Aging and motor control.

The goal of the two experiments of the present study was to determine whether in an aiming task performed within a relatively long movement time (MT) bandwidth, older adults make similar use of visual information for motor control as younger adults. Older and younger subjects practiced a manual aiming task toward one (Experiment 1), or one of many (Experiment 2) small target(s) while only the target to be reached was visible (proprioception only: P) or under normal lighting condition (proprioception+vision: PV). Following practice, all subjects were transferred to the P conditions. The results of both experiments indicate that the older subjects were, during practice, as accurate as the younger ones in the PV condition. Moreover, both groups suffered a large and similar increase in aiming error in the transfer condition. This underlines that a useful source of sensory information, namely vision, has been withdrawn in transfer. This result is different from those of earlier studies in which a shorter target MT had been used (Chaput & Proteau, 1996; Proteau, Charest, & Chaput, 1994). This suggests that older adults process the sensory information available in that type of task similarly to younger subjects but at a lower speed. However, when the temporal constraints of the task are stringent, older adults might rely more on modes of control in which sensory information plays a minimal role when compared to younger subjects. Finally, the results of the second experiment suggest that, when multiple targets are used, older adults appear to program a response which is optimally suited for a "central" target.