Ten patients, who may be children or adults, will be recruited for this study. Brain activity will be measured while they move the corner of their mouth and their fingers, wrists, arms, and feet. The baseline measurements will be done with scalp electrodes. Once subdural electrodes have been placed, a second set of measurements will be done. Surface EMG electrodes will be placed on the muscles whose movements are being tested. The tests will be done on no more than 3 separate days, in sessions no longer than 2 hours, for each patient.