The primary goal of this proposal is to study the dynamics of the transition from interictal to ictal state (ictogenesis). Using novel recording methods developed in our laboratory we have accumulated significant experience and ability to investigate human epileptogenic brain across the relevant range of spatial and frequency scales involved in the transition from normal brain activity to seizures. Using hybrid electrodes containing clinical macroelectrodes and microwire arrays we have identified three quantitative signatures of epileptogenic brain that are outside the range of conventional clinical intracranial EEG (IEEG). Decades of clinical IEEG using a restricted spatial and frequency bandwidth have often frustrated epileptologists looking for discrete, resectable electrographic lesions during evaluation for epilepsy surgery. Additionally, recent efforts to utilize direct brain stimulation t abort detected seizures have meet with only partial success. The inability to disrupt seizures after they are sufficiently established to be detected on millimeter scale macroelectrodes may explain the marginal efficacy of brain stimulation. Recent work by our group suggests that a significant impediment to localizing and controlling epileptic networks may be the narrow recording bandwidth (~0.5 - 100 Hz) and large, widely spaced electrodes used in conventional IEEG that have led to the paradigm that seizures occur as large-scale paroxysmal events. In this application, we will analyze continuous, wide-bandwidth iEEG across the relevant range spatial scales in order to probe and localize human epileptic networks and track ictogenesis. This work builds on our established effort in Translational Neuroengineering, melding state of the art epilepsy care with Engineering and Neuroscience at the Mayo Clinic.