Abstract 1429, Date 1:00 PM, Sunday February 22, 2004 (24 hours) Session D4:Vestibular: Clinical
Sensory Re-Weighting In Human Postural Control During Moving-Scene Perturbations
Arash Mahboobin, Patrick Loughlin, Mark Redfern, Patrick Sparto
Recent studies suggest that a "sensory re-weighting" postural control strategy is utilized depending upon environmental conditions and the reliability of sensory orientation and movement information (e.g., Peterka 2002, Peterka and Loughlin 2003). The aim of this study was to further investigate this hypothesis by evoking anterior-posterior (AP) body sway using visual stimuli during sway-referencing of the support surface.      Five healthy adults participated in this study. Subjects stood on a posture platform while looking at a visual scene that encompassed the full horizontal field of view. A sequence of scene movements was presented to the subjects consisting of 30 s of quiet stance (stationary scene), 2 s of visual push (scene moved with constant velocity 30 cm towards subjects over 2 s) followed by 10 s of no scene movement, then 2 s of visual pull (scene moved back to initial position over 2 s) and another 10 s of no scene movement. The scene then moved randomly (scene position driven by 0.05-0.5 Hz white Gaussian noise, 8 cm RMS power) towards and away from the subject for 60 s, immediately after which subjects experienced another set of push/pull sequences. This was followed by 30 s of quiet stance and then a third, final set of visual push/pull perturbations. Three trials were taken. Peak power of stimulus-response data (squared velocity of AP-COP) was computed over a 6 s interval after each push and pull. We hypothesized that the persistent visual perturbation (random moving scene) while standing on a sway-referenced platform would cause a sensory re-weighting resulting in a reduced push/pull response compared to the initial push/pull response prior to random scene movement. Results showed a significantly smaller response (p<0.05) in the second push/pull sequence compared to the first push/pull sequence. There was no significant difference between the first and third push/pull sequences. A trial effect was also found, with greater responses in the first trial compared to subsequent trials. These results suggest that sensory re-weighting occurs during persistent visual perturbation, and that habituation to moving scene perturbations can occur with repeated exposure. [Supported by NIH DC04435 and DC05205 ]