Chunk #57 — 3. Impact of spatial scale on CSD implementations — 3.3. Empirical considerations for planar (two-dimensional) scalp-recorded EEG — 3.3.2. CSD as a conservative description of neural current generators
With these cautions in mind, it is nevertheless instructive to compare CSD topographies with inverse-based simplifications. Fig. 5 illustrates the field potential topography corresponding to a single equivalent dipole located in the vicinity of the left primary auditory cortex, placed manually to approximate the group-averaged N1 topographies shown in Fig. 3. The topography was produced by Dipole Simulator (Berg, 2006), a forward-solution using the same volume-conduction model used by BESA, referenced to the estimated potential mean over the surface of the sphere. The resulting current sinks immediately anterior to the Sylvian fissure and sources posterior to it are not surprising for this austere model, because the generator was positioned to approximate this characteristic topography. The resulting source topographies are also represented in the corresponding sLORETA solution, although an uncritical interpretation of the sLORETA solution might suggest a contribution from the cortical gray matter throughout the temporal lobe.
