Cortical Contributions to Imagined Power Grip Task: An EEG-Triggered TMS Study

Area of Science:

• Neuroscience
• Motor Control
• Electrophysiology

Background:

• Motor imagery is known to cause alpha rhythm desynchronization in the motor cortex.
• The precise electrophysiological mechanisms behind this desynchronization during motor imagery are not fully understood.

Purpose of the Study:

• To investigate the electrophysiological mechanisms of alpha rhythm desynchronization during motor imagery.
• To explore the role of alpha oscillations in modulating corticospinal excitability during imagined movements.
• To differentiate functional network connectivity between index finger abduction and power grip imaginations.

Main Methods:

• Electroencephalography (EEG) and transcranial magnetic stimulation (TMS) were employed during index finger abduction and power grip imaginations.
• TMS, with varied coil orientations, stimulated corticospinal axons to probe early and late synaptic inputs.
• TMS was triggered by alpha power levels, and functional network analysis in the alpha band was performed.

Main Results:

• Negative correlations were found between alpha power and motor evoked potential (MEP) amplitude, and positive correlations with MEP latency.
• Functional network analysis revealed denser fronto-parietal connections during imagined index finger abduction compared to power grip.
• Network properties could differentiate between the two imagined tasks.

Conclusions:

• Alpha oscillations may suppress MEP amplitude and latency during imagined power grip.
• Imagined index finger abduction and power grip likely activate different cortical axon populations and densities.
• These findings provide functional evidence for the role of alpha oscillations in motor imagery.