Aging and Motor Adaptation: Increased Movement Variability, Slowing Rates of Adaptation, and Smaller Aftereffects

Studies over the past 3 decades have shown decreased motor adaptation with age. The most widely supported theory for this change proposes that older adults fail to successfully implement cognitive strategies to facilitate performance. However, increased movement variability may also affect adaptation with age, but this has to date remained unstudied. Here, we examine whether age-related increases in movement variability influence adaptation. Healthy older adults (N = 48) exhibited significantly higher levels of baseline movement variability than younger adults (N = 60) in a visuomotor adaptation task, with variability increasing modestly with advancing age. Across all participants, greater movement variability correlated with slower rates of adaptation and smaller aftereffects. In our study, we also manipulated perturbation magnitude and sensory feedback in the task: such manipulations should facilitate participants applying cognitive strategies to the larger, more identifiable perturbation. Altering perturbation magnitude and sensory feedback did not affect the relationship between age and measures of adaptation performance, suggesting that adaptive changes with age cannot be fully accounted for by changes in the generation or the application of cognitive strategies in this task. While our results are correlational, they suggest instead that increased movement variability may contribute to the age-related decline in visuomotor adaptation.