Affiliations: [a] Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL 60611, USA | [b] Department of Electrical Engineering and Computer Science, The University of Illinois at Chicago, Chicago, IL 60607, USA
Note: [*] Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Room 1406 – E809, 345 East Superior Street, Chicago, IL 60611, USA. Tel.: +1 312 238 2228; Fax: +1 312 238 2208; E-mail: eak@northwestern.edu
Abstract: We examined the effect of a 3-dimensional stereoscopic scene on segmental stabilization. Eight subjects participated in static sway and locomotion experiments with a visual scene that moved sinusoidally or at constant velocity about the pitch or roll axes. Segmental displacements, Fast Fourier Transforms, and Root Mean Square values were calculated. In both pitch and roll, subjects exhibited greater magnitudes of motion in head and trunk than ankle. Smaller amplitudes and frequent phase reversals suggested control of the ankle by segmental proprioceptive inputs and ground reaction forces rather than by the visual-vestibular signals. Postural controllers may set limits of motion at each body segment rather than be governed solely by a perception of the visual vertical. Two locomotor strategies were also exhibited, implying that some subjects could override the effect of the roll axis optic flow field. Our results demonstrate task dependent differences that argue against using static postural responses to moving visual fields when assessing more dynamic tasks.
