inhibitory currents (CSD source) along with decreased MUA. Finally, in a series of studies, it was found that CSD measures were more useful than traditional EEG measures to localize brain lesions as well as to characterize brain edema in patients with space-occupying brain lesions (Harmony et al., 1993; Fernandez-Bouzas et al., 1995, 1997). Harmony et al. (1993) found that the volume and density of the brain edema showed a significant correlation with Laplacian estimates of the absolute power of theta and alpha band, and further observed that spectral parameters obtained from the Laplacian estimates showed higher correlations with neuroimaging measures (computed tomography) than those calculated from the EEG potentials. They also found that Canonical correlations with the volume and the density of the edema showed a significant correlation with delta, theta and alpha power of scalp voltage and only with theta and alpha power computed from CSD. The authors explained that the absence of correlation with CSD delta power may 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
