Kenneth Robert Evans

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 affective disorders. In an attempt to examine the role of gender and widen the scope of the measurement probes used in these investigations, the traditional power and inter-hemispheric power ratio indices were supplemented with intra-hemispheric power ratios, mean frequency and both inter and intra-hemispheric coherence indices, in the comparison of depressed male patients and healthy controls. Resting (eyes closed), vigilance controlled EEG recordings from 21 scalp sites were collected from 70 male, unmedicated, unipolar major depressive disorder outpatients and 23 normal control male subjects. Absolute and relative power, frequency, asymmetry and coherence measures derived from spectrally analyzed EEGs were subjected to univariate analyses for group comparisons as well as to discriminant function analysis to examine their utility as classification indices. Compared with controls, patients evidenced greater overall relative beta power and, at bilateral anterior regions, greater absolute beta power and faster mean total spectrum frequency. Inter-hemispheric alpha power asymmetry index differences were noted, with controls exhibiting relatively reduced left hemisphere activation, and widespread reduced delta, theta, alpha and beta coherence indices. Whereas intra-hemispheric theta power asymmetry reduction was exhibited in patients bilaterally at all regions, group differences with intra-hemispheric beta power asymmetry were unilateral, being restricted to the right hemisphere. Discriminant analysis correctly classified 91.3% of the patients and controls. Quantitative EEG measurements in male depression appear to describe a pattern of aberrant inter-hemispheric synchrony/asymmetry and a profile of frontal activation.

EEG correlates of acute and chronic paroxetine treatment in depression

Single dose administration of efficacious antidepressant agents elicit characteristic pharmaco-electroencephalographic (EEG) profiles in healthy volunteers but acute and chronic pharmaco-EEG profiling of antidepressant action in depressed patients has been relatively lacking. This study sought to examine the quantitative topographic EEGs of depressed patients in response to paroxetine treatment. Thirty male patients, meeting DSM-IV criteria for major depression, were examined before and after a single 20 mg dose. These, and an additional 40 patients, were also assessed following 6 weeks of treatment. Eyes-closed resting EEG, collected from 21 scalp sites, was spectrally analyzed to yield regional measures of absolute/relative power and mean frequency in delta, theta, alpha, beta and total spectrum frequency bands. Chronic treatment resulted in a significant reduction in scores on the Hamilton Rating Scale for Depression (HAM-D), with 80% of treatment completers exhibiting a >50% reduction in depression ratings at the end of the 6th week. Acute paroxetine did not alter EEG in patients but chronic treatment was associated with significant alterations as shown by diffuse decreases in alpha power and increases in slow (delta and theta) and anterior fast (beta) wave power, Mean theta and alpha (occipital) frequency were slowed while mean total frequency was accelerated at frontal sites and decreased at occipital sites. The chronic pharmaco-EEG response pattern reflects both sedating and activating actions in regional specific areas which are relevant to the pathophysiology and the pharmacotherapeutic treatment of depression.