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At least 541 records · Page 30Linked to original sources

PubMed2003

Vertigo in virtual reality with haptics: case report.

A researcher was working with a desktop virtual environment system. The system was displaying vector fields of a cyclonic weather system, and the system incorporated a haptic display of the forces in the cyclonic field. As the subject viewed the rotating cyclone field, they would move a handle "through" the representation of the moving winds and "feel" the forces buffeting the handle as it moved. Stopping after using the system for about 10 min, the user experienced an immediate sensation of postural instability for several minutes. Several hours later, there was the onset of vertigo with head turns. This vertigo lasted several hours and was accompanied with nausea and motion illusions that exacerbated by head movements. Symptoms persisted mildly the next day and were still present the third and fourth day, but by then were only provoked by head movements. There were no accompanying symptoms or history to suggest an inner ear disorder. Physical examination of inner ear and associated neurologic function was normal. No other users of this system have reported similar symptoms. This case suggests that some individuals may be susceptible to the interaction of displays with motion and movement forces and as a result experience motion illusions. Operators of such systems should be aware of this potential and minimize exposure if vertigo occurs.

Computer Simulation↗

PubMed2003

Developing a virtual reality-based methodology for people with dementia: a feasibility study.

The aim of this study was to examine the feasibility of virtual reality (VR) technology for use by persons with dementia (PWD). Data were obtained directly from six PWD regarding their experiences with a virtual environment (VE) of a large outdoor park. A user-centered method was developed to assess: (a) presence; (b) user inputs; (c) display quality; (d) simulation fidelity; and (e) overall system usability. The extent to which PWD could perform four functional activities in the VE was also investigated (e.g., mailing a letter). In addition, physical and psychological well-being of PWD while interacting with the VE was assessed objectively by recording heart rate during the VR sessions and subjectively with discrete questionnaire items and real-time prompts. Symptom profiles associated with simulator sickness were assessed with an adapted version of the Simulator Sickness Questionnaire. The study found that PWD to some extent experienced presence; perceived that objects were realistic and moved naturally; generally felt in control of the interaction; and demonstrated little difficulty using a joystick for navigation. The study also demonstrated that VR is an appropriate medium for assessing functional behavior within the context of an ecologically valid VE. PWD did not experience any significant increase in symptoms associated with simulator sickness, or detriments to their psychological and physical well-being. These findings demonstrated that it is feasible to work in VEs with PWD.

Aged↗

PubMed2003

Multisensory integration in speed estimation during self-motion.

This study assessed the relative contributions of visual and proprioceptive/motor information during self-motion in a virtual environment using a speed discrimination task. Subjects wore a head-mounted display and rode a stationary bicycle along a straight path in an empty, seemingly infinite hallway with random surface texture. For each trial, subjects were required to pedal the bicycle along two paths at two different speeds (a standard speed and a comparison speed) and subsequently report whether the second speed travelled was faster than the first. The standard speed remained the same while the comparison speed was varied between trials according to the method of constant stimuli. When visual and proprioceptive/motor cues were provided separately or in combination, the speed discrimination thresholds were comparable, suggesting that either cue alone is sufficient. When the relation between visual and proprioceptive information was made inconsistent by varying optic flow gain, the resulting psychometric functions shifted along the horizontal axis (pedalling speed). The degree of separation between these functions indicated that both optic flow and proprioceptive cues contributed to speed estimation, with proprioceptive cues being dominant. These results suggest an important role for proprioceptive information in speed estimation during self-motion.

Adult↗

PubMed2002

Using CAVE technology for functional genomics studies.

We have established the first Java 3D-enabled CAVE (CAVE automated virtual environment). The Java application programming interface allows the complete separation of the program development from the program execution, opening new application domains for the CAVE technology. Programs can be developed on any Java-enabled computer platform, including Windows, Macintosh, and Linux workstations, and executed in the CAVE without modification. The introduction of Java, one of the major programming environments for bioinformatics, into the CAVE environment allows the rapid development applications for genome research, especially for the analysis of the spatial and temporal data that are being produced by functional genomics experiments. The CAVE technology will play a major role in the modeling of biological systems that is necessary to understand how these systems are organized and how they function.

Automation↗

PubMed2005

Virtual reality in psychotherapy: review.

Virtual reality (VR) has recently emerged as a potentially effective way to provide general and specialty health care services, and appears poised to enter mainstream psychotherapy delivery. Because VR could be part of the future of clinical psychology, it is critical to all psychotherapists that it be defined broadly. To ensure appropriate development of VR applications, clinicians must have a clear understanding of the opportunities and challenges it will provide in professional practice. This review outlines the current state of clinical research relevant to the development of virtual environments for use in psychotherapy. In particular, the paper focuses its analysis on both actual applications of VR in clinical psychology and how different clinical perspectives can use this approach to improve the process of therapeutic change.

Humans↗

PubMed2006

Virtual reality in the rehabilitation of the upper limb after stroke: the user's perspective.

Our group has developed a relatively low-cost virtual reality (VR) system for rehabilitation of the upper limb following stroke. Our system is immersive in that the participant views a representation of their arm and hand, reaching and retrieving objects in the virtual environment (VE), through a head-mounted display (HMD). This is thought to increase the participant's sense of presence in the VE and may lead to improved rehabilitation outcomes. However, use of immersion, particularly with our low-cost system, may increase the incidence of side effects reported. Therefore, the aim of this project was to assess the interaction of healthy users and those following stroke, in terms of their experience of presence in the VE and the rate of self-reported side effects. Differences in rates of perceived exertion, levels of enjoyment, and sense of control between both groups were also explored.

Adult↗

PubMed2006

A treadmill and motion coupled virtual reality system for gait training post-stroke.

A virtual reality (VR)-based locomotor training system has been developed for gait rehabilitation post-stroke. The system consists of a self-paced treadmill mounted onto a 6-degrees-of-freedom motion platform. Virtual environments (VEs) that are synchronized with the speed of the treadmill and the motions of the platform are rear-projected onto a screen in front of the walking subject. A feasibility study was conducted to test the capability of two stroke patients and one healthy control to be trained with the system. Three VE scenarios (corridor walking, street crossing, and park stroll) were woven into a gait-training program that provided three levels of complexity (walking speed, slopes, collision avoidances), progression criteria (number of successful trials) and knowledge of results. Results show that, with practice, patients can effectively increase their gait speed as demanded by the task and adapt their gait with respect to the change in physical terrain. However, successful completion of tasks requiring adaptation to increasing demands related to speed and physical terrains does not necessarily predict the patient's ability to anticipate and avoid collision with obstacles during walking. This feasibility study demonstrates that persons with stroke are able to adapt to this novel VR system and be immersed in the VEs for gait training.

Computer Simulation↗

PubMed2006

Influences of the perception of self-motion on postural parameters.

We examined how spatial and temporal characteristics of the perception of self-motion, generated by constant velocity visual motion, was reflected in orientation of the head and whole body of young adults standing in a CAVE, a virtual environment that presents wide field of view stereo images with context and texture. Center of pressure responses from a force plate and perception of self-motion through orientation of a hand-held wand were recorded. The influence of the perception of self-motion on postural kinematics differed depending upon the plane and complexity of visual motion. Postural behaviors generated through the perception of self-motion appeared to contain a confluence of the cortically integrated visual and vestibular signals and of other somatosensory inputs. This would suggest that spatial representation during motion in the environment is modified by both ascending and descending controls. We infer from these data that motion of the visual surround can be used as a therapeutic tool to influence posture and spatial orientation, particularly in more visually sensitive individuals following central nervous system (CNS) impairment.

Adult↗

PubMed2006

A virtual reality apartment as a measure of medication management skills in patients with schizophrenia: a pilot study.

Performance on a novel, virtual reality (VR) assessment of medication management skills, the Virtual Reality Apartment Medication Management Assessment (VRAMMA), was investigated in 25 patients with schizophrenia and 18 matched healthy controls. The VRAMMA is a virtual 4-room apartment consisting of a living room with an interactive clock and TV, a bedroom, a kitchen, and a bathroom with an interactive medicine cabinet. After an exploratory phase, participants were given a mock prescription regimen to be taken 15 minutes later from pill bottles located in the medicine cabinet in the bathroom of the virtual environment. The VRAMMA was administered with a validated measure of medication management skills, several neurocognitive tests, and a symptom scale. Results revealed that (1) schizophrenic patients made significantly more quantitative errors in the number of pills taken, were less accurate at taking the prescribed medications at the designated time, and checked the interactive clock less frequently than healthy controls; (2) in patients with schizophrenia, there was significant agreement in classification of adherence vs nonadherence between a validated measure of medication management skills and the VRAMMA; and (3) in patients with schizophrenia, years of education and a measure of verbal learning and memory were linked to quantitative errors on the VRAMMA, while positive symptoms, specifically delusional symptoms, were inversely linked to distance traveled within the VRAMMA. This is the first study, to our knowledge, to provide evidence for the utility of VR technology in the assessment of instrumental role functioning in patients with schizophrenia.

Adult↗

PubMed1996

Neuronal responses in the motion pathway of the macaque monkey to natural optic flow stimuli.

Neurones in higher visual motion areas in the superior temporal sulcus (STS) of the macaque monkey respond to abstract random dot optic flow stimuli. Higher motion areas may not only represent, but in a next computational stage also analyse the flow field to determine, for instance, the direction of heading for navigation purposes. Real world visual scenes differ in several aspects from these abstract optic flow stimuli. We tested the neuronal response to naturalistic optic flow stimuli which simulated egomotion in different virtual environments and contained different numbers of visual cues. Neuronal activity depended mainly on the position of the focus of expansion rather than on other visual cues. This finding supports the hypothesis that higher motion areas within the STS analyse optic flow in natural scenes and can thus signal the direction of heading.

Animals↗

PubMed1997

Visual working memory for shape and 3D-orientation: a PET study.

In order to determine the neural substrate of working memory for shape and 3D-orientation, regional cerebral blood flow (rCBF) changes were estimated using positron emission tomography (PET). Subjects were scanned during the performance of two delayed-matching-to-sample tasks using flat polydedrical objects of different shapes and 3D-orientations presented in a virtual environment. The shape matching task was associated with activation in the occipito-temporal junction, occipito-parietal cortex and mesial frontal pole of the right hemisphere. During the orientation matching task, rCBF increased in the mesial occipito-temporal cortex, superior temporal gyrus and middle frontal gyrus of the left hemisphere. The right supramarginal gyrus was also activated. These results suggest that both visual pathways are engaged in the processing of objects presented in different orientations. The dorsal stream is involved mainly in working memory of 3D-orientation, while the ventral stream is involved especially in shape working memory.

Adult↗

PubMed2002

Visible humans, vanishing bodies, and virtual nursing: complications of life, presence, place, and identity.

The emergence of the posthuman body and the disappearance of the humanist body serve as background for the rediscovery of the body as resource and problem in nursing. At the precise moment when the fleshy body is deemed increasingly irrelevant and immaterial in cyberspace come divergent moves in nursing toward not only resurrecting this body, but also toward virtual environments of nursing care, where fleshy bodies never encounter each other. The posthuman conflation of bodies and information poses the greatest challenge yet to the secure place, presence, and identity of nursing in health care.

Anatomy, Cross-Sectional↗

PubMed2004

Face, content and construct validity of the University of Washington virtual reality transurethral prostate resection trainer.

PURPOSE: We examined the face, content and construct validity of version 1.0 of the University of Washington transurethral prostate resection (TURP) trainer. MATERIALS AND METHODS: Version 1.0 of a virtual reality based simulator for transurethral skills was developed at our laboratory by integrating TURP hardware with our virtual 3-dimensional anatomy, irrigation control, cutting, bleeding and haptics force feedback. A total of 72 board certified urologists and 19 novices completed a pre-task questionnaire, viewed an introductory training video and performed a pre-compiled 5-minute resection task. The simulator logged operative errors, gm resected, blood loss, irrigant volume, foot pedal use and differential time spent with orientation, cutting or coagulation. Trainees and experts evaluated the simulator on a modified likert scale. The 2-tailed Levene t test was used to compare means between experts and novices. RESULTS: Overall version 1.0 content was between slightly and moderately acceptable. Experts spent less time with orientation (p < 0.0001), resected more total tissue (p < 0.0001), had more gm resected per cut (p = 0.002) and less blood loss per gm resected (p = 0.032), used less irrigant per gm resected (p = 0.02) and performed fewer errors (p < 0.0001) than novices. CONCLUSIONS: We established the face, content and construct validity for version 1.0 of the University of Washington TURP trainer to simulate the skills necessary to perform TURP. A predictive validity study showing a translation of skills from the virtual environment to the operating room will complete the validation of this model.

Adult↗

PubMedDate not supplied

Learning directions of objects specified by vision, spatial audition, or auditory spatial language.

The modality by which object azimuths (directions) are presented affects learning of multiple locations. In Experiment 1, participants learned sets of three and five object azimuths specified by a visual virtual environment, spatial audition (3D sound), or auditory spatial language. Five azimuths were learned faster when specified by spatial modalities (vision, audition) than by language. Experiment 2 equated the modalities for proprioceptive cues and eliminated spatial cues unique to vision (optic flow) and audition (differential binaural signals). There remained a learning disadvantage for spatial language. We attribute this result to the cost of indirect processing from words to spatial representations.

Adult↗

PubMed2000

Optimal digital filtering for tremor suppression.

Remote manually operated tasks such as those found in teleoperation, virtual reality, or joystick-based computer access, require the generation of an intermediate electrical signal which is transmitted to the controlled subsystem (robot arm, virtual environment, or a cursor in a computer screen). When human movements are distorted, for instance, by tremor, performance can be improved by digitally filtering the intermediate signal before it reaches the controlled device. This paper introduces a novel tremor filtering framework in which digital equalizers are optimally designed through pursuit tracking task experiments. Due to inherent properties of the man-machine system, the design of tremor suppression equalizers presents two serious problems: 1) performance criteria leading to optimizations that minimize mean-squared error are not efficient for tremor elimination and 2) movement signals show ill-conditioned autocorrelation matrices, which often result in useless or unstable solutions. To address these problems, a new performance indicator in the context of tremor is introduced, and the optimal equalizer according to this new criterion is developed. Ill-conditioning of the autocorrelation matrix is overcome using a novel method which we call pulled-optimization. Experiments performed with artificially induced vibrations and a subject with Parkinson's disease show significant improvement in performance. Additional results, along with MATLAB source code of the algorithms, and a customizable demo for PC joysticks, are available on the Internet at http:¿tremor-suppression.com.

Algorithms↗

PubMed2001

Virtual reality-enhanced stroke rehabilitation.

A personal computer (PC)-based desktop virtual reality (VR) system was developed for rehabilitating hand function in stroke patients. The system uses two input devices, a CyberGlove and a Rutgers Master II-ND (RMII) force feedback glove, allowing user interaction with a virtual environment. This consists of four rehabilitation routines, each designed to exercise one specific parameter of hand movement: range, speed, fractionation or strength. The use of performance-based target levels is designed to increase patient motivation and individualize exercise difficulty to a patient's current state. Pilot clinical trials have been performed using the above system combined with noncomputer tasks, such as pegboard insertion or tracing of two-dimensional (2-D) patterns. Three chronic stroke patients used this rehabilitation protocol daily for two weeks. Objective measurements showed that each patient showed improvement on most of the hand parameters over the course of the training. Subjective evaluation by the patients was also positive. This technical report focuses on this newly developed technology for VR rehabilitation.

Aged↗

PubMed2000

A virtual reality testbed for brain-computer interface research.

Virtual reality promises to extend the realm of possible brain-computer interface (BCI) prototypes. Most of the work using electroencephalograph (EEG) signals in VR has focussed on brain-body actuated control, where biological signals from the body as well as the brain are used. We show that when subjects are allowed to move and act normally in an immersive virtual environment, cognitive evoked potential signals can still be obtained and used reliably. A single trial accuracy average of 85% for recognizing the differences between evoked potentials at red and yellow stop lights will be presented and future directions discussed.

Adult↗

PubMed2006

In vivo mechanical behavior of intra-abdominal organs.

For realistic surgical simulation in a virtual environment, in vivo material properties of biological tissues are required for simulating the deformations and the reaction forces from the tool-tissue interactions. In this paper, the in vivo static and dynamic mechanical behavior of the liver and lower esophagus of pigs were presented both in linear and nonlinear regions under compressive and shear indentations. A robotic device was programmed to function as a mechanical stimulator with a 2-mm flat-tipped cylindrical probe attached to its tip. A series of ramp and hold stimuli, as well as sinusoidal indentation stimuli, were delivered to the organs and reaction forces were measured. The conditions for these indentation stimuli were designed such that they were similar to conditions in an operating room. Experiments were also carried out on the organs for ex vivo and in vitro conditions. Results show that the breathing and pulse rate significantly affect the measured force responses of the organs. From the obtained force-displacement relationships, steady-state impedances as well as dynamic impedances of both organs were calculated. The results also show that in vivo steady-state impedance of the lower esophagus is significantly higher than that of the liver. The in vivo steady-state response of the liver, however, exhibits a greater degree of nonlinearity than that of the lower esophagus. The in vivo steady-state response of the lower esophagus in the three orthogonal directions also indicates that the lower esophagus is not significantly anisotropic. The impedance of both organs under sinusoidal indentations (0-5 Hz) are fairly similar each other. Magnitudes of the impedance over the stimulus frequencies are fairly constant. The impedance phase angles decrease over the range of stimulus frequencies applied. Comparison of the measurements obtained from the in vivo, ex vivo, and in vitro experiments shows that the mechanical properties of the biological tissues change significantly after the death of the animal. The tissues generally become stiffer and exhibit greater nonlinearity. The degree of change in their mechanical properties is dependent on the amount of time after the death of the animal. These data can be further utilized in the computing of the material parameters of tissue models for laparoscopic surgery simulators as well as open surgery simulators.

Abdomen↗