title: Pairing virtual reality with dynamic posturography serves to differentiate between patients experiencing visual vertigo.
abstract: BACKGROUND
  To determine if increased visual dependence can be quantified through its impact on automatic postural responses, we have measured the combined effect on the latencies and magnitudes of postural response kinematics of transient optic flow in the pitch plane with platform rotations and translations.
  
  
  METHODS
  Six healthy (29-31 yrs) and 4 visually sensitive (27-57 yrs) subjects stood on a platform rotated (6 deg of dorsiflexion at 30 deg/sec) or translated (5 cm at 5 deg/sec) for 200 msec. Subjects either had eyes closed or viewed an immersive, stereo, wide field of view virtual environment (scene) moved in upward pitch for a 200 msec period for three 30 sec trials at 5 velocities. RMS values and peak velocities of head, trunk, and head with respect to trunk were calculated. EMG responses of 6 trunk and lower limb muscles were collected and latencies and magnitudes of responses determined.
  
  
  RESULTS
  No effect of visual velocity was observed in EMG response latencies and magnitudes. Healthy subjects exhibited significant effects (p < 0.05) of visual field velocity on peak angular velocities of the head. Head and trunk velocities and RMS values of visually sensitive subjects were significantly larger than healthy subjects (p < 0.05), but their responses were not modulated by visual field velocity. When examined individually, patients with no history of vestibular disorder demonstrated exceedingly large head velocities; patients with a history of vestibular disorder exhibited head velocities that fell within the bandwidth of healthy subjects.
  
  
  CONCLUSIONS
  Differentiation of postural kinematics in visually sensitive subjects when exposed to the combined perturbations suggests that virtual reality technology could be useful for differential diagnosis and specifically designed interventions for individuals whose chief complaint is sensitivity to visual motion.
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Room 1406, 345 East Superior St, Chicago, IL 60611, USA. ekeshner@temple.edu
authors.forename: Emily A
authors.initials: EA
authors.lastname: Keshner
authors.forename: Jefferson
authors.initials: J
authors.lastname: Streepey
authors.forename: Yasin
authors.initials: Y
authors.lastname: Dhaher
authors.forename: Timothy
authors.initials: T
authors.lastname: Hain
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D004576:Electromyography; D006801:Humans; D008875:Middle Aged; D004856:Postural Balance; D011930:Reaction Time; D014717:Vertigo / Q000175:diagnosis / Q000503:physiopathology*; D014796:Visual Perception