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Updated: Jan 1, 2026
Transcranial Magnetic Stimulation for Investigating Causal Brain-behavioral Relationships and their Time Course
Published on: July 18, 2014
A novel approach to localize cortical TMS effects
Konstantin Weise1, Ole Numssen2, Axel Thielscher3
1Methods and Development Group "Brain Networks", Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstr. 1a, 04103, Leipzig, Germany; Technische Universität Ilmenau, Advanced Electromagnetics Group, Helmholtzplatz 2, 98693, Ilmenau, Germany.
This study introduces a new method combining motor evoked potentials and electric field modeling to precisely locate the brain areas stimulated by transcranial magnetic stimulation (TMS). This improves the accuracy of TMS brain mapping for motor cortex research.
Area of Science:
- Neuroscience
- Biomedical Engineering
Background:
- Transcranial magnetic stimulation (TMS) is widely used, but precise localization of stimulated cortical sites remains challenging.
- Current mapping strategies rely on indirect methods like center of gravity or maximum electric field, leading to approximate localization.
Purpose of the Study:
- To develop and validate a novel method for reliably determining the effectively stimulated cortical site in individual subjects using TMS.
- To improve the precision of TMS-induced stimulation mapping, particularly in the motor cortex.
Main Methods:
- Combined measurements of motor evoked potentials (MEPs) across various coil positions and orientations with numerical modeling of induced electric fields.
- Identified effective stimulation sites by correlating MEPs with electric field characteristics.
Main Results:
- Identified sharply bounded cortical areas, specifically around the gyral crowns and rims of the motor hand area, as the origin of MEPs.
- Determined that the tangential component and overall magnitude of the electric field are most relevant for TMS effects.
- Validated the method by showing that the predicted optimal coil location/orientation produced MEPs more efficiently.
Conclusions:
- The developed approach significantly improves the localization accuracy of TMS-stimulated cortical areas.
- This generic method can be applied to other TMS applications, including language mapping, enhancing the precision of brain stimulation research.
