Surface energy, its density and distance: new measures with application to human cerebral potentials.

In this paper, we propose three new measures for topographic studies of event related potentials (ERP) called the surface energy (SE), its density (SED) and the distance of surface energy density fields (DSED) based on the entire scalp current density (SCD) field. These measures have a specific physical meaning, are free of the reference electrode and any physical conductive model of the head. They capture not only spatial properties, but also continuous time elements present and smeared in the original scalp potential records. They provide a common base for comparisons of recorded potentials among different time points, subjects, regions on the scalp, or experimental conditions. We also construct a statistical inference based on these new measures, and provide an application to human event-related potentials in a visual short-term memory experiment.