| Objective:To explore neural basis of cognitive function impairment in both first-episode and recurrent patients with depression using blood oxygenation level dependent functional magnetic resonance imaging(BOLD-fMRI);to evaluate whether the patients with depression have brain metabolite changes using MRS,and to assess the correlation between abnormal metabotite ratio of MRS and WSCT which has been considered as the most classic cognitive test,and to explore the neuropathophysiologic mechanism of depression.Materials and Methods:21 patients with depression,in whom there were 12 first-episode patients(group 2 or first-episode group)and 9 recurrent patients(group 3 or recurrent group)and 12 age- and gander-matched healthy volunteers(group 1 or normal controls)were included in this study.Stroop task in Chinese character was used as target stimulus,which included two kinds of task:①congruous color-naming task②incongruous color-naming task.Block-design fMRI was used to acquire resource data,including 4 stimulus blocks and 5 control blocks,each block was alternatively present.Imaging analysis was performed using analysis of functional neuroimaging(AFNI),all the activating voxels in each task were recorded respectively.After fMRI examinations were over,behavior tests of Stroop interference were performed for all subjects.Overall reaction time and error numbers were recorded respectively.Further more,22 patients with depression,in whom there were 12 first-episode patients and 10 recurrent patients and 12 age- and gander-matched healthy volunteers were included in this study.All subjects performed WCST before MR examination.MRS data in bilateral prefrontal lobe and cingulated cortex were acquired by point-resovled echo spin spectroscopy(PRESS) sequence of single voxel 1-hydrogen MRS.The software automatically completed metabolite content measurement,giving the ratio of all metabolite using Cr as a reference,including NAA/Cr,Cho/Cr,mIns/Cr,Glx/Cr.Results:①Behavior performance results:Subjects of three groups all need more reaction time when performed incongruous color-naming task than that of congruous color-naming task(P＜0.01).In the congruous color-naming task,subjects of three groups showed no significant difference in reaction time,while in the incongruous color-naming task patients both with first-episode and recurrent depression need more reaction time(P＜0.01).Subjects of three groups all had more errors when performed incongruous color-naming task than that of congruous color-naming task(P＜0.01).Both first-episode and recurrent depressive patients had more errors in performing incongruous color-naming task than health controls(P＜0.01),and without significant differecens in performing congruous color-naming task.There were no significant differences in reaction time as well as in error numbers in patients both with first-episode and recurrent depression.②Activated cerebral functional cortex and activated voxets:When normal controls performed congruous color-naming task,bilateral superior frontal gyrus,bilateral middle frontal gyrus,bilateral inferior frontal gyrus,bilateral parietal and temporal lobes were activated;while when they performed incongruous color-naming task,the activated voxels that mentioned above in congruous color-naming task were increased,especially in right superior frontal gyrus,left inferior frontal gyrus,left superior parietal lobe and left precuneus(P＜0.05),and there were also some other cortex were activated,including cingulate gyrus and anterior cingulated gyrus. Bilateral superior frontal gyrus,bilateral middle frontal gyrus,bilateral inferior frontal gyrus,left medial frontal lobe,bilateral cingulate gyrus and anterior cingulated gyrus, bilateral parietal and temporal lobes were activated in patients both with first-episode and recurrent depression when they performed congruous color-naming task;when performed incongruous color-naming task,larger activated voxel in left prefrontal lobe than that of congruous color-naming task in both first-episode and recurrent depression,and the voxel in left middle frontal gyrus increased significantly in patients with first-episode depression(P＜0.05),while the voxel in left superior frontal gyrus and left middle frontal gyrus increased significantly in patients with recurrent depression(P＜0.05).except for that,first-episode depressive patients showed increased activated voxel in bilateral precuneus(P＜0.05),and recurrent patients showed increased activated voxel in left inferior parietal lobule,right precuneus and left cuneus(P＜0.05).We compared activated symmetrical functional cortex in each group during each task.In normal controls,the activated voxels of symmetrical functional cortex in both task were no significant differences (P＞0.05).In congruous color-naming task,the activated voxets in left middle frontal lobe were larger than those of right side in both first-episode and recurrent depressive patients(P＜0.05).In congruous color-naming task,first-episode depressive patients showed meddile frontal lobe activated voxels larger in left side than those of right side(P＜0.01),and recurrent depressive patients showed both meddile and inferior frontal lobe activated voxels larger in left side than those of right side(P＜0.05).③Compared with normal controls,decreased Glx/Cr(P＜0.01)and increased mIns/Cr (P＜0.05)in both bilateral prefrontal lobes were detected in patients with recurrent depression,while,decreased Glx/Cr(P＜0.05)in bilateral prefrontal lobes and increased mIns/Cr(P＜0.05)in right side were detected in first-episode patients.There were no significant difference between first-episode and recurrent depressive patients, except that the recurrent patients shows higher mIns/Cr in left prefrontal lobe.④Compared with normal controls,the depressive patients had higher RA(P=0.01),PE (P＜0.01)and NPE(P＜0.05)in WCST,but the was no significant difference between first-episode and recurrent depressive patients.⑤Glx/Cr of right prefrontal lobe correlated negatively with PE of WCST significantly(r=-0.744,P＜0.05)in the first-episode patients with depression.Glx/Cr of bilateral prefrontal lobes all correlated negatively with PE of WCST significantly(r=-0.79,P＜0.05;r=-0.71, P＜0.01)in the recurrent patients with depression.Conclusion:①behavior data and fMRI results have demonstrated that the patients both with first-episode and recurrent depression all have cognitive impairment.The abnormal brain network of cingulated-prefrontal cortex-parietal lobe and the functional imbalance of bilateral prefrontal lobe are the neural basis of cognitive impairment of patients with depression.②there is no evidence both in behavior data and fMRI results shows that cognitive impairment of patients with recurrent depression more sever than those of with first-episode ones.③compared with normal controls,depressive patients have an abnormal metabolite changes in bilateral prefrontal lobes.Recurrent patients are present with decreased Glx/Cr and increased mIns/Cr in bilateral prefrontal lobes,and first-episode patients are present with decreased Glx/Cr in bilateral prefrontal lobes and increased mIns/Cr in right prefrontal lobe.Except for the higher mIns/Cr in recurrenct patients than in fist-episode patients,there are no significant metabolite difference between these two groups.④compared with normal controls,patients both with first-episode and recurrent depression all have higher RA,PE and NPE in WCST,but there were no significant difference between first-episode and recurrent depressive patients.⑤Glx/Cr of right prefrontal lobe correlated negatively with PE of WCST significantly in the first-episode patients with depression.Glx/Cr of bilateral prefrontal lobes all correlated negatively with PE of WCST significantlyin the recurrent patients with depression.These all indicate that glutamatergic systems dysregulation may be the pathophysiology basis of cognitive impairement of pantients with depression. |
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