TMS-EEG co-registration: on TMS-induced artifact

Area of Science:

• Neuroscience
• Biomedical Engineering
• Signal Processing

Background:

• Combining transcranial magnetic stimulation (TMS) with electroencephalography (EEG) offers valuable insights into human brain function.
• Recording EEG during TMS is challenging due to strong electromagnetic interference (EMI) from TMS pulses, which can saturate amplifiers.
• Advancements in TMS-compatible EEG equipment mitigate saturation issues, enabling simultaneous recordings.

Purpose of the Study:

• To identify stimulus-related artifacts in TMS-EEG recordings.
• To quantify the duration of the artifact induced by TMS.
• To investigate how experimental parameters affect artifact length.

Main Methods:

• A phantom head model was used to record TMS-induced artifacts, excluding biological brain responses.
• Various electrodes, TMS coils, stimulator models, stimulation frequencies, and intensities were tested.
• The duration of the electrical artifact under different experimental conditions was measured.

Main Results:

• The electrical artifact generated by TMS pulses persisted for approximately 5 ms after the pulse onset.
• The artifact duration remained consistent across different experimental settings and parameter variations.

Conclusions:

• Cortical evoked responses following TMS can be analyzed as early as 5 ms after stimulation onset.
• Studying early physiological responses to TMS has significant clinical and experimental implications for understanding direct cortical activity.