A FMRI Study On Default-mode Network Of First-episode Patients With Major Depressive Disorder Before And After Electroconvulsive Therapy

PART ONE A f MRI study on default-mode network of first-episode patients with major de pressive disorderObjective To investigate the change of the functional connectivity（FC） of default mode network（DMN） in first-episode, treatment-naive patients with major depressive disorder（MDD） us ing resting-state functional magnetic resonance imaging（rs-f MRI）, and to preliminarily discuss the role of DMN in the pathogenesis of depression.Methods Twenty-four first-episode, treatment-naive patients with major depressive disorder and twenty-five health control subjects underwent rs-f MRI scan and 24-item Hamilton depression rating scale(HDRS₂₄). Then to select respectively DMN component of two groups using independent component analysis（ICA）, and to analys is the difference between two groups using two samples t-test. Finally, the Pearson partial correlation was made between HDRS₂₄ scores and every regions changed in DMN by extracting value of FC in depression group.Results HDRS₂₄ scores were higher significantly in patients with MDD compared with health control subjects（t= 23.756,P=0.000）.Compared with control group, the FC of DMN in depression group decreased in right middle occipital gyrus, and increased in right inferior parietal lobule, bilateral precuneus and posterior cingulated cortex（FEW-corrected, P<0.01, clusters>50）. There were negatively correlation between FC in right middle occipital gyrus and HDRS₂₄ scores（r=-0.440,P=0.046）, but no correlation between FC in right inferior parietal lobule（r=0.256,P=0.211）, bilateral precuneus and posterior cingulated cortex（r=0.278,P=0.174）and HDRS₂₄ scores.Conclusion The functional connectivity of DMN in patients with MDD was changed, and this may play a key role in the pathogenesis of MDD.PART TWO A f MRI study on default-mode network of first-episode patients with major de pressive disorder before and after electroconvulsive therapyObjective To investigate the change of the functional connectivity of default mode network（DMN） in first-episode,treatment-naive patients with major depressive disorder（MDD） before and after electroconvuls ive therapy（ECT） using resting-state functional magnetic resonance imaging（rs-f MRI）.Methods First, Twenty-four first-episode, treatment-naive patients with MDD（before and after ECT） and twenty-five health control subjects underwent rs-f MRI scan and HDRS₂₄. Then to select the DMN component of patients with MDD before and after ECT and controls using independent component analys is（ICA）, and to compare the differences between before and after ECT using paired samples t-test and the difference between after ECT and control group using two samples t-test. Finally, to respectively analyze the correlation between the brain regions changed in DMN and HDRS₂₄ scores before and after ECT.Results HDRS₂₄ scores were lower significantly after ECT in patients with MDD（t=13.975, P=0.000）. Compared before ECT, the functional connectivity of DMN after ECT increased in the left angular gyrus（P<0.01,clusters>10）, and decreased in left middle temporal gyrus, right precuneus and left medial prefrontal cortex（P<0.01,clusters>10）. Compared control group, the functional connectivity of DMN after ECT increased in right inferior parietal lobules, bilateral precuneus and posterior cingulated, and had no brain regions decreased（P<0.01,clusters >50）. There were no significantly correlation between the changed brain regions in DMN and HDRS₂₄ scores before and after ECT（P>0.05）.Conclusion The functional connectivity of DMN of the patients with MDD after ECT was partly reversed, and this may be the important neuromechanism of ECT.