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Front. Neurosci. | doi: 10.3389/fnins.2018.00954

μ-rhythm extracted with personalized EEG filters correlates with corticospinal excitability in real-time phase-triggered EEG-TMS

  • 1Johann Wolfgang Goethe University, Frankfurt Institute for Advanced Studies, Germany
  • 2Department of Neurology & Stroke, and Hertie Institute for Clinical Brain Research, University of Tübingen, Germany
  • 3Institute of Medical Psychology and Behavioral Neurobiology, University of Tübingen, Germany

Ongoing brain activity has been implicated in the modulation of cortical excitability. The combination of electroencephalography (EEG) and transcranial magnetic stimulation (TMS) in a real-time triggered setup is a novel method for testing hypotheses about the relationship between spontaneous neuronal oscillations, cortical excitability, and synaptic plasticity. For this method, a reliable real-time extraction of the neuronal signal of interest from scalp EEG with high signal-to-noise ratio (SNR) is of crucial importance. Here we compare individually tailored spatial filters as computed by spatial-spectral decomposition (SSD), which maximizes SNR in a frequency band of interest, against established local C3-centered Laplacian filters for the extraction of the sensorimotor μ-rhythm. Single-pulse TMS over the left primary motor cortex was synchronized with the surface positive or negative peak of the respective extracted signal, and motor evoked potentials (MEP) were recorded with electromyography (EMG) of a contralateral hand muscle. Both extraction methods led to a comparable degree of MEP amplitude modulation by phase of the sensorimotor μ-rhythm at the time of stimulation. This could be relevant for targeting other brain regions with no working benchmark such as the local C3-centered Laplacian filter, as sufficient SNR is an important prerequisite for reliable real-time single-trial detection of EEG features.

Keywords: brain-state dependent stimulation, sensorimotor oscillations, EEG-TMS, Spatial Filtering, corticospinal excitability

Received: 25 Sep 2018; Accepted: 30 Nov 2018.

Edited by:

Arnaud Delorme, UMR5549 Centre de Recherche Cerveau et Cognition (CerCo), France

Reviewed by:

Mario Tombini, Campus Bio-Medico University, Italy
Samson Chota, Université Toulouse III Paul Sabatier, France  

Copyright: © 2018 Schaworonkow, Caldana Gordon, Belardinelli, Ziemann, Bergmann and Zrenner. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Ulf Ziemann, Department of Neurology & Stroke, and Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany, ulf.ziemann@uni-tuebingen.de