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Abstract:
Abstract: Maintaining the body in an upright orientation
while standing is heavily dependent upon the processing of visual,
somatosensory and vestibular information. Here upright stance
control is modeled as a combination of a 1st order process that
accounts for slow shifts of the mean body position and a 2nd order
process that accounts for damped-oscillatory components of body
sway (i.e., a 3rd order model). We investigated how different
combinations of sensory information influenced these two processes.
Subjects stood in front of a large visual display while lightly
touching a contact surface with their right index fingertip.
Applied forces to the contact surface were sensory, not
mechanically supportive (< 1 Newton). Four combinations of
sensory information were tested in four minute trials with each
condition repeated three times: no vision-no touch, vision-no
touch, no vision-touch, vision-touch. Parameter values of the 3rd
order model based upon center of mass trajectories showed that the
change in total variance due to additional sensory information is
primarily due to changes of the1st order process. Systematic
changes in the 2nd order component were also observed, but
accounted for less of the overall variance. The damped-oscillatory
component of postural sway is fairly well controlled without touch
or vision (e.g., by vestibular and proprioceptive inputs). The
major effect of adding touch and/or vision is to improve the
control of the slowly-changing mean position. Supported by NIH
grant R29 NS35070-01A2 .
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