Effect of Aging and Movement Variability on Motor Adaptation

Description

Aging is associated with a multitude of changes, including changes in the motor system. One such change that has been documented is increased levels of inherent movement variability (the inability to consistently replicate movements over time) with increasing age. Previous research has had controversial findings regarding the effect that movement variability has on motor learning and motor adaptation. Some research suggests that movement variability is beneficial to motor learning, while other research indicates that movement variability is the by-product of a noisy motor system and is a detriment to learning new skills. How do changes in movement variability associated with aging affect the ability to adapt to a mass perturbation? We tested younger and older individuals on a mass adaptation task (applying mass to the lateral side of the arm to perturb inertial forces of the limb during reaches). We analyzed baseline levels of movement variability, learning during the adaptation block and how baseline levels of movement variability explained differences in learning. We focused on measures of accuracy, speed and precision. We found that younger individuals displayed greater levels of movement variability throughout the experiment and that they also learned to adapt to the mass perturbation more successfully than their older counterparts. Multi-joint movements displayed greater degrees of learning in comparison to single-joint movements, likely due to the difference in difficulty when completing the two movements. Taken together, our results suggest that purposeful movement variability may be beneficial to motor adaptation.
Author Keywords: aging, mass adaptation, motor adaptation, motor learning, movement variability