A quantitative study on upper limb kinematic synergies in Parkinson’s patients: ON and OFF medication states

This paper evaluates and compares upper limb kinematic synergies in Parkinson's disease patients in On and Off Levodopa medication states. A dataset of 33 Parkinson's patients was used, each performing 24 upper limb tasks in both medication states. Each task was repeated six times while the patients were seated on a chair. The number of synergies, as well as their structure, activation, and timing, were calculated. The analysis focused on four degrees of freedom (DOFs) corresponding to shoulder angles (flexion/extension, abduction/adduction, internal/external rotation) and elbow angles (flexion/extension). Eulerian angles were used for angle calculation, and Non-Negative Matrix Factorization (NNMF) was employed for synergy extraction. The Global Variance Accounted For (VAF) method determined the number of synergies. Kinematic synergy analysis aimed to uncover the coupling between the movements across different DOFs and identify the fundamental movement maneuvers (synergy modules) that constitute the motor task. Preliminary results indicate that synergies, structure, and timing do not exhibit significant changes with medication state. Further investigations are required to explore additional factors contributing to kinematic synergy alterations in Parkinson's disease.