Multisensory information for postural control: sway-referencing gain shapes center of pressure variability and temporal dynamics

The authors investigated the multisensory control of posture by altering sensory information across the visual and somatosensory systems. The support surface and visual surround were sway-referenced to anterior/posterior center of mass sway and the gain between postural sway and degree of sway referencing was manipulated (gain settings were 0.2, 1.0, and 1.8). These alterations in the sensory environment lead to observed changes in the temporal structure of the center of pressure (COP) trajectories. COP path length increased across gain settings while COP coefficient of variation decreased. The COP became increasingly more deterministic across more challenging sensory organization test (SOT) conditions and with increasing gain, and more nonstationary across more challenging SOT conditions and when the support surface was sway-referenced using a 1.8 gain setting. These findings indicate that changes in the responsiveness of the support surface and/or visual surround within each of the sway-referenced SOT conditions had functional consequences for the control of posture as evidenced by the variations in postural sway dynamics.