Sensory Conflict Research Articles

Impact of Virtual Reality-Generated Construction Environments at Different Heights on Postural Stability and Fall Risk.

Falls due to postural instability are common in construction environments especially from a height. The purpose of the study was to investigate the impact of virtual reality (VR)-generated environments at different virtual heights on postural stability. Nineteen adults were analyzed for postural stability, tested in real (No VR) environment and in three VR environments, randomly assigned, at virtual heights of 0 ft. (VR0), 40 ft. (VR40), and 120 ft. (VR120). Postural stability was quantified using center of pressure postural sway variables and analyzed using a repeated measures analysis of variance (ANOVA). Participants also completed a simulation sickness questionnaire (SSQ) before and after VR exposure and a presence questionnaire (PQ) after VR exposure. Significant postural instability (p < .05) was identified between VR and No VR, in which increased postural instability was evident in all VR conditions compared with No VR. Scores from SSQ were within a pre-post score difference of five and the PQ score was (104.21 ± 14.03). Findings suggest that VR environments, regardless of virtual height, induced increased postural instability, which can be attributed to visual sensory conflicts to the postural control system created by VR exposure. Participants' subjective responses on SSQ and PQ confirmed the feasibility of using VR to represent realistic immersions in virtual heights. However, objectively, VR could potentially lead to postural instability, stressing caution. VR can be a potential tool for providing virtual high-altitude environment exposure for fall prevention training, however, more research is needed on postural adaptation with acute and chronic exposure to VR.

Sensory conflict alters visual perception of action capabilities during crossing of a closing gap in virtual reality.

The somatosensory, vestibular, and visual systems contribute to multisensory integration, which facilitates locomotion around obstacles in the environment. The joystick-controlled virtual reality (VR) locomotion interface does not preserve congruent sensory input like real-walking, yet is commonly used in human behaviour research. Our purpose was to determine if collision avoidance behaviours were affected during an aperture crossing task when somatosensory and vestibular input were incongruent, and only vision was accurate. Participants included 36 young adults who completed a closing gap aperture crossing task in VR using real-walking and joystick-controlled locomotion. Participants successfully completed the task using both interfaces. Switch point between passable and impassable apertures was larger for joystick-controlled locomotion compared with real-walking, but time-to-contact (TTC) was lower for real-walking than joystick-controlled locomotion. Increased joystick-controlled locomotion switch point may be attributed to incongruency between visual and non-visual information, causing underestimation of distance travelled towards the aperture. Performance on future VR applications incorporating dynamically changing gaps can be considered successful using joystick-controlled locomotion, while taking into account a potential behaviour difference. Differences in TTC may be explained by the requirement of gait termination in real-walking but not in joystick-controlled locomotion. Future VR studies would benefit from programming acceleration and deceleration into joystick-controlled locomotion interfaces.

Motion Sickness Manifestations and Prevention

Motion sickness is an ancient problem associated with transportation (ships and other vehicles), which is affecting humans since ages. Motion sickness is characteristically occurring during abnormal movements induced by the motion and when there is a conflict between various senses such as visual, vestibular and motor system. Depending on the type of motion, various kinds of sicknesses, such as air sickness, car sickness, train sickness, seasickness, etc. may occur. A very less per cent of individuals are highly susceptible to motion sickness and very less per cent of individuals are highly insusceptible for motion sickness. However, most of the population comes in between. The primary symptoms of motion sickness include nausea, vomiting, wanes, and cold sweating. Varieties of drugs are available to reduce susceptibility to motion sickness. However, nausea, pallor, sweating, headache, dizziness, malaise, increased salivation, apathy, drowsiness, belching, hyperventilation and stomach awareness are the other symptoms of motion sickness. Anti-cholinergics and anti-histamines are the most effective motion sickness prophylactics with apparent side effects such as dry mouth, drowsiness, and depression. There are theories and mechanisms which include intra-vestibular (Canal-Otolith) mismatch theory, sensory conflict theory, visual-vestibular mismatch theory, the poison theory, the postural instability theory, and the movement program theory. Benzodiazepines, anticholinergics, anti-histamines and monoamine antagonists have commonly used treatment regimes. The traditional way of tackling the problem is the consumption of ginger, peppermint, lemon, fennel, marjoram, rosemary, basil. This review summarizes prediction and evaluation, behavioural strategies to prevent or minimize symptoms of motion sickness and available countermeasures of motion sickness.

Multisensory integration and the experience of scene instability, presence and cybersickness in virtual environments

Multisensory integration is critical for supporting human spatial perception as we move around our environment. In this study, we used a modern head-mounted display (HMD) as a tool for studying the effects of visual-vestibular conflict on human spatial perception, feelings of presence and cybersickness in virtual reality (VR). Thirty participants were recruited and exposed to different levels of sensory conflict as they moved their heads in pitch. This sensory conflict was generated by artificially delaying updates to the visual representations of their virtual environment. On each trial we measured our participants': 1) perceived scene instability using an angular gauge figure task; 2) spatial presence using a subjective rating scale, and 3) cybersickness severity using the fast motion sickness (FMS) scale. As display lag was increased, perceived scene instability and cybersickness were both found to increase, whereas reported presence decreased. Importantly, the difference in the participant's virtual and physical head orientation (DVP) for the trial was also found to predict reported scene instability and cybersickness. Faster head rotations (at 1.0 Hz compared with 0.5 Hz) amplified both of these adverse effects (presumably due to the increase in DVP). These findings are consistent with the view that measurable low-level visual-vestibular conflicts can account for the cybersickness experienced during HMD VR.

Analyses of the cortical hemodynamic responses related to postural control during sensory conflict using near-infrared spectroscopy (NIRS)

Analyses of the cortical hemodynamic responses related to postural control during sensory conflict using near-infrared spectroscopy (NIRS)

Relationship between soleus H-reflex asymmetry and postural control in multiple sclerosis

Background Impaired postural control is a common symptom in people with multiple sclerosis. Multiple sclerosis frequently presents with asymmetric motor involvement. One measurement yet to be evaluated for asymmetry in people with multiple sclerosis is the soleus Hoffmann reflex. Purpose To measure the soleus Hoffmann reflex between limbs and correlate reflex asymmetry with postural control. Material and methods 16 participants completed four sessions of Hoffmann reflex testing and one session of balance testing. Results Multiple sclerosis participants had significantly greater reflex asymmetry (p = 0.01). The multiple sclerosis group had a significantly lower overall sensory organization testing composite score (p < 0.05), indicating sensory interpretation conflict that resulted in greater postural instability. Multiple sclerosis participants produced a significantly shorter endpoint and maximum excursion (p < 0.01) during limits of stability testing. Hoffmann reflex asymmetry was negatively related to forward endpoint excursion (p < 0.05), maximum excursion (p 0.01). Conclusions Multiple sclerosis participants had greater soleus Hoffmann reflex asymmetry, which appears to significantly influence forward postural control. Implications for rehabilitation Soleus Hoffmann reflex asymmetry appears to influence postural stability. The soleus Hoffmann reflex is capable of adapting to different modes of exercise; therefore, to reduce H-reflex asymmetry it is recommended to individualize physical rehabilitative programming. Assessing the soleus Hoffmann reflex in people with multiple sclerosis during health screenings could be of use to clinical and rehabilitative practitioners.

Contextual sensory integration training via head mounted display for individuals with vestibular disorders: a feasibility study

Purpose Virtual reality (VR) interventions can simulate real-world sensory environments. The purpose of this study was to test the feasibility of a novel VR application (app) developed for a Head Mounted Display (HMD) to target dizziness, imbalance and sensory integration in a functional context for patients with vestibular disorders. Here we describe the design of the app as well as self-reported and functional outcomes in vestibular patients before and after participating in vestibular rehabilitation using the app. Material and methods Our app includes a virtual street, airport, subway or a park. The clinician controls the visual and auditory load including several levels of direction, amount and speed of virtual pedestrians. Clinicians enrolled 28 patients with central (mild-traumatic brain injury [mTBI] or vestibular migraine) and peripheral vestibular disorders. We recorded the Simulator Sickness Questionnaire, Visual Vertigo Analogue Scale (VVAS), Dizziness Handicap Inventory (DHI), Activities-Specific Balance Confidence Scale (ABC), 8-foot up and go (8FUG) and Four-Step Square Test (FSST) before and after the intervention. Results Within the 15 patients who completed the study, 12 with peripheral hypofunction showed significant improvements on the VVAS (p = 0.02), DHI (p = 0.008) and ABC (p = 0.02) and a small significant improvement on the FSST (p = 0.015). Within-session changes in symptoms were minimal. Two patients with mTBI showed important improvements, but one patient with vestibular migraine, did not. Conclusion HMD training within increasingly complex immersive environments appears to be a promising adjunct modality for vestibular rehabilitation. Future controlled studies are needed to establish effectiveness. IMPLICATIONS FOR REHABILITATION Virtual Reality allows for gradual introduction of complex semi-real visual environments. Within VR training patients can re-learn to maintain balance when presented with a sensory conflict in a safe environment. Head Mounted Display training appears to be a promising adjunct modality for vestibular rehabilitation. Portability and affordability of the hardware and software enhance the potential clinical outreach.

Postural stability after treadmill and overground walking in young and elderly

BackgroundAgeing commonly disrupts the balance control and compensatory postural responses that contribute to maintaining balance and preventing falls during perturbation of posture. Improvement of compensatory postural responses during walking is one of the main goals in fall prevention programs which often include treadmill walking training. However, during treadmill walking, there is a sensory (visualsomatosensory and vestibular-somatosensory) conflict that can evoke aftereffects of self-motion sensation and could alter postural stability after training. Research questionThe aim of this study was to compare the effect of overground and treadmill walking on postural stability in healthy young and elderly subjects. Methods: Postural responses of 31 Young and 19 healthy Elderly before and after overground and treadmill walking were assessed by a force platform in four stance conditions: firm and foam surface with eyes open and eyes closed. ResultsIn Elderly group, velocity parameters significantly increased after treadmill walking but not after overground walking. This increase was found particularly in the conditions with eyes open in both types of surfaces (firm, foam). The velocity parameters values (expect Vx) were significantly increased in Elderly compared to Young almost in all four conditions after treadmill and overground walking. Significance: Our study suggests that Elderly become more unstable after treadmill walking and have greater difficulties to adapt to new balance circumstances caused by sensory conflict associated with treadmill walking. It seems that during treadmill walking and subsequent stance, vision is the major factor contributing to posture stabilization. Thus, the suitability of treadmill walking as a part of training programs for elderly adults with higher fall risk should be seriously considered.

Media sensory curation and family media conflict: replication and validation of short-form measures

ABSTRACT Media sensory curation theory conceptualizes sensory regulation within the built environment as a gratification of electronic media use and predictor of parent-child conflict over children’s media use. This paper replicates an initial survey of caregivers of children ages 3 to 14 with an independent replication survey of N = 754. As in the original study, media sensory curation was higher among children with sensory diagnoses (e.g., autism, ADHD) than without and was a moderate to strong predictor of problematic child media use and adult-child media conflict for all children. The 48-item Adult and Child Media Sensory Curation Inventories (MediaSCIs) were subject to scale-reduction analyses using the pooled samples (N = 1543) to create short-form scales. The resulting Adult MediaSCI-SF and Child MediaSCI-SF (12 items each) showed good reliability. The Child MediaSCI-SF predicted problematic child media use and media conflict as robustly as the 48-item Child MediaSCI. The MediaSCI-SF scales are parsimonious options for measuring media sensory curation.

Cerebral Hemodynamic Responses to the Sensory Conflict Between Visual and Rotary Vestibular Stimuli: An Analysis With a Multichannel Near-Infrared Spectroscopy (NIRS) System.

Sensory conflict among visual, vestibular, and somatosensory information induces vertiginous sensation and postural instability. To elucidate the cognitive mechanisms of the integration between the visual and vestibular cues in humans, we analyzed the cortical hemodynamic responses during sensory conflict between visual and horizontal rotatory vestibular stimulation using a multichannel near-infrared spectroscopy (NIRS) system. The subjects sat on a rotatory chair that was accelerated at 3°/s2 for 20 s to the right or left, kept rotating at 60°/s for 80 s, and then decelerated at 3°/s2 for 20 s. The subjects were instructed to watch white stripes projected on a screen surrounding the chair during the acceleration and deceleration periods. The white stripes moved in two ways; in the “congruent” condition, the stripes moved in the opposite direction of chair rotation at 3°/s2 (i.e., natural visual stimulation), whereas in the “incongruent” condition, the stripes moved in the same direction of chair rotation at 3°/s2 (i.e., conflicted visual stimulation). The cortical hemodynamic activity was recorded from the bilateral temporoparietal regions. Statistical analyses using NIRS-SPM software indicated that hemodynamic activity increased in the bilateral temporoparietal junctions (TPJs) and human MT+ complex, including the medial temporal (MT) area and medial superior temporal (MST) area in the incongruent condition. Furthermore, the subjective strength of the vertiginous sensation was negatively correlated with hemodynamic activity in the dorsal part of the supramarginal gyrus (SMG) in and around the intraparietal sulcus (IPS). These results suggest that sensory conflict between the visual and vestibular stimuli promotes cortical cognitive processes in the cortical network consisting of the TPJ, the medial temporal gyrus (MTG), and IPS, which might contribute to self-motion perception to maintain a sense of balance or equilibrioception during sensory conflict.

Hippocampal theta coordinates memory processing during visual exploration.

The hippocampus supports memory encoding and retrieval, which may occur at distinct phases of the theta cycle. These processes dynamically interact over rapid timescales, especially when sensory information conflicts with memory. The ability to link hippocampal dynamics to memory-guided behaviors has been limited by experiments that lack the temporal resolution to segregate encoding and retrieval. Here, we simultaneously tracked eye movements and hippocampal field potentials while neurosurgical patients performed a spatial memory task. Phase-locking at the peak of theta preceded fixations to retrieved locations, indicating that the hippocampus coordinates memory-guided eye movements. In contrast, phase-locking at the trough of theta followed fixations to novel object-locations and predicted intact memory of the original location. Theta-gamma phase amplitude coupling increased during fixations to conflicting visual content, but predicted memory updating. Hippocampal theta thus supports learning through two interleaved processes: strengthening encoding of novel information and guiding exploration based on prior experience.

CYBERSICKNESS AND EVALUATION OF A REMEDIATION SYSTEM: A PILOT STUDY

Many questions arise regarding the use of virtual reality (VR) in the naval military field. This is particularly the case from a human factors’ perspective, where system’s usability is supposed to guarantee user’s performance. Cybersickness, resulting from a sensory conflict between visual and vestibular systems, is one of the major limitations to the development of VR. Cybersickness can lead to nausea, oculomotor discomfort and disorientation. The major aim of the current study was to evaluate the efficiency of a remediation system for cybersickness. This system is designed to help remove the sensory conflict, thanks to miniature LED screens placed in the head mounted display (HMD). 18 subjects were confronted with a dynamic environment in VR, equipped with HMDs. Different physiological variables were measured during immersion. Every subject showed effects of cybersickness, starting, on average, after eight minutes of exposure, even if the system may reduce symptoms under certain conditions.

Presence, Cybersickness, Anxiety, and Heart Rate Variability in a Non-Clinical Population Using Virtual Reality Environments Designed For Specific Phobias' Treatment

The current study was performed to assess the phenomenon known as Presence, to measure Anxiety responses, simulator sickness and autonomic activation in subjects of the general population. The sample consisted in 37 Argentine participants (15 male, 22 female) between ages 20 and 40; who were exposed to 3 virtual environments designed to research and treat phobias. Instruments utilized for this study were the Symptom Checklist 90-R, Acrophobia Questionnaire, Fear of Spiders Questionnaire, The Claustrophobia Questionnaire, Igroup Presence Questionnaire, Simulator Sickness Questionnaire and the State-Trait Anxiety Inventory. All virtual environments generated sufficient feeling of presence. Cybersickness was only registered in the Elevator scenario. The Apartment and Spiders environments have shown not to be anxiety triggers within this population. As for Elevator, a significant increase in the level of state anxiety was generated. A possible hypothesis to account for this fact might be that reported anxiety responds to movement simulated in the virtual scenario while on the other two scenarios the subjects remained static. The existence of a correlation between HRV and state anxiety has been analyzed and no significant relation has been found between the variables. Even though there is a relation between anxiety and presence, no significant relation has been found between anxiety and presence. Regarding sensory conflict, a follow up study in the Elevator environment should be done, eliminating movement and exposing subjects to the stimuli while static at different heights. Future studies should consider broadening the size of the sample and studying clinical population to compare results.

Reduction of cybersickness during and immediately following noisy galvanic vestibular stimulation.

The mechanism underlying cybersickness during virtual reality (VR) exposure is still poorly understood, although research has highlighted a causal role for visual-vestibular sensory conflict. Recently established methods for reducing cybersickness include galvanic vestibular stimulation (GVS) to mimic absent vestibular cues in VR, or vibration of the vestibular organs to add noise to the sensory modality. Here, we examined if applying noise to the vestibular system using noisy-current GVS affects sickness severity in VR. Participants were exposed to one of the two VR games that were classified as either moderately or intensely nauseogenic. The VR content lasted for 50min and was broken down into three blocks: 30min of gameplay during exposure to either noisy GVS (± 1750μA) or sham stimulation (0μA), and 10min of gameplay before and after this block. We characterized the effects of noisy GVS in terms of post-minus-pre-exposure cybersickness scores. In the intense VR condition, we found a main effect of noisy vestibular stimulation on a verbal cybersickness scale, but not for questionnaire measures of cybersickness. Participants reported lower cybersickness scores during and directly after exposure to GVS. However, this difference was quickly extinguished (~ 3-6min) after further VR exposure, indicating that sensory adaptation did not persist after stimulation was terminated. In contrast, there were no differences between the sham and GVS group for the moderate VR content. The results show the potential for reducing cybersickness with non-invasive sensory stimulation. We address possible mechanisms for the observed effects, including noise-induced sensory re-weighting.

Evaluation of the effect of herbal extracts and their bioactive compounds against motion sickness by regulating neurotransmitter levels in vitro and in vivo

Motion sickness (MS) is caused due to sensory mismatch. Sensory conflict theory which proves acetylcholine, histamine elevations as the primary reason for MS provides a path for an effective pharmaco-therapy, by an attempt to inhibit the elevation of acetylcholine, histamine during travel. The present study aimed to screen herbal extracts and their bioactive compounds for anti-MS effect by using in vitro and in vivo models. Ten herbal extracts and their bioactive compounds were tested for its effect on acetylcholine esterase (AChE) activity, histamine and dopamine release in human leukaemia KU812 and rat pheochromocytoma PC12 cells respectively. Rutin hydrate, menthol, eugenol, linalool and hesperidin showed less inhibitory effect on AChE activity and promoting the degradation of acetylcholine and inhibited the release of histamine and dopamine from KU812 and PC12 cells. These bioactive compounds being present in Ocimum basilicum L. var. basilicum seed extract (OBSE) was chosen for further validation studies in vivo. Anti-MS effect was evaluated in BALB/c mice model using conditioned taste aversion. Pre-treatment with OBSE at 300 mg/kg bodyweight concentration prevented MS by reducing acetylcholine, histamine, dopamine, epinephrine levels, cholinergic receptor muscarinic 1 gene expression and increasing serotonin and norepinephrine levels and thus it could serve as a potent herbal antidote for MS.

«Сенсорный конфликт» как возможная причина нарушения постуральной устойчивости детей, лечившихся от онкологических заболеваний

«Сенсорный конфликт» как возможная причина нарушения постуральной устойчивости детей, лечившихся от онкологических заболеваний

Ameliorative Effect of Hesperidin Against Motion Sickness by Modulating Histamine and Histamine H1 Receptor Expression.

Motion sickness (MS) is the visceral discomfort caused due to contradicting visual and vestibular inputs to the brain leading to nausea and vomiting. Sensory conflict theory which proves histamine elevations as the primary reason for MS provides a path for an effective pharmaco-therapy. We aimed to evaluate the anti-MS effect of hesperidin (HSP) by modulating histamine and histamine receptor H1 (HRH1) expression. The inhibitory effect of HSP on histamine release was studied in KU812 cells treated with 10 µM calcium ionophore. The in vivo anti-MS effect of HSP was evaluated in Balb/c mice. Thirty six mice were divided into six groups namely, normal control (NC, no rotation), hesperidin at 80 mg/kg body weight control (HSP80, no rotation), motion sickness (MS, rotation induced), dimenhydrinate (Standard drug) at 20 mg/kg body weight + rotation (STD + MS), hesperidin at 40 mg/kg body weight + rotation (HSP40 + MS) and hesperidin at 80 mg/kg body weight + rotation (HSP80 + MS). Hypothalamus and brainstem samples were analysed for histamine levels and HRH1 expression by RT-PCR, Western blot and immunohistochemistry analysis. Calcium ionophore treated KU812 cells significantly increased histamine release when compared to control cells. Pre-treatment with HSP inhibited histamine, HRH1 mRNA and protein expression. Histamine, HRH1 mRNA and protein expression in hypothalamus and brainstem samples of MS group increased significantly when compared to the NC group. Pre-treatment with HSP significantly reduced histamine, HRH1 mRNA and protein expression. Thus, indicating that HSP has a potent anti- MS effect by decreasing the elevated levels of histamine, HRH1 mRNA and protein expression in hypothalamus and brainstem regions.

Introduction of Cybersickness

With an introduce of virtual reality (VR) technology, the issue of unpleasant side effect of VR immersion has been raised as “cybersickness.” Although exact mechanism of cybersickness is still elusive, sensory conflict theory has been generally accepted as in classic motion sickness. The absence of expected correlated vestibulo-proprioceptive sensory information during VR experience causes sensory conflict, which leads to dizziness, disorientation, nausea and fatigue. Herein, we review the recent literature to build the conceptual scheme for understanding cybersickness. From the brief description of motions sickness, assessment and management of cybersickness is also outlined. Key words: Dizziness ㆍ Motion sickness ㆍ Virtual reality

A study of cybersickness and sensory conflict theory using a motion-coupled virtual reality system

Sensory conflict theory explains that motion sickness in virtual reality (VR) systems can be caused due to the mismatch between visual and vestibular senses. This study examines whether coupling physical motions to visual stimuli in VR could reduce this discomfort. A motion-coupled VR system developed on a motion platform, providing vestibular cues to supplement visual roll from a head-mounted display (HMD), was used. Three conditions were tested: visual rotation only (stationary), visual-physical motion synchronised (synchronous), and vestibular motion with a self-referenced visual environment. Results show that when users are placed under a visual-vestibular synchronised condition, their subjective miserable score of cybersickness decreased while their comfort level of the overall experience increased. This indicates that a motion-coupled system, if integrated seamlessly in VR, could mitigate cybersickness symptoms.

Vection in virtual reality modulates vestibular-evoked myogenic potentials.

The popularity of virtual reality (VR) has increased rapidly in recent years. While significant technological advancements are apparent, a troublesome problem with VR is that between 20% and 80% of users will experience unpleasant side effects such as nausea, disorientation, blurred vision and headaches-a malady known as Cybersickness. Cybersickness may be caused by a conflict between sensory signals for self-motion: while vision signals that the user is moving in a certain direction with certain acceleration, the vestibular organs provide no corroborating information. To resolve the sensory conflict, vestibular cues may be down-weighted leading to an alteration of how the brain interprets actual vestibular information. This may account for the frequently reported after-effects of VR exposure. Here, we investigated whether exposure to vection in VR modulates vestibular processing. We measured vestibular-evoked myogenic potentials (VEMPs) during brief immersion in a vection-inducing VR environment presented via head-mounted display. We found changes in VEMP asymmetry ratio, with a substantial increase in VEMP amplitude recorded on the left sternocleidomastoid muscle following just one minute of exposure to vection in VR. Our results suggest that exposure to vection in VR modulates vestibular processing, which may explain common after-effects of VR.