The protocol presented here is for TMS-EEG studies utilizing intracortical excitability test-retest design paradigms. The intent of the protocol is to produce reliable and reproducible cortical excitability measures for assessing neurophysiological functioning related to therapeutic interventions in the treatment of neuropsychiatric diseases such as major depression.
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Method Article
Combined Transcranial Magnetic Stimulation and Electroencephalography of the Dorsolateral Prefrontal Cortex
In This Article
Summary
Abstract
Transcranial magnetic stimulation (TMS) is a non-invasive method that produces neural excitation in the cortex by means of brief, time-varying magnetic field pulses. The initiation of cortical activation or its modulation depends on the background activation of the neurons of the cortical region activated, the characteristics of the coil, its position and its orientation with respect to the head. TMS combined with simultaneous electrocephalography (EEG) and neuronavigation (nTMS-EEG) allows for the assessment of cortico-cortical excitability and connectivity in almost all cortical areas in a reproducible manner. This advance makes nTMS-EEG a powerful tool that can accurately assess brain dynamics and neurophysiology in test-retest paradigms that are required for clinical trials. Limitations of this method include artifacts that cover the initial brain reactivity to stimulation. Thus, the process of removing artifacts may also extract valuable information. Moreover, the optimal parameters for dorsolateral prefrontal (DLPFC) stimulation are not fully known and current protocols utilize variations from the motor cortex (M1) stimulation paradigms. However, evolving nTMS-EEG designs hope to address these issues. The protocol presented here introduces some standard practices for assessing neurophysiological functioning from stimulation to the DLPFC that can be applied in patients with treatment resistant psychiatric disorders that receive treatment such as transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), magnetic seizure therapy (MST) or electroconvulsive therapy (ECT).
Introduction
Transcranial magnetic stimulation (TMS) is a neurophysiological tool that allows for the non-invasive assessment of cortical neuronal activity through the use of rapid, time-varying magnetic field pulses1. These magnetic field pulses induce a weak current in the superficial cortex beneath the coil which results in membrane depolarization. The ensuing cortical activation or modulation is directly related to the characteristics of the coil, its angle and orientation to the skull2. The waveform of the pulse discharged from the coil and the underlying state of the neurons also influence the resultant cortical activation
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Protocol
All the experimental procedures presented here have been approved by our Local Ethical Committee following guidelines of the Declaration of Helsinki.
1. Head Registration for Neuronavigated TMS — EEG
- Obtain a high resolution whole head T1-weighted structural MRI for each participant. Scan according to the neuronavigation manufacturer guidelines.
- Upload the images on the navigation system. Check if MRIs are correctly scanned. Choose the cardinal points (pre-auricular points, the nasion and the tip of the nose). Insert the stimulation targets (based on anatomy or based on the head coordinates, MNI, or Talairach coo....
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Results
Figure 1A illustrates the TMSevoked potentials after DLPFC stimulation over the F3 electrode after averaging 100 epochs from each session for one healthy volunteer. In this illustration, we highlight the effect of the CS on the TS in comparison to the single pulse condition when TS is applied alone. The CS modulates the N100 deflection in a clear manner even in one subject. In the SICI and LICI sessions, N100 is usually increased and in ICF d.......
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Discussion
TMS-EEG enables the direct and noninvasive stimulation of most cortical areas and the acquisition of the resulting neuronal activity with very good spatio-temporal resolution30, especially when neuronavigation is utilized. The benefit of this methodological advance is based on the fact that TMS-evoked EEG signals originate from the electrical neural activity and it is an index of cortico-cortical excitability. This has tremendous potential in neuropsychiatric patient populations where TMS-EEG can .......
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Disclosures
Pantelis Lioumis has been a paid consultant for Nexstim Plc. (Helsinki, Finland) outside the submitted work (i.e., for the motor and speech mapping rTMS applications before 2017). Reza Zomorrodi is a member of the advisory board of Vielight Inc. (Toronto, Canada). Zafiris J. Daskalakis receives research support from the Canadian Institutes of Health Research (CIHR), National Institutes of Health - US (NIH), Weston Brain Institute, Brain Canada and the Temerty Family through the CAMH Foundation and the Campbell Research Institute. He received research support and in-kind equipment support for an investigator-initiated study from Brainsway Ltd. and he is the site principal investigator for three sponsor-initiated studies for Brainsway Ltd. He received in-kind equipment support from Magventure for this investigator-initiated study. Daniel M. Blumberger receives research support from the Canadian Institutes of Health Research (CIHR), National Institutes of Health - US (NIH), Weston Brain Institute, Brain Canada and the Temerty Family through the CAMH Foundation and the Campbell Research Institute. He received research support and in-kind equipment support for an investigator-initiated study from Brainsway Ltd. and he is the site principal investigator for three sponsor-initiated studies for Brainsway Ltd. He received in-kind equipment support from Magventure for this investigator-initiated study. He received medication supplies for an investigator-initiated trial from Indivior. He has participated in an advisory board for Janssen.
Acknowledgements
This work was funded in part by NIMH R01 MH112815. This work was also supported by the Temerty Family Foundation, Grant Family Foundation and Campbell Family Mental Health Research Institute at the Centre for Addiction and Mental Health.
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Materials
| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| CED Micro1401-3 | Cambridge Electronic Design Limited | CED Micro1401-3 | Digital Data Recocrder |
| BISTIM'2 Package Option 1 | Magstim | 3234-00 | TMS paired pulse stimulator |
| Magstim 200'2 Unit (2 items) | Magstim | 3010-00 | TMS stimulators |
| UI controller | Magstim | 3020-00 | TMS controller |
| BISTIM'2 UI controller | Magstim | 3021-00 | TMS controller |
| BISTIM connecting module | Magstim | 3330-00 | TMS connecting module |
| D70 Alpha Coil - P/N 4150-00 (Alpha 70 mm double coil) | Magstim | 4150-00 | TMS coil |
| Brainsight | Rogue-Resolutions | Brainsight 2 | Neuronavigator |
| Model 2024F | Intronix | 2024F | Electromyograph |
| Neuroscan SynAmps RT 64 channel System | Compumedics Neuroscan | 9032-0010-01 | Electroencephalograph |
| Quick-Cap electrode system 64 | Compumedics Neuroscan | 96050255 | EEG Cap |
References
- Barker, A. T., Jalinous, R., Freeston, I. L. Non-invasive magnetic stimulation of human motor cortex. Lancet. 1 (8437), London, England. 1106-1107 (1985).
- Ilmoniemi, R. J., Ruohonen, J., Karhu, J. Transcranial magnetic stimulation--a new tool for functional....
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