Evidence of direction loss in elderly movement preparation is not due to spatial orienting effects

Twenty elderly and young subjects performed matched movement plan restructuring and spatial orienting tasks. In the restructuring task, a precue stimulus was presented for 200 ms, followed by a preparation (PI; 250, 500, 1000, or 2000 ms), and the target stimulus. On 75% of the trials, the precue specified the aiming movement response enabling movement plan preparation concerning parameters of arm and direction. On 25% of the trials, the precue incorrectly specified the response requiring movement plan restructuring. The orienting task assessed shifts in perceptual localization of the precue and target stimuli for restructuring task conditions. At PIs of 1000 and 2000 ms, elderly, but not young, subjects restructured a movement plan for direction more quickly than for arm or both parameters. Spatial orienting shifts did not account for these effects.