be due to the fact that the Laplacian acts as a spatial filter which provides more weightage to local generators over distant ones. In another study by the same group of researchers (Fernandez-Bouzas et al., 1995), lesions (brain tumors) were better detected by CSD maps of the delta band, while brain edema was better represented by CSD maps in the theta range. Furthermore, in their follow-up study, Fernandez-Bouzas et al. (1997) measured the changes in the CSD and voltage measures of the EEG in relation to the volume of the lesions as well as the edema as measured by the CT scans in patients with space-occupying lesions before and after treatment. They found that the volume, site, and size of the lesion and edema were better represented by CSD maps than by voltage maps and suggested that more precise characterization (e.g., localization) of brain lesions can be obtained by CSD than by voltage estimates.
