EFFECTS OF AGING ON PLANNING AND IMPLEMENTING ARM MOVEMENTS

In Experiments 1 and 2, aiming movements were performed with and witho ut visual feedback in young and elderly adults. The initial (accelerat ion and deceleration phases) and secondary movement components were an alyzed. Although deceleration phase accuracy decreased without visual feedback in both age groups, accuracy diminished as movement amplitude increased only in the elderly. This suggested that the elderly were m ore dependent on visual feedback to modify motor programs for longer d uration movements. Velocity also increased less with increasing amplit ude and target size in the elderly, which was related to impaired prep rogramming (acceleration phase) and implementation (deceleration phase ) of higher forces. This conclusion was confirmed directly in Experime nt 2 because only the deceleration phase was affected by the removal o f visual feedback of arm position when availability of visual informat ion could not be predicted before movement.