Virtual reality walking and dopamine: Opening new doorways to understanding freezing of gait in Parkinson's disease

Stepping up to meet the challenge of freezing of gait in Parkinson's disease

There has been a growing appreciation for freezing of gait as a disabling symptom that causes a significant burden in Parkinson’s disease. Previous research has highlighted some of the key components that underlie the phenomenon, but these reductionist approaches have yet to lead to a paradigm shift resulting in the development of novel treatment strategies. Addressing this issue will require greater integration of multi-modal data with complex computational modeling, but there are a number of critical aspects that need to be considered before embarking on such an approach. This paper highlights where the field needs to address current gaps and shortcomings including the standardization of definitions and measurement, phenomenology and pathophysiology, as well as considering what available data exist and how future studies should be constructed to achieve the greatest potential to better understand and treat this devastating symptom.

Narrow doorways alter brain connectivity and step patterns in isolated REM sleep behaviour disorder

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iRBD had slower and more variable stepping compared to controls in this VR task.

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iRBD showed exaggerated responses when passing narrow compared to wide doorways iRBD had altered task-related brain connectivity which was correlated to motor deficits.

Background

Motor impairments in those with isolated REM sleep behaviour disorder (iRBD) significantly increases the likelihood of developing Lewy body disease (e.g. Parkinson’s disease and Dementia with Lewy Bodies).

Objective

This study sought to explore the prodromal process of neurodegeneration by examining the neural signature underlying motor deficits in iRBD patients.

Methods

A virtual reality (VR) gait paradigm (which has previously been shown to elicit adaptive changes in gait performance whilst navigating doorways in Parkinson’s Disease - PD) was paired with fMRI to investigate whether iRBD patients demonstrated worsened motor performance and altered connectivity across frontoparietal, motor and basal ganglia networks compared to healthy controls. Forty participants (23 iRBD and 17 healthy controls) completed the virtual reality gait task whilst in the MRI scanner, and an additional cohort of 19 Early PD patients completed the behavioural virtual reality gait task.

Results

As predicted, iRBD patients demonstrated slower and more variable stepping compared to healthy control participants and demonstrated an exaggerated response when navigating narrow compared to wide doorways, a phenomenon characteristically seen in PD. The iRBD patients also demonstrated less BOLD signal change in the left posterior putamen and right mesencephalic locomotor region, as well as reduced functional connectivity between the frontoparietal network and the motor network, when navigating narrow versus wide doorways compared to healthy control participants.

Conclusions

Taken together, this study demonstrates that iRBD patients have altered task-related brain connectivity, which may represent the neural underpinnings of early motor impairments that are evident in iRBD.

Designing Virtual Reality Assisted Psychotherapy for Anxiety in Older Adults Living with Parkinson's Disease: Integrating Literature for Scoping

Objective: This review integrates literature to discuss the potential use of virtual reality (VR) in treatment of anxiety in Parkinson's disease (PD) and inform next steps.Methods: A systematic search was performed to identify studies of VR use in PD, using four databases. Data were reported in accordance to the Preferred Reporting Items for Systematic reviews and Meta-Analyzes extension for Scoping Reviews (PRISMA-ScR).Results: Thirty-two studies met the inclusion criteria with four VR studies from the same study group directly assessing the effects of anxiety on motor symptoms in PD. Primary studies implementing a VR protocol in PD identified focus areas of understanding and alleviating freezing of gait (FOG), balance training, and cognitive and motor rehabilitation, and informed design considerations.Conclusion: VR in PD studies suggested established feasibility. With appropriate design considerations, a VR based protocol could improve anxiety outcomes in PD.Clinical implications: VR in PD provides control of a patient's field of view, which can be exploited to induce specific responses, provide visual feedback, analysis of patient actions, and introduce safe challenges in the context of training. VR assisted Cognitive Behavioral Therapy (CBT) tailored to suit subtypes of anxiety disorders in PD have the potential to improve the efficacy and effectiveness of psychotherapy in PD.

The use of virtual reality to modify and personalize interior home features in Parkinson's disease

As the second most common progressive neurodegenerative disorder with increased prevalence in the aging population, Parkinson's disease (PD) affects more than 10 million individuals worldwide with approximately 60,000 new cases occurring each year only in the US. While daily living abilities deteriorate in people with PD, they spend a significant amount of time in their homes. Unfortunately, most existing guidelines for home modification design reflect a standardized, singular plan. This study aimed to demonstrate the feasibility of using a virtual reality (VR) system for persons with PD to virtually walk through different home modifications and to adapt and personalize interior features. A sample of 15 participants with idiopathic PD and 24 healthy adults ambulated on a pressure mat, while using a VR headset and hand controller. Both groups envisioned walking through a virtual doorway from a simulated bedroom into its attached bathroom. Design features for the intervention included doorway width and door-frame color. Each participant was randomly assigned to one of three intervention conditions: (1) standard design, (2) enhanced design, and (3) co-design. The codesign module allowed participants to manipulate design features using a hand controller. We recorded 4 movement variables. Participants completed three questionnaires assessing anxiety, system usability, and satisfaction. Healthy control adults revealed no differences in movement or subjective assessment between the three intervention conditions. However, there were significant differences in the PD group between co-design and the other conditions. The changes were appreciated in the baseline measures of gait distance and strikes as well as in the composite gait component score. This study showed that using VR as a participatory design tool for persons with PD is safe and feasible. Additionally, the self-determination of interior design conditions may possibly affect movement performance measures and merits additional controlled trials.

Where Do Parkinson's Disease Patients Look while Walking?

BACKGROUND

Parkinson's disease (PD) is associated with gait and visuomotor abnormalities, but it is not clear where PD patients look during ambulation.

OBJECTIVE

We sought to characterize the visual areas of interest explored by PD patients, with and without freezing of gait (FOG), compared to healthy volunteers (HVs).

METHODS

Using an eye-tracking device, we compared visual fixation patterns in 17 HVs and 18 PD patients, with and without FOG, during an ambulatory and a nonambulatory, computer-based task.

RESULTS

During ambulation, PD patients with FOG fixated more on proximal areas of the ground and less on the target destination. PD patients without FOG displayed a fixation pattern more similar to that of HVs. Similar patterns were observed during the nonambulatory, computer-based task.

CONCLUSIONS

Our findings suggest increased dependence on visual feedback from nearby areas in the environment in PD patients with FOG, even in the absence of motor demands. © 2022 International Parkinson and Movement Disorder Society.

A Structured Approach to Test the Signal Quality of Electroencephalography Measurements During Use of Head-Mounted Displays for Virtual Reality Applications

Joint applications of virtual reality (VR) systems and electroencephalography (EEG) offer numerous new possibilities ranging from behavioral science to therapy. VR systems allow for highly controlled experimental environments, while EEG offers a non-invasive window to brain activity with a millisecond-ranged temporal resolution. However, EEG measurements are highly susceptible to electromagnetic (EM) noise and the influence of EM noise of head-mounted-displays (HMDs) on EEG signal quality has not been conclusively investigated. In this paper, we propose a structured approach to test HMDs for EM noise potentially harmful to EEG measures. The approach verifies the impact of HMDs on the frequency- and time-domain of the EEG signal recorded in healthy subjects. The verification task includes a comparison of conditions with and without an HMD during (i) an eyes-open vs. eyes-closed task, and (ii) with respect to the sensory- evoked brain activity. The approach is developed and tested to derive potential effects of two commercial HMDs, the Oculus Rift and the HTC Vive Pro, on the quality of 64-channel EEG measurements. The results show that the HMDs consistently introduce artifacts, especially at the line hum of 50 Hz and the HMD refresh rate of 90 Hz, respectively, and their harmonics. The frequency range that is typically most important in non-invasive EEG research and applications (<50 Hz) however, remained largely unaffected. Hence, our findings demonstrate that high-quality EEG recordings, at least in the frequency range up to 50 Hz, can be obtained with the two tested HMDs. However, the number of commercially available HMDs is constantly rising. We strongly suggest to thoroughly test such devices upfront since each HMD will most likely have its own EM footprint and this article provides a structured approach to implement such tests with arbitrary devices.

Validating a Seated Virtual Reality Threat Paradigm for Inducing Anxiety and Freezing of Gait in Parkinson's Disease

BACKGROUND

Although prior research has established that freezing of gait (FOG) in Parkinson's disease (PD) is associated with anxiety, only one study to date has directly manipulated anxiety levels to induce FOG.

OBJECTIVE

The current study aimed to replicate these previous findings and evaluate whether a seated version of a 'threat' virtual reality (VR) paradigm could induce anxiety and provoke FOG.

METHODS

Twenty-four PD patients with FOG were assessed across various threat conditions in both a walking VR paradigm (Experiment 1) and a seated VR paradigm (Experiment 2). Both paradigms manipulated the height (i.e., elevated vs ground) and width (wide vs narrow) of the planks participants were instructed to walk across.

RESULTS

Across both experiments, the Elevated + Narrow condition provoked significantly greater number of freezing episodes compared to all other conditions. Higher levels of self-reported anxiety were reported during the Elevated+Narrow condition compared to all other conditions in Experiment 1, and compared to the Ground condition in Experiment 2.

CONCLUSION

These findings confirm that anxiety contributes to FOG and validates the use of a seated VR threat paradigm for provoking anxiety-related freezing. This enables future studies to combine this paradigm with functional MRI to explore the neural correlates underlying the role of anxiety in FOG.

Visual cues added to a virtual environment paradigm do not improve motor arrests in Parkinson's disease

Objective. Elucidating how cueing alleviates freezing of gait (FOG) in Parkinson's disease (PD) would enable the development of more effective, personalized cueing strategies. Here, we aimed to validate a visual cueing virtual environment (VE) paradigm for future use in e.g. neuroimaging studies and behavioral studies on motor timing and scaling in PD patients with FOG.Approach. We included 20 PD patients with FOG and 16 age-matched healthy control subjects. Supine participants were confronted with a VE displaying either no cues, bars or staircases. They navigated forward using alternate suppression of foot pedals. Motor arrests (as proxy for FOG), and measures of motor timing and scaling were compared across the three VE conditions for both groups.Main results. VE cues (bars and staircases) did not reduce motor arrests in PD patients and healthy control subjects. The VE cues did reduce pedal amplitude in healthy control subjects, without effects on other motor parameters.Conclusion. We could not validate a visual cueing VE paradigm to study FOG. The VE cues possibly failed to convey the necessary spatial and temporal information to support motor timing and scaling. We discuss avenues for future research.

The development and pilot evaluation of virtual reality balance scenarios in people with multiple sclerosis (MS): A feasibility study

BACKGROUND

Balance deficits are considered a risk factor for falls in MS patients. Therefore, developing innovative approaches such as virtual reality (VR) to improve balance in MS is required.

OBJECTIVES

The aims of this study were to develop and evaluate feasibility and acceptability of VR scenarios that target balance in MS using a pilot trial.

METHODS

Participants were randomly allocated to either a VR training (i.e. intervention group) (n = 20) or a control group (n = 20). Intervention group received VR training for 6 weeks. Control group received home-based traditional balance exercises without the VR. Participants were assessed at baseline and follow-up on Berg Balance Scale (BBS), Timed Up and Go (TUG), the 10 Meter Walk Test (10-MWT), the 3 Minute Walk Distance (3-MWD), the Modified Fatigue Impact Scale (MFIS) Fall Efficacy Scale- International (FES-I) and the Short Form 36 (SF-36).

RESULTS

Six VR scenarios weer developed. Sixteen participants in the intervention and 16 in the control group completed the study. Significant differences between the two groups were observed at on BBS, MFIS and several outcomes of the SF-36 survey (P < 0.05). Participants reported overall level of satisfaction with the developed VR scenarios.

CONCLUSIONS

Findings demonstrated the feasibility and acceptability of a VR-based program in MS individuals. Our findings support the implementation of a larger trial of longer-term VR program.

Identifying the neural correlates of doorway freezing in Parkinson's disease

Freezing of gait (FOG) in Parkinson's disease (PD) is frequently triggered upon passing through narrow spaces such as doorways. However, despite being common the neural mechanisms underlying this phenomenon are poorly understood. In our study, 19 patients who routinely experience FOG performed a previously validated virtual reality (VR) gait paradigm where they used foot-pedals to navigate a series of doorways. Patients underwent testing randomised between both their "ON" and "OFF" medication states. Task performance in conjunction with blood oxygenation level dependent (BOLD) signal changes between "ON" and "OFF" states were compared within each patient. Specifically, as they passed through a doorway in the VR environment patients demonstrated significantly longer "footstep" latencies in the OFF state compared to the ON state. As seen clinically in FOG this locomotive delay was primarily triggered by narrow doorways rather than wide doorways. Functional magnetic resonance imaging revealed that footstep prolongation on passing through doorways was associated with selective hypoactivation in the presupplementary motor area (pSMA) bilaterally. Task-based functional connectivity analyses revealed that increased latency in response to doorways was inversely correlated with the degree of functional connectivity between the pSMA and the subthalamic nucleus (STN) across both hemispheres. Furthermore, increased frequency of prolonged footstep latency was associated with increased connectivity between the bilateral STN. These findings suggest that the effect of environmental cues on triggering FOG reflects a degree of impaired processing within the pSMA and disrupted signalling between the pSMA and STN, thus implicating the "hyperdirect" pathway in the generation of this phenomenon.

The virtual reality of Parkinson's disease freezing of gait: A systematic review

INTRODUCTION

Freezing of gait is an episodic inability to move the feet forward despite the intention to walk. It is a common cause of falls and subsequent morbidity and mortality in Parkinson's disease. Virtual reality paradigms provide an opportunity to safely evaluate freezing of gait, in order to better understand the underlying pathophysiology. This article focuses on the methodology, threshold used to define freezing of gait, results, limitations of studies using virtual reality paradigms, and proposes future directions of research. Summarizing these articles improves our understanding of freezing of gait in Parkinson's disease, and critical evaluation provides an opportunity for future studies to improve upon these efforts.

METHODS

We performed a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines, of studies using VR paradigms to elucidate the underlying pathophysiology of PD-FOG.

RESULTS

This review initially identified 57 articles, but after exclusion of duplicates, abstracts, and studies not focused on the underlying pathophysiology of this disorder, 12 peer-reviewed articles using virtual reality paradigms to evaluate freezing of gait in Parkinson's disease were found.

CONCLUSION

Virtual reality paradigms are able to reproduce freezing of gait. Studies using MRI compatible virtual reality to evaluate freezing of gait found dysfunctional connectivity between cortical and subcortical structures during episodes. However, several important limitations of these studies should caution our interpretation of these results. Future studies which improve the design and methodology are needed to ultimately identify the cause and subsequent treatments for freezing of gait in Parkinson's disease.

Entrenamiento motor en el continuo de la realidad a la virtualidad

Introducción. La trasformación de la capacidad de movimiento de las personas es un reto que el fisioterapeuta asume como estrategia de aprendizaje motor.Objetivo. Plantear los referentes teóricos y prácticos más relevantes en el uso de ambientes terapéuticos en el continuo de la realidad a la virtualidad en el entrenamiento motor de pacientes con accidente cerebrovascular y enfermedad de Parkinson. Materiales y métodos. Revisión de la literatura que analiza y aporta de manera conceptual, en el área de la rehabilitación y la fisioterapia, información sobre entrenamiento y aprendizaje motor.Resultados. Se evidencia potencial en el uso de la realidad virtual para la rehabilitación de alteraciones del movimiento debidas a disfunciones neurológicas. Las herramientas tecnológicas propias de la realidad virtual permiten un mayor conocimiento de los resultados con respecto a las características del movimiento, lo cual ayuda a mejorar el aprendizaje motor, en comparación con el entrenamiento tradicional.Conclusiones. Se requiere objetivar el proceso de rehabilitación para medir con precisión los cambios que producen estrategias de aprendizaje en las capacidades de movimiento de las personas con deficiencias del sistema neuromuscular para generar evidencia del impacto que tienen los programas de entrenamiento motor en el continuo de la realidad a la virtualidad.

Chemogenetic activation of dopamine neurons in the ventral tegmental area, but not substantia nigra, induces hyperactivity in rats

Hyperactivity is a core symptom in various psychiatric disorders, including attention-deficit/hyperactivity disorder, schizophrenia, bipolar disorders, and anorexia nervosa. Although hyperactivity has been linked to dopaminergic signalling, the causal relationship between midbrain dopamine neuronal activity and locomotor hyperactivity remains unknown. In this study, we test whether increased dopamine neuronal activity is sufficient to induce locomotor hyperactivity. To do so, we used designer receptors exclusively activated by designer drugs (DREADD) to chemogenetically enhance neuronal activity in two main midbrain dopamine neuron populations, i.e. the ventral tegmental area (VTA) and substantia nigra pars compacta (SN), in TH:Cre rats. We found that activation of VTA dopamine neurons induced a pronounced and long-lasting hyperactive phenotype, whilst SN dopamine neuron activation only modestly increased home cage locomotion. Furthermore, this hyperactive phenotype was replicated by selective activation of the neuronal pathway from VTA to the nucleus accumbens (NAC). These results show a clear functional difference between neuronal subpopulations in the VTA and SN with regards to inducing locomotor hyperactivity, and suggest that the dopaminergic pathway from VTA to NAC may be a promising target for the treatment of hyperactivity disorders.