For this test, an insulated wire coil is held over the scalp. A brief electrical current passes through the coil, creating a magnetic pulse that electrically stimulates the brain. The subject hears a click and may feel a pulling sensation on the scalp under the coil. The stimulation may also cause twitching in the muscles of the face, arm, or leg. During the stimulation, the subject may be asked to tense certain muscles slightly or perform other simple actions.