Kinematic Differences in Naive Mock-Prosthesis Usage during Action Observation: Effect of Limb Match Specificity

Abstract

Background: Despite advancements in upper-limb prosthetics, rejection rates remain high. A previous study demonstrated that amputee subjects exhibit differences in neural activation when they observe different performers, ie: intact actors vs prosthesis-users. The purpose of this study is to determine if this observed neural activation difference leads to differences in performance. If there is a performance difference, subjects observing an actor using a similar device (matched) will exhibit less variability in their joint kinematics than those watching an actor using his intact hand (mismatched). The "matched" observers should also perform the task more quickly than the "mismatched" observers. Methods: Twenty-two healthy subjects donned a "fictive amputee modeling system (FAMS) consisting of a socket that fit over the arm with an attached terminal device. Subjects watched a video of an actor performing a blockturning task; half watched a video with an intact actor and half watched an actor utilizing the same FAMS device. Subjects performed the task and kinematic data of the upper extremity was collected. Findings: The matched and mismatched groups utilized different strategies to complete the task. The mismatched group showed significant changes in motor control at the shoulder and elbow during the performance of the task. The matched group had no alterations in shoulder and elbow movement during the task. The matched group also consistently took longer to perform the task. Interpretation: The matched group tended to have more consistent motor performance throughout testing, suggesting earlier acquisition of behavioral consistency. This may suggest the benefits of matched limb training in amputees to hasten motor control of prostheses.