Projects per year
Background: Transcranial magnetic stimulation (TMS) allows non-invasive stimulation of the cortex. In multi-locus TMS (mTMS), the stimulating electric field (E-field) is controlled electronically without coil movement by adjusting currents in the coils of a transducer. Objective: To develop an mTMS system that allows adjusting the location and orientation of the E-field maximum within a cortical region. Methods: We designed and manufactured a planar 5-coil mTMS transducer to allow controlling the maximum of the induced E-field within a cortical region approximately 30 mm in diameter. We developed electronics with a design consisting of independently controlled H-bridge circuits to drive up to six TMS coils. To control the hardware, we programmed software that runs on a field-programmable gate array and a computer. To induce the desired E-field in the cortex, we developed an optimization method to calculate the currents needed in the coils. We characterized the mTMS system and conducted a proof-of-concept motor-mapping experiment on a healthy volunteer. In the motor mapping, we kept the transducer placement fixed while electronically shifting the E-field maximum on the precentral gyrus and measuring electromyography from the contralateral hand. Results: The transducer consists of an oval coil, two figure-of-eight coils, and two four-leaf-clover coils stacked on top of each other. The technical characterization indicated that the mTMS system performs as designed. The measured motor evoked potential amplitudes varied consistently as a function of the location of the E-field maximum. Conclusion: The developed mTMS system enables electronically targeted brain stimulation within a cortical region.
- Electric field
- Motor mapping
- Transcranial magnetic stimulation
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Ilmoniemi, R., Alkio, K., Valén, K., Aydogan, D. B., Souza, V., Nissilä, I., Granö, I., Metsomaa, J., Sinisalo, H., Kicic, D., Koistinen, L., Kahilakoski, O., Laine, M., Rantamäki, K., Li, L., Mäkinen, A., Nurmi, S., Pankka, H., Raij, T., Rantala, R., Lioumis, P., Makkonen, M., Parvin, S., Mahboubi, B., Vaalto, S., Rissanen, I., Soto de la Cruz, A., Tommila, T., Ylöstalo, T., Ukharova, E., Koponen, M., Roine, T. & Nieminen, A.
01/08/2019 → 31/08/2026
Project: EU: ERC grants