Attentional dynamics in postural control during perturbations in young and older adults.

Temporal dynamics of attention during postural perturbations in young and older adults were investigated. Nineteen young and older subjects performed simple reaction time tasks during translational platform perturbations. Auditory or visual stimuli were presented randomly at delays from the onset of the platform perturbation. Reaction time was slowed before and during the platform movement, particularly in older subjects. Reaction times to stimuli presented at a 250-millisecond delay or later were not influenced by perturbation. The reaction times to the auditory stimuli were influenced more by perturbation than were those to visual targets. The postural response was unaltered by the presence of the reaction time task, but it differed between groups. Attention is engaged in response to a perturbation during the preperturbation time and during the initiation of the postural response in young and older adults. Sensory selection occurs in young and older adults, but to a greater degree in older subjects.