We studied 4 epilepsy patients during presurgical evaluation. All patients had partial seizures defined by EEG recordings and behavior during seizures. The seizures were medically intractable, and the patients were evaluated with chronically indwelling subdural grids for definitive localization of the seizure focus. These patients were a subgroup of the patients in whom functional anatomy of somatosensory cortex was studied. For further details on the patients’ clinical seizure characteristics and lesion types see Section 4.1.1.1. All patients had given written informed consent to undergo invasive presurgical evaluation and to participate in the SEP studies.