Electroencephalographic (EEG) signals derive from the action of neuronal activity in the cerebral cortex, through the action of synchronously occurring post-synaptic potentials of neuronal masses (De Munck et al., 1992). Forming reciprocal combinations of interacting excitatory and inhibitory populations, these neuronal masses are believed to be the sources of the macroscopic EEG signal recorded on the scalp (Freeman, 1975; Wilson & Cowan, 1973; Lopes da Silva & van Leeuwen, 1978). In individuals with epilepsy, seizures emerge from ongoing cortical activity through incompletely understood mechanisms, but are likely related to a wide variety of biochemical, anatomic, physiologic, or genetic aberrations (Avanzini & Franceschetti, 2003; Bragin et al., 2002; D’Ambrosio et al., 2004; D’Ambrosio et al., 2005; Nemani & Binder, 2005; Noebels, 2003; Shah et al., 2004; Stables et al., 2002; White 2002). For over 50 years the paroxysmal EEG signals (“spikes” or “sharp waves”) recorded on the scalp, reflecting the abnormal behavior of cortical neuronal populations, have remained the most important laboratory findings in the clinical evaluation of patients with epilepsy (Niedermeyer, 1999). However, despite the indispensable role of the EEG, the standard assessment has significant limitations. Typically, 16-21 electrodes are placed over the upper portions of the cranium, and under these circumstances distances between individual electrodes are several cm, resulting in inadequate spatial resolution, and an even poorer assessment of cortical activity in basal brain regions. Research on the spatial frequency spectrum suggests that to maximize spatial information of the human EEG (“spatial Nyquist”), interelectrode distances on the cortical surface must be within 1.25 mm (Freeman et al, 2000), and on the scalp, less than 10 mm (Freeman, 2003). As a consequence, analysis of standard EEG recordings yields poor spatial resolution, often results in failure to detect significant pathology, and provides only limited insight into the extent of the involved cortical network and patterns of discharge propagation. It is anticipated that when detailed knowledge of the specific cortical regions activated during epileptiform discharges becomes readily available, that such information will prove to be critical in understanding the nature of an individual subject’s seizures and in improving therapy (Spencer, 2002). Major technological advances are becoming available and will likely change the role and utility of scalp-recorded EEG. One of these advances is the capability for rapid application of a dense array of electrodes, a technique that may also now be employed in the context of