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In previous quantitative EEG studies of depression, mostly patients with a lifetime history of depressive disorders were reported. This study examined quantitative EEG parameters obtained in the early stages of depression in comparison with age-matched healthy controls. EEG was recorded using two different montages in eyes closed and eyes open resting states. A significant increase in spectrum power in theta (4-7.5 Hz), alpha (7.5-14 Hz), and beta (14-20 Hz) frequency bands was found in depressed patients at parietal and occipital sites, both in eyes closed and eyes open conditions. These results suggest that an increase in slow (theta and alpha) activity in the EEG pattern may reflect a decreased cortical activation in these brain regions. Enhancement of beta power may correlate with anxiety symptoms that most likely play an important role on the onset of depressive disorder.

Electroencephalographic (EEG) findings on depressive patients indicate theta and alpha activity higher than in normal controls. Extensive literature reports on the effectiveness of neurofeedback techniques in the treatment of cognitive and behavioral disorders by training the patients to modulate their brain activities, as reflected in their electroencephalogram. Three unmedicated, depressed individuals participated in this study of infra-low frequency neurofeedback (ILF NF) training. Along with the pre-and posttreatment Depression Rating Scales assessment, quantitative EEGs (qEEG) were recorded in eyes-open and eyes-closed resting states and during the visual cued Go/NoGo task before and after 20 sessions of training. Along with remission of the clinical symptoms of depression, significant decrease of theta power over frontal and central areas was observed in all three patients under all test conditions. These qEEG dynamics might be a correlate of ILF NF-related recovery of the appropriate level of frontal cortical activation.Keywords: neurophysiology; neurofeedback; depression; qEEG; infra-low frequency