Attentional demands for postural control: the effects of aging and sensory reintegration.

The aim of this experiment was to examine if, with aging, the task of reintegrating sensory information perturbs balance and requires additional attentional demand. Young adults and the elderly were asked to maintain a stable upright posture while standing on a force platform. Visual and ankle proprioceptive information were removed or perturbed and suddenly reinserted. Subjects also had to respond vocally as quickly as possible to an unpredictable auditory stimulus presented before or following a sensory reintegration and in control conditions. Reaction times to the auditory stimuli were used as an index of the attentional demands necessary for calibrating the postural system. Reintegration of proprioception in absence of vision and under vision yielded a faster center of pressure velocity for both groups. This effect, however, was more important for the elderly than the young adults. An increased attentional demand was observed for both groups when proprioceptive information had to be reintegrated in absence of vision. Altogether, these results propose that, for the elderly persons, postural contexts requiring a reweighting of sensory inputs could lead to increased risk for loss of balance and falls if insufficient attentional resources are allocated to the postural task.