Visual-Motor Integration of Unexpected Sensory Events in Young and Older Participants: A Kinematic Analysis

Abstract

We report a single experiment that examined the ability of young and older participants to modify their movement plan on-line during movement execution. Participants performed a single phase aiming task under 2 different conditions. In the experimental condition, during 76% of the trials, the index of difficulty of the task remained constant at 4.8 bits (medium target). During 24% of the trials, target width changed unexpectedly at movement initiation to either a smaller (6.1 bits) or larger (3.5 bits) target. In the control setting, participants completed trials to each target (3.5, 4.8, or 6.1 bits); target width remained constant throughout movement in this condition. For both age groups, participants responded in the anticipated fashion during control trials; movement time increased as a function of target size, with older participants generally performing more slowly. In the experimental condition, the young participants adapted their performance to the new target characteristics. In contrast, older participants adopted a conservative control strategy, whereby they did not adapt their performance to the new target size but instead used their programmed response for the initial target. These data suggest that older adults were operating in an open-loop mode of control for the experimental trials and a closed-loop control mode during the control trials. Thus, the type of control older adults adopted was dependent on the environmental context.