Vestibular and proprioceptive estimation of imposed rotation and spatial updating in standing subjects

The aim of the study was to evaluate in standing subjects their perception of whole-body rotation and spatial updating, and to determine whether the brain uses mainly angular velocity or rotational duration to re-orient the body. Ten healthy blindfolded adults stood barefoot on a horizontal rotating platform. Participants had to maintain their balance while being passively rotated by a platform through 45°, 90°, 135°, 180° and 360°, clockwise (CW) and counter-clockwise (CCW). At the end of platform rotation, participants had to give their estimation of the angle. They then had to actively reproduce it in the opposite direction. Three different conditions were applied: one which involved different peak cosinusoidal angular velocity profiles (18°/s, 35°/s, 53°/s, 71°/s and 141°/s) at constant duration of stimulus (4 s); one which involved different stimulus durations (1.25 s, 2.5 s, 3.75 s, 5 s and 10 s) at constant peak velocity (57°/s); and one where subjects had to reproduce a specific angle without prior stimulus imposed by the platform. In the reproduction phase, results show overestimation of stimulus from -180° to 180° in all three conditions; however, ±360° rotations were underestimated only in the first two conditions. Comparing stimulus perception and reproduction, the perceived angle corresponded to that reproduced in the range from -180° to 180°; however, ±360° angles were correctly perceived but inaccurately reproduced. Thus, the interconnection between movement and information via the vestibular/proprioceptive systems is essential to evaluate the body position in space; however, the spatial errors show the key importance of sight in correcting the errors caused by the cue integration.