Vestibular, visual, and somatosensory contributions to human control of upright stance

We investigated the changes of human posture control of upright stance whic h occur when vestibular cues (VEST) are absent and visual and somatosensory orientation cues (VIS, SOM) are removed. Postural responses to sinusoidal tilts of a motion platform in the sagittal plane (+/-2 degrees, f = 0.05, 0 .1, 0.2 and 0.4 Hz) were studied in normal subjects (Ns) and patients with bilateral vestibular loss (Ps). We found that absence of VEST (Ps, visual r eference) and removal of VIS (Ns, no visual reference) had little effect on stabilization of upright body posture in space. In the absence of both VES T and VIS (Ps, no visual reference) somatosensory graviception still provid ed some information on body orientation in space at 0.05 and 0.1 Hz. Howeve r, at the higher frequencies Ps qualitatively changed their behavior; they then tended to actively align their bodies with respect to the motion platf orm. The findings confirm predictions of a novel postural control model. (C ) 2000 Elsevier Science Ireland Ltd, All rights reserved.