The dynamics of visual reweighting in healthy and fall-prone older adults.

Multisensory reweighting (MSR) is an adaptive process that prioritizes the visual, vestibular, and somatosensory inputs to provide the most reliable information for postural stability when environmental conditions change. This process is thought to degrade with increasing age and to be particularly deficient in fall-prone versus healthy older adults. In the present study, the authors investigate the dynamics of sensory reweighting, which is not well-understood at any age. Postural sway of young, healthy, and fall-prone older adults was measured in response to large changes in the visual motion stimulus amplitude within a trial. Absolute levels of gain, and the rate of adaptive gain change were examined when visual stimulus amplitude changed from high to low and from low to high. Compared with young adults, gains in both older adult groups were higher when the stimulus amplitude was high. Gains in the fall-prone elderly were higher than both other groups when the stimulus amplitude was low. Both older groups demonstrated slowed sensory reweighting over prolonged time periods when the stimulus amplitude was high. The combination of higher vision gains and slower down weighting in older adults suggest deficits that may contribute to postural instability.