Fourteen (14) patients will undergo epilepsy surgery with expected subdural grid coverage over primary motor cortex. Potential subjects will be identified at the weekly multi-disciplinary epilepsy conference. Subjects must have a recent (<2 years) MRI scan, and registration of the TMS coil to the MRI scan via the Brainsight neuronavigation system will be utilized to guide TMS coil placement (Gugino et al 2001). When a presurgical fMRI (functional magnetic resonance imaging) is available which demonstrates the patient's hand knob, the fMRI will be used with the Brainsight neuronavigation system. Subjects will be recruited and consented during a presurgical clinical visit where the patient's primary epileptologist will introduce members of the research team.