Targeting motor cortex high-excitability states defined by functional connectivity with real-time EEG–TMS
David Emanuel Vetter,
Christoph Zrenner,
Paolo Belardinelli,
Tuomas Petteri Mutanen,
Gábor Kozák,
Laura Marzetti,
Ulf Ziemann
Affiliations
David Emanuel Vetter
Department of Neurology & Stroke, University of Tübingen, Tübingen, Baden-Württemberg, Germany; Hertie-Institute for Clinical Brain Research, Tübingen, Baden-Württemberg, Germany
Christoph Zrenner
Department of Neurology & Stroke, University of Tübingen, Tübingen, Baden-Württemberg, Germany; Temerty Centre for Therapeutic Brain Intervention, Centre for Addiction and Mental Health, Toronto, Ontario, Canada; Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada; Institute for Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada
Paolo Belardinelli
Department of Neurology & Stroke, University of Tübingen, Tübingen, Baden-Württemberg, Germany; CIMeC, Center for Mind/Brain Sciences, University of Trento, Trento, Trentino-Alto Adige, Italy
Tuomas Petteri Mutanen
Department of Neuroscience and Biomedical Engineering, Aalto Yliopisto, Espoo, Uusimaa, Finland
Gábor Kozák
Department of Neurology & Stroke, University of Tübingen, Tübingen, Baden-Württemberg, Germany; Hertie-Institute for Clinical Brain Research, Tübingen, Baden-Württemberg, Germany
Laura Marzetti
Imaging and Clinical Sciences, Department of Neuroscience, University of Chieti-Pescara, Chieti, Abruzzo, Italy; Institute for Advanced Biomedical Technologies, University of Chieti-Pescara, Chieti, Abruzzo, Italy
Ulf Ziemann
Department of Neurology & Stroke, University of Tübingen, Tübingen, Baden-Württemberg, Germany; Hertie-Institute for Clinical Brain Research, Tübingen, Baden-Württemberg, Germany; Correspondence to: Department of Neurology & Stroke, University of Tübingen, Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany.
We tested previous post-hoc findings indicating a relationship between functional connectivity (FC) in the motor network and corticospinal excitability (CsE), in a real-time EEG-TMS experiment in healthy participants.We hypothesized that high FC between left and right motor cortex predicts high CsE.FC was quantified in real-time by single-trial phase-locking value (stPLV), and TMS single pulses were delivered based on the current FC. CsE was indexed by motor-evoked potential (MEP) amplitude in a hand muscle. Possible confounding factors (pre-stimulus μ-power and phase, interstimulus interval) were evaluated post hoc.MEPs were significantly larger during high FC compared to low FC. Post hoc analysis revealed that the FC condition showed a significant interaction with μ-power in the stimulated hemisphere. Further, inter-stimulus interval (ISI) interacted with high vs. low FC conditions. In summary, FC was confirmed to be predictive of CsE, but should not be considered in isolation from μ-power and ISI. Moreover, FC was complementary to μ-phase in predicting CsE. Motor network FC is another marker of real-time accessible CsE beyond previously established markers, in particular phase and power of the μ rhythm, and may help define a more robust composite biomarker of high/low excitability states of human motor cortex.
