Local brain-state dependency of effective connectivity: a pilot TMS-EEG study

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

doi:10.12688/openreseurope.14634.2

Local brain-state dependency of effective connectivity: a pilot TMS-EEG study

Open Res Eur. 2022 Jul 11:2:45. doi: 10.12688/openreseurope.14634.2. eCollection 2022.

Authors

Ida Granö^{1

2}, Tuomas P Mutanen^{1

2}, Aino Tervo^{1

2}, Jaakko O Nieminen^{1

2}, Victor H Souza^{1

2

3}, Matteo Fecchio^{4

5}, Mario Rosanova⁴, Pantelis Lioumis^{1

2}, Risto J Ilmoniemi^{1

2}

Affiliations

¹ Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland.
² BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
³ School of Physiotherapy, Federal University of Juiz de Fora, Juiz de Fora, MG, Brazil.
⁴ Department of Biomedical and Clinical Sciences "L. Sacco", University of Milan, Milan, Italy.
⁵ Center for Neurotechnology and Neurorecovery, Department of Neurology, Massachusetts General Hospital, Boston, MA, USA.

Abstract

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.

Keywords: Transcranial magnetic stimulation; electroencephalography; brain state; effective connectivity.

Grants and funding

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 810377); from the European Union's Horizon 2020 research and innovation programme under the grant agreement No. 945539 to M.R.; the Academy of Finland (Decisions No. 294625, 321631 and 327326); Jane and Aatos Erkko Foundation, the Finnish Cultural Foundation, and the Instrumentarium Science Foundation; by Fondazione Regionale per la Ricerca Biomedica (Regione Lombardia), Project ERAPERMED2019-101, GA 779282 (to M.R.), and from the Tiny Blue Dot Foundation (to M.R. and M.F.).