Methods: Eighteen healthy young adults stood on a force plate while wearing a Valve Index VR headset in eyes closed (EC), eyes open (EO), eyes open with anteroposterior visual perturbations (AP) and eyes open with mediolateral visual perturbations (ML) conditions.

Acute Effects of a Perturbation-Based Balance Training on Cognitive Performance in Healthy Older Adults: A Pilot Study.

Aging is accompanied by an alteration in the capacity to ambulate, react to external balance perturbations, and resolve cognitive tasks. Perturbation-based balance training has been used to induce adaptations of gait stability and reduce fall risk. The compensatory reactions generated in response to external perturbations depend on the activation of specific neural structures.

D3-Branes Wrapped on a Spindle.

We construct supersymmetric AdS_{3}×Σ solutions of minimal gauged supergravity in D=5, where Σ is a two-dimensional orbifold known as a spindle. Remarkably, these uplift on S^{5}, or more generally on any regular Sasaki-Einstein manifold, to smooth solutions of type IIB supergravity. The solutions are dual to d=2, N=(0,2) SCFTs and we show that the central charge for the gravity solution agrees with a field theory calculation associated with D3-branes wrapped on Σ.

Overground gait training using virtual reality aimed at gait symmetry.

This study investigated if training in a virtual reality (VR) environment that provides visual and audio biofeedback on foot placement can induce changes to spatial and temporal parameters of gait during overground walking. Eighteen healthy young adults walked for 23 min back and forth on an instrumented walkway in three different conditions: (i) real environment (RE), (ii) virtual environment (VE) with no biofeedback, and (iii) VE with biofeedback. Visual and audio biofeedback while stepping on virtual footprint targets appearing along a straight path encouraged participants to walk with an asymmetrical step length (SL).

Uncontrolled manifold analysis of the effects of a perturbation-based training on the organization of leg joint variance in cerebellar ataxia.

Walking patterns of persons affected by cerebellar ataxia (CA) are characterized by wide stride-to-stride variability ascribable to: the background pathology-related sensory-motor noise; the motor redundancy, i.e., an excess of elemental degrees of freedom that overcomes the number of variables underlying a specific task performance.

Age-related differences in gait adaptations during overground walking with and without visual perturbations using a virtual reality headset.

Older adults have difficulty adapting to new visual information, posing a challenge to maintain balance during walking. Virtual reality can be used to study gait adaptability in response to discordant sensorimotor stimulations. This study aimed to investigate age-related modifications and propensity for visuomotor adaptations due to continuous visual perturbations during overground walking in a virtual reality headset.

Dual-Motor-Task of Catching and Throwing a Ball During Overground Walking in Virtual Reality.

Virtual Reality is a versatile platform to study human behavior in simulated environments and to develop interventions for functional rehabilitation. In this work, we designed a dual-task paradigm in a virtual environment where both tasks demand motor skills. Twenty-one healthy adults (mean age: 24.

Phase I Single-Blinded Randomized Controlled Trial Comparing Balance and Aerobic Training in Degenerative Cerebellar Disease.

Introduction: Primary deficits in individuals with cerebellar degeneration include ataxia, unstable gait, and incoordination. Balance training is routinely recommended to improve function whereas little is known regarding aerobic training.

Objective: To determine the feasibility of conducting a randomized trial comparing balance and aerobic training in individuals with cerebellar degeneration.

Phase I randomized single-blinded controlled study investigating the potential benefit of aerobic exercise in degenerative cerebellar disease.

Objectives: To investigate whether people with cerebellar degeneration can perform rigorous aerobic exercise and to assess the clinical impact of training.

Design: Randomized single-blinded controlled, feasibility study comparing aerobic training to no training.

Setting: Home intervention, assessments conducted at an academic medical center.

Development of a Virtual Floor Maze Test - Effects of Distal Visual Cues and Correlations With Executive Function in Healthy Adults.

Virtual reality (VR) is a useful tool to assess and improve spatial navigation, a complex skill and relevant marker for progression of dementia. A fully-immersive VR system that allows the user to physically navigate in the space can provide an ecologically valid environment for early detection and remediation of cognitive and navigational deficits. The aim of this study was to develop a virtual version of the floor maze test (VR-FMT), a navigational test that requires navigating through an unfamiliar two-dimensional floor maze.

Stand Trainer With Applied Forces at the Pelvis and Trunk: Response to Perturbations and Assist-As-Needed Support.

Functional rehabilitation of patients with spinal cord injury remains a current challenge. Training these patients to successfully stand is the first step towards restoring advanced skills such as walking. To address this need, we have developed a novel robotic stand trainer that can apply controlled forces on the trunk and the pelvis of a user, while controlling the knee angle.

Effects of repeated waist-pull perturbations on gait stability in subjects with cerebellar ataxia.

Background: Damage to the cerebellum can affect neural structures involved in locomotion, causing gait and balance disorders. However, the integrity of cerebellum does not seem to be critical in managing sudden and unexpected environmental changes such as disturbances during walking. The cerebellum also plays a functional role in motor learning.

Gait adaptations during overground walking and multidirectional oscillations of the visual field in a virtual reality headset.

Background: Virtual reality (VR) has been used to study locomotor adaptability during balance-demanding tasks by exploring how humans react and adapt to the virtual environment (VE) and discordant sensorimotor stimulations. Previous research primarily focused on treadmill walking and little is known regarding the propensity for gait adaptations during overground walking and over time.

Research Question: To what extent healthy young adults modify and adapt gait during overground walking in a VE and with continuous multidirectional perturbations of the visual field while wearing a VR headset?

Methods: Twelve healthy young adults walked for 6 min on an instrumented walkway in four different conditions: RE, VE, and VE with antero-posterior (AP) and medio-lateral (ML) pseudo-random oscillations of the visual field.

Adaptation of Stability during Perturbed Walking in Parkinson's Disease.

Gait and balance disorders are major problems that contribute to falls among subjects with Parkinson's disease (PD). Strengthening the compensatory responses through the use of balance perturbations may improve balance in PD. To date, it is unclear how PD affects the ability to react and adapt to perturbations delivered while walking.

A single session of perturbation-based gait training with the A-TPAD improves dynamic stability in healthy young subjects.

Gait and balance disorders are among the most common causes of falls in older adults. Most falls occur as a result of unexpected hazards while walking. In order to improve the effectiveness of current fall-prevention programs, new balance training paradigms aim to strengthen the control of the compensatory responses required after external perturbations.

Aging does not affect the intralimb coordination elicited by slip-like perturbation of different intensities.

This study was aimed at verifying whether aging modifies intralimb coordination strategy during corrective responses elicited by unexpected slip-like perturbations delivered during steady walking on a treadmill. To this end, 10 young and 10 elderly subjects were asked to manage unexpected slippages of different intensities. We analyzed the planar covariation law of the lower limb segments, using the principal component analysis, to verify whether elevation angles of older subjects covaried along a plan before and after the perturbation.

Exploration of Two Training Paradigms Using Forced Induced Weight Shifting With the Tethered Pelvic Assist Device to Reduce Asymmetry in Individuals After Stroke: Case Reports.

Many robotic devices in rehabilitation incorporate an assist-as-needed haptic guidance paradigm to promote training. This error reduction model, while beneficial for skill acquisition, could be detrimental for long-term retention. Error augmentation (EA) models have been explored as alternatives.

Principal component analysis can decrease neural networks performance for incipient falls detection: A preliminary study with hands and feet accelerations.

Fall-related accidents constitute a major problem for elderly people and a burden to the health-care national system. It is therefore important to design devices (e.g.

Stability against backward balance loss: Age-related modifications following slip-like perturbations of multiple amplitudes.

Falls are one of the most serious problems in the elderly. Although previous studies clearly link the increased risk of falls with ageing, the mechanisms responsible for the modifications of reactive motor behaviours in response to external perturbations are not yet fully understood. This study investigated how the stability against backward balance loss is affected by aging and intensity of perturbations.