Cognitive demands of executing postural reactions: does aging impede attention switching?

A new dual-task paradigm was used to investigate age-related differences in attentional dynamics during rapid balancing reactions evoked by small, unp redictable antero-posterior platform movements. The perturbations were deli vered while subjects performed a continuous visuo-motor pursuit-tracking ta sk. Onset of significant deviation in tracking was inferred to indicate swi tching of attentional resources between tracking and balancing tasks. Altho ugh tracking deviation was equally likely to occur subsequent to postural p erturbation in healthy young and older adults, deviation onset was delayed, on average, by 67% (123 ms) in the older subjects. Delay in onset of track ing deviation correlated with subsequent delay in generating the peak stabi lizing postural response at the ankle. These results suggest that impaired attentional dynamics may exacerbate postural instability in older adults. ( C) 2001 Lippincott Williams & Wilkins.