Postural research and rehabilitation in an immersive virtual environment

We have united an immersive dynamic virtual environment with motion of a posture platform to record biomechanical and physiological responses to combined visual, vestibular, and proprioceptive inputs. A 6 degree-of-freedom force plate provides measurements of moments exerted on the base of support. Kinematic data from the head, trunk, and lower limb is collected using 3-D video motion analysis. The virtual image is projected via a stereo-capable projector mounted behind the back-projection screen. This system allows us to explore complex behaviors necessary for rehabilitation. We are currently examining how a dynamic visual field affects posture and spatial orientation, and whether visual task demands interfere with our ability to react to a loss of balance in healthy adults and in adults with labyrinthine deficit. Our data suggest that when there is a confluence of meaningful inputs, none of the inputs are suppressed in healthy adults; the postural response is modulated by all existing sensory signals in a non-additive fashion. Labyrinthine deficient adults suppress visual inputs. Individual perception of the sensory structure also appears to be a significant component of the postural response in these protocols. We will discuss the implications of these results for the design of clinical interventions for balance disorders.