Abstract
BackgroundVirtual reality (VR) provides interactive multimodal sensory stimuli and biofeedback, and can be a powerful tool for physical and cognitive rehabilitation. However, existing systems have generally not implemented realistic full-body avatars and/or a scaling of visual movement feedback. We developed a “virtual mirror” that displays a realistic full-body avatar that responds to full-body movements in all movement planes in real-time, and that allows for the scaling of visual feedback on movements in real-time. The primary objective of this proof-of-concept study was to assess the ability of healthy subjects to detect scaled feedback on trunk flexion movements.MethodsThe “virtual mirror” was developed by integrating motion capture, virtual reality and projection systems. A protocol was developed to provide both augmented and reduced feedback on trunk flexion movements while sitting and standing. The task required reliance on both visual and proprioceptive feedback. The ability to detect scaled feedback was assessed in healthy subjects (n = 10) using a two-alternative forced choice paradigm. Additionally, immersion in the VR environment and task adherence (flexion angles, velocity, and fluency) were assessed.ResultsThe ability to detect scaled feedback could be modelled using a sigmoid curve with a high goodness of fit (R2 range 89-98%). The point of subjective equivalence was not significantly different from 0 (i.e. not shifted), indicating an unbiased perception. The just noticeable difference was 0.035 ± 0.007, indicating that subjects were able to discriminate different scaling levels consistently. VR immersion was reported to be good, despite some perceived delays between movements and VR projections. Movement kinematic analysis confirmed task adherence.ConclusionsThe new “virtual mirror” extends existing VR systems for motor and pain rehabilitation by enabling the use of realistic full-body avatars and scaled feedback. Proof-of-concept was demonstrated for the assessment of body perception during active movement in healthy controls. The next step will be to apply this system to assessment of body perception disturbances in patients with chronic pain.
Highlights
Virtual reality (VR) provides interactive multimodal sensory stimuli and biofeedback, and can be a powerful tool for physical and cognitive rehabilitation
One of the few successful examples is a study by Koritnik et al who created a full-body “virtual mirror” by recording kinematic data to animate a virtual mirror-image in real-time, while healthy adults were stepping in place [13]
Prior to the development of any intervention protocols, it is important to establish normative data regarding body perception during active movement in VR, for example by assessing the ability to detect different levels and directions of scaled feedback in healthy subjects [18]. To attain this goal we developed a “virtual mirror” that: 1) displays a realistic full-body avatar, 2) responds to full-body movements in all movement planes in real-time, and that 3) allows for the scaling of visual feedback on movements at any given joint in real-time
Summary
Virtual reality (VR) provides interactive multimodal sensory stimuli and biofeedback, and can be a powerful tool for physical and cognitive rehabilitation. The normalization of body perception disturbances and of abnormal movement patterns is an important goal in both physical and pain rehabilitation This requires an understanding of the complex relationship between body perception and movement kinematics, which can to the individual needs of patients. One of the few successful examples is a study by Koritnik et al who created a full-body “virtual mirror” by recording kinematic data to animate a virtual mirror-image (non-realistic avatar) in real-time, while healthy adults were stepping in place [13]. Another example is a very recent study by Barton and colleagues that implemented a virtual mirror for amputee patients. Some studies have used full-body video-capture to display a full-body mirror-image [3,15] or avatar [16] of the subject onto a virtual reality scene
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