& Tenke, 2012), these other references are thought to index both proximal (frontal) and distal (parietal and occipital) sources, so it is not surprising that discrepant findings emerged for resting data as a function of reference mode. CSD is advantageous as a reference-free algorithm that eliminates volume conduction contributions to EEG alpha power, and in contrast to conventional scalp EEG reference measures, results in unambiguous indices of current sources underlying EEG topography (Kayser & Tenke, 2012). Findings of the present study indicate that CSD-transformed EEG asymmetry may be a liability marker, identifying a vulnerability to develop depression, since its reduced relative left frontal activity characterizes depressed individuals independent of emotional state (during approach and withdrawal conditions as well as at rest, and independent of current levels of depression severity, see Stewart, Bismark, et al., 2010). In contrast to resting EEG results, which reflected some inconsistencies as a function of reference and gender differences, EEG findings from the emotional challenge task demonstrated consistent findings across all four reference modes, consistent with the idea that emotional challenges produce much more powerful asymmetry effects that overcome method variance.
