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

Ida GranöTuomas P MutanenAino TervoJaakko O NieminenAndré Salles Cunha PeresMatteo FecchioMario RosanovaPantelis LioumisRisto J Ilmoniemi
Published in: Open research Europe (2022)
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.
Keyphrases
  • transcranial magnetic stimulation
  • resting state
  • high frequency
  • functional connectivity
  • working memory
  • white matter
  • multiple sclerosis
  • mass spectrometry
  • ms ms
  • clinical trial
  • study protocol
  • blood brain barrier