The surface Laplacian of the potential: theory and application

The use of the surface Laplacian of the potential (L/sub s/) in bioelectricity is discussed. Different estimates of L/sub s/, in particular the field measured by coaxial electrodes, are compared to that of the true Laplacian. A method to compute L/sub s/ on the surface of an inhomogeneous volume conductor of arbitrary shape resulting from assumed electrical sources is introduced. In two applications the sensitivity of the body surface Laplacian is compared to that of body surface potentials. This comparison is carried out for dipolar sources within the human brain as well as for distributed sources within the heart.