Temporally Interfering TMS: Focal and Dynamic Stimulation Location

Area of Science:

• Neuroscience
• Biophysics
• Biomedical Engineering

Background:

• Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique.
• Current TMS methods face challenges in achieving both deep and focal stimulation.
• The depth-focality trade-off limits the precision of targeted neural modulation.

Purpose of the Study:

• To introduce and evaluate a novel temporal interference (TI) concept for TMS.
• To achieve focal and steerable neural stimulation in targeted brain regions.
• To overcome the limitations of conventional TMS regarding stimulation depth and focality.

Main Methods:

• Utilizing temporal interference (TI) by inducing two high-frequency electric fields with a slight frequency difference.
• Employing a low-pass filter effect of the nerve membrane to activate neurons at the intersection of fields.
• Using the finite element method (FEM) with 3D MRI-derived head models to compute electric fields, penetration depth, and activated volumes.
• Optimizing coil position, orientation, and voltage ratio for dynamic control and deeper, focused stimulation.

Main Results:

• Demonstrated that TI can resolve the electric field depth-focality trade-off.
• Showcased the ability to achieve deeper stimulation with acceptable spatial spread.
• Validated dynamic steering of stimulation by adjusting coil voltage ratio, not mechanical orientation.
• Computational results confirmed TI as an efficient alternative to complex coil designs.

Conclusions:

• Temporal interference (TI) is a promising technique for advanced transcranial magnetic stimulation (TMS).
• The TI system enables more dynamic and focused magnetic stimulation of the brain.
• This approach offers a viable alternative for precise, non-invasive neural targeting.