Motor cortex excitability states in chronic stroke patients probed by EEG-TMS

Area of Science:

• Neuroscience
• Motor Control
• Neurorehabilitation

Background:

• The sensorimotor mu-rhythm's phase differentiates motor cortex (M1) excitability in healthy individuals.
• This excitability differentiation is crucial for understanding motor function recovery after stroke.

Purpose of the Study:

• To investigate M1 excitability differentiation in chronic stroke patients.
• To correlate this differentiation with motor function recovery in the affected upper extremity.

Main Methods:

• Single-pulse transcranial magnetic stimulation (TMS) and EEG were used in 19 chronic stroke patients.
• Excitability states (high/low) were determined by the mu-rhythm phase during TMS over ipsilesional (iM1) and contralesional M1 (cM1).
• TMS-evoked potentials and beta-band power were analyzed; motor function was assessed using the Fugl-Meyer Assessment Upper Extremity (FMA-UE).

Main Results:

• Contralesional M1 showed significant excitability differentiation in TMS-evoked potentials and beta-band power.
• Ipsilesional M1 exhibited less pronounced differentiation, mainly in post-pulse beta power.
• The degree of excitability differentiation in iM1 significantly correlated with FMA-UE scores.

Conclusions:

• Excitability differentiation in the ipsilesional M1, based on sensorimotor mu-rhythm phase, is linked to upper extremity motor function in stroke survivors.
• This differentiation may serve as a novel biomarker for assessing motor recovery post-stroke.