Exploring Muscle Synergy Consistency and Physiological Interpretability in Speech Evaluation Using High-Density sEMG.

Area of Science:

• Motor control
• Biomechanics
• Speech science

Background:

• Speech production requires complex muscle coordination, posing challenges for motor control analysis.
• Muscle synergies offer a framework for understanding how neural systems simplify motor commands for complex movements.

Purpose of the Study:

• To investigate muscle synergies in speech production using high-density surface electromyography (HD-sEMG).
• To identify the number and roles of muscle synergies during speech tasks.
• To assess the stability and reproducibility of these synergies.

Main Methods:

• Ten healthy participants performed vowel and consonant tasks in phonated and silent speech modes.
• High-density surface electromyography (HD-sEMG) recorded muscle activity from facial, jaw, and neck regions.
• Muscle activation patterns were analyzed to identify underlying muscle synergies.

Main Results:

• Three key muscle synergies were identified, explaining over 95% of muscle activation variance.
• These synergies exhibited hierarchical roles: core articulation, auxiliary support, and fine motor refinement.
• High intra-subject stability and moderate inter-subject reproducibility of synergies were observed.

Conclusions:

• Muscle synergies provide a fundamental organizational principle for speech motor control.
• Synergy-based features improve speech classification, offering potential for clinical applications.
• Findings advance understanding of vocalization biomechanics and support development of speech prosthetics and interfaces.