Abstract: A method of estimating potential distribution over a cortical surface of a brain of a subject is disclosed. The method comprises: obtaining encephalogram (EG) data recorded from a scalp surface of the head, and head model data describing a geometry of the head and electrical property distribution of tissues within the head. The method further comprises calculating differentials of the EG data over the scalp surface, calculating volumetric distribution of electrical potential between the cortex and scalp surfaces using the EG data and the differentials, and estimating the potential distribution over the cortical surface based on the volumetric distribution.