Effects of Parkinson’s disease on optic flow perception for heading direction during navigation

Visuoperceptual disorders have been identified in individuals with Parkinson’s disease (PD) and may affect the perception of optic flow for heading direction during navigation. Studies in healthy subjects have confirmed that heading direction can be determined by equalizing the optic flow speed (OS) between visual fields. The present study investigated the effects of PD on the use of optic flow for heading direction, walking parameters, and interlimb coordination during navigation, examining the contributions of OS and spatial frequency (dot density). Twelve individuals with PD without dementia, 18 age-matched normal control adults (NC), and 23 young control adults (YC) walked through a virtual hallway at about 0.8 m/s. The hallway was created by random dots on side walls. Three levels of OS (0.8, 1.2, and 1.8 m/s) and dot density (1, 2, and 3 dots/m2) were presented on one wall while on the other wall, OS and dot density were fixed at 0.8 m/s and 3 dots/m2, respectively. Three-dimensional kinematic data were collected, and lateral drift, walking speed, stride frequency and length, and frequency, and phase relations between arms and legs were calculated. A significant linear effect was observed on lateral drift to the wall with lower OS for YC and NC, but not for PD. Compared to YC and NC, PD veered more to the left under OS and dot density conditions. The results suggest that healthy adults perceive optic flow for heading direction. Heading direction in PD may be more affected by the asymmetry of dopamine levels between the hemispheres and by motor lateralization as indexed by handedness.Published versio

Flexible Virtual Reality System for Neurorehabilitation and Quality of Life Improvement

As life expectancy is mostly increasing, the incidence of many neurological disorders is also constantly growing. For improving the physical functions affected by a neurological disorder, rehabilitation procedures are mandatory, and they must be performed regularly. Unfortunately, neurorehabilitation procedures have disadvantages in terms of costs, accessibility and a lack of therapists. This paper presents Immersive Neurorehabilitation Exercises Using Virtual Reality (INREX-VR), our innovative immersive neurorehabilitation system using virtual reality. The system is based on a thorough research methodology and is able to capture real-time user movements and evaluate joint mobility for both upper and lower limbs, record training sessions and save electromyography data. The use of the first-person perspective increases immersion, and the joint range of motion is calculated with the help of both the HTC Vive system and inverse kinematics principles applied on skeleton rigs. Tutorial exercises are demonstrated by a virtual therapist, as they were recorded with real-life physicians, and sessions can be monitored and configured through tele-medicine. Complex movements are practiced in gamified settings, encouraging self-improvement and competition. Finally, we proposed a training plan and preliminary tests which show promising results in terms of accuracy and user feedback. As future developments, we plan to improve the system's accuracy and investigate a wireless alternative based on neural networks.Comment: 47 pages, 20 figures, 17 tables (including annexes), part of the MDPI Sesnsors "Special Issue Smart Sensors and Measurements Methods for Quality of Life and Ambient Assisted Living

Sensorimotor control of gait: a novel approach for the study of the interplay of visual and proprioceptive feedback

Sensorimotor control theories propose that the central nervous system exploits expected sensory consequences generated by motor commands for movement planning, as well as online sensory feedback for comparison with expected sensory feedback for monitoring and correcting, if needed, ongoing motor output. In our study, we tested this theoretical framework by quantifying the functional role of expected versus actual proprioceptive feedback for planning and regulation of gait in humans. We addressed this question by using a novel methodological approach to deliver fast perturbations of the walking surface stiffness, in conjunction with a virtual reality system that provided visual feedback of upcoming changes of surface stiffness. In the predictable experimental condition, we asked subjects to learn associating visual feedback of changes in floor stiffness (sand patch) during locomotion to quantify kinematic and kinetic changes in gait. In the unpredictable experimental condition, we perturbed floor stiffness at unpredictable instances during the gait to characterize the gait-phase dependent strategies in recovering the locomotor cycle. For the unpredictable conditions, visual feedback of changes in floor stiffness was absent or inconsistent with tactile and proprioceptive feedback. The investigation of these perturbation-induced effects on legs kinematics revealed that visual feedback of upcoming changes in floor stiffness allows for both early (preparatory) and late (post-perturbation) changes in leg kinematics. However, when proprioceptive feedback is not available, the early responses do not occur while the late responses are preserved although in a, slightly attenuated form. The methods proposed and the preliminary results of this study open new directions for the investigation of the relative role of visual, tactile, and proprioceptive feedback on gait control, with potential implications for designing novel robot-assisted gait rehabilitation approaches

Animating Virtual Human for Virtual Batik Modeling

This research paper describes a development of animating virtual human for virtual batik modeling project. The objectives of this project are to animate the virtual human, to map the cloth with the virtual human body, to present the batik cloth, and to evaluate the application in terms of realism of virtual human look, realism of virtual human movement, realism of 3D scene, application suitability, application usability, fashion suitability and user acceptance. The final goal is to accomplish an animated virtual human for virtual batik modeling. There are 3 essential phases which research and analysis (data collection of modeling and animating technique), development (model and animate virtual human, map cloth to body and add a music) and evaluation (evaluation of realism of virtual human look, realism of virtual human movement, realism of props, application suitability, application usability, fashion suitability and user acceptance). The result for application usability is the highest percentage which 90%. Result show that this application is useful to the people. In conclusion, this project has met the objective, which the realism is achieved by used a suitable technique for modeling and animating

ReLiPh: rehabilitation for lower limb with phantom pain

O membro fantasma ou sensação fantasma, ao longo dos anos, têm se destacado por ser originada de diferentes causas. Pesquisas e estudos mostram que, após uma amputação, na maioria dos casos, experienciam a sensação de membro fantasma e em muitos desses casos dolorosos. A presente tese baseia-se em uma pequena parte deste amplo tópico. Baseada na terapia de espelho usada na reabilitação e tratamento da dor fantasma. Ao longo do projeto, nós estudamos quais são os componentes mais relevantes para a reorganização/reestruturação, a fim de eliminar os sintomas negativos e futuros distúrbios/perturbações. Associada na relação do cérebro com o corpo, ou seja, as imagens formadas pelo cérebro em relação ao corpo físico desempenhando um papel crucial na relação do membro fantasma e da dor no membro fantasma, bem como no processo de cura e tratamento através de exercícios e no relacionamento da imagem que o cérebro tem do corpo físico. Esta dissertação tem como objetivo na construção de uma nova abordagem tecnológica, baseando-se nos princípios e critérios utilizados na terapia de espelho. A metodologia assenta na criação de um ambiente de realidade virtual controlado por um dispositivo que captura a atividade muscular em tempo real. Implementado num jogo baseado em movimentos/exercícios simples e naturais, sem uso de força ou esforço. Os elevados resultados verificados e testados, em indivíduos saudáveis e em um estudo de caso, na redução da dor fantasma, gerando um interesse e motivação, além de um melhor senso de presença e foco durante o seu uso. Concluindo, o projeto abre novas direções futuras de como novas abordagens tecnológicas podem ser usados nas pesquisas médicas na área do membro e na dor fantasma, em ambientes controlados e contextualizados. Melhorando a eficácia e eficiência, garantindo uma maior flexibilidade nos diferentes casos de amputação.The phantom limb or phantom sensation, over the years, has stood out being originated from different causes. Research and studies show that after an amputation, in most cases, they experience the sensation of a phantom limb and in many of those painful feelings. This thesis is based on a small part of this wide topic. Based on the mirror therapy used in rehabilitation and treatment for phantom pain. Throughout the project, we study what are the most relevant components to reorganization/restructuring in order to eliminate negative symptoms and future disturbances. Moreover it is established in the relationship of the brain with the body, that the images formed by the brain in relation to the physical body play a crucial role in the relationship with the phantom limb and phantom limb pain, as well as in the process of healing and treatment throughout exercises and the relationship of the image that the brain has to the physical body. This dissertation aims to build a new technological approach, based on the principles and criteria used in mirror therapy. The methodology is based on the creation of a virtual reality environment controlled by a device which captures the muscle activity in real time. Implemented in a game based on natural and simple effortless exercises without the use of strength. The high results verified and tested, in healthy subjects and in a case study, to reduce phantom pain, generating an interest and motivation, as well as a better sense of presence and focus during its use. In conclusion, the project opens up new future directions of how new technological approaches can be used in medical research in the field of phantom limbs and in phantom pain, in a controlled and contextualized environments and/or movements. Improving effectiveness and efficiency ensuring greater flexibility in different cases of amputation

Virtual reality obstacle crossing: adaptation, retention and transfer to the physical world

Virtual reality (VR) paradigms are increasingly being used in movement and exercise sciences with the aim to enhance motor function and stimulate motor adaptation in healthy and pathological conditions. Locomotor training based in VR may be promising for motor skill learning, with transfer of VR skills to the physical world in turn required to benefit functional activities of daily life. This PhD project aims to examine locomotor adaptations to repeated VR obstacle crossing in healthy young adults as well as transfers to the untrained limb and the physical world, and retention potential of the learned skills. For these reasons, the current thesis comprises three studies using controlled VR obstacle crossing interventions during treadmill walking. In the first and second studies we investigated adaptation to crossing unexpectedly appearing virtual obstacles, with and without feedback about crossing performance, and its transfer to the untrained leg. In the third study we investigated transfer of virtual obstacle crossing to physical obstacles of similar size to the virtual ones, that appeared at the same time point within the gait cycle. We also investigated whether the learned skills can be retained in each of the environments over one week. In all studies participants were asked to walk on a treadmill while wearing a VR headset that represented their body as an avatar via real-time synchronised optical motion capture. Participants had to cross virtual and/or physical obstacles with and without feedback about their crossing performance. If applicable, feedback was provided based on motion capture immediately after virtual obstacle crossing. Toe clearance, margin of stability, and lower extremity joint angles in the sagittal plane were calculated for the crossing legs to analyse adaptation, transfer, and retention of obstacle crossing performance. The main outcomes of the first and second studies were that crossing multiple virtual obstacles increased participants’ dynamic stability and led to a nonlinear adaptation of toe clearance that was enhanced by visual feedback about crossing performance. However, independent of the use of feedback, no transfer to the untrained leg was detected. Moreover, despite significant and rapid adaptive changes in locomotor kinematics with repeated VR obstacle crossing, results of the third study revealed limited transfer of learned skills from virtual to physical obstacles. Lastly, despite full retention over one week in the virtual environment we found only partial retention when crossing a physical obstacle while walking on the treadmill. In summary, the findings of this PhD project confirmed that repeated VR obstacle perturbations can effectively stimulate locomotor skill adaptations. However, these are not transferable to the untrained limb irrespective of enhanced awareness and feedback. Moreover, the current data provide evidence that, despite significant adaptive changes in locomotion kinematics with repeated practice of obstacle crossing under VR conditions, transfer to and retention in the physical environment is limited. It may be that perception-action coupling in the virtual environment, and thus sensorimotor coordination, differs from the physical world, potentially inhibiting retained transfer between those two conditions. Accordingly, VR-based locomotor skill training paradigms need to be considered carefully if they are to replace training in the physical world

The Impact of Extreme Virtual Elevation above Grade on Construction Workers\u27 Physiological Responses, Physical Responses, and Task Performance

On average, in every two work hours, one person dies from work-related injuries at construction sites. Most incidents are due to falling from elevated surfaces. Slips, trips, and loss of balance are the main causes. Studies suggest that instigating visual mismatch and physiological changes are among the most important reasons behind falling from narrow elevated surfaces. By using advanced virtual reality models, this dissertation aims to highlight some of the possible effects of a destabilizing environment (i.e., elevation above grade) on workers’ physiological responses and task performance. More specifically, this dissertation strives to find potential effects of elevation above grade and a moving structural beam as destabilizing environments on construction workers’ postural sway, gait pattern, and task performance accuracy. To that end, a series of virtual reality experiments was conducted on thirty volunteers, all students from the University of Nebraska - Lincoln. There were three required VR tasks asked from the subjects once on the ground and again on the 20th floor of an unfinished building: walking on virtual structural beams, standing still on the virtual platform (force plate in reality), and performing hand-steadiness and pursuit tests (physiological battery tests). In addition, to study the plausible relationship between self-perceived fear (and acrophobia) and physiological responses, all subjects were instructed to complete the electronic James Geer’s fear and Cohen’s acrophobia questionnaires. The result of this study showed that elevation above grade has a substantial effect on the gait pattern. More specifically, exposure to elevation increases gait stride height variability and decreases gait stride length. As a result, subjects spend more time on gait tasks executed on narrow elevated surfaces. Also, the findings indicated that the presence of the virtual avatar significantly affects gait parameters. The presence of synchronized virtual legs caused subjects to increase their stride height and spend more time on similar virtual tasks on the ground. However, the subjects did not exhibit similar differences once exposed to virtual elevation. Furthermore, the moving structural beam significantly increased the heart rate of the subjects. As part of the steel erection simulation, the experimental results implied that construction workers could show noticeable physiological responses in the vicinity of large moving objects. In terms of task performance, working at height affects the result of the posturography and battery tests. This finding suggests that dual-tasks performed in a static position, and in the presence of elevation-related visual stimuli, can cause a reduction in the postural sway. In contrast, in the absence of visual depth, fear of height can positively influence the outcome of the construction tasks performed on elevated platforms. Advisors: Jay Puckett and Terry Stent