We will use a 275-channel whole-head MEG System (CTF Systems 2001 Inc). Patients will undergo a supine resting MEG-EEG recording prior to any surgical procedure. The resulting data will be integrated with the data obtained during the patient's standard pre-surgical evaluation, and compared with the invasive data obtained during chronic invasive monitoring (if clinically indicated), and/or intra-operative electrocorticography (all patients-standard of care). When analyzing the data, readers will be blinded to the results of the other modality (MEG vs. EEG, non-invasive vs. invasive).