Central and peripheral mechanisms controlling human balance control

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We have all seen or experienced the effect that anxiety can have on the ability to control balance. Just think of someone trying to walk across a balance beam or log. If the beam or log is on the ground, people will likely have no problems to walk across it; however, if it were raised high in the air, many people would lose their balance and fall. Interestingly, the only thing that has changed in those two conditions is the threat or consequence of a fall. The effect of threat and anxiety is one factor that we believe may contribute to balance problems and falls in older adults and people with balance disorders. Our research has shown that increased anxiety in otherwise healthy individuals can influence the way they control balance when standing quietly or reacting to an unexpected balance disturbance. However, the specific way in which anxiety may influence the brain's ability to control balance is currently unknown. The long-term goal of proposed research program is to discover how anxiety may contribute to balance problems in older adults and patients with neurological disorders. The short term goals of the research program are to identify the specific areas of the brain and nervous system that promote the effects of anxiety on balance control. We will manipulate anxiety by having subjects perform balance tasks while standing on a physical, or virtual (using 3D virtual reality), platform that can be raised to different heights. A series of studies will be performed to assess how anxiety influences different areas of the brain and pathways that are responsible for transmitting balance signals to the muscles, adjusting the sensitivity of stretch-dependent receptors in the muscles, and relaying relevant sensory information back to the brain. Balance performance will be assessed from ground-reaction forces, motion analysis and muscular activity recorded during quiet standing and balance perturbations. Knowledge developed from the proposed research program will be used to identify the specific neural mechanisms that are involved in anxiety-related changes in human balance control and will improve our understanding of how links between anxiety and balance may contribute to balance deficits and falls.