State-Dependent Neuromodulation Reveals Link Between Online and Offline Corticospinal Excitability

Area of Science:

• Neuroscience
• Motor Control
• Rehabilitation Science

Background:

• Post-intervention effects of neuromodulation are vital for neurorehabilitation.
• State-dependent interventions modulate corticospinal excitability (CSE), but online-offline relationships are unclear.

Purpose of the Study:

• To investigate the association between online CSE changes and offline plasticity during state-dependent neuromodulation.
• To determine if during-intervention effects predict post-intervention plasticity in the corticospinal pathways.

Main Methods:

• Healthy participants received five combinations of single-pulse transcranial magnetic stimulation (TMS) and robotic peripheral stimulation (PS).
• Stimulation was triggered by event-related beta-band desynchronization (ERD) during motor imagery (MI).
• Motor-evoked potential (MEP) amplitudes were quantified online, and plateau corticospinal recruitment (MEPmax) was measured post-intervention.

Main Results:

• MI-based interventions progressively increased online CSE, with maximal facilitation during synchronous TMS and PS delivery coinciding with ERD.
• This combined intervention uniquely demonstrated a significant correlation between online MEP changes and offline MEPmax.
• Control conditions showed no progressive online effects and decreased offline CSE.

Conclusions:

• Online CSE changes can serve as a biomarker for closed-loop neuromodulation.
• Findings support individualized dosing strategies for translational neurorehabilitation.
• Synchronized TMS and PS during ERD optimizes state-dependent neuromodulation for motor recovery.