Early cortical processing of coherent vs. non-coherent motion stimuli in younger and older adults: An event-related potential (ERP) study investigating visually induced vection

The neurophysiological basis of vection (i.e., the illusion of self-motion) is not well understood. Preliminary evidence suggests that neural predictors of vection can be identified through event-related potentials (ERPs) and that these markers may correlate with vection intensity. The current study examined age-related differences in neurocortical activity during the early stages of sensory processing of vection-inducing stimuli. Twenty-two younger (age range: 20-35 years) and 25 older adults (age range: 65-83) observed optokinetic stimuli in two blocks, a short (∼3s) presentation block and a long (35s) presentation block. In both types of blocks, the optokinetic stimuli varied in motion coherence (coherent vs. non-coherent motion). During the short presentation block, EEG was used to measure neural activity in the form of ERPs time-locked to the onset of visual motion, whereas subjective ratings of vection intensity, duration, and onset latency were collected during the long presentation block. Vection was significantly stronger following coherent vs. non-coherent motion for both age groups. ERP analyses revealed differences between coherent and non-coherent motion at parietal-occipital electrodes around 100-150 ms (P1) and 150-230 ms (P2), with greater area under the curve (AUC) during non-coherent vs. coherent motion. Neither vection ratings nor ERPs showed significant age differences for coherent visual motion; however, age differences in ERPs were observed during the processing of non-coherent visual motion. These findings indicate that the subjective experience of vection and the neurophysiological mechanisms underlying visual processing preceding vection remain relatively stable with age. However, they also reveal age-related differences in the processing of non-coherent motion.

The presence of an avatar can reduce cybersickness in Virtual Reality

Virtual Reality (VR) applications are increasingly being utilized for research, healthcare, and education. Despite their benefits, many VR users report motion sickness-like sensations (cybersickness), such as headache, disorientation, or nausea. Previous studies suggest that the sense of presence ("being there") in the virtual world may contribute to the severity of cybersickness; however, results have been contradictory, with some studies reporting a negative and some reporting a positive relationship between the two. The goal of the current study was to further investigate how presence and cybersickness are related. Participants (N = 54) were exposed to a VR scene presented on a head-mounted display showing a 15-minute-long passive movement through space. The level of presence was manipulated by including an avatar (astronaut suit with hand-tracking) or no avatar in the virtual environment. Results showed that the avatar group reported significantly less severe cybersickness compared to the no-avatar group. We also found significant, negative correlations between some of the presence metrics (immersion, sensory fidelity) and cybersickness, indicating that cybersickness severity decreased as the level of presence increased. These findings suggest that more immersive VR experiences using an avatar may potentially reduce the risk of experiencing cybersickness.

Electrophysiological markers of vestibular-mediated self-motion perception - A pilot study

Peripheral vestibular activation results in multi-level responses, from brainstem-mediated reflexes (e.g. vestibular ocular reflex - VOR) to perception of self-motion. While VOR responses indicate preserved vestibular peripheral and brainstem functioning, there are no automated measures of vestibular perception of self-motion - important since some patients with brain disconnection syndromes manifest a vestibular agnosia (intact VOR but impaired self-motion perception). Electroencephalography ('EEG') - may provide a surrogate marker of vestibular perception of self-motion. A related objective is obtaining an EEG marker of vestibular sensory signal processing, distinct from vestibular-motion perception. We performed a pilot study comparing EEG responses in the dark when healthy participants sat in a vibrationless computer-controlled motorised rotating chair moving at near threshold of self-motion perception, versus a second situation in which subjects sat in the chair at rest in the dark who could be induced (or not) into falsely perceiving self-motion. In both conditions subjects could perceive self-motion perception, but in the second there was no bottom-up reflex-brainstem activation. Time-frequency analyses showed: (i) alpha frequency band activity is linked to vestibular sensory-signal activation; and (ii) theta band activity is a marker of vestibular-mediated self-motion perception. Consistent with emerging animal data, our findings support the role of theta activity in the processing of self-motion perception.

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.

Concussion can increase the risk of visually induced motion sickness

Concussion can lead to various symptoms such as balance problems, memory impairments, dizziness, and/or headaches. It has been previously suggested that during self-motion relevant tasks, individuals with concussion may rely heavily on visual information to compensate for potentially less reliable vestibular inputs and/or problems with multisensory integration. As such, concussed individuals may also be more sensitive to other visually-driven sensations such as visually induced motion sickness (VIMS). To investigate whether concussed individuals are at elevated risk of experiencing VIMS, we exposed participants with concussion (n = 16) and healthy controls (n = 15) to a virtual scene depicting visual self-motion down a grocery store aisle at different speeds. Participants with concussion were further separated into symptomatic and asymptomatic groups. VIMS was measured with the SSQ before and after stimulus exposure, and visual dependence, self-reported dizziness, and somatization were recorded at baseline. Results showed that concussed participants who were symptomatic demonstrated significantly higher SSQ scores after stimulus presentation compared to healthy controls and those who were asymptomatic. Visual dependence was positively correlated with the level of VIMS in healthy controls and participants with concussion. Our results suggest that the presence of concussion symptoms at time of testing significantly increased the risk and severity of VIMS. This finding is of relevance with regards to the use of visual display devices such as Virtual Reality applications in the assessment and rehabilitation of individuals with concussion.

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.

An old approach to a novel problem: effect of combined balance therapy on virtual reality induced motion sickness: a randomized, placebo controlled, double-blinded study

BACKGROUND

The objective of this study was to investigate the impact of a rehabilitation program aimed at addressing vestibular and proprioceptive deficits, which are believed to underlie the pathophysiology of motion sickness.

METHODS

A total of 121 medical students with motion sickness participated in this study and were randomly divided into intervention (n = 60) and placebo control (n = 61) groups. The intervention group underwent combined balance, proprioception, and vestibular training three times a week for 4 weeks, while the control group received placebo training. The study assessed various measurements, including the Virtual reality sickness questionnaire (VRSQ), tolerance duration, enjoyment level measured by VAS, stability levels using Biodex, and balance with the Flamingo balance test (FBT). All measurements were conducted both at baseline and 4 weeks later.

RESULTS

There was no significant difference in pre-test scores between the intervention and control groups, suggesting a similar baseline in both groups (p > 0.05). The results showed a significant improvement in VRSQ, tolerance duration, VAS, Biodex, and FBT scores in the intervention group (p < 0.05). While, the control group showed a significant increase only in VAS scores after 4 weeks of training (p < 0.05). A statistically significant improvement was found between the groups for VRSQ (p < 0.001), tolerance duration (p < 0.001), VAS (p < 0.001), Biodex (p = 0.015), and FBT scores (p < 0.05), in favor of the intervention group.

CONCLUSIONS

A combined balance training program for motion sickness proves to be effective in reducing motion sickness symptoms, enhancing user enjoyment, and extending the usage duration of virtual reality devices while improving balance and stability. In contrast, placebo training did not alter motion sickness levels. These findings offer valuable insights for expanding the usage of virtual reality, making it accessible to a broader population.

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 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.

EEG analysis of the visual motion activated vection network in left- and right-handers

Visually-induced self-motion perception (vection) relies on interaction of the visual and vestibular systems. Neuroimaging studies have identified a lateralization of the thalamo-cortical multisensory vestibular network, with left-handers exhibiting a dominance of the left hemisphere and right-handers exhibiting a dominance of the right hemisphere. Using electroencephalography (EEG), we compare the early processing of a vection-consistent visual motion stimulus against a vection-inconsistent stimulus, to investigate the temporal activation of the vection network by visual motion stimulation and the lateralization of these processes in left- versus right-handers. In both groups, vection-consistent stimulation evoked attenuated central event-related potentials (ERPs) in an early (160-220 ms) and a late (260-300 ms) time window. Differences in estimated source activity were found across visual, sensorimotor, and multisensory vestibular cortex in the early window, and were observed primarily in the posterior cingulate, retrosplenial cortex, and precuneus in the late window. Group comparisons revealed a larger ERP condition difference (i.e. vection-consistent stimulation minus vection-inconsistent stimulation) in left-handers, which was accompanied by group differences in the cingulate sulcus visual (CSv) area. Together, these results suggest that handedness may influence ERP responses and activity in area CSv during vection-consistent and vection-inconsistent visual motion stimulation.

Motion sickness: current concepts and management

PURPOSE OF REVIEW

Motion sickness is an ancient phenomenon that affects many people. Nausea, vomiting, disorientation, sweating, fatigue, and headache are just few of the many signs and symptoms that are commonly experienced during an episode of motion sickness. In the present review, we will provide an overview of the current research trends and topics in the domain of motion sickness, including theoretical considerations, physiological and neural mechanisms, individual risk factors, and treatment options, as well as recommendations for future research directions.

RECENT FINDINGS

More recently, motion sickness has been in the focus of attention in the context of two global technological trends, namely automated vehicles and virtual reality. Both technologies bear the potential to revolutionize our daily lives in many ways; however, motion sickness is considered a serious concern that threatens their success and acceptance. The majority of recent research on motion sickness focuses on one of these two areas.

SUMMARY

Aside from medication (e.g. antimuscarinics, antihistamines), habituation remains the most effective nonpharmacological method to reduce motion sickness. A variety of novel techniques has been investigated with promising results, but an efficient method to reliably prevent or minimize motion sickness has yet to emerge.

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.

Multisensory Effects on Illusory Self-Motion (Vection): the Role of Visual, Auditory, and Tactile Cues

A critical component to many immersive experiences in virtual reality (VR) is vection, defined as the illusion of self-motion. Traditionally, vection has been described as a visual phenomenon, but more recent research suggests that vection can be influenced by a variety of senses. The goal of the present study was to investigate the role of multisensory cues on vection by manipulating the availability of visual, auditory, and tactile stimuli in a VR setting. To achieve this, 24 adults (Mage = 25.04) were presented with a rotating stimulus aimed to induce circular vection. All participants completed trials that included a single sensory cue, a combination of two cues, or all three cues presented together. The size of the field of view (FOV) was manipulated across four levels (no-visuals, small, medium, full). Participants rated vection intensity and duration verbally after each trial. Results showed that all three sensory cues induced vection when presented in isolation, with visual cues eliciting the highest intensity and longest duration. The presence of auditory and tactile cues further increased vection intensity and duration compared to conditions where these cues were not presented. These findings support the idea that vection can be induced via multiple types of sensory inputs and can be intensified when multiple sensory inputs are combined.

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 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.