the relative magnitudes of different spatial frequencies (i.e., the surface Laplacian transform acts as a spatial filter) are not affected by different brain-to-skull conductivity ratios. Most importantly, however, surface Laplacian estimates based on more rigid splines become gradually more sensitive to broader dipole layers (approximate maxima for m = 4–7 were 5, 7, 8 and 9 cm, respectively; Fig. 15C and D). Thus, the sensitivity of spherical spline SL estimates varies with the spline flexibility constant, with m = 7 closely corresponding to the spatial scale of surface potentials, and these relations are also not affected by different brain-to-skull conductivity ratios.
