The scalp surface Laplacian is an alternative way of viewing EEG data with higher spatial resolution. It is most closely related to the local current density flowing radially through the skull into the scalp.
EGI’s Technical Note “Theory and Calculation of the Scalp Surface Laplacian” discusses further the motivation for using the scalp surface Laplacian in EEG research and its algorithmic computation.
The surface Laplacian is calculated based on spline interpolation, and is also affected by the choice of the reference.
The calculation of the surface Laplacian is a feature implemented in Net Station Review through the Current Density button.