Is event-related desynchronization a biomarker representing corticospinal excitability?

Area of Science:

• Neuroscience
• Rehabilitation Engineering
• Biomedical Engineering

Background:

• Brain-computer interfaces (BCIs) utilizing electroencephalogram (EEG)-based event-related desynchronization (ERD) are explored for upper limb motor function rehabilitation in stroke survivors.
• ERD is hypothesized to indicate sensorimotor cortex activation, but its direct correlation with corticospinal excitability remains unconfirmed.

Purpose of the Study:

• To investigate the association between the magnitude of ERD during motor imagery and the excitability of the primary motor cortex (M1) and spinal motoneurons.

Main Methods:

• Transcranial magnetic stimulation (TMS) was used to assess M1 excitability via motor evoked potentials (MEPs), short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF).
• Peripheral nerve stimulation was employed to evaluate spinal motoneuronal excitability through F-waves.
• EEG-based ERD during motor imagery was measured and correlated with TMS and F-wave parameters.

Main Results:

• A significant positive correlation was found between large ERD during motor imagery and increased F-wave persistence.
• Reduced SICI was observed with larger ERD, indicating enhanced cortical excitability.
• No significant changes were detected in ICF or the average F-wave amplitude response.

Conclusions:

• The magnitude of ERD during motor imagery accurately reflects the instantaneous excitability of both the primary motor cortex and spinal motoneurons.
• This study provides electrophysiological evidence that ERD-based BCIs, through motor imagery, can enhance corticospinal excitability, mimicking changes seen during actual movements.