CSD analysis is the simplest of a number of generator localization approaches based on the volume conduction model, which may be expressed as a vector form of Ohms law: (1)J=σEwhere J is current flow density, E is the electric field (i.e., gradient of the measured field potential) and σ is the conductivity tensor of the medium. The most concrete application of Equation (1) is a direct simplification in the form of Poisson’s source equation, which allows the quantification of current generators (sources and sinks) in intracranial (CSD laminar profile of cortical regions) or scalp data (surface Laplacian; radial scalp current density1). This relationship applies equally to measured and inferred intracranial fields, and thereby provides a common, multiresolutional framework into which findings from scalp ERPs, inverse models (e.g., brain electrical source analysis (BETA), low resolution brain electromagnetic tomography (LORETA)), and intracranial studies may be integrated (Tenke & Kayser, 2005).
