Muscle and Motoneuron Synergies in Biomimetic and Non-Biomimetic 3-DoF Tasks

Area of Science:

• Neuroscience
• Biomedical Engineering
• Motor Control

Background:

• The central nervous system organizes neural control into low-dimensional modules (synergies) for coordinated movements.
• Research has focused on muscle synergies, but recent evidence suggests distinct motoneuron synergistic groups may exist.
• Understanding neural organization is key for intuitive myoelectric prostheses control.

Purpose of the Study:

• To investigate differences in encoded information at muscle and motoneuron levels during myoelectric control.
• To analyze muscle and motoneuron synergies using high-density surface electromyography (EMG).
• To assess neuromuscular adaptation under different control mappings.

Main Methods:

• Participants performed a 3-degree-of-freedom (DoF) goal-reaching task.
• Biomimetic and non-biomimetic control mappings were used to assess neuromuscular adaptation.
• High-density surface EMG was employed to analyze muscle and motoneuron synergies.

Main Results:

• Motoneuron synergies occupy a higher-dimensional manifold compared to muscle synergies.
• Motoneuron synergies showed more spatially and temporally distinct activation patterns.
• Both muscle and motoneuron synergies maintained high spatial and temporal consistency across different control maps.

Conclusions:

• Motoneuron synergies may enable a wider range of movement outputs in myoelectric control.
• Existing motor strategies can adapt to new control paradigms without forming entirely new synergy patterns.
• Findings support the development of personalized, adaptive myoelectric controllers.