Background: Dysfunctions of neuronal circuits are involved in the pathophysiology of depression.
The aim of the study was to investigate patients with major depression (MD) and matched
controls using resting state EEG with respect to spectrotemporal dynamics of brain
electric activity and connectivity. A subsample of patients undergoing electroconvulsive
therapy (ECT) was investigated accordingly, in order to evaluate functional effects
of ECT. Methods: The sample comprised 228 patients with MD, 215 matched healthy subjects, and 20 depressed
subjects before and under ECT. Spectro-temporal dynamics during resting state were
analysed in sensor and source space. Quantitative measures of power, asymmetry, coherence,
current density and brain connectivity were calculated from artifact free EEG epochs.
Results: Compared to controls patients showed an increase in delta, theta and alpha power
in all brain regions with a frontal focus and significant hemispheric differences
(l>r). There were increased connectivity measures for frontotemporal and parietal
regions. Patients under ECT showed an increase in frontal slow activity, but a decrease
in frontal hyperconnectivity. Conclusion: Dysfunctions of frontal cortical networks together with alterations of functional
connectivity (hyperconnectivity) may contribute to the pathophysiology of major depression.
These alterations appear to be influenced by electroconvulsive therapy.
