Coherence between cortical and muscular activities after subcortical stroke

Area of Science:

• Neuroscience
• Motor Control
• Rehabilitation Science

Background:

• The functional connection between the motor cortex and muscles is crucial for motor control.
• Electroencephalogram-electromyogram (EEG-EMG) coherence is a key measure for assessing this connection.
• Pyramidal tract lesions, common after stroke, can disrupt motor pathways.

Purpose of the Study:

• To evaluate functional connections between motor cortices (contralateral and ipsilateral) and muscles after subcortical stroke.
• To investigate the impact of pyramidal tract lesions on motor cortex-muscle communication.
• To assess EEG-EMG coherence in patients with chronic subcortical stroke.

Main Methods:

• Recorded high-resolution EEG and EMG from hand, forearm, and biceps muscles during tonic contractions (elbow flexion, wrist extension, power grip).
• Computed EEG-EMG coherence to assess cortical control over muscle activity.
• Investigated 6 patients with chronic subcortical stroke.

Main Results:

• EEG-EMG coherence was consistently localized to the contralateral sensorimotor area, with no significant ipsilateral coherence.
• Significantly reduced EEG-EMG coherence was observed for affected hand and forearm muscles, but not biceps muscles.
• Findings indicate a dominant contralateral motor cortex influence on muscle activation post-stroke.

Conclusions:

• Direct functional connections to muscles after stroke recovery predominantly originate from the contralateral motor cortex.
• The differential impact of lesions on proximal (biceps) versus distal (hand, forearm) muscles relates to corticospinal pathway integrity.
• Understanding these pathways is vital for targeted neurorehabilitation strategies.