What we do during TMS experiments:
Before administering TMS, we must do a bit of preparation. First, we will apply an EEG cap. At each electrode, we gently exfoliate the skin and fill the electrode with gel so that we can record the brain’s natural activity. After setting up the cap, we apply a headband that allows us to register a participant with an MRI. To do this, we use a tool to point to different locations on the head in order to match a person’s real head with an MRI of their brain. Finally, we calibrate the coil so that we can accurately determine what part of the brain to stimulate.
Next, we administer TMS to measure the “motor threshold”. This is simply a measure of how strongly we should stimulate the brain. When doing this, we will try to make your fingers move a tiny bit. This is similar to when a doctor taps your knee in order to assess your reflexes. During rTMS, most people don’t feel anything. If they do, it is typically a tapping sensation or a slight muscle twitch. The coil makes a clicking noise with each magnetic pulse, so we have participants listen to a noisy recording in order to mask the sound.