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- Evaluation of a low-cost virtual reality surround-screen projection systemPublication . Gonçalves, Afonso; Borrego, Adrián; Latorre, Jorge; Llorens, Roberto; Bermúdez i Badia, SergiTwo of the most popular mediums for virtual reality are head-mounted displays and surround-screen projection systems, such as CAVE Automatic Virtual Environments. In recent years, HMDs suffered a significant reduction in cost and have become widespread consumer products. In contrast, CAVEs are still expensive and remain accessible to a limited number of researchers. This study aims to evaluate both objective and subjective characteristics of a CAVE-like monoscopic low-cost virtual reality surround-screen projection system compared to advanced setups and HMDs. For objective results, we measured the head position estimation accuracy and precision of a low-cost active infrared (IR) based tracking system, used in the proposed low-cost CAVE, relatively to an infrared marker-based tracking system, used in a laboratory-grade CAVE system. For subjective characteristics, we investigated the sense of presence and cybersickness elicited in users during a visual search task outside personal space, beyond arms reach, where the importance of stereo vision is diminished. Thirty participants rated their sense of presence and cybersickness after performing the VR search task with our CAVE-like system and a modern HMD. The tracking showed an accuracy error of 1.66 cm and .4 mm of precision jitter. The system was reported to elicit presence but at a lower level than the HMD, while causing significant lower cybersickness. Our results were compared to a previous study performed with a laboratory-grade CAVE and support that a VR system implemented with low-cost devices could be a viable alternative to laboratory-grade CAVEs for visual search tasks outside the user’s personal space.
- Open Rehab initiative: second development iterationPublication . Freitas, Diogo; Paulino, Teresa; Bermúdez i Badia, Sergi; Llorens, Roberto; Deutsch, Judith E.A substantial part of rehabilitation tools are developed in the context of research projects, which rarely reach their target audience, in particular clinicians and patients. To address this challenge, the Open Rehab Initiative (ORI) emerged as an international independent online portal with the goal of connecting clinicians, scientists, engineers, game developers, and end-users to interact and share virtual rehabilitation tools. The quality and efficacy of such platform can only be attained iteratively based on a user-centered design approach. This paper describes the design process and features implemented on the second development iteration subsequent to a formative evaluation of the first version of ORI. The main goal of the second iteration was to implement new features and make the platform functional and ready for a second evaluation process with beta testers, which will certainly prompt new features for improvement and will serve as a step toward the final release of the site.
- Virtual reality for sensorimotor rehabilitation post stroke: design principles and evidencePublication . Bermúdez i Badia, Sergi; Fluet, Gerard G.; Llorens, Roberto; Deutsch, Judith E.n the recent years, the use of virtual reality (VR) to enhance motor skills of persons with activity and participation restriction due to disease or injury has been become an important area of research. In this chapter, we describe the design of such VR systems and their underlying principles, such as experience-dependent neuroplasticity and motor learning. Further, psychological constructs related to motivation including salience, goal setting, and rewards are commonly utilized in VR to optimize motivation during rehabilitation activities. Hence, virtually simulated activities are considered to be ideal for (1) the delivery of specifi c feedback, (2) the a bility to perform large volumes of training, and (3) the presentation of precisely calibrated diffi culty levels, which maintain a high level of challenge throughout long training sessions. These underlying principles are contrasted with a growing body of research comparing the effi cacy of VR with traditionally presented rehabilitation activities in persons with stroke that demonstrate comparable or better outcomes for VR. In addition, a small body of literature has utilized direct assays of neuroplasticity to evaluate the effects of virtual rehabilitation interventions in persons with stroke. Promising developments and fi ndings also arise from the use of off-the-s helf video game systems for virtual rehabilitation purposes and the integration of VR with robots and brain-computer interfaces. Several challenges limiting the translation of virtual rehabilitation into routine rehabilitation practice need to be addressed but the fi eld continues to hold promise to answer key issues faced by modern healthcare.
- Body schema plasticity after stroke: subjective and neurophysiological correlates of the rubber hand illusionPublication . Llorens, Roberto; Borrego, Adrián; Palomo, Priscila; Cebolla, Ausiàs; Noé, Enrique; Bermúdez i Badia, Sergi; Baños, RosaStroke can lead to motor impairments that can affect the body structure and restraint mobility. We hypothesize that brain lesions and their motor sequelae can distort the body schema, a sensorimotor map of body parts and elements in the peripersonal space through which human beings embody the reachable space and ready the body for forthcoming movements. Two main constructs have been identified in the embodiment mechanism: body-ownership, the sense that the body that one inhabits is his/her own, and agency, the sense that one can move and control his/her body. To test this, the present study simultaneously investigated different embodiment subcomponents (body-ownership, localization, and agency) and different neurophysiological measures (galvanic skin response, skin temperature, and surface electromyographic activity), and the interaction between them, in clinically-controlled hemiparetic individuals with stroke and in healthy subjects after the rubber hand illusion. Individuals with stroke reported significantly stronger body-ownership and agency and reduced increase of galvanic skin response, skin temperature, and muscular activity in the stimulated hand. We suggest that differences in embodiment could have been motivated by increased plasticity of the body schema and pathological predominance of the visual input over proprioception. We also suggest that differences in neurophysiological responses could have been promoted by a suppression of the reflex activity of the sympathetic nervous system and by the involvement of the premotor cortex in the reconfiguration of the body schema. These results could evidence a body schema plasticity promoted by the brain lesion and a main role of the premotor cortex in this mechanism.
- A virtual reality bus ride as an ecologically valid assessment of balance: a feasibility studyPublication . Gonçalves, A.; Montoya, M. F.; Llorens, R.; Bermúdez i Badia, S.Balance disorders can have substantial adverse implications on the performance of daily activities and lead to an increased risk of falls, which often have severe negative consequences for older adults. Quantitative assessment through computer ized force plate-based posturography enables objective assessment of postural control but could not successfully represent specifc abilities required during daily activities. The use of virtual reality (VR) could improve the representative design of functional activities and increase the ecological validity of posturographic tests, which would enhance the transferability of results to the real world. In this work, we investigate the feasibility of a simulated bus ride experienced in a surround-screen VR system to assess balance with increased ecological validity. Participants were frst evaluated with a posturography test and then with the VR-based bus ride test, while the reactions of their centre of pressure were registered. Lastly, participants provided self-reported measures of the elicited sense of presence during the test. A total of 16 healthy young adults completed the study. Results showed that the simulation could elicit signifcant medial–lateral excursions of the centre of pressure in response to variations in the optical fow. Furthermore, these responses’ amplitude negatively correlated with the participants’ posturography excursions when fxating a target. Although the sense of presence was moderate, likely due to the passive nature of the test, the results support the feasibility of our proposed paradigm, based in the context of a meaningful daily living activity, in assessing balance control components.