 For TMS, the subject sits in a comfortable chair. An insulated wire coil is placed on the scalp, and brief electrical currents are passed through the coil, creating magnetic pulses that stimulate the brain. The pulses may cause a pulling sensation on the skin under the coil and twitching in muscles of the arm or leg. Electrodes are taped to the skin over some muscles of the hands to record the electrical activity of the muscles. Pulses are delivered in trains or short bursts of impulses, each lasting half a second. Participants receive 90 trains for a total of 900 pulses. TMS is applied during the first part of the memory study, when the words and shapes are first presented on the computer screen, but not during the second presentation for memory testing. The entire procedure takes up to 2 hours, with breaks in between. 