IntroductionDyfunctions of prefrontal neuronal circuits contribute to the pathophysiology of depression. Previous studies showed increased functional MRI and EEG connectivity in patients with depression. In this study we investigated a large sample of patients with major depression (n=228) and healthy subjects (n=215).MethodsSpectrotemporal dynamics during resting state with closed eyes were analyzed in sensor and source space to examine functional EEG connectivity (fcEEG) alterations between groups. Quantitative measures of delta, theta, alpha, beta and gamma power, hemispheric asymmetry, coherence, phase and current source density (CSD, eLORETA) analyses were calculated from artifact-free EEG recordings.ResultsEEG theta power was increased in all brain regions in the group of patients with a focus in frontal regions and increased frontal theta and alpha power. Excessive coherence differences were detected in the delta, theta and alpha-bands in frontal, frontal-temporal and frontal-parietal regions. There were changes in phase differences in the delta, theta, alpha-bands between patients and healthy subjects. Differences in CSD were found for the delta, theta, alpha-band in the (rostral and subgenual) anterior cingulate cortex (ACC) with increased CSD in the patients.ConclusionThe main finding of the present study was an increase in cortical slow-wave activity in sensor and source space in patients with depression revealing marked differences in prefrontal cortical networks. Functional delta, theta and alpha connectivity (coherence and phase) were altered with a predominance in the left hemisphere. Dysfunctions of the ACC, together with alterations in fcEEG may contribute to the pathophysiology of major depression.