Effects of spatial and nonspatial cognitive activity on postural stability

Is postural stability controlled automatically, or is it affected by concur rent cognitive activity? Are the effects influenced by the nature of the co gnitive activity required, and do they increase in old age ? To address the se questions, 70 participants aged 20-79 years were asked to stand as still as possible on a force platform (postural control task) while performing ( a) no cognitive task, (b) a spatial memory task, and (c) a nonspatial memor y task. The memory tasks were also performed while seated as a comparison c ondition. Both spatial and nonspatial memory recall declined with increasin g age but were unaffected by position (standing vs, seated). Postural stabi lity declined with age; moreover, there was support for an earlier finding that age decline was greatest when performing the spatial memory task. Each recording period was split into two phases which, for the spatial and nons patial memory tasks, corresponded to encoding and maintaining the stimuli. In comparison with no task, participants were more stable when encoding sti muli (particularly in the spatial task), but they were less stable when mai ntaining stimuli (particularly in the nonspatial task). The results suggest that postural stability can be affected by cognitive activity in complex w ays, depending on the age of participants, the type of cognitive task (spat ial vs. nonspatial), and the cognitive processing required (encoding vs, ma intenance).