due to variations in sample characteristics and other methodological factors (e.g., sample matching, signal processing parameters, etc.). Replication studies with identical methodology are required to validate the phenomena under study (e.g., sensory, cognitive, emotional phenomena) in a given neuropsychiatric condition and to arrive at CSD-based clinical markers. Further, most of the studies have made only a visual, qualitative comparison rather than a statistical or computational procedure to compare the CSD topographies between groups or conditions; however, some studies have used ANOVA to compare specific regions, and a few studies have used randomization tests to compare the whole topographies, e.g., Kamarajan et al. (2005) who have statistically compared whole CSD topographies between controls and alcoholics using randomization tests. It is suggested that application of statistical methods to compare topographic maps can provide objective and quantitative measures for comparison (e.g., effect size, cross-validation, etc.) and to help evaluate relative merits of CSD methods in comparison to traditional scalp potential maps. Furthermore, methodological improvements for the CSD techniques have been very rare and slow. One obvious exception to this limitation is the work by Kayser, Tenke and Colleagues, who have innovated some methods, for example, to extract PCA components of the CSD (Kayser
