Depression-related Brain Connectivity Emerged By Phase Synchronization

Depression is a affective disorder. The incidence of this disease is high. EEG can reflect different state of brain, including abnormal state. So it is a commonly used tool in clinical psychiatric examination. Our research hope that some different EEG features between normal people and depression can be found. So that we can understand the mechanism of depression disease deeply and it is help to diagnosis and to evaluate the therapeutic effect.To identify the abnormal brain connectivity for depression, the synchronous activity of brain was investigated in depressive disorder. In this study, Sixty-four-channel event-related potentials(ERP,event-related potential) were acquired during a visual oddball task in patients with depressive disorder and healthy subjects.Finally, the EEG data were computed using event-related phase coherence(ERPCOH,event-related phase coherence) to get the brain functional network of coherences.10 patients with depression disorders were compared with 10 healthy controls to identify alteration of phase synchronization index(PSI, phase synchronization index) of brain functional network.We found that decreased number of scalp significant electrode pairs in delta phase synchronization, and increased number of scalp significant electrode pairs in theta, alpha and beta phase synchronization in depressive patients. In overall increase of PSI among all significant pairs in delta frequency bands, the significant PSI increase in depression disorders was lower than that in healthy subjects. In theta, alpha and beta frequency bands, the overall PSI increase in depression disorders showed significant enhancement compared with that in healthy subjects.Depressive patients showed lower evoked PSI increase in the fronto-parietal-occipital electrode pairs in delta frequency band than healthy subjects, but showed higher evoked PSI increase in the frontopolar–central- temporal sites for the theta frequency band, and higher evoked PSI increase in frotopolar sites for alpha frequency band,and higher evoked PSI increase in the left parietal regions and right hemisphere for the beta frequency band than healthy subjects. In depressive disorder, the present study identify:(a)decreased PSI of the delta band activity in depressive patients, which might affect the circuit of frontal, parietal, temporal and occipital region to produce P3b;(b) increased frontal andprefrontal PSI of theta, alpha and beta band activities which may operate to the detriment of delta brain processing. This may provide a new method to explain the metastable dysregulation in target discrimination process in depressive patients.