Surface Laplacian with spline and nearest neighbour interpolations for topographic brain mapping

In the construction of topographic maps from the EEG, the Laplacian (or Source Derivation) operation improves the localisation of sources, by reducing the smearing effect in conducting layers of the head. Due to the use of a limited number of electrodes, interpolation techniques are employed either before or after applying the Laplacian. In the present work, two such approaches, Spline interpolation followed by Laplacian and Laplacian followed by four nearest neighbour interpolation, are applied to scalp potential distributions derived from simulated dipole sources. The results prove both approaches to be similarly effective in demonstrating the presence of multiple dipoles