Automated search of stimulation targets with closed-loop transcranial magnetic stimulation

Aino E. Tervo, Johanna Metsomaa, Jaakko O. Nieminen*, Jukka Sarvas, Risto J. Ilmoniemi

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

27 Citations (Scopus)
183 Downloads (Pure)


Transcranial magnetic stimulation (TMS) protocols often include a manual search of an optimal location and orientation of the coil or peak stimulating electric field to elicit motor responses in a target muscle. This target search is laborious, and the result is user-dependent. Here, we present a closed-loop search method that utilizes automatic electronic adjustment of the stimulation based on the previous responses. The electronic adjustment is achieved by multi-locus TMS, and the adaptive guiding of the stimulation is based on the principles of Bayesian optimization to minimize the number of stimuli (and time) needed in the search. We compared our target-search method with other methods, such as systematic sampling in a predefined cortical grid. Validation experiments on five healthy volunteers and further offline simulations showed that our adaptively guided search method needs only a relatively small number of stimuli to provide outcomes with good accuracy and precision. The automated method enables fast and user-independent optimization of stimulation parameters in research and clinical applications of TMS.

Original languageEnglish
Article number117082
Number of pages10
Publication statusPublished - 15 Oct 2020
MoE publication typeA1 Journal article-refereed


  • Bayesian optimization
  • Closed-loop TMS
  • Multi-locus TMS
  • Stimulation targeting
  • Transcranial magnetic stimulation


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