Local brain-state dependency of effective connectivity: A pilot TMS-EEG study [version 2; peer review: 2 approved]

Ida Granö, Tuomas P. Mutanen, Aino Tervo, Jaakko O. Nieminen, Victor H. Souza, Matteo Fecchio, Mario Rosanova, Pantelis Lioumis, Risto J. Ilmoniemi

Research output: Contribution to journalArticleScientificpeer-review


Background: Spontaneous cortical oscillations have been shown to modulate cortical responses to transcranial magnetic stimulation (TMS). However, whether these oscillations influence cortical effective connectivity is largely unknown. We conducted a pilot study to set the basis for addressing how spontaneous oscillations affect cortical effective connectivity measured through TMS-evoked potentials (TEPs). Methods: We applied TMS to the left primary motor cortex and right pre-supplementary motor area of three subjects while recording EEG. We classified trials off-line into positive- and negative-phase classes according to the mu and beta rhythms. We calculated differences in the global mean-field amplitude (GMFA) and compared the cortical spreading of the TMS-evoked activity between the two classes. Results: Phase affected the GMFA in four out of 12 datasets (3 subjects × 2 stimulation sites × 2 frequency bands). Two of the observed significant intervals were before 50 ms, two between 50 and 100 ms, and one after 100 ms post-stimulus. Source estimates showed complex spatial differences between the classes in the cortical spreading of the TMS-evoked activity. Conclusions: TMS-evoked effective connectivity seems to depend on the phase of local cortical oscillations at the stimulated site. This work paves the way to design future closed-loop stimulation paradigms.

Original languageEnglish
Article number45
JournalOpen research Europe
Number of pages17
Publication statusPublished - 8 Dec 2022
MoE publication typeA1 Journal article-refereed

Bibliographical note

Publisher Copyright:
© 2022 Granö I et al.

Fields of Science

  • Transcranial magnetic stimulation; electroencephalography; brain state; effective connectivity
  • 3126 Surgery, anesthesiology, intensive care, radiology

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