Transcranial Magnetic Stimulation (TMS) is a non-invasive technique to gather information about brain function. It is very useful when studying the areas of the brain related to motor activity (motor cortex, corticospinal tract, spinal cord and nerve roots). The procedure is conducted by transmitting a magnetic signal into the brain to stimulate an area of the body. Electrodes (small pieces of metal taped to areas of the body) are used in order to measure electrical activity. A magnetic signal is sent from a metal instrument held close to the patient's head, to an area of the brain responsible for motor activity of a certain area of the body. The electrodes pick up and record the electrical activity in the muscles.