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Results for “virtual environment”

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PubMed2001

Retraining movement in patients with acquired brain injury using a virtual environment.

We report preliminary results of an ongoing study in which a virtual environment (VE) system is used to facilitate motor relearning of a pouring task in patients with Acquired Brain Injury (ABI). Four subjects were evaluated pre- and post-VE training using virtual-world and real-world tests in which subjects performed a pouring motion while holding a cup. Standard clinical tests of motor and functional ability were also used. Three of four subjects demonstrated improvement in end-point trajectories (cup path) performed during the virtual and real world tests. Clinical test scores also improved. Results indicate that subjects with ABI were able to learn a movement in VE, and generalize this ability to real-world performance of similar and unrelated tasks. VE training appears to be a feasible and promising approach to the rehabilitation of subjects with ABI.

Adolescent↗

PubMed1999

The nauseogenicity of two methods of navigating within a virtual environment.

This study compared the nauseogenicity of two different strategies for exploring virtual environments whilst wearing an immersive head-mounted display. In the first, the head was kept still and movement was achieved solely by manipulating a hand-control. In the second, the subject was free (and encouraged) to move his or her head when exploring the virtual world. Fourteen subjects completed both of the 20 min trials, three further subjects withdrew from the study after one trial. Subjects reported increases in adverse symptoms when using each strategy and, for the group as a whole, nausea increased steadily during each immersion period. However, significantly larger changes were reported when the head moved than when it was still, as predicted from sensory conflict theory.

Adult↗

PubMed2006

An experimental study on fear of public speaking using a virtual environment.

This paper examines a necessary condition for successful exploitation of a virtual environment (VE) in therapeutic intervention for fear of public speaking. The condition is that clients experience a degree of anxiety in the VE that is similar to what they would have been expected to experience in a similar real world setting. We refer to this as a "presence" response. The experimental study involved 20 people who were confident public speakers and 16 who were phobic, assessed on a standard psychological scale. Half of each group spoke within a VE depicting an empty seminar room, and the other half within the same room but populated by a neutrally behaving virtual audience of five people. Three responses were measured--a questionnaire-based measure of anxiety, a measure of self-focused attention on somatic responses, and actual heart rate. On all responses, the people with phobia showed a significant increase in signs of anxiety when speaking to the virtual audience compared to the empty room, whereas the confident people did not. The result was strong in spite of the relatively low representational and behavioral fidelity of the virtual characters.

Adult↗

PubMed2000

Training in virtual environments: transfer to real world tasks and equivalence to real task training.

Virtual environments (VEs) are extensively used in training but there have been few rigorous scientific investigations of whether and how skills learned in a VE are transferred to the real world. This research aimed to measure and evaluate what is transferring from training a simple sensorimotor task in a VE to real world performance. In experiment 1, real world performances after virtual training, real training and no training were compared. Virtual and real training resulted in equivalent levels of post-training performance, both of which significantly exceeded task performance without training. Experiments 2 and 3 investigated whether virtual and real trained real world performances differed in their susceptibility to cognitive and motor interfering tasks (experiment 2) and in terms of spare attentional capacity to respond to stimuli and instructions which were not directly related to the task (experiment 3). The only significant difference found was that real task performance after training in a VE was less affected by concurrently performed interference tasks than was real task performance after training on the real task. This finding is discussed in terms of the cognitive load characteristics of virtual training. Virtual training therefore resulted in equivalent or even better real world performance than real training in this simple sensorimotor task, but this finding may not apply to other training tasks. Future research should be directed towards establishing a comprehensive knowledge of what is being transferred to real world performance in other tasks currently being trained in VEs and investigating the equivalence of virtual and real trained performances in these situations.

Acoustic Stimulation↗

PubMed1999

A portable virtual environment knee arthroscopy training system with objective scoring.

We have developed a Virtual Environment Knee Arthroscopy Training System (VE-KATS). Formative analysis indicated several features which surgical trainees indicated were necessary for a system to be useful. We have addressed this need by incorporating both rigid and deformable objects, simultaneous use of camera and surgical instrument, improved optical modeling, portability and low cost. A major advance has been the incorporation of automated objective scoring of performance. VE-KATS has now progressed to a viable training system which will be of practical benefit to trainee orthopaedic surgeons.

Arthroscopy↗

PubMed1998

The influence of body movement on subjective presence in virtual environments.

We describe an experiment to assess the influence of body movements on presence in a virtual environment. In the experiment 20 participants were to walk through a virtual field of trees and count the trees with diseased leaves. A 2 x 2 between subjects design was used to assess the influence of two factors on presence: tree height variation and task complexity. The field with greater variation in tree height required participants to bend down and look up more than in the lower variation tree height field. In the higher complexity task participants were told to remember the distribution of diseased trees in the field as well as to count them. The results showed a significant positive association between reported presence and the amount of body movement in particular, head yaw--and the extent to which participants bent down and stood up. There was also a strong interaction effect between task complexity and gender: Women in the more-complex task reported a much lower sense of presence than in the simpler task. For applications in which presence is an important requirement, the research in this paper suggests that presence will be increased when interaction techniques are employed that permit the user to engage in whole-body movement.

Female↗

PubMed2004

Bias to experience approaching motion in a three-dimensional virtual environment.

We used two-frame apparent motion in a three-dimensional virtual environment to test whether observers had biases to experience approaching or receding motion in depth. Observers viewed a tunnel of tiles receding in depth, that moved ambiguously either toward or away from them. We found that observers exhibited biases to experience approaching motion. The strengths of the biases were decreased when stimuli pointed away, but size of the display screen had no effect. Tests with diamond-shaped tiles that varied in the degree of pointing asymmetry resulted in a linear trend in which the bias was strongest for stimuli pointing toward the viewer, and weakest for stimuli pointing away. We show that the overall bias to experience approaching motion is consistent with a computational strategy of matching corresponding features between adjacent foreshortened stimuli in consecutive visual frames. We conclude that there are both adaptational and geometric reasons to favor the experience of approaching motion.

Adaptation, Physiological↗

PubMed2004

Design and implementation of haptic virtual environments for the training of the visually impaired.

This paper presents a haptic virtual reality (VR) tool developed for the training of the visually impaired. The proposed approach focuses on the development of a highly interactive and extensible haptic VR training system (the ENORASI VR training system) that allows visually impaired, to study and interact with various virtual objects in specially designed virtual environments, while allowing designers to produce and customize these configurations. Based on the system prototype and the use of the CyberGrasp haptic device, a number of custom applications have been developed. An efficient collision detection algorithm is also introduced, by extending the proximity query package (PQP) algorithm to handle five points of contact (a case studied with the use of CyberGrasp). Two test categories were identified and corresponding tests were developed for each category. The training scenarios include: object recognition and manipulation and cane simulation, used for performing realistic navigation tasks. Twenty-six blind persons conducted the tests and the evaluation results have shown the degree of acceptance of the technology and the feasibility of the proposed approach.

Adult↗

PubMed1995

Natural problems for stereoscopic depth perception in virtual environments.

The use of virtual reality (VR) display systems has escalated over the last 5 yr and may have consequences for those working within vision research. This paper provides a brief review of the literature pertaining to the representation of depth in stereoscopic VR displays. Specific attention is paid to the response of the accommodation system with its cross-links to vergence eye movements, and to the spatial errors that arise when portraying three-dimensional space on a two-dimensional window. It is suggested that these factors prevent large depth intervals of three-dimensional visual space being rendered with integrity through dual two-dimensional arrays.

Accommodation, Ocular↗

PubMed2004

Ergonomics of virtual environments for clinical use.

Usability is defined by the International Standards Organization as "the effectiveness, efficiency and satisfaction with which a certain user may achieve a specific objective in a particular environment" (ISO DIS 9241-11). This definition highlights the need for considering the specific destination of a certain technology and reflects the current trends in Human-Computer Interaction (HCI). In compliance with these remarks, the evaluation will be described here of a Virtual Environment (VE) for the treatment of male sexual dysfunctions; the common assumption will be avoided according to which a VE is a space separated from its "real" surroundings [6, 7] and the full environment where the Virtual session takes place will be addressed instead. After a description of the conceptual framework adopted, the paper will dwell on one method among those deployed for the evaluation, namely the analysis of "situated actions". Four aspects will be dealt with: (a) the interplay of various concurrent settings during the virtual session; (b) the users' comprehension of the symbols used in the VE; (c) the structure of the relationship between users and guide; (d) the breakdowns during the human-VE interaction. The goals and the intended meanings of the simulation as set by the designers became the main parameters for the evaluation.

Ergonomics↗

PubMed1998

Males and females use different distal cues in a virtual environment navigation task.

The study of navigational ability in humans is often limited by the restricted availability and inconvenience of using large novel environments. In the present study we use a computer-generated virtual environment to study sex differences in human spatial navigation. Adult male and female participants navigated through a virtual water maze where both landmarks and room geometry were available as distal cues. Manipulation of environmental characteristics revealed that females rely predominantly on landmark information, while males more readily use both landmark and geometric information. We discuss these results as a possible link between recent human research reporting hippocampal activation in spatial tasks and animal work showing sex differences in both spatial ability and hippocampal development.

Adult↗

PubMed2003

Effects of haptic feedback and turbulence on landing performance using an immersive cave automatic virtual environment (CAVE).

An investigation was conducted in which subjects had to land a simulated F-16 aircraft using a CAVE (Cave Automatic Virtual Environment) facility. This was a three-dimensional virtual setting consisting of multiple mirrors, 3-D video-projected displays in a highly stressful environment employing a haptic joystick. 6 subjects learned a task which required landing in wind turbulence with a reduced visual scene. Analyses indicated that during landing, performance error variables which occurred in the same direction as the haptic forces were significantly reduced. This was true, especially when the visual scene was occluded and more reliance on the proprioceptive condition was beneficial.

Adult↗

PubMed2001

The effects of levels of immersion on memory and presence in virtual environments: a reality centered approach.

Simulation fidelity is characterized as the extent to which a Virtual Environment (VE) and relevant interactions with it are indistinguishable from a user's interaction with a real environment. The growing number of VE training applications which target a high level of simulation fidelity, mainly for transfer of training in the real world, have made it crucial to examine the manner in which these particular implementations and designs are evaluated. The methodology presented in this study focuses on real versus simulated virtual worlds, comparing participants' level of presence, task performance, and cognition state employed to complete a memory task. A 15-minute seminar was presented in four different conditions including real, 3D desktop, 3D Head Mounted Display (HMD) and Audio-only (between-subjects design). Four independent groups of 18 participants took part in the experiment, which investigated the effects of levels of immersion on participants' memory recall and memory awareness state (relevant to episodic and semantic memory types) as well as on their perception of the experimental space and sense of presence for every condition. The level of reported presence was not positively associated with accurate memory recall in all conditions, although the scores for both presence and seminar memory recall in the "real" condition were statistically higher. Memory awareness states' analysis gave a invaluable insight into "how" participants remembered both communicated information and space, as opposed to "what," most interestingly across specific conditions where results for presence and accurate memory recall were not proven to be significant.

Adult↗

PubMed2003

Social anxiety in virtual environments: results of a pilot study.

This paper reports on a pilot study of the extent to which social anxiety can be generated within a virtual environment. Ten subjects were exposed to a virtual reality experience depicting a London underground train and also a wine bar. The first provided a social setting with virtual characters (avatars) that had relatively neutral behaviors towards the subject, and the second was more socially demanding--with subjects required to interact with relatively disinterested avatars. The purpose was to assess whether social anxiety would be greater for the wine bar experience than the train journey experience, taking into account prior tendencies to social anxiety, and the order of presentation. The results suggest that social anxiety was higher for the wine bar experience, but lower for the second exposure.

Humans↗

PubMed2003

Responding to a fire emergency in a virtual environment: different patterns of action for different situations.

This paper presents an experimental study of participants' response to the sudden appearance of a fire emergency in a virtual environment (VE) and of the adaptivity of their response pattern. A VE has been built in which participants meet two situations: first an explorative navigation and afterwards a hurried escape from the unexpected outbreak of fire. Fire intensity and participants' distance from the exit at the outbreak of fire have been varied as well, to create different degrees of danger and different degrees of difficulty in the task of leaving the premises. Participants' action has been collected automatically for quantitative analysis by registering each individual activation of the interaction devices (a triple button joystick). In addition, the movements in both virtual and real environment of additional groups of participants have been videorecorded for qualitative analysis. Results show that the appearance of the fire emergency triggers important changes in the way people move in the VE, and that such changes are all adaptive responses to an emergency situation. In conclusion, people show recognition of a dangerous situation in a VE and readily produce adaptive responses, making the VE suitable for emergency simulations and for use as an effective training tool.

Adaptation, Psychological↗

PubMed2003

Modelling human burn injuries in a three-dimensional virtual environment.

This paper gives a work-in-progress report on our research project BurnCase, a virtual environment for modelling human burn injuries. The goal of the project is to simplify and improve the diagnosis and medical treatment of burns. Due to the lack of electronic and computational support for current diagnosis methods, enormous variations regarding the approximated size of burned skin regions exist. And although Simplifications like the Rule-Of-Nines-Method ([Weidringer, 2002]), Lund and Browder ([LundBrowder, 1944]) and others try to compensate for these errors, the fact remains that different physicians overestimate the BSA (Body Surface Area) by 20% up to 50%, depending on the different experience and subjectivity of the approximation process. Nevertheless, different supporting mechanisms have been developed to assist the process of burn region transfer so that after transferring all burned regions on the virtual human body, calculations can be applied in order to evaluate standard indices like the ABSI (Abbreviated Burn Severity Index), and Baux ([Baux, 1989]) as well as ICD10 (International Classification of Diseases) diagnosis encoding. The virtual body simulation is based on state-of-the-art 3D computer graphics (OpenGL). Thus a simulation system, providing a graphical user interface, allows surgeons to transfer a patient's burn injury regions onto an appropriate 3-dimensional model. As such, the BurnCase system improves surface determination by calculating region surfaces up to a precision of one cm2. This improves the average variation to less than 5%, limited by the precision of the surface transfer onto the virtual model. The system already allows the transfer of burned regions by using standard input devices. For this purpose different reference models of human bodies have been created in order to receive appropriate results based on measured physical data of different patients. Moreover, an underlying database stores all entered case studies so that it is possible to perform comparisons of burn cases and animation sequences of the healing process of single wounds or whole bodies. When used as centralized burn accident registration service, a huge knowledge base of burn diagnoses and consequent medical treatment will emerge. This knowledge base will allow medical advices and diagnosis support for any kind of burn accidents, and it will consequently improve and support the primary diagnosis process of burn accidents. Thus, an enormous reduction of time and costs of medical burn treatment will be reached.

Burns↗

PubMed2005

Effects of low stereo acuity on performance, presence and sickness within a virtual environment.

To examine the effect of stereo vision on performance, presence and oculomotor disturbances within a virtual environment (VE), two groups of 23 participants (good stereo acuity/low stereo acuity) were evaluated. Groups were matched in terms of gender, age and VE design factors (the latter were accounted for to ensure a similar VE experience between groups). Participants were immersed in a VE maze for up to 1h during which time they interacted with the environment while performing a number of stationary and movement-based tasks. Individuals with low stereo acuity traveled further to complete two tasks in the VE, yet performance time on these tasks was comparable to participants with good stereo acuity. Although participants with impaired stereo vision likely did not fully benefit from a stereoscopic view of the scene, they may have received sufficient depth information from movement-based cues to efficiently accomplish these tasks in a comparable amount of time. Overall performance, based on both the number of tasks completed and the total translational distance moved (based on input device movement) within the VE was not hindered for those with low stereo acuity. In addition, the expected increase in oculomotor disturbances for this group was not evident in this study, and both groups reported comparable amounts of presence from VE exposure. These results suggest that when head tracking is included as part of the VE experience (i.e., motion parallax cues exist), participants with low stereo acuity can be expected to perform comparable to normal sighted individuals, experience a comparable sense of presence, and report no increase in adverse effects when viewing scenes via stereoscopic displays. Thus, motion parallax cues may adequately provide a sense of depth within a VE, and alleviate theorized performance decrements for individuals with low stereo acuity. The results of this study have implications for those designing entertainment simulations or other such applications open to the general public, where people with low stereo acuity may routinely participate.

Female↗

PubMed1998

Static posture tests for the assessment of postural instability after virtual environment use.

The aim of this experiment was to measure the effect of immersion in a virtual environment (VE) on postural stability and examine the relationship between postural stability and self-reported simulator sickness. Forty healthy subjects were exposed to 20 min of immersion in an interactive VE with restricted user movement. The VE was viewed on a head mounted display (HMD) and the subject remained standing throughout the immersion period. Two static postures, normal stance and tandem romberg, were recorded before immersion, immediately after immersion and again at 10 min postimmersion. Performance in each posture was simultaneously measured by recording time that the posture could be maintained and mm path length of body sway over a 30-s period. The results demonstrated differences in the sensitivity of postural stability measurement techniques and variations in inter- and intraindividual responses to measures. Sway magnetometry measured a significant increase in postural instability in normal stance after VE immersion. None of the other measures were sensitive to this change. Postimmersion reports of simulator sickness symptoms indicate that the VE stimulus was provocative and correlation was found between reports of simulator sickness and balance-related symptoms. However, no association between self-reported symptoms and performance measures of postural instability was found.

Adolescent↗