Muscle Synergies Control during Hand-Reaching Tasks in Multiple Directions Post-stroke

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Biomedical Engineering

Background:

• Motor control relies on simplifying mechanisms like muscle synergies, originating from the brainstem and spinal cord.
• Understanding these mechanisms is crucial for developing effective rehabilitation strategies for post-stroke individuals.

Purpose of the Study:

• To investigate the feasibility of muscle synergy models in post-stroke motor control.
• To compare hand-reaching movement execution in multiple directions between post-stroke and non-stroke individuals.

Main Methods:

• Extracted muscle synergies from EMG data using the Non-negative Matrix Factorization (NMF) algorithm.
• Utilized Variance Accounted For (VAF) and Mean Squared Error (MSE) to determine optimal synergy numbers.
• Applied similarity index and K-means clustering to compare synergy modulation across movement directions between groups.

Main Results:

• Four muscle synergies optimally captured EMG data variance in both groups (VAF > 0.88).
• Post-stroke individuals showed different muscle activation balances and synergy classifications compared to controls.
• Control group demonstrated gradual synergy modulation; post-stroke group showed significant differences across movement directions.

Conclusions:

• Post-stroke individuals modulate muscle synergy activation differently for various movement directions compared to non-stroke individuals.
• Differences in muscle activation balance and synergy classification support distinct motor control strategies post-stroke.