patients who were undergoing subdural grid implantation for seizure localization and chronically implanted with multicontact microelectrodes. They found that two distinct intracortical CSD/MUA patterns were related to the propagated interictal spikes: 1) a granular pattern with layer IV CSD sink and MUA onset, delayed CSD sink and MUA in layer III, and also delayed sources and MUA in layers V–VI; and 2) a supragranular pattern with a major layer I–III CSD sink with enhanced MUA, and later sinks and sources in the deep layers. In another intra-cortical EEG study by the same group of researchers, Fabo et al. (2008) implanted laminar microelectrodes at subiculum and lateral temporal lobe under anesthesia in drug-resistant epilepsy patients undergoing temporal lobectomy in order to understand mechanisms underlying generation, maintenance and propagation of epileptic activity. They identified two types of interictal spikes in the subiculum that were related to epileptic activity: 1) initial excitatory currents (CSD sink) in the pyramidal cell layer; and 2) later inhibitory currents (CSD source) along with decreased MUA. Finally, in a series of studies, it was found that CSD measures were more useful than traditional EEG measures to localize brain lesions as well as to characterize brain edema in patients
