A method of identifying an epileptogenic zone of a subject's brain includes receiving a plurality of electrical signals from a corresponding plurality of surgically implanted electrodes, calculating a first plurality of connectivities between each pair of electrodes based on a portion of each of the plurality of electrical signals corresponding to a first time period, assigning a rank corresponding to each electrode for the first period of time based on the first plurality of connectivities to provide a first plurality of ranks, calculating a second plurality of connectivities between each pair of electrodes based on a portion of each of the plurality of electrical signals corresponding to a second time period, assigning a rank corresponding to each electrode for the second period of time based on the second plurality of connectivities to provide a second plurality of ranks, identifying a cluster of electrodes among the plurality of electrodes based on relative changes between the first plurality of ranks from the first time period and the second plurality of ranks at the second time period, and identifying the epileptogenic zone based on the cluster of electrodes.