Inter-muscular coherence and functional coordination in the human upper extremity after stroke

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Biomedical Engineering

Background:

• Stroke survivors experience motor impairments affecting muscle coordination.
• Previous research identified altered muscle synergies post-stroke.
• Functional connectivity of these muscle synergies remains poorly understood.

Purpose of the Study:

• To quantify alterations in inter-muscular coherence (IMC) of upper extremity muscles in stroke survivors.
• To investigate IMC differences in synergistic versus non-synergistic muscle pairs.
• To explore the relationship between muscle synergies and functional connectivity post-stroke.

Main Methods:

• Collected surface EMG signals during a 3D isometric force matching task from 10 stroke patients and 6 healthy controls.
• Utilized non-negative matrix factorization (NMF) to identify muscle synergies.
• Calculated IMC for synergistic and non-synergistic muscle pairs across different frequency bands (alpha, low gamma).

Main Results:

• Synergistic muscle pairs exhibited higher IMC in both control and stroke groups.
• Stroke patients showed significantly weaker IMC in the alpha band for synergistic anterior and middle deltoids.
• Distinct IMC alterations were observed in synergistic anterior-posterior deltoids (low gamma) and anterior deltoid-pectoralis major (alpha band) in stroke patients.

Conclusions:

• Muscle synergy and IMC analyses provide complementary insights into post-stroke motor recovery mechanisms.
• Altered functional connectivity, specifically IMC, is a key characteristic of motor impairments in stroke survivors.
• Findings highlight specific neural pathway changes impacting coordinated movement after stroke.