EEG power, frequency, asymmetry and coherence in male depression

Quantitative electroencephalographic (EEG) power topography has served as a useful tool for investigating brain regional mechanisms underlying affecti ve disorders. In an attempt to examine the role of gender and widen the sco pe of the measurement probes used in these investigations, the traditional power and inter-hemispheric power ratio indices were supplemented with intr a-hemispheric power ratios, mean frequency and both inter and intra-hemisph eric coherence indices. in the comparison of depressed male patients and he althy controls. Resting (eyes closed), vigilance controlled EEG recordings from 21 scalp sites were collected from 70 male, unmedicated, unipolar majo r depressive disorder outpatients and 23 normal control male subjects. Abso lute and relative power, frequency, asymmetry and coherence measures derive d from spectrally analyzed EEGs were subjected to univariate analyses for g roup comparisons as well as to discriminant function analysis to examine th eir utility as classification indices. Compared with controls, patients evi denced greater overall relative beta power and, at bilateral anterior regio ns, greater absolute beta power and faster mean total spectrum frequency. I nter-hemispheric alpha power asymmetry index differences were noted, with c ontrols exhibiting relatively reduced left hemisphere activation, and wides pread reduced delta, theta, alpha and beta coherence indices. Whereas intra -hemispheric theta power asymmetry reduction was exhibited in patients bila terally at all regions, group differences with intra-hemispheric beta power asymmetry were unilateral, being restricted to the right hemisphere. Discr iminant analysis correctly classified 91.3% of the patients and controls. Q uantitative EEG measurements in male depression appear to describe a patter n of aberrant inter-hemispheric synchrony/asymmetry and a profile of fronta l activation. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.