LARGER TOPOGRAPHICAL VARIANCE AND DECREASED DURATION OF BRAIN ELECTRIC MICROSTATES IN DEPRESSION

The topographical configuration of the spontaneous brain electric fiel ds is considered to contain relevant information about the pattern of the generating cortical electrochemical activation and the associated cognitive processes. Space oriented segmentation allows to break down the stream of the spontaneous EEG into brain electric microstates with stable configuration of the fields. It has been shown that the mean d uration of the microstates was consistent with the duration of element ary steps of cognitive processes, and that different topographies of t he microstates are associated with different cognitive modalities. Spa ce-oriented segmentation was applied to the resting EEG of 22 depressi ve patients and of 22 controls. The topographical variance was larger, and the most prominent brain electrical microstates of the EEG epochs were significantly shorter in the depressive group than in controls. No differences were found for the shortest microstates. This result ca nnot be explained by group differences in the frequency domain of the EEG. No topographical differences were found between the microstates o f depressives and those of controls. Based on previous results in heal thy volunteers during spontaneous cognition and in schizophrenic patie nts, the findings indicate that formal aspects rather than the modalit ies of the stream of cognition are altered in depression. Automatic an d schematic processing, and attentional deficits as described in depre ssive patients might account for the finding of less sustained brain e lectrical microstates.