Estimation of large scale neocortical source activity with EEG surface Laplacians.

Relationships between neural current sources recorded at different spatial and temporal scales are considered. A number of computer simulations using a three-concentric spheres model of the head are used to illustrate relationships between distributed neocortical sources at the macrocolumn scale and resulting scalp potentials. Computer simulations also illustrate the advantages of calculating surface Laplacians which are more sensitive than potentials to local sources. Surface Laplacians of interictal, epileptic spikes and auditory evoked potentials (including P300) are presented as examples of this sensitivity.