Motor Learning and Parkinson Disease: Refinement of Movement Velocity and Endpoint Excursion in a Limits of Stability Balance Task

Effects of protective step training on proactive and reactive motor adaptations in Parkinson's disease patients

The aim of this study was to investigate to what extent PD affects the ability to walk, respond to balance perturbations in a single training session, and produce acute short-term effects to improve compensatory reactions and control of unperturbed walking stability. Understanding the mechanism of compensation and neuroplasticity to unexpected step perturbation training during walking and static stance can inform treatment of PD by helping to design effective training regimens that remediate fall risk. Current rehabilitation therapies are inadequate at reducing falls in people with Parkinson's disease (PD). While pharmacologic and surgical treatments have proved largely ineffective in treating postural instability and gait dysfunction in people with PD, studies have demonstrated that therapy specifically focusing on posture, gait, and balance may significantly improve these factors and reduce falls. The primary goal of this study was to assess the effectiveness of a novel and promising intervention therapy (protective step training - i.e., PST) to improve balance and reduce falls in people with PD. A secondary goal was to understand the effects of PST on proactive and reactive feedback responses during stance and gait tasks. Multiple-baseline, repeated measures analyses were performed on the multitude of proactive and reactive performance measures to assess the effects of PST on gait and postural stability parameters. In general, the results indicate that participants with PD were able to use experiences with perturbation training to integrate and adapt feedforward and feedback behaviors to reduce falls. The ability of the participants with PD to adapt to changes in task demands suggests that individuals with PD could benefit from the protective step training to facilitate balance control during rehabilitation.

Motor Memory Consolidation Deficits in Parkinson's Disease: A Systematic Review with Meta-Analysis

BACKGROUND

The ability to encode and consolidate motor memories is essential for persons with Parkinson's disease (PD), who usually experience a progressive loss of motor function. Deficits in memory encoding, usually expressed as poorer rates of skill improvement during motor practice, have been reported in these patients. Whether motor memory consolidation (i.e., motor skill retention) is also impaired is unknown.

OBJECTIVE

To determine whether motor memory consolidation is impaired in PD compared to neurologically intact individuals.

METHODS

We conducted a pre-registered systematic review (PROSPERO: CRD42020222433) following PRISMA guidelines that included 46 studies.

RESULTS

Meta-analyses revealed that persons with PD have deficits in retaining motor skills (SMD = -0.17; 95% CI = -0.32, -0.02; p = 0.0225). However, these deficits are task-specific, affecting sensory motor (SMD = -0.31; 95% CI -0.47, -0.15; p = 0.0002) and visuomotor adaptation (SMD = -1.55; 95% CI = -2.32, -0.79; p = 0.0001) tasks, but not sequential fine motor (SMD = 0.17; 95% CI = -0.05, 0.39; p = 0.1292) and gross motor tasks (SMD = 0.04; 95% CI = -0.25, 0.33; p = 0.7771). Importantly, deficits became non-significant when augmented feedback during practice was provided, and additional motor practice sessions reduced deficits in sensory motor tasks. Meta-regression analyses confirmed that deficits were independent of performance during encoding, as well as disease duration and severity.

CONCLUSION

Our results align with the neurodegenerative models of PD progression and motor learning frameworks and emphasize the importance of developing targeted interventions to enhance motor memory consolidation in PD.

Tai chi-muscle power training for children with developmental coordination disorder: a randomized controlled trial

This study compared the effectiveness of tai chi (TC) muscle power training (MPT), TC alone, MPT alone, and no training for improving the limits of stability (LOS) and motor and leg muscular performance and decreasing falls in children with developmental coordination disorder (DCD). One hundred and twenty-one children with DCD were randomly assigned to the TC-MPT, TC, MPT, or control group. The three intervention groups received TC-MPT, TC, or MPT three times per week for 3 months. Measurements were taken before and after the intervention period. The primary outcomes were the LOS completion time and dynamic LOS scores. The secondary outcomes included the Movement Assessment Battery for Children-Second Edition total test score and percentile rank, knee muscle peak force and time to peak force, and the number of falls. None of the interventions affected the LOS test scores. Improvements in the peak forces of the knee extensors and flexors were demonstrated in the TC (p = 0.006) and MPT groups (p = 0.032), respectively. The number of falls also decreased in these two groups (p < 0.001). Thus, clinicians may prescribe TC or MPT for children with DCD to increase their knee muscle strength and reduce their risk of falls.

What Can Altered Auditory Feedback Paradigms Tell Us About Vocal Motor Control in Individuals With Voice Disorders?

Purpose

The goal of this review article is to provide a summary of the progression of altered auditory feedback (AAF) as a method to understand the pathophysiology of voice disorders. This review article focuses on populations with voice disorders that have thus far been studied using AAF, including individuals with Parkinson's disease, cerebellar degeneration, hyperfunctional voice disorders, vocal fold paralysis, and laryngeal dystonia. Studies using AAF have found that individuals with Parkinson's disease, cerebellar degeneration, and laryngeal dystonia have hyperactive auditory feedback responses due to differing underlying causes. In persons with PD, the hyperactivity may be a compensatory mechanism for atypically weak feedforward motor control. In individuals with cerebellar degeneration and laryngeal dystonia, the reasons for hyperactivity remain unknown. Individuals with hyperfunctional voice disorders may have auditory-motor integration deficits, suggesting atypical updating of feedforward motor control.

Conclusions

These findings have the potential to provide critical insights to clinicians in selecting the most effective therapy techniques for individuals with voice disorders. Future collaboration between clinicians and researchers with the shared objective of improving AAF as an ecologically feasible and valid tool for clinical assessment may provide more personalized therapy targets for individuals with voice disorders.

Parkinson's disease: Alterations of motor plasticity and motor learning

This chapter reviews the alterations in motor learning and motor cortical plasticity in Parkinson's disease (PD), the most common movement disorder. Impairments in motor learning, which is a hallmark of basal ganglia disorders, influence the performance of motor learning-related behavioral tasks and have clinical implications for the management of disturbance in gait and posture, and for rehabilitative management of PD. Although plasticity is classically induced and assessed in sliced preparation in animal models, in this review we have concentrated on the results from non-invasive brain stimulation techniques such as transcranial magnetic stimulation (TMS), transcranial alternating current stimulation (tACS) and transcranial direct current stimulation (tDCS) in patients with PD, in addition to a few animal electrophysiologic studies. The chapter summarizes the results from different cortical and subcortical plasticity investigations. Plasticity induction protocols reveal deficient plasticity in PD and these plasticity measures are modulated by medications and deep brain stimulation. There is considerable variability in these measures that are related to inter-individual variations, different disease characteristics and methodological considerations. Nevertheless, these pathophysiologic studies expand our knowledge of cortical excitability, plasticity and the effects of different treatments in PD. These tools of modulating plasticity and motor learning improve our understanding of PD pathophysiology and help to develop new treatments for this disabling condition.

A Mobile Phone App-Based Tai Chi Training in Parkinson's Disease: Protocol for a Randomized Controlled Study

Introduction: With an increasing number of China's aging population, Parkinson's disease (PD) increases year by year. Persons with PD exhibit abnormal balance functions, leading to motor skills difficulties, such as unstable walking or even falling. Therefore, activities of daily living and quality of life are affected. This study aims to explore the effectiveness of Tai Chi training based on the mobile phone app in improving the balance ability of persons with PD. Methods and Analysis: A randomized, single-blind, parallel controlled trial will be conducted in this study. One hundred forty-four persons with PD who meet the inclusion criteria will be randomly divided into a 1:1:1 ratio: (1) control group, (2) basic experimental group (basic app with no Tai Chi training features), and (3) balanced-enhanced experimental group (basic app with Tai Chi training features). Individuals with PD will be evaluated on balance and motor function outcomes. The primary outcome measure is the limits of stability (including the maximum excursion and direction control); the secondary outcome measures include the Unified Parkinson's Disease Rating Scale III (UPDRS-III), Berg Balance Scale (BBS), Functional Reach Test (FRT), Timed Up & Go (TUG), 6-Minute Walk Test (6MWT), and 39-item Parkinson's Disease Questionnaire (PDQ-39). Each group of patients will go through an assessment at baseline, 17 and 33 weeks. Discussion: This study will evaluate the effectiveness of the mobile phone app Tai Chi training on the balance function of persons with PD. We assume that a challenging Tai Chi project based on a mobile phone app will improve balance in the short and long term. As walking stability progresses, it is expected that daily activities and quality of life improve. These findings will be used to improve the effectiveness of future home management measures for persons with PD. Ethics and Dissemination: This study has been approved by the ethical review committee of the Shanghai University of Sport (approval number: 102772019RT056). Informed consent will be obtained from all participants or their guardians. The authors intend to submit the study findings to peer-reviewed journals or academic conferences to be published. Clinical Trial Registration: Chinese Clinical Trial Registry (ChiCTR2000029135).

Role of muscle coactivation in adaptation of standing posture during arm reaching

The ability to maintain stable, upright standing in the face of perturbations is a critical component of daily life. A common strategy for resisting perturbations and maintaining stability is muscle coactivation. Although arm muscle coactivation is often used during adaptation of seated reaching movements, little is known about postural muscle activation during concurrent adaptation of arm and standing posture to novel perturbations. In this study we investigate whether coactivation strategies are employed during adaptation of standing postural control, and how these strategies are prioritized for adaptation of standing posture and arm reaching, in two different postural stability conditions. Healthy adults practiced planar reaching movements while grasping the handle of a robotic arm and standing on a force plate; the robotic arm generated a velocity-dependent force field that created novel perturbations in the forward (more stable) or backward (less stable) direction. Surprisingly, the degree of arm and postural adaptation was not influenced by stability, with similar adaptation observed between conditions in the control of both arm movement and standing posture. We found that an early coactivation strategy can be used in postural adaptation, similar to what is observed in adaptation of arm reaching movements. However, the emergence of a coactivation strategy was dependent on perturbation direction. Despite similar adaptation in both directions, postural coactivation was largely specific to forward perturbations. Backward perturbations led to less coactivation and less modulation of postural muscle activity. These findings provide insight into how postural stability can affect prioritization of postural control objectives and movement adaptation strategies.NEW & NOTEWORTHY Muscle coactivation is a key strategy for modulating movement stability; this is centrally important in the control of standing posture. Our study investigates the little-known role of coactivation in adaptation of whole body standing postural control. We demonstrate that an early coactivation strategy can be used in postural adaptation, but muscle activation strategies may differ depending on postural stability conditions.

Error Augmentation Improves Visuomotor Adaptation during a Full-Body Balance Task

Visual amplification of kinematic errors has successfully been applied to improve performance for upper limb movements. In this study, we investigated whether visual error augmentation can promote faster adaptation during a full-body balance task. Healthy volunteers controlled a cursor by shifting their weight on the THERA-Trainer coro platform. Two experimental groups and one control group were asked to reach visual targets. For the two experimental groups, the cursor's deviation from the ideal straight line trajectory was augmented by a gain of 1.5 and 2, respectively, while the control group did not experience visual error amplification (gain of 1). Error augmentation with a gain of 1.5 enhanced the speed and the amount of motor adaptation, while the highest gain might have decreased the stability of adaptation. As visual feedback is commonly used in balance training, our preliminary data suggest that integrating visual error augmentation in postural exercises may facilitate balance control.

Balance Assessment in Traumatic Brain Injury: A Comparison of the Sensory Organization and Limits of Stability Tests

Balance problems are common after a traumatic brain injury (TBI). Symptoms of dizziness, unsteadiness, or imbalance have been most frequently attributed to sensory organization problems involving the use of visual, proprioceptive, and/or vestibular information for postural control. These problems can be assessed with the Sensory Organization Test (SOT). However, as head trauma can affect any brain region, areas responsible for voluntary control of movements involved in dynamic balance tasks, such as the motor cortex and its projections, could also be compromised, which would likely affect one's limits of stability. The Limits of Stability (LOS) balance test has received little attention in TBI. In the present study, we compared the prevalence of SOT versus LOS abnormalities in a cohort of 48 patients, the majority classified as having mild or moderate chronic TBI. Compared with a normative database provided by the balance testing manufacturer, a larger portion of our cohort presented abnormalities in the LOS test. Dizziness Handicap Inventory (DHI) results indicated mild disability, with the five activities most frequently endorsed as problematic being: looking up, performing quick head movements, performing ambitious such as sports or dancing activities, feeling frustrated, and performing strenuous house/yard work. Although regression analysis revealed that both tests significantly predicted subjective scores on the DHI, more LOS than SOT testing variables were important predictors of DHI results indicating disability. These results suggest that the LOS test is an informative tool that should be included in any objective balance evaluations that screen TBI patients with balance complaints.

Impaired Motor Skill Acquisition Using Mirror Visual Feedback Improved by Transcranial Direct Current Stimulation (tDCS) in Patients With Parkinson's Disease

Recent non-invasive brain stimulation techniques in combination with motor training can enhance neuroplasticity and learning. It is reasonable to assume that such neuroplasticity-based interventions constitute a useful rehabilitative tool for patients with Parkinson's Disease (PD). Regarding motor skill training, many kinds of tasks that do not involve real motor movements have been applied to PD patients. The purpose of this study is to elucidate whether motor skill training using mirror visual feedback (MVF) is useful to patients with PD in order to improve untrained hand performance dependent on the time course of training; and whether MVF combined with anodal transcranial direct current stimulation (tDCS) over primary motor cortex (M1) causes an additional effect based on increased motor cortical excitability. Eighteen right-handed patients with PD in the off-medication state and 10 age-matched healthy subjects (HS) performed four sessions of right-hand ball rotation using MVF (intervention) on two separate days, 1 week apart (day 1 and day 2). HS subjects received only sham stimulation. The intervention included four sessions of motor-skill training using MVF for 20 min comprised of four sets of training for 30 s each. PD patients were randomly divided into two intervention groups without or with anodal tDCS over the right M1 contralateral to the untrained hand. As the behavior evaluation, the number of ball rotations of the left hand was counted before (pre) and immediately after (post) intervention on both days (pre day 1, post day 1, pre day 2, and post day 2). Motor evoked potential (MEP), input-output function, and cortical silent period were recorded to evaluate the motor cortical excitatory and inhibitory system in M1 pre day 1 and post day 2. The number of ball rotations of the left hand and the facilitation of MEP by intervention were significantly impaired in patients with PD compared to HS. In contrast, if anodal tDCS was applied to right M1 of patients with PD, the number of ball rotations in accordance with I-O function at 150% intensity was significantly increased after day 1 and retained until day 2. This finding may help provide a new strategy for neurorehabilitation improving task-specific motor memory without real motor movements in PD.

Motor Learning Deficits in Parkinson's Disease (PD) and Their Effect on Training Response in Gait and Balance: A Narrative Review

Parkinson's disease (PD) is a neurological disorder traditionally associated with degeneration of the dopaminergic neurons within the substantia nigra, which results in bradykinesia, rigidity, tremor, and postural instability and gait disability (PIGD). The disorder has also been implicated in degradation of motor learning. While individuals with PD are able to learn, certain aspects of learning, especially automatic responses to feedback, are faulty, resulting in a reliance on feedforward systems of movement learning and control. Because of this, patients with PD may require more training to achieve and retain motor learning and may require additional sensory information or motor guidance in order to facilitate this learning. Furthermore, they may be unable to maintain these gains in environments and situations in which conscious effort is divided (such as dual-tasking). These shortcomings in motor learning could play a large part in degenerative gait and balance symptoms often seen in the disease, as patients are unable to adapt to gradual sensory and motor degradation. Research has shown that physical and exercise therapy can help patients with PD to adapt new feedforward strategies to partially counteract these symptoms. In particular, balance, treadmill, resistance, and repeated perturbation training therapies have been shown to improve motor patterns in PD. However, much research is still needed to determine which of these therapies best alleviates which symptoms of PIGD, the needed dose and intensity of these therapies, and long-term retention effects. The benefits of such technologies as augmented feedback, motorized perturbations, virtual reality, and weight-bearing assistance are also of interest. This narrative review will evaluate the effect of PD on motor learning and the effect of motor learning deficits on response to physical therapy and training programs, focusing specifically on features related to PIGD. Potential methods to strengthen therapeutic effects will be discussed.

Dopamine Replacement Medication Does Not Influence Implicit Learning of a Stepping Task in People With Parkinson's Disease

INTRODUCTION

Treatment of Parkinson's disease (PD) with exogenous dopamine (ie, levodopa) may positively affect motor symptoms, but may negatively affect other functions such as the learning of motor skills necessary for rehabilitation. This study aimed to determine whether levodopa medication affects general and sequence-specific learning of a stepping task and the transfer of movement skill to untrained balance tasks in people with PD.

METHODS

Participants with PD were randomized to practice "on" (n = 14) or "off" (n = 13) levodopa medication. Participants practiced 6 blocks of 6 trials of 24 steps of a stepping task over an acquisition period of 3 consecutive days, followed by single retention blocks of 6 trials 2 and 9 days later. Participants were also assessed on untrained balance (ie, transfer) tasks "on" levodopa before practice and following late retention.

RESULTS

There were no between-group differences in general learning, sequence-specific learning, or transfer of skill to untrained balance tasks ( P > .05). Both groups demonstrated general and sequence-specific learning ( P < .001) and trends for improvement in untrained tasks ( P < .001 to P = .26) following practice. Detailed analysis of early acquisition revealed no difference between medication groups.

CONCLUSION

People with PD improved performance on the stepping task with practice. The between-group effect sizes were small, suggesting that levodopa medication status ("on" versus "off") during practice did not significantly affect general or sequence-specific learning of the task or components of early acquisition. The practice dose required to optimally result in functional improvements in untrained balance tasks, including reductions in falls, remains to be determined.

Reduced striatal dopamine release during motor skill acquisition in Parkinson's disease

Background

Striatal dopamine is functionally important for the acquisition of motor skills. However, it remains controversial as to whether intrinsic processing of motor learning is impaired in patients with Parkinson’s disease (PD), and if yes, whether the impairment is associated with altered striatal dopamine release. Additionally, most neuro-imaging studies of patients with PD have focused on motor sequence learning. In contrast, skill acquisition, specifically, the reconstruction of muscle control of isolated movements, has barely been studied.

Method

In this study, we used a repetitive skill training task to measure the peak acceleration of left thumb movement during a process to achieve fine tuning of motor skill. Using ¹¹C-raclopride (RAC) positron emission tomography, we investigated changes in striatal dopamine levels in two conditions of a skill acquisition task: initial skill training (Day 1) and acquired condition (Day 2) with eight patients with PD and age-matched healthy subjects (HS).

Result

In HS, the mean acceleration of each session improved through repeated training sessions on Day 1. However, in patients with PD, the training-associated increase was less than that for HS, and this suggests that repetitive skill training does not result in the effective improvement of motor performance. The regions of interest (ROI) analysis revealed that the RAC-binding potential (BP) was significantly reduced in the right putamen on Day 1 compared with Day 2 in HS. In patients with PD, BP within the right putamen was unchanged. Further, we found that patients with PD had increased dopamine levels within the right ventral striatum (VST) and right caudate (CAU) on Day 2, which was greater than that in HS. These results suggest the impaired activation of the putamen during skill acquisition in patients with PD and compensated hyperactivation of the VST and CAU for the reduced dopamine release within the dorsal putamen (DPU).

Conclusion

Our findings suggest that patients with PD had insufficiency in the process to improve motor skills. Different patterns of striatal dopamine release are relevant to the impairment of these motor functions in patients with PD, at the early stage of the disease.

Motor learning in people with Parkinson's disease: Implications for fall prevention across the disease spectrum

BACKGROUND

Falls are a significant burden for people with Parkinson's disease (PD), however, individuals across the spectrum of disease severity respond differently to fall prevention interventions. Despite the multifactorial causes of falls in people with PD, recent work has provided insight into interventions that hold promise for fall prevention. Further, studies have begun to identify patient characteristics that may predict responsiveness to such interventions.

RESEARCH QUESTION

We discuss (i) the postural motor learning abilities of people with mild versus severe PD that could affect their ability to benefit from fall prevention interventions, (ii) how people with different severity of PD respond to such interventions, and (iii) the practical considerations of providing effective fall prevention interventions for people with PD across the spectrum of disease severity.

METHODS

This narrative review consolidates recent work on postural motor learning and fall prevention rehabilitation involving exercise in people with PD.

RESULTS

People with PD are able to improve postural motor control through practice, enabling them to benefit from exercise which challenges their gait and balance to reduce falling. Worsening of axial and cognitive symptoms may result in diminished learning, and those with more severe PD may require fully supervised, high intensity programs to reduce falls.

SIGNIFICANCE

Understanding how people with PD across the spectrum of disease severity differ in their postural motor learning ability and response to different fall prevention interventions will enable researchers and clinicians to refine such interventions and their delivery to minimize falls and their negative sequelae in people with PD.

Gait, Balance, and Coordination Impairments in Niemann Pick Disease, Type C1

This is the first study to objectively measure gait, balance, and upper limb coordination in a group of patients with NPC1 and compare the results to age and gender matched controls. This is also the first study to report effect sizes in these measures. Spatiotemporal gait analysis, static and dynamic posturography, and upper limb reaching motion analysis were performed. The findings showed that the NPC1 subjects had statistically significant deficits on 12 out of the 16 parameters investigated compared to controls, and large effect sizes for all but 1 parameter. When ranking the variables in terms of the effect sizes, the top 5 included at least 1 parameter from each of the 3 motor domains investigated. These results can provide insight to clinical researchers on the selection of outcome measures for longitudinal and interventional studies.

Postural motor learning in Parkinson's disease: The effect of practice on continuous compensatory postural regulation

INTRODUCTION

Although balance training is considered the most effective treatment for balance impairments in Parkinson's disease (PD), few studies have examined if learning for balance control remains intact with PD. This study aimed to determine if learning for automatic postural responses is preserved in people with PD.

METHODS

Eleven participants with moderate PD (68±6.4years; H&Y: 2-3) on their usual medication maintained balance on a platform that oscillated forward and backward with variable amplitude and constant frequency. Participants completed 42 trials during one training session, and retention and transfer tests following a 24-h delay. Performance was measured by comparing spatial and temporal measures of whole-body centre of mass (COM) with platform displacements. Learning was compared between participants with PD and previously reported, age-matched older adults (Van Ooteghem et al., 2010).

RESULTS

Although postural responses in participants with PD were impaired compared to control participants, a majority of PD participants improved their postural responses with practice as revealed by reduced COM displacements and improved phase relationships between COM and platform motion. Rates of improvement were comparable between groups demonstrating preserved adaptive capacity for participants with PD. Similar to control participants, the PD group moved toward anticipatory COM control as a strategy for improving stability, exhibited short-term retention of performance improvements, and demonstrated generalizability of the learned responses. Rate of improvement with practice, but not retention, was related to severity of motor impairments.

CONCLUSIONS

Patients with moderate PD on medication demonstrate retention of improvements in automatic postural responses with practice suggesting that intrinsic postural motor learning is preserved in this group.

Effects of a balance-based exergaming intervention using the Kinect sensor on posture stability in individuals with Parkinson's disease: a single-blinded randomized controlled trial

Background

The present study examined the effects of a balance-based exergaming intervention using the Kinect sensor on postural stability and balance in people with Parkinson’s disease (PD).

Methods

We conducted a subject-blinded, randomized controlled study. Twenty people with PD (Hoehn and Yahr stages I through III) were recruited and randomly assigned to either a balance-based exergaming group (N = 10) or a balance training group (N = 10) for an 8-week balance training period. Postural stability was assessed using the limits of stability (LOS) and one-leg stance (OLS) tests. Balance was assessed using the Berg Balance Scale (BBS) and the timed up and go (TUG) test. Participants were assessed pre- and post-training.

Results

After training, participants in the balance-based exergaming group showed significant improvements in LOS performance, and in the eyes-closed condition of the OLS test. Both training programs led to improvements in BBS and TUG performance. Furthermore, balance-based exergaming training resulted in significantly better performance in directional control in the LOS test (78.9 ± 7.65 %) compared with conventional balance training (70.6 ± 9.37 %).

Conclusions

Balance-based exergaming training resulted in a greater improvement in postural stability compared with conventional balance training. Our results support the therapeutic use of exergaming aided by the Kinect sensor in people with PD.

Trial registration

ClinicalTrials.gov.NCT02671396

Electronic supplementary material

The online version of this article (doi:10.1186/s12984-016-0185-y) contains supplementary material, which is available to authorized users.

Retraining function in people with Parkinson's disease using the Microsoft kinect: game design and pilot testing

Background

Computer based gaming systems, such as the Microsoft Kinect (Kinect), can facilitate complex task practice, enhance sensory feedback and action observation in novel, relevant and motivating modes of exercise which can be difficult to achieve with standard physiotherapy for people with Parkinson’s disease (PD). However, there is a current need for safe, feasible and effective exercise games that are appropriate for PD rehabilitation. The aims of this study were to i) develop a computer game to rehabilitate dynamic postural control for people with PD using the Kinect; and ii) pilot test the game’s safety and feasibility in a group of people with PD.

Methods

A rehabilitation game aimed at training dynamic postural control was developed through an iterative process with input from a design workshop of people with PD. The game trains dynamic postural control through multi-directional reaching and stepping tasks, with increasing complexity across 12 levels of difficulty. Nine people with PD pilot tested the game for one session. Participant feedback to identify issues relating to safety and feasibility were collected using semi-structured interviews.

Results

Participants reported that they felt safe whilst playing the game. In addition, there were no adverse events whilst playing. In general, the participants stated that they enjoyed the game and seven of the nine participants said they could imagine themselves using the game at home, especially if they felt it would improve their balance. The Flow State Scale indicated participants were immersed in the gameplay and enjoyed the experience. However, some participants reported that they found it difficult to discriminate between different types and orientations of visual objects in the game and some also had difficulty with the stepping tasks, especially when performed at the same time as the reaching tasks.

Conclusion

Computer-based rehabilitation games using the Kinect are safe and feasible for people with PD although intervention trials are needed to test their safety, feasibility and efficacy in the home.

Factors influencing turning and its relationship with falls in individuals with Parkinson's disease

BACKGROUND

Falls are a major problem for people with Parkinson's disease (PD). Many studies indicate that more than 50% of people with PD have difficulty in turning that may lead to falls during daily activities. The aims of this study were to identify the relationship between turning performance and falls, and to determine the factors that influence turning performance.

METHODS

This study examined 45 patients with idiopathic PD (Hoehn and Yahr stage 1-3) using a battery of tests, including 180° turn time, balance, and muscle strength. The levels of disease severity and freezing of gait were also measured. The number of falls in the past 6 months was recorded.

RESULTS

Sixteen out of forty-five participants experienced falls in the past 6 months. A receiver operating characteristic curve showed that turn time was highly related to falls [more affected side: sensitivity = 0.81, specificity = 0.79, area under the curve (AUC) = 0.83; less affected side: sensitivity = 0.88, specificity = 0.76, AUC = 0.83]. The most important factor influencing turn time was balance ability (both sides: p = 0.000) according to the regression model. Correlations between turn time and dynamic balance were further established with reaction time, movement velocity, endpoint excursion, and maximal excursion of the LOS (limits of stability) test.

CONCLUSION

The time needed to complete a 180° turn during the SQT (step/quick turn) test is a good index to differentiate fallers from non-fallers in persons with PD. Turn time is most influenced by balance. Furthermore, balance control, especially in an anterior or sideways direction, is important for turning performance.

Balance and Gait Training With Augmented Feedback Improves Balance Confidence in People With Parkinson’s Disease

Background. Fear of falling has been identified as an important and independent fall-risk predictor in patients with Parkinson’s disease (PD). However, there are inconsistent findings on the effects of balance and gait training on balance confidence. Objective. To explore whether balance and gait training with augmented feedback can enhance balance confidence in PD patients immediately after treatment and at 3- and 12-month follow-ups. Methods. A total of 51 PD patients were randomly assigned to a balance and gait training (BAL) group or to an active control (CON) group. The BAL group received balance and gait training with augmented feedback, whereas CON participants received lower-limb strength training for 12 weeks. Outcome measures included Activities-Specific Balance Confidence (ABC) Scale, limits-of-stability test, single-leg-stance test, and spatiotemporal gait characteristics. All tests were administered before intervention (Pre), immediately after training (Post), and at 3 months (Post3m) and 12 months (Post12m) after treatment completion. Results. The ABC score improved marginally at Post and significantly at Post3m and Post12m only in the BAL group ( P < .017). Both participant groups increased their end point excursion at Post, but only the BAL group maintained the improvement at Post3m. The BAL group maintained significantly longer time-to-loss-of-balance during the single-leg stance test than the CON group at Post3m and Post12m ( P < .05). For gait characteristics, both participant groups increased gait velocity, but only the BAL group increased stride length at Post, Post3m, and Post12m ( P < .017). Conclusions. Positive findings from this study provide evidence that BAL with augmented feedback could enhance balance confidence and balance and gait performance in patients with PD.

Performance of a motor task learned on levodopa deteriorates when subsequently practiced off

Studies in animals and in people with Parkinson's disease (PD) demonstrate complex effects of dopamine on learning motor tasks; its effect on retention of motor learning has received little attention. Recent animal studies demonstrate that practicing a task in the off state, when initially learned in the on state, leads to progressive deterioration in performance. We measured the acquisition and retention of 3 different motor tasks in the presence and absence of levodopa. Twenty individuals with Hoehn and Yahr Stage 1.5 to 3 PD practiced the tasks daily for two 4-day weeks, one half practicing on L-dopa the first week and off the second week. The other half practiced off l-dopa both weeks. The tasks were (1) alternate tapping of 2 keys, (2) moving the body toward 2 targets on a posturography device, and (3) mirror drawing of a star. For the tapping and body movement tests, those who practiced on the first week had a progressive decline in performance with practice during week 2, while subjects off during week 1 maintained or improved. In contrast, for the mirror task, subjects on L-dopa initially had much more difficulty completing the task compared to subjects who practiced off. Both groups improved with practice the first week and had flat performance the second week. These data suggest that performance of speed-accuracy tasks learned in the on state may progressively worsen if subsequently practiced in the off state. In addition, performance, but not learning, of some tasks may be impeded by L-dopa.

The effects of practice on the concurrent performance of a speech and postural task in persons with Parkinson disease and healthy controls

Purpose. Persons with Parkinson disease (PD) demonstrate deficits in motor learning as well as bidirectional interference (the performance of one task concurrently interferes with the performance of another task) during dual-task performance. Few studies have examined the practice dosages necessary for behavioral change in rehabilitation relevant tasks. Therefore, to compare the effects of age and PD on motor learning during dual-task performance, this pilot study examined persons with PD as well as neurologically healthy participants during concurrent performance of postural and speaking tasks. Methods. Seven persons with PD and 7 healthy age-matched and 10 healthy young control subjects were tested in a motion capture facility. Task performances were performed concurrently and recorded during 3 time periods (acquisition (beginning and ending), 48-hour retention, and 1-week retention). Postural control and speech articulatory acoustic variables were measured. Results. Healthy young participants consistently performed better than other groups on all measured postural and speech variables. Healthy young participants showed decreased variability at retention, while persons with PD and healthy age-matched controls were unable to consistently improve their performance as a result of practice. No changes were noted in the speech variables. Conclusion. The lack of consistent changes in motor performance in any of the tasks, except in the healthy young group, suggests a decreased efficiency of motor learning in the age-matched and PD groups and argues for increased practice dosages during balance training.

A cane improves postural recovery from an unpracticed slip during walking in people with Parkinson disease

BACKGROUND

Little is known about the effects of use of a cane on balance during perturbed gait or whether people with Parkinson disease (PD) benefit from using a cane.

OBJECTIVES

The purpose of this study was to evaluate the effects of cane use on postural recovery from a slip due to repeated surface perturbations in individuals with PD compared with age- and sex-matched individuals who were healthy.

DESIGN

This was a prospective study with 2 groups of participants.

METHODS

Fourteen individuals with PD (PD group) and 11 individuals without PD (control group) walked across a platform that translated 15 cm rightward at 30 cm/s during the single-limb support phase of the right foot. Data from 15 trials in 2 conditions (ie, with and without an instrumented cane in the right hand) were collected in random order. Outcome measures included lateral displacement of body center of mass (COM) due to the slip and compensatory step width and length after the perturbation.

RESULTS

Cane use improved postural recovery from the first untrained slip, characterized by smaller lateral COM displacement, in the PD group but not in the control group. The beneficial effect of cane use, however, occurred only during the first perturbation, and those individuals in the PD group who demonstrated the largest COM displacement without a cane benefited the most from use of a cane. Both PD and control groups gradually decreased lateral COM displacement across slip exposures, but a slower learning rate was evident in the PD group participants, who required 6, rather than 3, trials for adapting balance recovery.

LIMITATIONS

Future studies are needed to examine the long-term effects of repeated slip training in people with PD.

CONCLUSIONS

Use of a cane improved postural recovery from an unpracticed slip in individuals with PD. Balance in people with PD can be improved by training with repeated exposures to perturbations.

The influence of movement initiation deficits on the quantification of retention in Parkinson's disease

In patients with an impaired motor system, like Parkinson’s disease (PD), deficits in motor learning are expected and results of various studies seem to confirm these expectations. However, most studies in this regard are behaviorally based and quantify learning by performance changes between at least two points in time, e.g., baseline and retention. But, performance in a retention test is also dependent on other factors than learning. Especially in patients, the functional capacity of the control system might be altered unspecific to a certain task and learning episode. The aim of the study is to test whether characteristic temporal deficits exist in PD patients that affect retention performance. We tested the confounding effects of typical PD motor control deficits, here movement initiation deficits, on retention performance in the motor learning process. 12 PD patients and 16 healthy control participants practiced a virtual throwing task over 3 days with 24 h rest between sessions. Retention was tested comparing performance before rest with performance after rest. Movement initiation deficits were quantified by the timing of throwing release that should be affected by impairments in movement initiation. To scrutinize the influence of the initiation deficits on retention performance we gave participants a specific initiation intervention prior to practice on one of the three practice days. We found that only for the PD patients, post-rest performance as well as release timing was better with intervention as compared to without intervention. Their performance could be enhanced through a tuning of release initiation. Thus, we suggest that in PD patients, performance decline after rest that might be easily interpreted as learning deficits could rather result from disease-related deficiencies in motor control.

Stability limits modulate whole-body motor learning

Our daily movements exert forces upon the environment and also upon our own bodies. To control for these forces, movements performed while standing are usually preceded by anticipatory postural adjustments (APAs). This strategy is effective at compensating for an expected perturbation, as it reduces the need to compensate for the perturbation in a reactive manner. However, it can also be risky if one anticipates the incorrect perturbation, which could result in movements outside stability limits and a loss of balance. Here, we examine whether the margin for error defined by these stability limits affects the amount of anticipation. Specifically, will one rely more on anticipation when the margin for error is lower? Will the degree of anticipation scale with the margin for error? We took advantage of the asymmetric stability limits (and margins for error) present in the sagittal plane during upright stance and investigated the effect of perturbation direction on the magnitude of APAs. We also compared anticipatory postural control with the anticipatory control observed at the arm. Standing subjects made reaching movements to multiple targets while grasping the handle of a robot arm. They experienced forward or backward perturbing forces depending on the target direction. Subjects learned to anticipate the forces and generated APAs. Although subjects had the biomechanical capacity to adapt similarly in the forward and backward directions, APAs were reduced significantly in the backward direction, which had smaller stability limits and a smaller margin for error. Interestingly, anticipatory control produced at the arm, where stability limits are not as relevant, was not affected by perturbation direction. These results suggest that stability limits modulate anticipatory control, and reduced stability limits lead to a reduction in anticipatory postural control.

Upper Extremity Motor Learning among Individuals with Parkinson's Disease: A Meta-Analysis Evaluating Movement Time in Simple Tasks

Motor learning has been found to occur in the rehabilitation of individuals with Parkinson's disease (PD). Through repetitive structured practice of motor tasks, individuals show improved performance, confirming that motor learning has probably taken place. Although a number of studies have been completed evaluating motor learning in people with PD, the sample sizes were small and the improvements were variable. The purpose of this meta-analysis was to determine the ability of people with PD to learn motor tasks. Studies which measured movement time in upper extremity reaching tasks and met the inclusion criteria were included in the analysis. Results of the meta-analysis indicated that people with PD and neurologically healthy controls both demonstrated motor learning, characterized by a decrease in movement time during upper extremity movements. Movement time improvements were greater in the control group than in individuals with PD. These results support the findings that the practice of upper extremity reaching tasks is beneficial in reducing movement time in persons with PD and has important implications for rehabilitation.

Redução do limite de estabilidade direção-específica em indivíduos leve a moderadamente afetados pela doença de Parkinson

A instabilidade postural na doença de Parkinson (DP) tem sido associada a uma diminuição do limite de estabilidade (LE) na direção ântero-posterior (AP). Entretanto, ainda que possíveis alterações do LE na direção látero-lateral (LL) tenham sido sugeridas, tal direção não tem sido avaliada nos estudos com DP, principalmente quando o teste de limite de estabilidade (TLE) envolve movimentos intencionais que deslocam o centro de massa corporal (CMC). O objetivo do presente estudo foi investigar o LE na postura de pé durante movimentos voluntários que promovem deslocamento do CMC nas direções AP e LL de indivíduos com e sem a DP. Doze indivíduos com DP (Hoehn & Yahr=II, III) e 12 sem a doença realizaram o TLE nos sentidos anterior, posterior, direito e esquerdo. A velocidade de movimento (VM), excursão máxima (EM) e o controle direcional (CD) do CMC foram avaliados em cada sentido. Os indivíduos com DP foram significativamente mais lentos em todos os sentidos de deslocamento do CMC (p<0,05). Não houve diferença significativa na EM e CD no sentido anterior entre os grupos (p>0,05). Por outro lado, a EM e CD do CMC foram menores para o grupo DP no sentido posterior (P) e na direção LL (p<0,05). Indivíduos leves a moderadamente afetados pela DP apresentaram redução do LE no sentido P e na direção LL quando comparados ao grupo controle. Os resultados sugerem que tal direção e sentido devam ser treinados em ortostatismo, com movimentos que deslocam voluntariamente o CMC, desde fases iniciais da DP.

Motor Skill Learning, Retention, and Control Deficits in Parkinson's Disease

Parkinson's disease, which affects the basal ganglia, is known to lead to various impairments of motor control. Since the basal ganglia have also been shown to be involved in learning processes, motor learning has frequently been investigated in this group of patients. However, results are still inconsistent, mainly due to skill levels and time scales of testing. To bridge across the time scale problem, the present study examined de novo skill learning over a long series of practice sessions that comprised early and late learning stages as well as retention. 19 non-demented, medicated, mild to moderate patients with Parkinson's disease and 19 healthy age and gender matched participants practiced a novel throwing task over five days in a virtual environment where timing of release was a critical element. Six patients and seven control participants came to an additional long-term retention testing after seven to nine months. Changes in task performance were analyzed by a method that differentiates between three components of motor learning prominent in different stages of learning: Tolerance, Noise and Covariation. In addition, kinematic analysis related the influence of skill levels as affected by the specific motor control deficits in Parkinson patients to the process of learning. As a result, patients showed similar learning in early and late stages compared to the control subjects. Differences occurred in short-term retention tests; patients' performance constantly decreased after breaks arising from poorer release timing. However, patients were able to overcome the initial timing problems within the course of each practice session and could further improve their throwing performance. Thus, results demonstrate the intact ability to learn a novel motor skill in non-demented, medicated patients with Parkinson's disease and indicate confounding effects of motor control deficits on retention performance.

Effects of virtual reality-augmented balance training on sensory organization and attentional demand for postural control in people with Parkinson disease: a randomized controlled trial

BACKGROUND

There is a lack of studies related to virtual reality (VR)-augmented balance training on postural control in people with Parkinson disease (PD).

OBJECTIVE

The purposes of this study were: (1) to examine the effects of VR-augmented balance training on the sensory integration of postural control under varying attentional demands and (2) to compare the results with those of a conventional balance training (CB) group and an untrained control group.

DESIGN

A longitudinal, randomized controlled trial was used.

SETTING

The intervention was conducted in the clinic, and the assessment was performed in a research laboratory.

PATIENTS

Forty-two people with PD (Hoehn and Yahr stages II-III) were recruited.

INTERVENTION

The VR and CB groups received a 6-week balance training program.

MEASUREMENTS

The sensory organization tests (SOTs) of computerized posturography with single- and dual-task conditions were conducted prior to training, after training, and at follow-up. Equilibrium scores, sensory ratios, and verbal reaction times (VRTs) were recorded.

RESULTS

There were no significant differences in equilibrium scores or VRTs between the VR and CB groups. However, the equilibrium scores in SOT-6 (ie, unreliable vision and somatosensation) of the VR group increased significantly more than that of the control group after training. The equilibrium scores in SOT-5 (ie, unreliable somatosensation with eyes closed) of the CB group also increased significantly more than that of the control group after training.

LIMITATIONS

The functional significance of the improvements in equilibrium scores in the SOTs was not known, and the sample size was small.

CONCLUSIONS

Both VR and CB training improved sensory integration for postural control in people with PD, especially when they were deprived of sensory redundancy. However, the attentional demand for postural control was not changed after either VR or CB training.

Effect of step training and rhythmic auditory stimulation on functional performance in Parkinson patients

BACKGROUND

Rhythmic auditory stimulation (RAS) can influence movement during straight line walking and direction transition in individuals with Parkinson disease (PD).

OBJECTIVE

The authors studied whether multidirectional step training with RAS would generalize to functional gait conditions used in daily activities and balance.

METHODS

In a matched-pairs design, 8 patients practiced externally paced (EP) stepping (RAS group), and 8 patients practiced internally paced (IP) stepping (no RAS group) for 6 weeks. Participants were evaluated on the first and last days of practice, and 1 week, 4 weeks, and 8 weeks after practice termination. Evaluations included a primary measurement--the Dynamic Gait Index (DGI)--and secondary measurements--the Unified Parkinson's Disease Rating Scale (UPDRS), Tinetti-gait and balance tests, Timed-Up-and-Go (TUG), and Freezing of Gait Questionnaire (FOGQ).

RESULTS

The RAS group significantly improved performance on the DGI and several secondary measures, and they maintained improvements for the DGI, Tinetti, FOGQ, and balance and gait items of the UPDRS above pretraining values at least 4 weeks after practice termination. The no RAS group revealed several improvements with training but could not maintain these improvements for as long as the other group.

CONCLUSIONS

Individuals with PD can generalize motor improvements achieved during multidirectional step training to contexts of functional gait and balance. Training with RAS is advantageous for enhancing functional gait improvements and the maintenance of functional gait and balance improvements over 8 weeks.

Three-dimensional motion analysis of postural adjustments during over-ground locomotion in a rat model of Parkinson's disease

Postural instability, a symptom of Parkinson's disease (PD) patients, leads to frequent falls and difficulty in forward motion during gait. These motor deficits are mainly caused by neurodegenerative processes in the brain leading to reduced levels of the neurotransmitter dopamine. Postural studies involving animal models of PD are mainly based on movement scores or descriptive approaches to discerning differences in behaviour or function. Our aim was to describe postural adjustments in a rat model of PD utilising a quantitative three dimensional motion analysis technique during gait to investigate the effects of unilateral dopamine depletion on rat locomotion while walking on beams of varying widths (wide, narrow and graduated). Tail orientation, limb positions on the beam, range of motion and kinematic waveforms of the Roll, Pitch and Yaw of male Lister Hooded rats were investigated using passive markers placed in locations that were representative of their body axis. Hemiparkinsonian rats moved on the wide beam with a significantly higher Roll range of motion coupled with a positively biased Roll kinematic waveform during one gait cycle. While walking on the narrow beam they displayed an increased use of the ledge and placed their tail towards the right. These results are brought about by the rats' inability to shift body posture using the impaired limb. Our data demonstrate that marker-based motion capture can provide an effective and simple approach to quantifying postural adjustments for rat models of PD.

The Relationships Between the Unified Parkinson’s Disease Rating Scale and Lower Extremity Functional Performance in Persons With Early-Stage Parkinson’s Disease

Background. The Unified Parkinson’s Disease Rating Scale (UPDRS) is the “gold standard” assessment tool for characterizing impairments in persons with Parkinson’s disease (PD); however, this scale’s ability to predict functional capabilities across different functional tasks has not been adequately assessed in persons with early-stage PD. Methods. Thirty persons with PD within 3 years of diagnosis and without motor fluctuation performed self-selected walking, fast walking, and sit-to-stand and stair-climbing tasks. Pearson’s correlation coefficients were used to calculate correlations with a standard UPDRS examination ( P < .05). Simple linear regression models were used to fit each functional performance outcome measure with the UPDRS total predictor scores. Results. The correlations between the UPDRS motor (section III), UPDRS total scores, and all timed functional performance measures were fair to good (range, 0.45-0.57). Conversely, only greater self-selected time to walk 50 ft correlated with a higher UPDRS activities of daily living (II) score ( r = .386; P < .05). Conclusions. The UPDRS motor (III) and total scores may be good predictors of overall lower extremity function in persons with early-stage PD. Understanding the relationships between UPDRS scores and functional capabilities may allow clinicians to better quantify early physical functioning, longitudinally assess disease progression, and assess the efficacy of interventions.

Relationships between gait and dynamic balance in early Parkinson's disease

This study examined the relationships between gait and dynamic balance in people with early-stage Parkinson's disease (PD). We assessed 18 participants diagnosed with stage I-II idiopathic PD and 17 healthy age-matched volunteers. Temporo-spatial gait variables were analyzed using the GAITRite system and participants were asked to walk at a comfortable walking speed. Dynamic balance was assessed using the Balance Master. Movement velocity (MV), maximal excursion (ME), and directional control (DC), obtained through the limits of stability test, quantified dynamic balance. People with early stage PD exhibited significantly slower walking speed, shorter stride length, and smaller forward MV than the comparison group. In the PD group, stride length and speed significantly correlated with forward MV, forward ME, and forward DC. Thus, in people with early PD, gait speed and stride length are correlated with dynamic balance, particularly in the forward direction in standing.

Enhanced function in the good forelimb of hemi-parkinson rats: compensatory adaptation for contralateral postural instability?

In this paper we present two new assays of rat motor behavior which can be used to assess function linked to postural stability in each forelimb independently. Postural instability is a major deficit in Parkinson's disease that is resistant to levodopa therapy and contributes to the risk of falling. We applied both tests, one forelimb at a time, to normal rats as well as rats extensively depleted of dopamine by unilateral infusion of 6-hydroxydopamine (6-OHDA, given in the medial forebrain bundle) to produce a hemi-parkinsonian syndrome. The 6-OHDA rats showed severe postural instability in the impaired forelimb, but unexpectedly showed enhanced function in the non-impaired forelimb. The data suggest that the intact hemisphere may undergo rapid reorganization subsequent to unilateral dopamine depletion, which allows for compensatory function of the "intact" limb. Measurements of amphetamine-induced striatal c-fos expression, as well as behavior results gathered when animals were under the influence of apomorphine or haloperidol, indicate that this potential reorganization may require non-dopaminergic neural plasticity. The relevance of these findings for unilateral rat models of neurological disease is discussed.

Diagnosis of fall risk in Parkinson disease: an analysis of individual and collective clinical balance test interpretation

BACKGROUND AND PURPOSE

Parkinson disease (PD) results in an increased frequency of falls relative to the frequency in neurologically healthy people. The purpose of this study was to compare the accuracy of PD fall risk diagnosis based on one test with that based on the collective interpretation of multiple tests.

PARTICIPANTS

Seventy people with PD (mean age=73.91 years) participated in this study.

METHOD

Clinical balance tests were conducted during the initial examinations of people with PD. Validity indices were calculated for individual tests and compared with validity indices calculated for a combination of multiple tests.

RESULTS

Thirty-six participants reported a fall history. Analysis of individual tests revealed broad variations in validity indices, whereas the collective interpretation of multiple tests improved sensitivity and negative likelihood ratios.

DISCUSSION AND CONCLUSION

Collective interpretation of clinical balance tests resulted in fewer false-negative results and more substantial adjustments to the posttest probability of being a "faller" than the interpretation of one test alone. These results should be confirmed in a prospective examination of fall risk in PD.

Determining the Optimal Challenge Point for Motor Skill Learning in Adults With Moderately Severe Parkinson's Disease

Objective. To test the predictions of the Challenge Point Framework (CPF) for motor learning in individuals with Parkinson's disease (PD) by manipulating nominal task difficulty and conditions of practice. Methods. Twenty adults with PD and 20 nondisabled controls practiced 3 variations of a laboratory-based goal-directed arm movement over 2 days. A between-group (PD, nondisabled) 2-factor design compared 2 levels of nominal task difficulty (low, high) and 2 levels of practice condition (low, high demand). Learning was assessed with a no-feedback recall test 1 day after practice. Performance was quantified using a root mean square error difference between the goal and participant-generated movement. Results. All participants improved with practice. Under the low-demand practice condition, adults with PD demonstrated comparable learning to that of controls when nominal task difficulty was low but not high. In contrast, under the high-demand practice condition, adults with PD demonstrated preserved motor learning for both levels of task difficulty, but only if recall was tested under the same context as that used during practice. Conclusions. In general, the predictions of CPF were supported. Together, the level of nominal task difficulty and the inherent demand of the practice condition played a critical role in determining the optimal challenge point for motor learning in individuals with PD. More important, and in contrast to the predictions of CPF, a high-demand practice condition appeared to have a facilitative effect on motor learning. However, this benefit revealed the context specificity of motor learning in adults with PD.