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At least 649 records · Page 36Linked to original sources
PubMed1993

Changes in the dark focus of accommodation associated with simulator sickness.

The relationship between the dark focus of accommodation and simulator sickness, a form of motion sickness, was examined in three experiments. In Experiment 1, dark focus was measured in 18 college students in a laboratory setting before and after they viewed a projected motion scene depicting low altitude helicopter flight. In Experiments 2 and 3, dark focus was measured in pilots (N = 16 and 23, respectively) before and after they "flew" in moving-base helicopter flight simulators with optical infinity CRT visual systems. The results showed that individuals who experienced simulator sickness had either an inward (myopic) change in dark focus (Experiments 1 and 3) or attenuated outward shifts in dark focus (Experiment 2) relative to participants who did not get sick. These results are consonant with the hypothesis that parasympathetic activity, which may be associated with simulator sickness, should result in changes in dark focus that are in a myopic direction. Night vision goggles, virtual environments, extended periods in microgravity, and heads-up displays all produce related visual symptomatology. Changes in dark focus may occur in these conditions, as well, and should be measured.

Accommodation, Ocular↗
PubMed1996

[The power of odors--pathogenic or unpleasant].

Modern toxicological studies have prompted us to rethink the role of olfaction and odours in our world. Our sense of smell is able to discriminate between an almost unlimited number of compounds of different chemical composition at extremely low threshold levels. Olfaction is classified as a chemical sense because of the bimolecular excitation process between the stimulant and receptor molecule. Receptor molecules of the olfactory epithelium have a variable region of the molecule which can differentiate between an unlimited number of aromatics. The sense of smell--the oldest phylogenetic sense--is therefore in very intensive contact with the "chemical" environment. Virtually all of the aromatic products which we are exposed to are highly complex chemical mixtures of numerous individual components which have a toxic potential little investigated to date. The perception of odours can be interpreted as a warning--a protective mechanism necessary for survival. At the same time, however, the exaggerated use of perfumes is held to be indicative of a highly cultured status. Unlike any other sense, that of smell is directly connected to archaic areas of the paleocortex region of the cerebral hemisphere, so that an odour will fill us with joy or abhorrence outside of our control. Odours cannot, therefore, be analyzed rationally without eliciting instinctive reactions, positive or negative, which result in acceptance or rejection. The highly developed memory for odour types is believed to be coupled to the route of the olfactory tract. The use of olfactometry today enables odours to be reliably quantified and characterized in a reproducible manner.

Humans↗
PubMed1997

Virtual extracorporeal circulation process.

Virtual instruments for an extracorporeal circulation (ECC) process were developed to simulate the reactions of a patient to different artificial perfusion conditions. The computer simulation of the patient takes into account the hydraulic, volume, thermal and biochemical phenomena and their interaction with the devices involved in ECC (cannulae dimensions, oxygenator and filter types, pulsatile or continuous pump and thermal exchangers). On the basis of the patient's initialisation data (height, weight, Ht) and perfusion variables (pump flow rate, water temperature, gas flow rate and composition) imposed by the operator, the virtual ECC monitors simulated arterial and venous pressure tracings in real time, along with arterial and venous flow rate tracings, urine production tracing and temperature levels. Oxyhemoglobin arterial and venous blood saturation together with other related variables (pO2, pCO2, pH, HCO3 are also monitored. A drug model which allows the simulation of the effect of vasodilator and diuretic drugs is also implemented. Alarms are provided in order to check which variables (pressure, saturation, pH, urine flow) are out of the expected ranges during the ECC simulation. Consequently the possibility of modifying the control parameters of the virtual devices of the ECC in run-time mode offers an interaction mode between the operator and the virtual environment.

Blood Gas Analysis↗
PubMed2002

Intelligibility of speech in a virtual 3-D environment.

In a simulated air traffic control task, improvement in the detection of auditory warnings when using virtual 3-D audio depended on the spatial configuration of the sounds. Performance improved substantially when two of four sources were placed to the left and the remaining two were placed to the right of the participant. Surprisingly, little or no benefits were observed for configurations involving the elevation or transverse (front/back) dimensions of virtual space, suggesting that position on the interaural (left/right) axis is the crucial factor to consider in auditory display design. The relative importance of interaural spacing effects was corroborated in a second, free-field (real space) experiment. Two additional experiments showed that (a) positioning signals to the side of the listener is superior to placing them in front even when two sounds are presented in the same location, and (b) the optimal distance on the interaural axis varies with the amplitude of the sounds. These results are well predicted by the behavior of an ideal observer under the different display conditions. This suggests that guidelines for auditory display design that allow for effective perception of speech information can be developed from an analysis of the physical sound patterns.

Accidents, Aviation↗
PubMed1998

The effects of immersiveness on physiology.

The effects of varying levels of immersion in virtual reality environments on participant's heart rate, respiration rate, peripheral skin temperature, and skin resistance levels were examined. Subjective reports of presence were also noted. Participants were presented with a virtual environment of an airplane flight both as seen from a two-dimensional computer screen and as seen from within a head-mounted display. Subjects were randomly assigned to different order of conditions presented, but all subjects received both conditions. Differences between the non-phobics' physiological responses and the phobic's response when placed in a virtual environment related to the phobia were noted. Also noted were changes in physiology based on degree of immersion.

Adult↗
PubMed2001

Cubes in the cube: a comparison of a puzzle-solving task in a virtual and a real environment.

In this study we compared collaboration on a puzzle-solving task carried out by two persons in a virtual and a real environment. The task, putting together a cube consisting of different colored blocks in a "Rubiks" cube-type puzzle, was performed both in a shared virtual environment (VE) setting, using a Cave-type virtual reality (VR) system networked with a desktop VR system, and with cardboard colored blocks in an equivalent real setting. The aims of the study were to investigate presence, co-presence, collaboration, leadership, and performance in the two settings. We found that the participants contributed unequally to the task in the VE, and also found differences in collaboration between the virtual and the real setting.

Form Perception↗
PubMedDate not supplied

Benefits of a virtual play rehabilitation environment for children with cerebral palsy on perceptions of self-efficacy: a pilot study.

This paper presents the results of a clinical trial of a virtual reality play-based intervention. The results of three single case studies are presented. The virtual reality intervention used the Mandala Gesture Xtreme technology. It was applied to three school-aged children with cerebral palsy. A pre-test-post-test design was used. The relevant outcome of interest was self-efficacy as measured with the Canadian Occupational Performance Measure (COPM). Group scores on the COPM indicated clinically significant changes in self-efficacy for all children. Two of the participants demonstrated the greatest changes in both perceived performance abilities and satisfaction with performance with respect to task specific domain areas. Qualitative comments from the participants revealed a high degree of motivation, interest, pleasure, and opportunity for engagement in play, activities not previously engaged in. Overall, this pilot study suggests the viability of a virtual reality play-based intervention as part of the rehabilitation process for children with cerebral palsy. These results form the basis of a larger scale randomized clinical trial.

Cerebral Palsy↗
PubMed2007

Critical illness VR rehabilitation device (X-VR-D): evaluation of the potential use for early clinical rehabilitation.

We present a new critical illness VR rehabilitation device (X-VR-D) that enables diversified self-training and is applicable early in the rehabilitation of severely injured or ill patients. The X-VR-D consists of a VR program delivering a virtual scene on a flat screen and simultaneously processing commands to a moving chair mounted on a motion system. Sitting in the moving chair and exposed to a virtual reality environment the device evokes anticipatory and reactive muscle contractions in trunk and extremities for postural control. In this study we tested the device in 10 healthy subjects to evaluate whether the enforced perturbations indeed evoke sufficient and reproducible EMG muscle activations. We found that particular fast roll and pitch movements evoke adequate trunk and leg muscle activity. Higher angular velocities and higher angles of inclination elicited broader EMG bursts and larger amplitudes. The muscle activation pattern was highly consistent between different subjects and although we found some habituation of EMG responses in consecutive training sessions, the general pattern was maintained and was predictable for specific movements. The habituation was characterized by more efficient muscle contractions and better muscle relaxation during the rest positions of the device. Furthermore we found that the addition of a virtual environment to the training session evoked more preparatory and anticipatory muscle activation than sessions without a virtual environment. We conclude that the X-VR-D is safe and effective to elicit consistent and reproducible muscle activity in trunk and leg muscles in healthy subjects and thus can be used as a training method.

Abdominal Muscles↗
PubMed1997

Human factors consideration in clinical applications of virtual reality.

Virtual reality environments have many potential applications in medicine, including surgical training, tele-operated robotic surgery, assessment and rehabilitation of behavioural and neurological disorders and diagnosis, therapy and rehabilitation of physical disabilities. Although there is much potential for the use of immersive virtual reality environments in clinical applications, there are problems which could limit their ultimate usability. Some users have experienced side-effects during and after exposure to virtual reality environments. The symptoms include ocular problems, disorientation and balance disturbances, and nausea. Susceptibility to side-effects can be affected by age, ethnicity, experience, gender and physical fitness, as well as the characteristics of the display, the virtual environment and the tasks. The characteristics of the virtual reality system have also been shown to affect the ability of users to perform tasks in a virtual environment. Many of these effects can be attributed to delays between the sampling of head and limb positions and the presentation of an appropriate image on the display. The introduction of patients to virtual reality environments, for assessment, therapy or rehabilitation, raises particular safety and ethical issues. Patients exposed to virtual reality environments for assessment and rehabilitation may have disabilities which increase their susceptibility to certain side-effects. Special precautions therefore need to be taken to ensure the safety and effectiveness of such virtual reality applications. These precautions include minimisation of possible side-effects at the design stage. Factors are identified which are likely to affect the incidence of side-effects during and after exposures, and which need to be understood in order to minimise undesirable consequences. There is also a need for the establishment of protocols for monitoring and controlling exposures of patients to virtual reality environments. Issues are identified which need to be included in such protocols.

Computer Graphics↗
PubMed1997

Internet conferences in glycobiology.

In this article we describe recent activities in the use of electronic conferencing in glycobiology focusing on our experiences with the organization and development of the Second Electronic Glycoscience Conference (EGC-2), which was held on the Internet and World Wide Web in September 1996. EGC-2 involved the presentation and discussion of scientific research results in a virtual conferencing environment which incorporated virtual replicas of many activities usually observed at a physical conference in addition to features unique to the electronic medium. Highlights of the scientific program and technical developments in the design and use of these facilities are briefly described. EGC-3 will be held in October 1997.

Computer Communication Networks↗
PubMed1995

Mentally simulated movements in virtual reality: does Fitts's law hold in motor imagery?

This study was designed to investigate mentally simulated actions in a virtual reality environment. Naive human subjects (n = 15) were instructed to imagine themselves walking in a three-dimensional virtual environment toward gates of different apparent widths placed at three different apparent distances. Each subject performed nine blocks of six trials in a randomised order. The response time (reaction time and mental walking time) was measured as the duration between an acoustic go signal and a motor signal produced by the subject. There was a combined effect on response time of both gate width and distance. Response time increased for decreasing apparent gate widths when the gate was placed at different distances. These results support the notion that mentally simulated actions are governed by central motor rules.

Adult↗
PubMed2006

Visual hallucinations in Parkinson's disease: clues to separate origins.

Our paper discusses two experimental studies suggesting that Visual Hallucinations (VH) in Parkinson's Disease (PD) may have separate origins. The first is a prospective 8years study evaluating the appearance of VH, visual abnormalities assessed by Visual Evoked Potentials (VEPs) and REM sleep Behaviour Disorder (RBD), in 80 PD patients treated with l-Dopa and Dopaminoagonists (DA). In chronically treated, cognitively unimpaired, PD patients VH were statistically related (p=0.001) to RBD occurrence and high DA doses. Visual abnormalities were significantly reduced by l-Dopa or DA intake, and were statistically unrelated to VH. The second study involved PD patients placed in a Virtual Reality Environment, to decontextualize visual input. When motor symptoms worsened and VEP abnormalities developed patients consistently described hallucinatory dysperceptions of the virtual environment. The two studies therefore show that VH can occur in two seemingly distinct conditions, one is related to chronic treatment and to a sleep disorder frequently observed in PD, the other is probably related to a hypodopaminergic state. Our studies support a recently proposed integrative model of VH, and show that the neural circuits purported to explain VH must include the retinal dopaminergic system and the REM sleep regulatory system.

Antiparkinson Agents↗
PubMed1999

Human spatial navigation: cognitive maps, sexual dimorphism, and neural substrates.

Recent research on navigation has been particularly notable for the increased understanding of the factors affecting human navigation and the neural networks supporting it. The use of virtual reality environments has made it possible to explore the effect of environment layout and content on way-finding performance, and it has shown that these effects may interact with the sex and age of subjects. Functional brain imaging, combined with the use of virtual environments, has revealed strong parallels between humans and other animals in the neural basis of navigation.

Aging↗
PubMedDate not supplied

Elastodynamic shape modeler: a tool for defining the deformation behavior of virtual tissues.

A main goal of surgical simulators is the creation of virtual training environments for prospective surgeons. Thus, students can rehearse the various steps of surgical procedures on a computer system without any risk to the patient. One main condition for realistic training is the simulated interaction with virtual medical devices, such as endoscopic instruments. In particular, the virtual deformation and transection of tissues are important. For this application, a neuro-fuzzy model has been developed, which allows the description of the visual and haptic deformation behavior of the simulated tissue by means of expert knowledge in the form of medical terms. Pathologic conditions affecting the visual and haptic tissue response can be easily changed by a medical specialist without mathematical knowledge. By using the personal computer-based program Elastodynamic Shape Modeler, these conditions can be adjusted via a graphical user interface. With a force feedback device, which is similar to a real laparoscopic instrument, virtual deformations can be performed and the resulting haptic feedback can be felt. Thus, use of neuro-fuzzy technologies for the definition and calculation of virtual deformations seems applicable to the simulation of surgical interventions in virtual environments.

Computer Graphics↗
PubMed2006

Development, implementation and pilot evaluation of a Web-based Virtual Patient Case Simulation environment--Web-SP.

BACKGROUND: The Web-based Simulation of Patients (Web-SP) project was initiated in order to facilitate the use of realistic and interactive virtual patients (VP) in medicine and healthcare education. Web-SP focuses on moving beyond the technology savvy teachers, when integrating simulation-based education into health sciences curricula, by making the creation and use of virtual patients easier. The project strives to provide a common generic platform for design/creation, management, evaluation and sharing of web-based virtual patients. The aim of this study was to evaluate if it was possible to develop a web-based virtual patient case simulation environment where the entire case authoring process might be handled by teachers and which would be flexible enough to be used in different healthcare disciplines. RESULTS: The Web-SP system was constructed to support easy authoring, management and presentation of virtual patient cases. The case authoring environment was found to facilitate for teachers to create full-fledged patient cases without the assistance of computer specialists. Web-SP was successfully implemented at several universities by taking into account key factors such as cost, access, security, scalability and flexibility. Pilot evaluations in medical, dentistry and pharmacy courses shows that students regarded Web-SP as easy to use, engaging and to be of educational value. Cases adapted for all three disciplines were judged to be of significant educational value by the course leaders. CONCLUSION: The Web-SP system seems to fulfil the aim of providing a common generic platform for creation, management and evaluation of web-based virtual patient cases. The responses regarding the authoring environment indicated that the system might be user-friendly enough to appeal to a majority of the academic staff. In terms of implementation strengths, Web-SP seems to fulfil most needs from course directors and teachers from various educational institutions and disciplines. The system is currently in use or under implementation in several healthcare disciplines at more than ten universities worldwide. Future aims include structuring the exchange of cases between teachers and academic institutions by building a VP library function. We intend to follow up the positive results presented in this paper with other studies looking at the learning outcomes, critical thinking and patient management. Studying the potential of Web-SP as an assessment tool will also be performed. More information about Web-SP: http://websp.lime.ki.se.

Attitude of Health Personnel↗
PubMed2001

Virtual reality in the assessment of selected cognitive function after brain injury.

OBJECTIVE: To assess selected cognitive functions of persons with traumatic brain injury using a computer-simulated virtual reality environment. STUDY DESIGN: A computer-simulated virtual kitchen was used to assess the ability of 30 patients with brain injury and 30 volunteers without brain injury to process and sequence information. The overall assessment score was based on the number of correct responses and the time needed to complete daily living tasks. Identical daily living tasks were tested and scored in participants with and without brain injury. Each subject was evaluated twice within 7 to 10 days. A total of 30 tasks were categorized as follows: information processing, problem solving, logical sequencing, and speed of responding. RESULTS: Persons with brain injuries consistently demonstrated a significant decrease in the ability to process information (P = 0.04-0.01), identify logical sequencing (P = 0.04-0.01), and complete the overall assessment (P < 0.01), compared with volunteers without brain injury. The time needed to process tasks, representing speed of cognitive responding, was also significantly different between the two groups (P < 0.01). CONCLUSION: A computer-generated virtual reality environment represents a reproducible tool to assess selected cognitive functions and can be used as a supplement to traditional rehabilitation assessment in persons with acquired brain injury.

Activities of Daily Living↗
PubMed1998

Virtual reality in psychotherapy: the MYTHSEEKER software.

This chapter outlines the use in psychotherapy and medical diagnosis of an intelligent software system that helps clients to explore Personal Myth within virtual reality environments. Patented MYTHSEEKER software will allow clients to work with mythic analogues of lifeshapes and aspirations. This can help to focus therapy directions, find ways to participate with the person's world, and allow a kind of personal expression not previously possible. The software phases of assessment, facilitation, and enaction are described by which the client is assisted to explore systems of mythology or spirituality (called Depth Systems) that are traditional, ancient or newly-arising. The client builds a Personal Depth System representing Personal Myth, based on experiencing other Depth Systems, which can itself be experienced in the virtual environment. This paper outlines our methodology and technology to realize these operations. Space limitations prevent further description in the present chapter of MYTHSEEKER software technology or psychotherapy scenarios of involvement.

Artificial Intelligence↗