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Inter-trial phase coherence of visually evoked postural responses in virtual reality.

ABSTRACT: Vision plays a central role in maintaining balance. When humans perceive their body as moving, they trigger counter movements. This results in body sway, which has typically been investigated by measuring the body's center of pressure (COP). Here, we aimed to induce visually evoked postural responses (VEPR) by simulating self-motion in virtual reality (VR) using a sinusoidally oscillating "moving room" paradigm. Ten healthy subjects participated in the experiment. Stimulation consisted of a 3D-cloud of random dots, presented through a VR headset, which oscillated sinusoidally in the anterior-posterior direction at different frequencies. We used a force platform to measure subjects' COP over time and quantified the resulting trajectory by wavelet analyses including inter-trial phase coherence (ITPC). Subjects exhibited significant coupling of their COP to the respective stimulus. Even when spectral analysis of postural sway showed only small responses in the expected frequency bands (power), ITPC revealed an almost constant strength of coupling to the stimulus within but also across subjects and presented frequencies. Remarkably, ITPC even revealed a strong phase coupling to stimulation at 1.5 Hz, which exceeds the frequency range that has generally been attributed to the coupling of human postural sway to an oscillatory visual scenery. These findings suggest phase-locking to be an essential feature of visuomotor control.

SUBMITTER: Engel D

PROVIDER: S-EPMC7237531 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Inter-trial phase coherence of visually evoked postural responses in virtual reality.

Engel David D Schütz Adrian A Krala Milosz M Schwenk Jakob C B JCB Morris Adam P AP Bremmer Frank F

Experimental brain research 20200401 5

Vision plays a central role in maintaining balance. When humans perceive their body as moving, they trigger counter movements. This results in body sway, which has typically been investigated by measuring the body's center of pressure (COP). Here, we aimed to induce visually evoked postural responses (VEPR) by simulating self-motion in virtual reality (VR) using a sinusoidally oscillating "moving room" paradigm. Ten healthy subjects participated in the experiment. Stimulation consisted of a 3D-c ...[more]

PMID: 32239245

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Project description:IntroductionUltra low vision (ULV) refers to profound visual impairment where an individual cannot read even the top line of letters on an ETDRS chart from a distance of 0.5 m. There are limited tools available to assess visual ability in ULV. The aim of this study was to develop and calibrate a new performance test, Wilmer VRH, to assess hand-eye coordination in individuals with ULV.MethodsA set of 55 activities was developed for presentation in a virtual reality (VR) headset. Activities were grouped into 2-step and 5-step items. Participants performed a range of tasks involving reaching and grasping, stacking, sorting, pointing, throwing, and cutting. Data were collected from 20 healthy volunteers under normal vision (NV) and simulated ULV (sULV) conditions, and from 33 participants with ULV. Data were analyzed using the method of successive dichotomizations (MSD), a polytomous Rasch model, to estimate item (difficulty) and person (ability) measures. MSD was applied separately to 2-step and 5-step performance data, then merged to a single equal interval scale.ResultsThe mean ±SD of completion rates were 98.6 ± 1.8%, 78.2 ± 12.5% and 61.1 ±34.2% for NV, sULV and ULV, respectively. Item measures ranged from -1.09 to 5.7 logits and - 4.3 to 4.08 logits and person measures ranged from -0.03 to 4.2 logits and -3.5 to 5.2 logits in sULV and ULV groups, respectively. Ninety percent of item infits were within the desired range of [0.5,1.5], and 97% of person infits were within that range. Together with item and person reliabilities of 0.94 and 0.91 respectively, this demonstrates unidimensionality of Wilmer VRH. A Person Item map showed that the items were well-targeted to the sample of individuals with ULV in the study.DiscussionWe present the development of a calibrated set of activities in VR that can be used to assess hand-eye coordination in individuals with ULV. This helps bridge a gap in the field by providing a validated outcome measure that can be used in vision restoration trials that recruit people with ULV, and to assess rehabilitation outcomes in people with ULV.

Project description:BackgroundDementia is becoming a relevant problem worldwide. A simple screening at an early stage will be important to detect the risk of developing dementia. Vestibular dysfunction is likely to be associated with cognitive impairment. Since head-mounted display (HMD) virtual reality (VR) technology has the potential to activate the vestibular function, assessing postural sway with visual stimulation using HMD VR technology could be potentially useful for dementia screening.ObjectiveThe purpose of this study is to evaluate the effect of HMD-based VR visual stimuli on posture in older adults and the relationship between the stimulated body sway behaviors and cognitive performance.MethodUsing a cross-sectional study design, we investigated the effect of an optokinetic design-based room with stripes (OKR) VR environment oscillating forwards and backwards at 23/60Hz. Center of pressure (COP) displacement was measured in older adults aged 65 years and over in the OKR VR environment. The frequency response of COP was compared to the cognitive performance of the Montreal Cognitive Assessment (MoCA).Results20 healthy older adults (70.4 ± 4.9 years; 27.2 ± 1.6 MoCA score) and 3 people with mild cognitive impairment (74.7 ± 4.0 years; 20.3 ± 2.1 MoCA score) were assessed. The results reveal that the oscillating OKR VR environment induced different postural sway in the anterior-posterior direction in the real world. Correlation analysis shows that the cognitive test score was associated with the frequency response of stimulated postural sway in the anterior-posterior direction (frequency Band 1 of 0-0.5Hz related to the visual and vestibular systems: r s = 0.45, P = 0.03).ConclusionOutcomes would suggest that a potential link may emerge between cognition and posture when the HMD-based VR visual stimuli are applied. The simple screening of stimulated postural sway could explain cognitive functioning. Further studies are warranted to clarify the vestibular system and spatial cognitive function more specifically in the proposed assessment system.

Project description:BackgroundThe implementation of regular prolonged, and effective rehabilitation in people with Parkinson's disease is essential for ensuring a good quality of life. However, the continuity of rehabilitation care may find barriers related to economic, geographic, and social issues. In these scenarios, telerehabilitation could be a possible solution to guarantee the continuity of care.AimTo investigate the efficacy of non-immersive virtual reality-based telerehabilitation on postural stability in people with Parkinson's disease, compared to at-home self-administered structured conventional motor activities.DesignMulticenter randomized controlled trial.SettingFive rehabilitation hospitals of the Italian Neuroscience and Rehabilitation Network.PopulationIndividuals diagnosed with Parkinson's disease.MethodsNinety-seven participants were randomized into two groups: 49 in the telerehabilitation group (non-immersive virtual reality-based telerehabilitation) and 48 in the control group (at-home self-administered structured conventional motor activities). Both treatments lasted 30 sessions (3-5 days/week for, 6-10 weeks). Static and dynamic balance, gait, and functional motor outcomes were registered before and after the treatments.ResultsAll participants improved the outcomes at the end of the treatments. The primary outcome (mini-Balance Evaluation Systems Test) registered a greater significant improvement in the telerehabilitation group than in the control group. The gait and endurance significantly improved in the telerehabilitation group only, with significant within-group and between-group differences.ConclusionsOur results showed that non-immersive virtual reality-based telerehabilitation is feasible, improves static and dynamic balance, and is a reasonably valuable alternative for reducing postural instability in people with Parkinson's disease.Clinical rehabilitation impactNon-immersive virtual reality-based telerehabilitation is an effective and well-tolerated modality of rehabilitation which may help to improve access and scale up rehabilitation services as suggested by the World Health Organization's Rehabilitation 2030 agenda.

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Inter-trial phase coherence of visually evoked postural responses in virtual reality.

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Inter-trial phase coherence of visually evoked postural responses in virtual reality.

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