title: Using visuo-kinetic virtual reality to induce illusory spinal movement: the MoOVi Illusion.
abstract: BACKGROUND
  Illusions that alter perception of the body provide novel opportunities to target brain-based contributions to problems such as persistent pain. One example of this, mirror therapy, uses vision to augment perceived movement of a painful limb to treat pain. Since mirrors can't be used to induce augmented neck or other spinal movement, we aimed to test whether such an illusion could be achieved using virtual reality, in advance of testing its potential therapeutic benefit. We hypothesised that perceived head rotation would depend on visually suggested movement.
  
  
  METHODS
  In a within-subjects repeated measures experiment, 24 healthy volunteers performed neck movements to 50oof rotation, while a virtual reality system delivered corresponding visual feedback that was offset by a factor of 50%-200%-the Motor Offset Visual Illusion (MoOVi)-thus simulating more or less movement than that actually occurring. At 50oof real-world head rotation, participants pointed in the direction that they perceived they were facing. The discrepancy between actual and perceived direction was measured and compared between conditions. The impact of including multisensory (auditory and visual) feedback, the presence of a virtual body reference, and the use of 360oimmersive virtual reality with and without three-dimensional properties, was also investigated.
  
  
  RESULTS
  Perception of head movement was dependent on visual-kinaesthetic feedback (p= 0.001, partial eta squared = 0.17). That is, altered visual feedback caused a kinaesthetic drift in the direction of the visually suggested movement. The magnitude of the drift was not moderated by secondary variables such as the addition of illusory auditory feedback, the presence of a virtual body reference, or three-dimensionality of the scene.
  
  
  CONCLUSIONS
  Virtual reality can be used to augment perceived movement and body position, such that one can perform a small movement, yet perceive a large one. The MoOVi technique tested here has clear potential for assessment and therapy of people with spinal pain.
authors.affiliation: Recover Injury Research Centre, Centre of Research Excellence in Road Traffic Injury, Menzies Health Institute QLD, Griffith University, Griffith University , Gold Coast , Australia.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Harvie
authors.affiliation: Wearable Computer Lab, University of South Australia , Adelaide , Australia.
authors.forename: Ross T
authors.initials: RT
authors.lastname: Smith
authors.affiliation: Recover Injury Research Centre, Centre of Research Excellence in Road Traffic Injury, Menzies Health Institute QLD, Griffith University, Griffith University , Gold Coast , Australia.
authors.forename: Estin V
authors.initials: EV
authors.lastname: Hunter
authors.affiliation: Wearable Computer Lab, University of South Australia , Adelaide , Australia.
authors.forename: Miles G
authors.initials: MG
authors.lastname: Davis
authors.affiliation: Recover Injury Research Centre, Centre of Research Excellence in Road Traffic Injury, Menzies Health Institute QLD, Griffith University, Griffith University , Gold Coast , Australia.
authors.forename: Michele
authors.initials: M
authors.lastname: Sterling
authors.affiliation: Sansom Institute for Health Research, University of South Australia, Adelaide, Australia; Neuroscience Research Australia, Sydney, Australia.
authors.forename: G Lorimer
authors.initials: GL
authors.lastname: Moseley
keywords: Bodily illusion; Brain training; Central mechanisms; Chronic pain; Virtual reality