Pairing Virtual Reality with Dynamic Posturography Serves To Differentiate Patients with Visual Vertigo

To determine if increased visual dependence can be quantified through its impact on automatic postural responses, we have measured the combined effect of transient optic flow in the pitch plane with platform rotations and translations on the latencies and magnitudes of postural response kinematics. Six healthy (29-31 yrs) and 4 visually sensitive (27-57 yrs) subjects stood on a platform that was rotated (6 deg of dorsiflexion at 30 deg/sec) or translated (5 cm at 5 deg/sec) for 200 ms. Subjects either had eyes closed or viewed an immersive, stereo, wide field of view virtual environment (scene) that moved in upward pitch at 5 velocities for a 200 ms period. Three 30 sec trials were presented for each visual condition. Kinematics were collected with a motion analysis system and angular displacement 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 for each trial. No effect of visual velocity was observed in the EMG response latencies and magnitudes. Large effects of visual field velocity were observed on the magnitudes of head angular displacement in each of the visually sensitive subjects with unique characteristics that can be related to their particular clinical history