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Assessing Primary Motor Cortex Excitability and Excitability Modulation by Pairing Transcranial Magnetic Stimulation with Electromyography
Published on: October 7, 2025
Variability of motor cortical excitability using a novel mapping procedure
Andrew E Littmann1, Colleen L McHenry, Richard K Shields
1Department of Physical Therapy, Rueckert-Hartman College for Health Professions, Regis University, Denver, CO 80221, United States.
Journal of Neuroscience Methods
|January 30, 2013
Summary
This study found a new transcranial magnetic stimulation (TMS) method reliably maps the motor cortex efficiently. This technique offers a quicker and more clinically useful way to assess brain excitability.
Area of Science:
- Neuroscience
- Motor Control
- Neuromodulation
Background:
- Transcranial Magnetic Stimulation (TMS) is a non-invasive technique used to study and modulate brain activity.
- Accurate mapping of the motor cortex is crucial for understanding motor control and for clinical applications.
- Existing TMS motor cortex mapping procedures can be time-consuming and may lack optimal clinical utility.
Purpose of the Study:
- To evaluate the reliability of a novel, time-efficient TMS motor cortex mapping procedure.
- To determine the clinical usefulness of a streamlined TMS mapping protocol.
- To identify reliable subregions within the motor cortex map for assessing global cortical excitability.
Main Methods:
- A novel TMS procedure using a 15-point grid was applied to 6 participants.
- Resting motor evoked potentials (MEPs) were recorded from the first dorsal interosseous muscle.
- MEP amplitudes, map center of gravity (CoG), and stimulus-response curves were assessed before and after a 30-minute rest period.
- Test-retest reliability was analyzed using intraclass correlation coefficients (ICCs).
Main Results:
- Mean MEP amplitudes demonstrated high test-retest reliability (ICC=0.90-0.92).
- MEP reproducibility was highest along a specific axis (approx. 45° to nasion-inion).
- Stimulus-response MEP amplitudes showed moderate to high reliability (ICC 0.54-0.95).
- The mean CoG shift between sessions was minimal (2.79±1.2mm).
Conclusions:
- The novel TMS motor cortex mapping procedure is reliable for assessing cortical excitability.
- The method is efficient, requiring fewer stimuli and scalp locations.
- This technique holds promise for enhanced clinical utility in neuroscience research and practice.
