EEG Responses to Transcranial Magnetic Stimulation with Different Intensities over the Motor Cortex.

Area of Science:

• Neuroscience
• Neurophysiology
• Brain Stimulation

Background:

• Transcranial Magnetic Stimulation (TMS) is a non-invasive technique for modulating neural activity.
• Previous research predominantly used single-intensity TMS, leaving the effects of varying intensities unclear.
• Understanding intensity-dependent responses is crucial for optimizing TMS protocols.

Purpose of the Study:

• To investigate electroencephalogram (EEG) responses under different Transcranial Magnetic Stimulation (TMS) intensities.
• To characterize the relationship between TMS stimulation intensity and induced neural changes.
• To explore the dose-response effects of TMS on brain activity.

Main Methods:

• Twenty-four healthy participants received TMS over the left motor cortex at varying intensities (sham, 80%, 100%, 120% of resting motor threshold).
• Concurrent EEG recordings were obtained during stimulation.
• Analyses included TMS-evoked potentials (TEPs), event-related spectral perturbation (ERSP), and inter-trial coherence (ITC) to assess neural changes.

Main Results:

• Significant intensity-dependent changes in EEG responses were observed.
• Lower intensity TMS (80% rMT) primarily affected phase-specific changes (ITC).
• Higher intensities (100%, 120% rMT) induced more comprehensive neural modulation, altering TEP, ERSP, and ITC.

Conclusions:

• A clear dose-response relationship exists between TMS intensity and the magnitude of neural modulation.
• Higher TMS intensities lead to more pronounced changes in brain activity as measured by EEG.
• These findings inform the optimization of TMS protocols for targeted neural modulation.