Vection and visually induced motion sickness: how are they related?

Effects of within-day intervals on adaptation to visually induced motion sickness in a virtual-reality motorcycling simulator

This study investigated the effects of the time interval between virtual reality (VR) sessions on visually induced motion sickness (VIMS) reduction to better understand adaptation to and recovery from a nauseating VR experience. The participants experienced two 6-min VR sessions of a first-person motorcycle ride through a head-mounted display with (1) a 6-min interval, (2) an interval until the VIMS score reached zero, and (3) a 60-min interval. The results showed that for each condition, VIMS in the second session was aggravated, unchanged, or attenuated, respectively, indicating that additional resting time was necessary for VIMS adaptation. This study suggests that a certain type of multisensory learning attenuates VIMS symptoms within a relatively short time, requiring at least 20 min of additional resting time after subjective recovery from VIMS symptoms. This finding has important implications for reducing the time interval between repeated challenges when adapting to nauseating stimuli during VR experiences.

The U.S. Army Aeromedical Research Laboratory Virtual Reality Vection System

INTRODUCTION

Vection is a stationary individual's illusory experience of self-motion. This illusory self-motion is operationally important for aviation, particularly military aviation, since vection is a dramatic example of spatial disorientation (SD), which is an individual's failure to correctly sense the aircraft's position, motion, and/or attitude with respect to the fixed coordinate system of the Earth's surface and its gravitational vertical. Notably, SD is a major cause of fatal aviation mishaps, and the visual system is particularly prone to provoking vection. This article describes the Virtual Reality Vection System (VRVS), which uses computer-controlled virtual reality technology to induce vection under controlled conditions for training, demonstration, testing, and research.

MATERIALS AND METHODS

The VRVS enables the precise specification of the number and appearance of visual stimulus elements intended to generate vection, including photorealistic images. The VRVS can present visual stimuli on any OpenXR-capable virtual reality headset. The VRVS currently records 2 types of behavioral responses, button presses to indicate the presence and duration of vection and the voltage of a handheld linear potentiometer to indicate the presence, duration, and magnitude of vection.

RESULTS

An approved test plan helped guide, organize, document, and validate the VRVS during its development. Under this plan, a pair of tests guided hardware and software development of the VRVS system. Although the first test verified the ability of the VRVS to generate and measure vection, it also demonstrated that the VRVS can quickly manipulate the visual stimuli from one trial to the next so that the VRVS can support complex experimental designs. The second test used these capabilities to verify that the VRVS can characterize vection in a more analytic fashion using a masking paradigm. Specifically, the test assessed whether random stimulus elements injected into the vection-inducing stimulus disrupted vection in a quantifiable fashion. This work opens the door to studies that characterize the necessary and sufficient visual elements for vection-based SD.

DISCUSSION

The VRVS is currently used to research, develop, test, and evaluate mitigation strategies targeting vection-related SD in degraded visual environments. Similarly, the VRVS is supporting research to develop methods to predict individual differences in visually induced motion sickness susceptibilities. The VRVS is currently being integrated with a precision motor-controlled rotating Barany chair for multisensory studies. It should be noted that since the VRVS was developed to support United States Army Aeromedical Research Laboratory projects, it is an Army product representing government intellectual property and may be freely available to other government institutions.

The Effects of Auditory, Visual, and Cognitive Distractions on Cybersickness in Virtual Reality

Cybersickness (CS) is one of the challenges that has hindered the widespread adoption of Virtual Reality (VR). Consequently, researchers continue to explore novel means to mitigate the undesirable effects associated with this affliction, one that may require a combination of remedies as opposed to a solitary stratagem. Inspired by research probing into the use of distractions as a means to control pain, we investigated the efficacy of this countermeasure against CS, studying how the introduction of temporally time-gated distractions affects this malady during a virtual experience featuring active exploration. Downstream of this, we studied how other aspects of the VR experience are affected by this intervention. We discuss the results of a between-subjects study manipulating the presence, sensory modality, and nature of periodic and short-lived (5-12 seconds) distractor stimuli across four experimental conditions: 1) no-distractors (ND); 2) auditory distractors (AD); 3) visual distractors (VD); 4) cognitive distractors (CD). Two of these conditions (VD and AD) formed a yoked control design wherein every matched pair of 'seers' and 'hearers' was periodically exposed to distractors that were identical in terms of content, temporality, duration, and sequence. In the CD condition, each participant had to periodically perform a 2-back working memory task, the duration and temporality of which was matched to distractors presented in each matched pair of the yoked conditions. These three conditions were compared to a baseline control group featuring no distractions. Results indicated that the reported sickness levels were lower in all three distraction groups in comparison to the control group. The intervention also increased the amount of time users were able to endure the VR simulation and avoided causing detriments to spatial memory and virtual travel efficiency. Overall, it appears that it may be possible to make users less consciously aware and bothered by the symptoms of CS, thereby reducing its perceived severity.

Motion sickness resistant people showed suppressed steady-state visually evoked potential (SSVEP) under vection-inducing stimulation

Visual stimulation can generate illusory self-motion perception (vection) and cause motion sickness among susceptible people, but the underlying neural mechanism is not fully understood. In this study, SSVEP responses to visual stimuli presented in different parts of the visual field are examined in individuals with different susceptibilities to motion sickness to identify correlates of motion sickness. Alpha band SSVEP data were collected from fifteen university students when they were watching roll-vection-inducing visual stimulation containing: (1) an achromatic checkerboard flickering at 8.6 Hz in the central visual field (CVF) and (2) rotating dots pattern flickering at 12 Hz in the peripheral visual field. Rotating visual stimuli provoked explicit roll-vection perception in all participants. The motion sickness resistant participants showed reduced SSVEP response to CVF checkerboard during vection, while the motion sickness susceptible participants showed increased SSVEP response. The changes of SSVEP in the presence of vection significantly correlated with individual motion sickness susceptibility and rated scores on simulator sickness symptoms. Discussion on how the findings can support the sensory conflict theory is presented. Results offer a new perspective on vection and motion sickness susceptibility.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11571-023-09991-7.

Individual factors and vection in younger and older adults: How sex, field dependence, personality, and visual attention do (or do not) affect illusory self-motion

An important aspect to an immersive experience in Virtual Reality is vection, defined as the illusion of self-motion. Much of the literature to date has explored strategies to maximize vection through manipulations of the visual stimulus (e.g., increasing speed) or the experimental context (e.g., framing of the study instructions). However, the role of individual differences (e.g., age, biological sex) in vection susceptibility has received little attention. The objective of the current study was to investigate the influence of individual-difference factors on vection perception in younger and older adults. Forty-six younger adults (M age = 25.1) and 39 older adults (M age = 72.4) completed assessments of personality traits, field dependence, and visual attention prior to observing a moving visual stimulus aimed at inducing circular vection. Vection was measured using self-reports of onset latency, duration, and intensity. Results indicated that, in both age groups, females experienced longer-lasting vection compared to males. Additionally, the level of field dependence was related to vection intensity and duration in males but not in females. Variability in vection intensity was best explained by a mixture of biological, perceptual, cognitive, and personality variables. Taken together, these findings suggest that individual factors are important for understanding differences in vection susceptibility.

Changes in Navigation Controls and Field-of-View Modes Affect Cybersickness Severity and Spatiotemporal Gait Patterns After Exposure to Virtual Environments

OBJECTIVE

To examine the effects of navigation controls and field-of-view modes on cybersickness severity and gait dynamics after cessation of exposure to a virtual environment (VE).

BACKGROUND

The applications of virtual reality are increasing in various fields; however, whether changes in interaction techniques and visual contents could mitigate the potential gait disturbance following VE exposure remains unclear.

METHOD

Thirty healthy adults wore a head-mounted display to complete six sessions of 12-min run-and-gun tasks using different navigation controls (gamepad, head, natural) and field-of-view modes (full, restricted). Forward and backward walking tasks were performed before and after VE exposure. The degrees of cybersickness and presence were evaluated using questionnaires, along with the in-session task performance. Spatiotemporal gait measures and their variabilities were calculated for each walking task.

RESULTS

The participants experienced less cybersickness with the head and natural controls than with the gamepad. Natural control, based on matching body movements, was associated with the highest degree of presence and best performance. VE navigation using the gamepad showed reduced cadences and increased stride times during postexposure forward-walking tasks. When the VE was presented via the restricted field-of-view mode, increased gait variabilities were observed from backward-walking tasks after VE exposure.

CONCLUSION

Body movement-based navigation controls may alleviate cybersickness. We observed gait adaptation during both ambulation tasks, which was influenced by the navigation control method and field-of-view mode.

APPLICATION

This study provides the first evidence for gait adaptation during balance-demanding tasks after VE exposure, which is valuable for designing guidelines for virtual reality interactions.

The Effects of Secondary Task Demands on Cybersickness in Active Exploration Virtual Reality Experiences

Active exploration in virtual reality (VR) involves users navigating immersive virtual environments, going from one place to another. While navigating, users often engage in secondary tasks that require attentional resources, as in the case of distracted driving. Inspired by research generally studying the effects of task demands on cybersickness (CS), we investigated how the attentional demands specifically associated with secondary tasks performed during exploration affect CS. Downstream of this, we studied how increased attentional demands from secondary tasks affect spatial memory and navigational performance. We discuss the results of a multi-factorial between-subjects study, manipulating a secondary task's demand across two levels and studying its effects on CS in two different sickness-inducing levels of an exploration experience. The secondary task's demand was manipulated by parametrically varying $n$ in an aural $n$-back working memory task and the provocativeness of the experience was manipulated by varying how frequently users experienced a yaw-rotational reorientation effect during the exploration. Results revealed that increases in the secondary task's demand increased sickness levels, also resulting in a higher temporal onset rate, especially when the experience was not already highly sickening. Increased attentional demand from the secondary task also vitiated navigational performance and spatial memory. Overall, increased demands from secondary tasks performed during navigation produce deleterious effects on the VR experience.

VR.net: A Real-world Dataset for Virtual Reality Motion Sickness Research

Researchers have used machine learning approaches to identify motion sickness in VR experience. These approaches would certainly benefit from an accurately labeled, real-world, diverse dataset that enables the development of generalizable ML models. We introduce 'VR.net', a dataset comprising 165-hour gameplay videos from 100 real-world games spanning ten diverse genres, evaluated by 500 participants. VR.net accurately assigns 24 motion sickness-related labels for each video frame, such as camera/object movement, depth of field, and motion flow. Building such a dataset is challenging since manual labeling would require an infeasible amount of time. Instead, we implement a tool to automatically and precisely extract ground truth data from 3D engines' rendering pipelines without accessing VR games' source code. We illustrate the utility of VR.net through several applications, such as risk factor detection and sickness level prediction. We believe that the scale, accuracy, and diversity of VR.net can offer unparalleled opportunities for VR motion sickness research and beyond.We also provide access to our data collection tool, enabling researchers to contribute to the expansion of VR.net.

Analysis of cybersickness in virtual nursing simulation: a German longitudinal study

BACKGROUND

Innovative educational approaches such as simulation-based nursing education using virtual reality (VR) technologies provide new opportunities for nursing education. However, there is a lack of information on side effects, especially health-related side effects, of head-mounted displays (HMDs) on the human body when using VR devices for nursing simulation. This study aims to validate the German version of the Virtual Reality Sickness Questionnaire (VRSQ) and to evaluate its associations with sex and age, as reflected in the VRSQG scores (total score, oculomotor, and disorientation) over time.

METHODS

A longitudinal-sectional study was conducted. In addition to the VRSQG (pre-, post-, and 20 min post-intervention), participants (all nursing students) completed data on personal characteristics. Participants completed a VR simulation of a blood draw. Confirmatory factor analysis (CFA) was used to evaluate whether the measured construct was consistent with the original. In addition to the validity, internal consistency was analyzed and generalized linear models (GLMs) were used for data analysis.

RESULTS

A total of 38 nursing students (mean age 26.8 years; SD = 7.1, 79.0% female) participated. The mean time spent in the VR simulation was 21 min. All participants completed the entire simulation. The CFA indicates (CFI = 0.981, SRMR = 0.040) VRSQG structure is given. Internal consistency showed low values for the subdomain Oculomotor (Cronbach alpha 0.670). For Disorientation and the Total score values showed a sufficient internal consistency. GLMs showed significant between subject associations with age over time with VRSQG total score, oculomotor, and disorientation. Older nursing students start with higher VRSQG-Scores. Over time, an approximation occurs, so that all participants reach a similar level by the final measurement point. No associations were found between sex (male/female) and VRSQG scores.

CONCLUSIONS

The VRSQG is a reliable and valid self-assessment for measuring cybersickness in VR based nursing simulations, with cybersickness symptoms positively associated with age. However, in depth-evaluation regarding age-associations with cybersickness should be done. As well as studies to explore additional associations and emphasizes the importance of establishing cut-off values to assess the clinical relevance of the scores.

Body representation drives auditory spatial perception

In contrast to the large body of findings confirming the influence of auditory cues on body perception and movement-related activity, the influence of body representation on spatial hearing remains essentially unexplored. Here, we use a disorientation task to assess whether a change in the body's orientation in space could lead to an illusory shift in the localization of a sound source. While most of the participants were initially able to locate the sound source with great precision, they all made substantial errors in judging the position of the same sound source following the body orientation-altering task. These results demonstrate that a change in body orientation can have a significant impact on the auditory processes underlying sound localization. The illusory errors not only confirm the strong connection between the auditory system and the representation of the body in space but also raise questions about the importance of hearing in determining spatial position.

Measuring vection: a review and critical evaluation of different methods for quantifying illusory self-motion

The sensation of self-motion in the absence of physical motion, known as vection, has been scientifically investigated for over a century. As objective measures of, or physiological correlates to, vection have yet to emerge, researchers have typically employed a variety of subjective methods to quantify the phenomenon of vection. These measures can be broadly categorized into the occurrence of vection (e.g., binary choice yes/no), temporal characteristics of vection (e.g., onset time/latency, duration), the quality of the vection experience (e.g., intensity rating scales, magnitude estimation), or indirect (e.g., distance travelled) measures. The present review provides an overview and critical evaluation of the most utilized vection measures to date and assesses their respective merit. Furthermore, recommendations for the selection of the most appropriate vection measures will be provided to assist with the process of vection research and to help improve the comparability of research findings across different vection studies.

Multisensory Conflict Impairs Cortico-Muscular Network Connectivity and Postural Stability: Insights from Partial Directed Coherence Analysis

Sensory conflict impacts postural control, yet its effect on cortico-muscular interaction remains underexplored. We aimed to investigate sensory conflict's influence on the cortico-muscular network and postural stability. We used a rotating platform and virtual reality to present subjects with congruent and incongruent sensory input, recorded EEG (electroencephalogram) and EMG (electromyogram) data, and constructed a directed connectivity network. The results suggest that, compared to sensory congruence, during sensory conflict: (1) connectivity among the sensorimotor, visual, and posterior parietal cortex generally decreases, (2) cortical control over the muscles is weakened, (3) feedback from muscles to the cortex is strengthened, and (4) the range of body sway increases and its complexity decreases. These results underline the intricate effects of sensory conflict on cortico-muscular networks. During the sensory conflict, the brain adaptively decreases the integration of conflicting information. Without this integrated information, cortical control over muscles may be lessened, whereas the muscle feedback may be enhanced in compensation.

Keeping track of reality: embedding visual memory in natural behaviour

Since immersive virtual reality (IVR) emerged as a research method in the 1980s, the focus has been on the similarities between IVR and actual reality. In this vein, it has been suggested that IVR methodology might fill the gap between laboratory studies and real life. IVR allows for high internal validity (i.e., a high degree of experimental control and experimental replicability), as well as high external validity by letting participants engage with the environment in an almost natural manner. Despite internal validity being crucial to experimental designs, external validity also matters in terms of the generalizability of results. In this paper, we first highlight and summarise the similarities and differences between IVR, desktop situations (both non-immersive VR and computer experiments), and reality. In the second step, we propose that IVR is a promising tool for visual memory research in terms of investigating the representation of visual information embedded in natural behaviour. We encourage researchers to carry out experiments on both two-dimensional computer screens and in immersive virtual environments to investigate visual memory and validate and replicate the findings. IVR is valuable because of its potential to improve theoretical understanding and increase the psychological relevance of the findings.

Virtual Reality Sickness Reduces Attention During Immersive Experiences

In this paper, we show that Virtual Reality (VR) sickness is associated with a reduction in attention, which was detected with the P3b Event-Related Potential (ERP) component from electroencephalography (EEG) measurements collected in a dual-task paradigm. We hypothesized that sickness symptoms such as nausea, eyestrain, and fatigue would reduce the users' capacity to pay attention to tasks completed in a virtual environment, and that this reduction in attention would be dynamically reflected in a decrease of the P3b amplitude while VR sickness was experienced. In a user study, participants were taken on a tour through a museum in VR along paths with varying amounts of rotation, shown previously to cause different levels of VR sickness. While paying attention to the virtual museum (the primary task), participants were asked to silently count tones of a different frequency (the secondary task). Control measurements for comparison against the VR sickness conditions were taken when the users were not wearing the Head-Mounted Display (HMD) and while they were immersed in VR but not moving through the environment. This exploratory study shows, across multiple analyses, that the effect mean amplitude of the P3b collected during the task is associated with both sickness severity measured after the task with a questionnaire (SSQ) and with the number of counting errors on the secondary task. Thus, VR sickness may impair attention and task performance, and these changes in attention can be tracked with ERP measures as they happen, without asking participants to assess their sickness symptoms in the moment.

Exploring neurophysiological correlates of visually induced motion sickness using electroencephalography (EEG)

Visually induced motion sickness (VIMS) is a common phenomenon when using visual devices such as smartphones and virtual reality applications, with symptoms including nausea, fatigue, and headache. To date, the neuro-cognitive processes underlying VIMS are not fully understood. Previous studies using electroencephalography (EEG) delivered mixed findings, with some reporting an increase in delta and theta power, and others reporting increases in alpha and beta frequencies. The goal of the study was to gain further insight into EEG correlates for VIMS. Participants viewed a VIMS-inducing visual stimulus, composed of moving black-and-white vertical bars presented on an array of three adjacent monitors. The EEG was recorded during visual stimulation and VIMS ratings were recorded after each trial using the Fast Motion Sickness Scale. Time-frequency analyses were conducted comparing neural activity of participants reporting minimal VIMS (n = 21) and mild-moderate VIMS (n = 12). Results suggested a potential increase in delta power in the centro-parietal regions (CP2) and a decrease in alpha power in the central regions (Cz) for participants experiencing mild-moderate VIMS compared to those with minimal VIMS. Event-related spectral perturbations (ERSPs) suggested that group differences in EEG activity developed with increasing duration of a trial. These results support the hypothesis that the EEG might be sensitive to differences in information processing in VIMS and minimal VIMS contexts, and indicate that it may be possible to identify neurophysiological correlate of VIMS. Differences in EEG activity related to VIMS may reflect differential processing of conflicting visual and vestibular sensory information.

A modularity design approach to behavioral research with immersive virtual reality: A SkyrimVR-based behavioral experimental framework

Virtual reality (VR) has been shown to be a potential research tool, yet the gap between traditional and VR behavioral experiment systems poses a challenge for many behavioral researchers. To address the challenge posed, the present study first adopted a modularity design strategy and proposed a five-module architectural framework for a VR behavioral experiment system that aimed to reduce complexity and costs of development. Applying the five-module architectural framework, the present study developed the SkyrimVR-based behavioral experimental framework (SkyBXF) module, a basic experimental framework module that adopted and integrated the classic human behavior experiment structure (i.e., session-block-trial model) with the modifiable VR massive gaming franchise The Elder Scrolls V: Skyrim VR. A modified version of previous behavioral research to investigate the effects of masked peripheral vision on visually-induced motion sickness in an immersive virtual environment was conducted as a proof of concept to showcase the feasibility of the proposed five-module architectural framework and the SkyBXF module developed. Behavioral data acquired through the case study were consistent with those from previous behavioral research. This indicates the viability of the proposed five-module architectural framework and the SkyBXF module developed, and provides proof that future behavioral researchers with minimal programming proficiency, 3D environment development expertise, time, personnel, and resources may reuse ready-to-go resources and behavioral experiment templates offered by SkyBXF to swiftly establish realistic virtual worlds that can be further customized for experimental need on the go.

Serial dependencies in visual stability during self-motion

Every time we move our head, the brain must decide whether the displacement of the visual scene is the result of external or self-produced motion. Gaze shifts generate the biggest and most frequent disturbance of vision. Visual stability during gaze shifts is necessary for both, dissociating self-produced from external motion and retaining bodily balance. Here, we asked participants to perform an eye-head gaze shift to a target that was briefly presented in a head-mounted display. We manipulated the velocity of the scene displacement across trials such that the background moved either too fast or too slow in relation to the head movement speed. Participants were required to report whether they perceived the gaze-contingent visual motion as faster or slower than what they would expect from their head movement velocity. We found that the point of visual stability was attracted to the velocity presented in the previous trial. Our data reveal that serial dependencies in visual stability calibrate the mapping between motor-related signals coding head movement velocity and visual motion velocity. This process is likely to aid in visual stability as the accuracy of this mapping is crucial to maintain visual stability during self-motion.NEW & NOTEWORTHY We report that visual stability during self-motion is maintained by serial dependencies between the current and the previous gaze-contingent visual velocity that was experienced during a head movement. The gaze-contingent scene displacement velocity that appears normal to us thus depends on what we have registered in the recent history of gaze shifts. Serial dependencies provide an efficient means to maintain visual stability during self-motion.

Augmented Reality for Perioperative Anxiety in Patients Undergoing Surgery: A Randomized Clinical Trial

Importance

Both augmented reality (AR) and virtual reality (VR) have had increasing applications in medicine, including medical training, psychology, physical medicine, rehabilitation, and surgical specialties, such as neurosurgery and orthopedic surgery. There are little data on AR's effect on patients' anxiety and experiences.

Objective

To determine whether the use of an AR walkthrough effects patient perioperative anxiety.

Design, Setting, and Participants

This randomized clinical trial was conducted at an outpatient surgery center in 2021 to 2022. All patients undergoing elective orthopedic surgery with the senior author were randomized to the treatment or control group. Analyses were conducted per protocol. Data analysis was performed in November 2022.

Intervention

AR experience explaining to patients what to expect on their day of surgery and walking them through the surgery space. The control group received the standard educational packet.

Main Outcomes and Measures

The main outcome was change in State-Trait Anxiety Inventory (STAI) from the screening survey to the preoperative survey.

Results

A total of 140 patients were eligible, and 45 patients either declined or were excluded. Therefore, 95 patients (63 [66.3%] male; mean [SD] age, 38 [16] years) were recruited for the study and included in the final analysis; 46 patients received the AR intervention, and 49 patients received standard instructions. The AR group experienced a decrease in anxiety from the screening to preoperative survey (mean score change, -2.4 [95% CI, -4.6 to -0.3]), while the standard care group experienced an increase (mean score change, 2.6 [95% CI, 0.2 to 4.9]; P = .01). All patients postoperatively experienced a mean decrease in anxiety score compared with both the screening survey (mean change: AR, -5.4 [95% CI, -7.9 to -2.9]; standard care, -6.9 [95% CI, -11.5 to -2.2]; P = .32) and preoperative survey (mean change: AR, -8.0 [95% CI, -10.3 to -5.7]; standard care, -4.2 [95% CI, -8.6 to 0.2]; P = .19). Of 42 patients in the AR group who completed the postoperative follow-up survey, 30 (71.4%) agreed or strongly agreed that they enjoyed the experience, 29 (69.0%) agreed or strongly agreed that they would recommend the experience, and 28 (66.7%) agreed or strongly agreed that they would use the experience again. No differences were observed in postoperative pain levels or narcotic use.

Conclusions and Relevance

In this randomized clinical trial, the use of AR decreased preoperative anxiety compared with traditional perioperative education and handouts, but there was no significant effect on postoperative anxiety, pain levels, or narcotic use. These findings suggest that AR may serve as an effective means of decreasing preoperative patient anxiety.

Trial Registration

ClinicalTrials.gov Identifier: NCT04727697.

A virtual reality study investigating the train illusion

The feeling of self-movement that occurs in the absence of physical motion is often referred to as vection, which is commonly exemplified using the train illusion analogy (TIA). Limited research exists on whether the TIA accurately exemplifies the experience of vection in virtual environments (VEs). Few studies complemented their vection research with participants' qualitative feedback or by recording physiological responses, and most studies used stimuli that contextually differed from the TIA. We investigated whether vection is experienced differently in a VE replicating the TIA compared to a VE depicting optic flow by recording subjective and physiological responses. Additionally, we explored participants' experience through an open question survey. We expected the TIA environment to induce enhanced vection compared to the optic flow environment. Twenty-nine participants were visually and audibly immersed in VEs that either depicted optic flow or replicated the TIA. Results showed optic flow elicited more compelling vection than the TIA environment and no consistent physiological correlates to vection were identified. The post-experiment survey revealed discrepancies between participants' quantitative and qualitative feedback. Although the dynamic content may outweigh the ecological relevance of the stimuli, it was concluded that more qualitative research is needed to understand participants' vection experience in VEs.

Recovery time from VR sickness due to susceptibility: Objective and quantitative evaluation using electroencephalography

With the increasing use of virtual reality (VR) devices, interest in reducing their negative effects, such as VR sickness, is also increasing. This study used electroencephalography (EEG) to investigate participants' VR sickness recovery time after watching a VR video. We tested 40 participants in advance using a motion sickness susceptibility questionnaire (MSSQ). We classified the participants into two groups (sensitive group/non-sensitive group) depending on their MSSQ scores. We used a simulator sickness questionnaire (SSQ) and EEG to evaluate VR sickness. The SSQ score increased significantly after watching the VR sickness-inducing video (VR video) in both groups (p < 0.001). The recovery time based on the SSQ was 11.3 ± 6.6 min for the sensitive group and 9.1 ± 5.2 min for the non-sensitive group. The difference in recovery time between the two groups was not significant (p > 0.05). EEG results showed that recovery time took an average of 11.5 ± 7.1 min in both groups. The EEG data showed that the delta wave increased significantly across all brain areas (p < 0.01). There was no statistical difference between groups in recovering VR sickness depending on individual characteristics. However, we confirmed that subjective and objective VR recovery required at least 11.5 min. This finding can inform recommendations regarding the VR sickness recovery times.

The Visually Induced Motion Sickness Susceptibility Questionnaire (VIMSSQ): Estimating Individual Susceptibility to Motion Sickness-Like Symptoms When Using Visual Devices

OBJECTIVE

Two studies were conducted to develop and validate a questionnaire to estimate individual susceptibility to visually induced motion sickness (VIMS).

BACKGROUND

VIMS is a common side-effect when watching dynamic visual content from various sources, such as virtual reality, movie theaters, or smartphones. A reliable questionnaire predicting individual susceptibility to VIMS is currently missing. The aim was to fill this gap by introducing the Visually Induced Motion Sickness Susceptibility Questionnaire (VIMSSQ).

METHODS

A survey and an experimental study were conducted. Survey: The VIMSSQ investigated the frequency of nausea, headache, dizziness, fatigue, and eyestrain when using different visual devices. Data were collected from a survey of 322 participants for the VIMSSQ and other related phenomena such as migraine. Experimental study: 23 participants were exposed to a VIMS-inducing visual stimulus. Participants filled out the VIMSSQ together with other questionnaires and rated their level of VIMS using the Simulator Sickness Questionnaire (SSQ).

RESULTS

Survey: The most prominent symptom when using visual devices was eyestrain, and females reported more VIMS than males. A one-factor solution with good scale reliability was found for the VIMSSQ. Experimental study: Regression analyses suggested that the VIMSSQ can be useful in predicting VIMS (R² = .34) as measured by the SSQ, particularly when combined with questions pertaining to the tendency to avoid visual displays and experience syncope (R² = .59).

CONCLUSION

We generated normative data for the VIMSSQ and demonstrated its validity.

APPLICATION

The VIMSSQ can become a valuable tool to estimate one's susceptibility to VIMS based on self-reports.

Effect of spatial distortions in head-mounted displays on visually induced motion sickness

Incomplete optical distortion correction in VR HMDs leads to spatial dynamic distortion, which is a potential cause of VIMS. A perception experiment is designed for the investigation with three spatial distortion levels, with the subjective SSQ, five-scale VIMS level rating, and objective postural instability adopted as the evaluation metrics. The results show that the factor of spatial distortion level has a significant effect on all metrics increments (p<0.05). As the spatial distortion level drops off, the increments of VIMS symptoms decrease. The study highlights the importance of perfect spatial distortion correction in VR HMDs for eliminating the potential VIMS aggravation effect.

Effects of exposure to immersive computer-generated virtual nature and control environments on affect and cognition

Previous research has shown that exposure to immersive virtual nature environments is able to induce positive affective and physiological effects. However, research on the effects on cognitive performance is scarce. Additionally, the effects of virtual nature exposure compared to a virtual control environment with a comparable amount of virtual objects have not been examined so far. Therefore, we conducted an experiment with 27 participants to study the psychological effects of such exposure. The virtual nature consisted of a 3D model of a typical forest environment, whereas the control environment was an abstract replication of the virtual forest environment. In both environments, a virtual wooden cart was used to transport the users from the start to the end of the virtual road. The typical background noise of moving such a cart was integrated into both environments as well. In addition, the virtual nature environment included typical forest sounds in the background, whereas the control condition did not have such background sounds. Both environments were compared with regard to their effects on cognitive performance (using trail making tests (TMTA, TMTB, and TMTB-A) as well as digit span forward and digit span backward tests), perceived restorativeness, mood, stress, sense of presence, and simulator sickness. The results showed that in comparison to the control environment, exposure to the virtual nature resulted in significantly higher cognitive performance, higher perceived restorativeness, higher positive affect, higher sense of presence, lower perceived stress, and lower simulator sickness.

Potential of the omnidirectional walking platform with virtual reality as a rehabilitation tool

Introduction

The combination of virtual reality (VR) with an omnidirectional walking platform (ODWP) may have potential in rehabilitation settings. However, its use, acceptance, safety, and effectiveness are unclear. This preliminary study aims to understand the feasibility, safety, and user experience (including investigating the onset of cybersickness) while walking on the ODWP with fully immersive VR.

Methods

Participants engaged with eight immersive VR walking scenarios. The scenarios were created using 360-degree videos and were programmed to run with the ODWP. Safety modifications for the ODWP were made, with the addition of parallel bars. Quantitative feedback on the perceived safety and acceptance of using VR with an ODWP for rehabilitation was collected. Cybersickness was evaluated using the Simulation Symptoms Questionnaire (SSQ).

Results

Thirty-five participants (n = 8 physiotherapists, n = 27 healthy adults) were recruited for this study. The mean perceived safety score was 78.9/100 and acceptance was 64.5/100. Seventy-one percent of participants experienced mild to moderate symptoms of cybersickness as reported on the SSQ. The SSQ scores were not correlated to participant age or simulation exposure time.

Conclusion

VR while using ODWP has the potential for rehabilitation, however, more consideration is needed to address acceptance and cybersickness.

Motion sickness and cybersickness - Sensory mismatch

The use of virtual reality (VR) with head-mounted displays (HMD) may cause side effects called cybersickness with symptoms comparable to those of motion sickness. In this study, we explored whether individual balance characteristics and self-reported tendency to motion sickness could be related to cybersickness vulnerability. Healthy young people (N = 45) were exposed to a VR application with HMD for four minutes, standing with no support. Balance characteristics were measured before (Sensory orientation test) and during (balance platform) the VR exposure. Symptoms of cybersickness were recorded by the Simulator sickness questionnaire (SSQ). Data were analyzed for subgroups with and without a tendency to motion sickness. The participants were negatively affected by the VR exposure: SSQ-before: 21.3 (19.5); SSQ-after: 31.8 (25.2); p<0.01, and 73% experienced increased discomfort. The SSQ sub-scores Nausea and Disorientation were affected, but not the sub-score for Oculomotor disturbance. Surprisingly, the participants described discomfort already after the initial balance assessment (Sensory orientation test). Participants with a self-reported tendency to motion sickness were relatively more affected by this challenge to their sensory integration. Increased postural instability was evident during the VR exposure, but there was a sizeable individual variance in the postural response. The study identified no individual balance characteristics which could be associated with the cybersickness vulnerability. The adverse effect of the Sensory orientation test is a novel finding and it became a bias that diminished subgroup differences in cybersickness vulnerability.

Piton: Investigating the Controllability of a Wearable Telexistence Robot

The COVID-19 pandemic impacted collaborative activities, travel, and physical contact, increasing the demand for real-time interactions with remote environments. However, the existing remote communication solutions provide limited interactions and do not convey a high sense of presence within a remote environment. Therefore, we propose a snake-shaped wearable telexistence robot, called Piton, that can be remotely used for a variety of collaborative applications. To the best of our knowledge, Piton is the first snake-shaped wearable telexistence robot. We explain the implementation of Piton, its control architecture, and discuss how Piton can be deployed in a variety of contexts. We implemented three control methods to control Piton: HM-using a head-mounted display (HMD), HH-using an HMD and hand-held tracker, and FM-using an HMD and a foot-mounted tracker. We conducted a user study to investigate the applicability of the proposed control methods for telexistence, focusing on body ownership (Alpha IVBO), mental and physical load (NASA-TLX), motion sickness (VRSQ), and a questionnaire to measure user impressions. The results show that both the HM and HH provide relevantly high levels of body ownership, had high perceived accuracy, and were highly favored, whereas the FM control method yielded the lowest body ownership effect and was least favored. We discuss the results and highlight the advantages and shortcomings of the control methods with respect to various potential application contexts. Based on our design and evaluation of Piton, we extracted a number of insights and future research directions to deepen our investigation and realization of wearable telexistence robots.

Dynamic changes of brain networks during standing balance control under visual conflict

Stance balance control requires a very accurate tuning and combination of visual, vestibular, and proprioceptive inputs, and conflict among these sensory systems may induce posture instability and even falls. Although there are many human mechanics and psychophysical studies for this phenomenon, the effects of sensory conflict on brain networks and its underlying neural mechanisms are still unclear. Here, we combined a rotating platform and a virtual reality (VR) headset to control the participants’ physical and visual motion states, presenting them with incongruous (sensory conflict) or congruous (normal control) physical-visual stimuli. Further, to investigate the effects of sensory conflict on stance stability and brain networks, we recorded and calculated the effective connectivity of source-level electroencephalogram (EEG) and the average velocity of the plantar center of pressure (COP) in healthy subjects (18 subjects: 10 males, 8 females). First, our results showed that sensory conflict did have a detrimental effect on stance posture control [sensor F(1, 17) = 13.34, P = 0.0019], but this effect decreases over time [window*sensor F(2, 34) = 6.72, P = 0.0035]. Humans show a marked adaptation to sensory conflict. In addition, we found that human adaptation to the sensory conflict was associated with changes in the cortical network. At the stimulus onset, congruent and incongruent stimuli had similar effects on brain networks. In both cases, there was a significant increase in information interaction centered on the frontal cortices (p < 0.05). Then, after a time window, synchronized with the restoration of stance stability under conflict, the connectivity of large brain regions, including posterior parietal, visual, somatosensory, and motor cortices, was generally lower in sensory conflict than in controls (p < 0.05). But the influence of the superior temporal lobe on other cortices was significantly increased. Overall, we speculate that a posterior parietal-centered cortical network may play a key role in integrating congruous sensory information. Furthermore, the dissociation of this network may reflect a flexible multisensory interaction strategy that is critical for human posture balance control in complex and changing environments. In addition, the superior temporal lobe may play a key role in processing conflicting sensory information.

Prediction of Specific Anxiety Symptoms and Virtual Reality Sickness Using In Situ Autonomic Physiological Signals During Virtual Reality Treatment in Patients With Social Anxiety Disorder: Mixed Methods Study

BACKGROUND

Social anxiety disorder (SAD) is the fear of social situations where a person anticipates being evaluated negatively. Changes in autonomic response patterns are related to the expression of anxiety symptoms. Virtual reality (VR) sickness can inhibit VR experiences.

OBJECTIVE

This study aimed to predict the severity of specific anxiety symptoms and VR sickness in patients with SAD, using machine learning based on in situ autonomic physiological signals (heart rate and galvanic skin response) during VR treatment sessions.

METHODS

This study included 32 participants with SAD taking part in 6 VR sessions. During each VR session, the heart rate and galvanic skin response of all participants were measured in real time. We assessed specific anxiety symptoms using the Internalized Shame Scale (ISS) and the Post-Event Rumination Scale (PERS), and VR sickness using the Simulator Sickness Questionnaire (SSQ) during 4 VR sessions (#1, #2, #4, and #6). Logistic regression, random forest, and naïve Bayes classification classified and predicted the severity groups in the ISS, PERS, and SSQ subdomains based on in situ autonomic physiological signal data.

RESULTS

The severity of SAD was predicted with 3 machine learning models. According to the F1 score, the highest prediction performance among each domain for severity was determined. The F1 score of the ISS mistake anxiety subdomain was 0.8421 using the logistic regression model, that of the PERS positive subdomain was 0.7619 using the naïve Bayes classifier, and that of total VR sickness was 0.7059 using the random forest model.

CONCLUSIONS

This study could predict specific anxiety symptoms and VR sickness during VR intervention by autonomic physiological signals alone in real time. Machine learning models can predict the severe and nonsevere psychological states of individuals based on in situ physiological signal data during VR interventions for real-time interactive services. These models can support the diagnosis of specific anxiety symptoms and VR sickness with minimal participant bias.

TRIAL REGISTRATION

Clinical Research Information Service KCT0003854; https://cris.nih.go.kr/cris/search/detailSearch.do/13508.

Enhanced vection in older adults: Evidence for age-related effects in multisensory vection experiences

The illusion of self-motion (vection) is a multisensory phenomenon elicited by visual, auditory, tactile, or other sensory cues. Aging is often associated with changes in sensory acuity, visual motion perception, and multisensory integration, processes which may influence vection perception. However, age-related differences in vection have received little study to date. Thus, the objective of the present study was to investigate age-related differences in vection during multisensory stimulation. Nineteen younger adults and 19 older adults were exposed to rotating visual, auditory, and tactile stimuli (separately or in combination) at a speed of 45°/s inside a VR laboratory inducing circular vection. The size of the field-of-view (FOV) was large (240°), medium (75°), small (30°), or contained no visuals. Vection intensity and duration were reported verbally after each trial. Overall, older adults experienced significantly stronger and longer vection compared to younger adults. Additionally, there were main effects of FOV and sensory cues, such that larger FOVs and the presence of auditory and tactile stimulation increased vection ratings for both age groups. These findings support the idea that vection is a multisensory experience that can be elicited by visual, auditory, and tactile stimuli and demonstrates these effects for the first time in older adults.

A New Vestibular Stimulation Mode for Motion Sickness With Emphatic Analysis of Pica

Motion sickness (MS) was frequently introduced for rodents in research work through passive motion that disturbed vestibular signals in the presence of visual and aleatory, proprioceptive inputs. Inducement of MS in this way causes conflicting signals that activate intermixed neural circuits representing multimodal stimulation. From reductionism, a lab setup to elicit rat MS via vestibular stimulation was configured in the present study for MS study in connection with dissection of the central vestibular component causally underlying MS. The individual animal was blinded to light with a custom-made restrainer, and positioned at an inclination of 30° for otolith organs to receive unusual actions by gravitoinertial vector. Following a 2-h double-axis (earth-vertical) rotation involving angular acceleration/deceleration, a suit of behaviors characterizing the MS was observed to be significantly changed including pica (eating non-nutritive substance like kaolin), conditioned taste avoidance and locomotion (p < 0.05). Notably, for the statistical hypothesis testing, the utility of net increased amount of kaolin consumption as independent variables in data processing was expounded. In addition, Fos-immunostained neurons in vestibular nucleus complex were significantly increased in number, suggesting the rotation-induced MS was closely related to the vestibular activation. In conclusion, our work indicated that the present setup could effectively elicit the MS by disturbing vestibular signals in rat in the context of well-controlled proprioceptive inputs and lack of visual afference.

VR Sickness Adaptation With Ramped Optic Flow Transfers From Abstract To Realistic Environments

VR sickness is a major concern for many users as VR continues its expansion towards widespread everyday use. VR sickness is thought to arise, at least in part, due to the user's intolerance of conflict between the visually simulated self-motion and actual physical movement. Many mitigation strategies involve consistently modifying the visual stimulus to reduce its impact on the user, but this individualized approach can have drawbacks in terms of complexity of implementation and non-uniformity of user experience. This study presents a novel alternative approach that involves training the user to better tolerate the adverse stimulus by tapping into natural adaptive perceptual mechanisms. In this study, we recruited users with limited VR experience that reported susceptibility to VR sickness. Baseline sickness was measured as participants navigated a rich and naturalistic visual environment. Then, on successive days, participants were exposed to optic flow in a more abstract visual environment, and strength of the optic flow was successively increased by increasing the visual contrast of the scene, because strength of optic flow and the resulting vection are thought to be major causes of VR sickness. Sickness measures decreased on successive days, indicating that adaptation was successful. On the final day, participants were again exposed to the rich and naturalistic visual environment, and the adaptation was maintained, demonstrating that it is possible for adaptation to transfer from more abstract to richer and more naturalistic environments. These results demonstrate that gradual adaptation to increasing optic flow strength in well-controlled, abstract environments allows users to gradually reduce their susceptibility to sickness, thereby increasing VR accessibility for those prone to sickness.

Cybersickness and Its Severity Arising from Virtual Reality Content: A Comprehensive Study

Virtual reality (VR) experiences often elicit a negative effect, cybersickness, which results in nausea, disorientation, and visual discomfort. To quantitatively analyze the degree of cybersickness depending on various attributes of VR content (i.e., camera movement, field of view, path length, frame reference, and controllability), we generated cybersickness reference (CYRE) content with 52 VR scenes that represent different content attributes. A protocol for cybersickness evaluation was designed to collect subjective opinions from 154 participants as reliably as possible in conjunction with objective data such as rendered VR scenes and biological signals. By investigating the data obtained through the experiment, the statistically significant relationships—the degree that the cybersickness varies with each isolated content factor—are separately identified. We showed that the cybersickness severity was highly correlated with six biological features reflecting brain activities (i.e., relative power spectral densities of Fp1 delta, Fp 1 beta, Fp2 delta, Fp2 gamma, T4 delta, and T4 beta waves) with a coefficient of determination greater than 0.9. Moreover, our experimental results show that individual characteristics (age and susceptibility) are also quantitatively associated with cybersickness level. Notably, the constructed dataset contains a number of labels (i.e., subjective cybersickness scores) that correspond to each VR scene. We used these labels to build cybersickness prediction models and obtain a reliable predictive performance. Hence, the proposed dataset is supposed to be widely applicable in general-purpose scenarios regarding cybersickness quantification.

A Deep Motion Sickness Predictor Induced by Visual Stimuli in Virtual Reality

In a virtual reality (VR) environment, where visual stimuli predominate over other stimuli, the user experiences cybersickness because the balance of the body collapses due to self-motion. Accordingly, the VR experience is accompanied by unavoidable sickness referred to as visually induced motion sickness (VIMS). In this article, our primary purpose is to simultaneously estimate the VIMS score by referring to the content and calculate the temporally induced VIMS sensitivity. To seek our goals, we propose a novel architecture composed of two consecutive networks: 1) neurological representation and 2) spatiotemporal representation. In the first stage, the network imitates and learns the neurological mechanism of motion sickness. In the second stage, the significant feature of the spatial and temporal domains is expressed over the generated frames. After the training procedure, our model can calculate VIMS sensitivity for each frame of the VR content by using the weakly supervised approach for unannotated temporal VIMS scores. Furthermore, we release a massive VR content database. In the experiments, the proposed framework demonstrates excellent performance for VIMS score prediction compared with existing methods, including feature engineering and deep learning-based approaches. Furthermore, we propose a way to visualize the cognitive response to visual stimuli and demonstrate that the induced sickness tends to be activated in a similar tendency, as done in clinical studies.

Eye Movement Patterns Reflecting Cybersickness: Evidence from Different Experience Modes of a Virtual Reality Game

This study investigated whether the degree of cybersickness varies depending on different virtual reality experience modes (playing vs. watching) and whether specific eye movement parameters reflect changes in cybersickness. Simulator Sickness Questionnaire results from 20 participants (10 playing and 10 watching) showed that cybersickness was much more severe in the watching mode, particularly during the second of the three total trials. Moreover, cybersickness' changing pattern was reflected in the center gaze ratio and scan-path length. These findings imply the importance of physiological measurements for a deeper understanding of cybersickness in theoretical and practical respects.

Virtual reality-based monitoring test for MCI: A multicenter feasibility study

OBJECTIVES

As the significance of the early diagnosis of mild cognitive impairment (MCI) has emerged, it is necessary to develop corresponding screening tools with high ecological validity and feasible biomarkers. Virtual reality (VR)-based cognitive assessment program, which is close to the daily life of the older adults, can be suitable screening tools for MCI with ecological validity and accessibility. Meanwhile, dehydroepiandrosterone (DHEA) has been observed at a low concentration in the older adults with dementia or cognitive decline, indicating its potential as a biomarker of MCI. This study aimed to determine the efficacy and usability of a VR cognitive assessment program and salivary DHEA for screening MCI.

METHODS

The VR cognitive assessment program and the traditional Montreal Cognitive Assessment (MOCA) test were performed on 12 patients with MCI and 108 healthy older adults. The VR program operates in a situation of caring for a grandchild, and evaluates the memory, attention, visuospatial, and executive functions. An analysis of covariance (ANCOVA), a partial correlation analysis, and receiving operating characteristic (ROC) curve analysis were conducted for statistical analysis.

RESULTS

According to the ANCOVA, no significant difference in MOCA scores was found between the normal and MCI groups (F = 2.36, p = 0.127). However, the VR total score of the MCI group was significantly lower than that of the normal group (F = 8.674, p = 0.004). There was a significant correlation between the MOCA and VR scores in the total and matched subdomain scores. The ROC curve analysis also showed a larger area under the curve (AUC) for the VR test (0.765) than for the MOCA test (0.598), and the sensitivity and specificity of the VR program were 0.833 and 0.722, respectively. Salivary DHEA was correlated with VR total (R ² = 0.082, p = 0.01) and attention scores (R ² = 0.086, p = 0.009).

CONCLUSION

The VR cognitive test was as effective as the traditional MOCA test in the MCI classification and safe enough for older adults to perform, indicating its potential as a diagnostic tool. It has also been shown that salivary DHEA can be used as a biomarker for MCI.

A systematic review and meta-analysis on the use of tactile stimulation in vection research

Vection is classically defined as the illusory perception of self-motion induced via visual stimuli. The utility of vection research lies in its potential to enhance simulation fidelity, as measured through presence, and reduce the probability that motion sickness symptoms occur. Studies have shown a multimodal interaction of various sensory systems in facilitating vection, and the utility of co-stimulating some of these sensory systems along with the presentation of visual stimuli have been reviewed. However, a review on the use of tactile stimulation in vection research appears to be missing from literature. The purpose of this review was to evaluate the current methodologies, and outcomes, of tactile stimulation in vection research. We searched for articles through EBSCOHost, Scopus and Web of Science. Studies were included only if they detailed an experiment on the effect of tactile stimulation on vection. Twenty-four studies were obtained and distilled in tabular form. Eighteen studies contained sufficient information to be included in a meta-analysis. We identified that tactile stimulation has mostly been applied in the form of vibrational stimulation to the feet. Furthermore, tactile stimulation is most effective when it is presented in a temporally congruent manner to other sensory cues, whereas tactile stimulation as a unisensory stimulus does not appear to be effective in eliciting vection. We discuss the need for more qualitative research to reduce methodological inhomogeneities and recommend future research in tactile-mediated vection to investigate stimulation to the torso and investigate the use of forces as a tactile stimulus.

Evaluating the effect of multi-sensory stimulations on simulator sickness and sense of presence during HMD-mediated VR experience

Some lines of evidence have shown that sensory input, especially related to vestibular and somatosensory stimulation, may reduce the symptoms related to simulator sickness and increase the sense of presence in VR. The present study aims at understanding how mechanical vibration and auditory stimulation can be used to improve user experience in the context of VR mediated by head-mounted displays. Four different groups comprising a total of 80 participants were tested under different conditions of sensory input (visual and vibration, visual-auditory, combined visual-auditory and vibratory, and visual only), during a VR roller-coaster experience. No significant differences in simulator sickness were found between the groups exposed to seat vibration and/or audio. However, sense of presence showed to be increased when vibratory stimuli were included. Post-hoc analyses showed that female users but not male ones, experienced an increase of sense of presence when vibratory stimulation was used. Practitioner summary: The study showed that including sound or vibration stimulation during VR experience does not reduce simulator sickness. However, sense of presence is promoted by vibratory stimulation. Post-hoc analyses showed that female users experienced an increase of sense of presence by vibratory stimulation, but not male ones.

Mismatch of Visual-Vestibular Information in Virtual Reality: Is Motion Sickness Part of the Brains Attempt to Reduce the Prediction Error?

Visually induced motion sickness (VIMS) is a relevant limiting factor in the use of virtual reality (VR) devices. Understanding the origin of this problem might help to develop strategies to circumvent this limitation. Previous studies have attributed VIMS to a mismatch between visual, and vestibular information, causing ambiguity of the position of the body in relation to its surrounding. Studies using EEG have shown a shift of the power spectrum to lower frequencies while VIMS is experienced. However, little is known about the relationship between the intensity of the VIMS and the changes in these power spectra. Moreover, the effect of different varieties of VIMS on the causal relationship between brain areas is largely unknown. Here, we used EEG to study 14 healthy subjects in a VR environment who were exposed to increasing levels of mismatch between vestibular and visual information. The frequency power and the bivariate transfer entropy as a measure for the information transfer were calculated. We found a direct association between increasing mismatch levels and subjective VIMS. With increasing VIMS, the proportion of slow EEG waves (especially 1–10 Hz) increases, especially in temporo-occipital regions. Furthermore, we found a general decrease in the information flow in most brain areas but especially in brain areas involved in the processing of vestibular signals and the detection of self-motion. We hypothesize that the general shift of frequency power and the decrease in information flow while experiencing high intensity VIMS represent a brain state of a reduced ability to receive, transmit and process information. We further hypothesize that the mechanism of reduced information flow is a general reaction of the brain to an unresolvable mismatch of information. This reaction aims on transforming a currently unstable model with a high prediction error into a stable model in an environment of minimal contradictory information.

Using Visual Guides to Reduce Virtual Reality Sickness in First-Person Shooter Games: Correlation Analysis

BACKGROUND

The virtual reality (VR) content market is rapidly growing due to an increased supply of VR devices such as head-mounted displays (HMDs), whereas VR sickness (reported to occur while experiencing VR) remains an unsolved problem. The most widely used method of reducing VR sickness is the use of a rest frame that stabilizes the user's viewpoint by providing fixed visual stimuli in VR content (including video). However, the earth-fixed grid and natural independent visual background that are widely used as rest frames cannot maintain VR fidelity, as they reduce the immersion and the presence of the user. A visual guide is a visual element (eg, a crosshair of first-person shooter [FPS]) that induces a user's gaze movement within the VR content while maintaining VR fidelity, whereas there are no studies on the correlation of visual guide with VR sickness.

OBJECTIVE

This study aimed to analyze the correlation between VR sickness and crosshair, which is widely used as a visual guide in FPS games.

METHODS

Eight experimental scenarios were designed and evaluated, including having the visual guide on/off, the game controller on/off, and varying the size and position of the visual guide to determine the effect of visual guide on VR sickness.

RESULTS

The results showed that VR sickness significantly decreased when visual guide was applied in an FPS game. In addition, VR sickness was lower when the visual guide was adjusted to 30% of the aspect ratio and positioned in the head-tracking direction.

CONCLUSIONS

The experimental results of this study indicate that the visual guide can achieve VR sickness reduction while maintaining user presence and immersion in the virtual environment. In other words, the use of a visual guide is expected to solve the existing limitation of distributing various types of content due to VR sickness.

Self-initiation Inhibits the Postural and Electrophysiological Responses to Optic Flow and Button Pressing

As we move through our environment, our visual system is presented with optic flow, a potentially important cue for perception, navigation and postural control. How does the brain anticipate the optic flow that arises as a consequence of our own movement? Converging evidence suggests that stimuli are processed differently by the brain if occurring as a consequence of self-initiated actions, compared to when externally generated. However, this has mainly been demonstrated with auditory stimuli. It is not clear how this occurs with optic flow. We measured behavioural, neurophysiological and head motion responses of 29 healthy participants to radially expanding, vection-inducing optic flow stimuli, simulating forward transitional motion, which were either initiated by the participant's own button-press ("self-initiated flow") or by the computer ("passive flow"). Self-initiation led to a prominent and left-lateralized inhibition of the flow-evoked posterior event-related alpha desynchronization (ERD), and a stabilisation of postural responses. Neither effect was present in control button-press-only trials, without optic flow. Additionally, self-initiation also produced a large event-related potential (ERP) negativity between 130-170 ms after optic flow onset. Furthermore, participants' visual induced motion sickness (VIMS) and vection intensity ratings correlated positively across the group - although many participants felt vection in the absence of any VIMS, none reported the opposite combination. Finally, we found that the simple act of making a button press leads to a detectable head movement even when using a chin rest. Taken together, our results indicate that the visual system is capable of predicting optic flow when self-initiated, to affect behaviour.

The role of binocular disparity and active motion parallax in cybersickness

Cybersickness is an enduring problem for users of virtual environments. While it is generally assumed that cybersickness is caused by discrepancies in perceived self-motion between the visual and vestibular systems, little is known about the relative contribution of active motion parallax and binocular disparity to the occurrence of cybersickness. We investigated the role of these two depth cues in cybersickness by simulating a roller-coaster ride using a head-mounted display. Participants could see the tracks via a virtual frame placed at the front of the roller-coaster cart. We manipulated the state of the frame, so it behaved like: (1) a window into the virtual scene, (2) a 2D screen, (3) and (4) a window for one of the two depth cues, and a 2D screen for the other. Participants completed the Simulator Sickness Questionnaire before and after the experiment, and verbally reported their level of discomfort at repeated intervals during the ride. Additionally, participants' electrodermal activity (EDA) was recorded. The results of the questionnaire and the continuous ratings revealed the largest increase in cybersickness when the frame behaved like a window, and least increase when the frame behaved like a 2D screen. Cybersickness scores were at an intermediate level for the conditions where the frame simulated only one depth cue. This suggests that neither active motion parallax nor binocular disparity had a more prominent effect on the severity of cybersickness. The EDA responses increased at about the same rate in all conditions, suggesting that EDA is not necessarily coupled with subjectively experienced cybersickness.

Feasibility of full immersive virtual reality video game on balance and cybersickness of healthy adolescents

Various virtual reality (VR) games with head-mounted displays (HMDs) can provide immersive experiences, but are often accompanied by negative experiences. We investigated the feasibility of immersive virtual reality game on balance and cybersickness in healthy adolescents. This is cross-over design. This study included 11 healthy adolescents. Balance and cybersickness were measured in the following three conditions. First, as a baseline, only balance was measured while no immersive virtual reality game was being played. Second, balance and cybersickness were measured while the participants played an immersive virtual reality game with a fixed background. Third, balance and cybersickness were measured while the participants played an immersive virtual reality game with a moving background. A force plate was used to measure balance, while the Questionnaire (VRSQ) and Simulator Sickness Questionnaire (SSQ) were used to measure cybersickness. Sway velocity and length significantly increased during the game with a moving background compared to baseline and a fixed background game (p < 0.05). VRSQ and SSQ scores significantly increased during the game with a fixed and moving background compared to baseline (p < 0.05) and were significantly higher with use of the moving versus fixed background (p < 0.05). This study demonstrated that playing an immersive virtual reality game with a moving background could negatively affect balance and cybersickness. These results will help to select game contents that can reduce side effects when applying VR HMD to various fields in the future.

To Sit or Not to Sit in VR: Analyzing Influences and (Dis)Advantages of Posture and Embodied Interaction

Virtual Reality (VR) users typically either sit or stand/walk when using VR; however, the impact of this is little researched, and there is a lack of any broad or systematic analysis of how this difference in physical posture might affect user experience and behavior. To address this gap, we propose such a systematic analysis that was refined through discussions and iterations during a dedicated workshop with VR experts. This analysis was complemented by an online survey to integrate the perspectives of a larger and more diverse group of VR experts, including developers and power users. The result is a validated expert assessment of the impact of posture and degree of embodiment on the most relevant aspects of VR experience and behavior. In particular, we posit potential strong effects of posture on user comfort, safety, self-motion perception, engagement, and accessibility. We further argue that the degree of embodiment can strongly impact cybersickness, locomotion precision, safety, self-motion perception, engagement, technical complexity, and accessibility. We provide a compact visualization of key findings and discuss areas where posture and embodiment do or do not have a known influence, as well as highlight open questions that could guide future research and VR design efforts.

Development of an 360-degree virtual reality video-based immersive cycle training system for physical enhancement in older adults: a feasibility study : Development of immersive virtual cycle for older adults

Background

Recently, there is an increased number of studies that use 360° virtual reality (VR) video for medical and rehabilitative purposes. However, the 360° VR video experience for older adults has not yet been investigated. This study aimed to examine the validity of an 360° VR video-based immersive cycling training system (360° VRCTS) for older adults and to provide preliminary evidence of efficacy.

Methods

We developed a new virtual reality training system using an immersive environment 360° VRCTS. Five healthy older adults (2 males and 3 females) participated in this study. The system was tested in a single training session (biking for 20 min while viewing a 360° VR video scene through a large curved screen) to identify its strengths and weakness. The usability and acceptability of our system were measured using the system usability scale (SUS) and the simulator sickness questionnaire (SSQ).

Results

All participants successfully completed the session without any discomfort. The average score for the SUS was 94.60 (range, 90–100), indicating high usability of the technology. The average score for the SSQ was 2.24 (standard deviation = 2.05), indicating that the system is well tolerated and has few side effects.

Conclusions

The 360° VRCTS may be a useful indoor training system for older adults due to its easy manipulation, high usability, and limited cybersickness.

Trial registration number

Clinical Research Information Services (CRiS), KCT0003555, Registered February 25, 2019, https://cris.nih.go.kr/cris/index/index.do.

Vestibular Rehabilitation after Vestibulopathy Focusing on the Application of Virtual Reality

Human postural control is regulated by the vestibular, somatosensory, and visual systems. These types of sensory information are integrated in the central nervous system to ascertain the body’s position in space. Proper functioning of the vestibular, somatosensory, and visual senses is necessary for the body to maintain equilibrium. Bilateral vestibulopathy (BVP) is a condition in which bilateral peripheral vestibular function is reduced. Its treatment includes vestibular rehabilitation (VeR), balance training, counseling, treating the underlying cause, and avoiding further damage to the vestibular system. As VeR is often tedious for patients, patient motivation is required or patients may drop out of the program. To solve this problem, in recent years, there have been increasing reports of VeR using virtual reality, which increases vestibulo-ocular reflex gain and decreased dizziness by inducing adaptation. In this review, we discuss VeR, particularly for BVP, and VeR using virtual reality.

Feasibility of training using full immersion virtual reality video game in young stroke survivor: A case report

BACKGROUND

With the recent developments in science, full-immersion virtual reality devices have been developed, which may have feasibility for stroke rehabilitation.

OBJECTIVE

This case report investigated the feasibility of training using a full-immersion virtual reality video game for improving motor function, balance, and gait in a young stroke survivor.

METHOD

The case was a 27-year-old woman with stroke. A training using full-immersion virtual reality video game (Sony PlayStation®VR) was performed for 30 minutes per session, 3 sessions per week, for 6 weeks, with a total of 18 sessions. Before training and at each training for 6 weeks, with a total of 19 times, the motor function, balance, and gait were assessed using the Motor Assessment Scale (MAS), Berg Balance Scale (BBS), Timed Up and Go (TUG) Test, and Tinetti Balance Assessment, 10 Meter Walk Test (10MWT), Tinetti Gait Assessment, and Dynamic Gait Index (DGI).

RESULTS

During the training, there were no adverse events reported. The case achieved 14 points higher than the pre-assessment with 34 points on the MAS, 16 points higher than the pre-assessment with 48 points on BBS, 6.85 sec lower than the pre-assessment, with 13.58 sec on TUG, 5 points higher than the pre-assessment with 13 points on the Tinetti Balance Assessment, 5.36 sec lower than the pre-assessment, with 8.15 sec on the 10MWT, 4 points higher than the pre-assessment with 10 points on the Tinetti Gait Assessment, and 10 points higher than the pre-assessment with 21 points on the DGI.

CONCLUSION

This case report suggests that training using a full-immersion virtual reality video game may be a safe and effective method to improve motor function, balance, and gait in a young stroke survivor.

The Influence of Virtual Reality Head-Mounted Displays on Balance Outcomes and Training Paradigms: A Systematic Review

Background: Falls are the leading causes of (non)fatal injuries in older adults. Recent research has developed interventions that aim to improve balance in older adults using virtual reality (VR).

Purpose: We aimed to investigate the validity, reliability, safety, feasibility, and efficacy of head mounted display (HMD) systems for assessing and training balance in older adults.

Methods: We searched EBSCOhost, Scopus, Web of Science, and PubMed databases until 1 September 2020 to find studies that used HMD systems for assessing or training balance. The methodological quality was assessed using a modified version of Downs and Black. We also appraised the risk of bias using Risk of Bias Assessment tool for Non-randomized Studies (RoBANS).

Results: A total of 19 articles (637 participants) were included for review. Despite heterogenous age ranges and clinical conditions across studies, VR HMD systems were valid to assess balance and could be useful for fall prevention and for improving postural control and gait patterns. These systems also have the capacity to differentiate healthy and balance-impaired individuals. During VR versions of traditional balance tests, older adults generally acquire a cautious behavior and take more time to complete the tasks.

Conclusion: VR HMD systems can offer ecologically valid scenarios to assess and train functional balance and can be used alone or in addition to other interventions. New norms and protocols should be defined according to participants' age, health status, and severity of their illness when using VR HMD systems for balance assessment and training. For safe and feasible training, attention must be given to display type, VR elements and scenarios, duration of exposure, and system usability. Due to high risk of bias and overall poor quality of the studies, further research is needed on the effectiveness of HMD VR training in older adults.

The effect of water immersion on vection in virtual reality

Research about vection (illusory self-motion) has investigated a wide range of sensory cues and employed various methods and equipment, including use of virtual reality (VR). However, there is currently no research in the field of vection on the impact of floating in water while experiencing VR. Aquatic immersion presents a new and interesting method to potentially enhance vection by reducing conflicting sensory information that is usually experienced when standing or sitting on a stable surface. This study compares vection, visually induced motion sickness, and presence among participants experiencing VR while standing on the ground or floating in water. Results show that vection was significantly enhanced for the participants in the Water condition, whose judgments of self-displacement were larger than those of participants in the Ground condition. No differences in visually induced motion sickness or presence were found between conditions. We discuss the implication of this new type of VR experience for the fields of VR and vection while also discussing future research questions that emerge from our findings.

The role of cognitive factors and personality traits in the perception of illusory self-motion (vection)

Vection is a perceptual phenomenon that describes the visually induced subjective sensation of self-motion in the absence of physical motion. Previous research has discussed the potential involvement of top-down cognitive mechanisms on vection. Here, we quantified how cognitive manipulations such as contextual information (i.e., expectation) and plausibility (i.e., chair configuration) alter vection. We also explored how individual traits such as field dependence, depersonalization, anxiety, and social desirability might be related to vection. Fifty-one healthy adults were exposed to an optic flow stimulus that consisted of horizontally moving black-and-white bars presented on three adjacent monitors to generate circular vection. Participants were divided into three groups and given experimental instructions designed to induce either strong, weak, or no expectation with regard to the intensity of vection. In addition, the configuration of the chair (rotatable or fixed) was modified during the experiment. Vection onset time, duration, and intensity were recorded. Results showed that expectation altered vection intensity, but only when the chair was in the rotatable configuration. Positive correlations for vection measures with field dependence and depersonalization, but no sex-related effects were found. Our results show that vection can be altered by cognitive factors and that individual traits can affect the perception of vection, suggesting that vection is not a purely perceptual phenomenon, but can also be affected by top-down mechanisms.

Evaluating Balance Recovery Techniques for Users Wearing Head-Mounted Display in VR

Room-scale 3D position tracking enables users to explore a virtual environment by physically walking, which improves comfort and the level of immersion. However, when users walk with their eyesight blocked by a head-mounted display, they may unexpectedly lose their balance and fall if they bump into real-world obstacles or unintentionally shift their center of mass outside the margin of stability. This paper evaluates balance recovery methods and intervention timing during the use of VR with the assumption that the onset of a fall is given. Our experiment followed the tether-release protocol during clinical research and induced a fall while a subject was engaged in a secondary 3D object selection task. The experiment employed a two-by-two design that evaluated two assistive techniques, i.e., video-see-through and auditory warning at two different timings, i.e., at fall onset and 500ms prior to fall onset. The data from 17 subjects showed that video-see-through triggered 500 ms before the onset of fall can effectively help users recover from falls. Surprisingly, video-see-through at fall onset has a significant negative impact on balance recovery and produces similar results to those of the baseline condition (no intervention).