The Study On The Neural Mechanism In The Process Of Depression

Depression’s main characteristic are black mood and lack of pleasure, there is fatigue, concentration, no value, suicidal ideation and other symptoms.Depression has become the world’s fifth largest disease, become the leading cause of disabled people over the age of five.It not only bring a heavy economic burden for the family and the whole society, but also have a seriously effect on the individual social, work, and the field of other important function. Past studies on the pathogenesis of depression has made great progress.The study found that depression may have negative deviation, processing bias, memory bias and so on;Brain imaging studies also show that depression is a top-down control system coordinated with the mood of the machining system from bottom to top. However, depression has a higher recurrence rate, suggesting that the pathogenesis of depression is not yet clear.Previous studies of depression in patients with brain structural abnormalities are unilateral, choose a type of depression patients compared with control group, concluded some different brain regions, those results are not consistent;And previous studies using morphological analysis structure based on voxel, some study shows that this method is not very good reflect the essential attribute of the cerebral cortex.Therefore, in this study we selected the cortical gray matter volume as indicators of structural abnormalities to explore depression structural abnormalities of brain regions (researches show that gray matter volume can better reflect the essential attribute of cortex); At the same time, in order to explore the depression’s core abnormal brain regions, for the first time we study depression patients in different stages of depression (the starting stage withnot treament, with treatment and recurrence); In addition, in order to explore the brain function in patients with depression, we chose the use Amplitude of low frequency fluctuation (ALFF) and Regional Homogeneity (ReHo) as two indicators to explore brain function in depression.The experiment is divided into two parts:Experiment one:To investigate the common structural lesion in brain areas and abnormal brain areas in the covariant network in the process of depression, we collected 235 depression patients’(including 188 first-episode depression patients and 43 recurrence depression patients) and 223 control subjects’3D T1 data structure. First, using structure data, calculate the volume of gray matter of each participant.To compare the abnormal brain size in the different process of depression, we divided the depression patients into three groups:first-episode patients without medication, first-episode patients with medication, and a group of patients with recurrence.Then, we used the linear model analysis, treat the age, gender, education level and intracranial volume as regression.The results show that compared with control group, the superior parietal gyrus is increased significantly in all the patients. In addition, the prefrontal area is shink in the patients with recurrence. Then, to explore the abnormal brain areas in the covariant network in the process of depression, the superior parietal gyrus was choosen as a seed point on in the covariance structure analysis. Results show that, compared with control group, the abnormal covariance structure of the network was shown in the first-episode patients without medication, this abnormal frontoparietal structure covariant network disappeared was shown in the group of first-episode patients with medication. Compared with control group, the abnormal frontoparietal structure covariant network was shown in the group of patients with recurrence.Experiment two:In order to provide a further study on the internal mechanism, we collected 235 depression patients’(including 188 first-episode depression patients and 43 recurrence depression patients) and 223 control subjects’functional data. We compared the depression and the control group on the index of the Amplitude of low-frequency fluctuation (ALFF) and Regional Homogeneity (ReHo) respectively. The results found that, compared with the control group, the the ALFF and ReHo index of depression patients’parietal gyrus, were significantly weakened.Combined with the results of those two experiments, we found that the single, recurrence, medication and unmedicated depressed patients were bigger than the control group in the superior parietal gyrus. While the function of the superior parietal gyrus is to alert and oriented in cognitive processes in the human space searching, we deduced that the superior parietal gyrus’volume is larger, its function is more weak according to the previous proposed cell pruning theory; in addition function analysis we also proves that the activity intensity and the local consistency of the superior parietal gyrus are clearly decreased. Key brain regions according to the above results we concluded that the superior parietal is the key abnormal brain region of depression patients. The structure covariance network analysis found disruption of frontoparietal structural brain networks in different periods of depression patients. Finally, through comparison between medication group and non medication group, comparison between medication group and the control group, comparison between non medication group and the control group, we infer that depression drugs have an effect on the connection of frontoparietal structural brain networks, and have little effect on the key brain region of the superior parietal. In depression, frontoparietal structural brain networks is a negative note commander, parietal gyrus is responsible for negative attention scouts. The the superior parietal gyrus is abnormal in various symptoms of depression shows that it could be the key region of depression. And now the depression treatment has an effect to the commander, but has no effect on the Scout, This may explain the reason why depression patients are repeated usually.