Multi-locus transcranial magnetic stimulation system for electronically targeted brain stimulation

Jaakko O. Nieminen; Heikki Sinisalo; Victor H. Souza; Mikko Malmi; Mikhail Yuryev; Aino E. Tervo; Matti Stenroos; Diego Milardovich; Juuso T. Korhonen; Lari M. Koponen; Risto J. Ilmoniemi

Brain Stimulation (Jan 2022)

Multi-locus transcranial magnetic stimulation system for electronically targeted brain stimulation

Jaakko O. Nieminen,
Heikki Sinisalo,
Victor H. Souza,
Mikko Malmi,
Mikhail Yuryev,
Aino E. Tervo,
Matti Stenroos,
Diego Milardovich,
Juuso T. Korhonen,
Lari M. Koponen,
Risto J. Ilmoniemi

Affiliations

Jaakko O. Nieminen: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland; Corresponding author. Postal address: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, P.O. Box 12200, FI-00076 AALTO, Finland.
Heikki Sinisalo: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
Victor H. Souza: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland; School of Physiotherapy, Federal University of Juiz de Fora, Juiz de Fora, MG, Brazil
Mikko Malmi: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
Mikhail Yuryev: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland
Aino E. Tervo: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland; AMI Centre, Aalto NeuroImaging, Aalto University School of Science, Espoo, Finland
Matti Stenroos: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland
Diego Milardovich: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland; Institute for Microelectronics, Technische Universität Wien, Vienna, Austria
Juuso T. Korhonen: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland
Lari M. Koponen: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland
Risto J. Ilmoniemi: Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland; BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland

Journal volume & issue: Vol. 15, no. 1
pp. 116 – 124

Abstract

Read online

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.

Published in Brain Stimulation

ISSN: 1935-861X (Print); 1876-4754 (Online)
Publisher: Elsevier
Country of publisher: United States
LCC subjects: Medicine: Internal medicine: Neurosciences. Biological psychiatry. Neuropsychiatry
Website: https://www.journals.elsevier.com/brain-stimulation

About the journal

Abstract

Keywords