3. Transcranial magnetic stimulation: For this test, the subject sits in a comfortable chair. An insulated coil is held on the scalp. A magnetic pulse from the coil stimulates the brain. The subject may hear a click and feel a snap or pulling sensation on the scalp under the coil. The stimulation may also cause twitching in the muscles of the arm or leg. During the stimulation, the subject may be asked to move certain muscles or perform other simple actions.