Visual Control of Posture Within the Normal Range of Motion

9601351 STOFFREGEN Most people don't have to think about standing up; we just do it and are very successful at it. We are not aware of our stance, so much so that the average person is unaware that s/he sways very slowly back and forth 1-2 inches. The control of posture, unconscious for most of us, is a critical issue for many people. People with neurological problems sometimes have unusual postural motion, or increased instability. In addition, postural instability is a cause of falling in elderly persons. This can have catastrophic effects, since it often leads to broken hips and lengthy hospitalization. At the beginning of life, toddlers fall frequently in the process of learning to stand and walk. How does postural control work? A common belief is that postural motion is perceived by the inner ear (the vestibular system). However, scientists have learned that vision plays an important role in the perception and control of our own movement. This is most clear to people at Omnimax or Imax theaters, in which visual stimulation causes a powerful feeling of self-motion. This visual-based feeling of self motion is critical in state-of-the- art flight simulators used in civilian and military aviation. This research will investigate relations between vision and the control of ordinary standing posture. People will stand inside a 'moving room', a large box mounted on wheels and moved back and forth under computer control. The moving room does not have a floor; subjects stand on the concrete floor of the laboratory. Thus, motion of the room produces only visual stimulation. The visual stimulation is similar to what we normally create during ordinary postural sway in stationary rooms. Earlier research has shown that visual motion can cause people to sway, fall down, or develop motion sickness. But that research has used very large visual motions, sometimes several feet, motions which are not representative of the visual stimulation caused by ordinary sway, in which the body moves less than two inches. This research will investigate relations between vision and posture when visual stimulation is nearly identical to the natural stimulation caused by our own movements. Motion of the participant will be compared to motion of the room to determine how closely the body responds to different kinds of visual motion. A fuller understanding of the control of ordinary postural sway should help us to develop interventions to prevent falls in the elderly. This research also has promise for understanding the development of stance in children, particularly in special populations, such as children with physical or mental disabilities. Finally, this research will help us to understand perception and control of body motion in general, so that we can design better, more effective simulations of self-motion, especially in the area of flight training. ***