Background & Aims

High-frequency repetitive transcranial magnetic stimulation (rTMS) applied to the primary motor cortex (M1) is a useful intervention to induce analgesic effects in chronic pain. However, the mechanisms driving these effects are not well understood. The present study utilized the combination of transcranial magnetic stimulation and electroencephalography (TMS-EEG) to explore how rTMS influences brain activity. We aimed to understand the changes in TMS evoked EEG potentials (TEPs), particularly in the M1 area following real and sham rTMS.

Methods

In 20 healthy individuals, the TMS-EEG and the rTMS protocols were targeted to the left M1 region. Using TMS-EEG, the brain activity was recorded before and after 10 Hz rTMS (15 minutes of stimulation, with 30 trains of 10-second pulses and 20-second intertrain interval). Changes in TEPs were assessed using metrics such as event-related spectrum perturbation (ERSP) and inter-trial coherence (ITC) in selected frequency bands relevant to pain processing (?, lower-?, and higher-?). Additionally, we measured motor-evoked potentials (MEPs) by TMS and thermal pain thresholds.

Results

Active rTMS led to an increase in high ?-band (25-35Hz) synchronization (ITC) in TEPs around the stimulated area and in corresponding regions of the opposite hemisphere (p<0.05 for both). This increase was followed by a rise in low ?-band (15-25 Hz) power (ERSP), both locally and in the distal contralateral hemisphere (p<0.05 for both). These changes suggest an immediate alteration in brain activity related to the application of 10 Hz rTMS. Interestingly, no significant differences were found in MEPs and thermal pain thresholds.

Conclusions

Our findings highlight that active rTMS to M1 can modify cortical oscillation, not only locally but also in distant brain areas. This insight can be useful for exploring rTMS-induced neuroplasticity within and beyond the primary motor cortex, which could pave the way for new approaches in non-invasive pain management therapies.

References

1 J.-P. Lefaucheur et al. Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS): An update (2014–2018). Clinical Neurophysiology 131 (2020) 474–528.
2. M. Rosanova et al., Natural Frequencies of Human Corticothalamic Circuits. The Journal of Neuroscience, June 17, 2009 • 29(24):7679 –7685 • 7679

Presenting Author

Enrico De Martino

Poster Authors

Enrico De Martino

MD, PhD

Aalborg University

Lead Author

Adenauer Girardi Casali

Federal University of São Paulo

Lead Author

Bruno Andry Couto

Aalborg University

Lead Author

Maryam Mahmoodi Omandani

Aalborg University

Lead Author

Thomas Graven-Nielsen

Thomas Graven-Nielsen

Lead Author

Daniel de Andrade

University of Aalborg

Lead Author

Topics

  • Treatment/Management: Interventional Therapies – Neuromodulation