Study On Brain Functional Network Of Reward Dysfunction In Unipolar And Bipolar Depression Disorders

Unipolar disorder(UD)and bipolar depression disorder(BDD)are two common mental disorders characterized by deficits in emotion,cognition,behavior,and psychomotor.The specific clinical symptoms are long-term depression,loss of interest,anhedonia,mental retardation,memory loss and so on.BDD is more complex than UD,depression and mania occur alternately,the mood fluctuations and fluctuations are large.The etiology of BDD and UD is complex,and the pathogenesis of BDD and UD is still unknown.In addition,the clinical symptoms of BDD and UD are similar,resulting in a high rate of clinical misdiagnosis.Therefore,it is urgent to find objective neural markers to distinguish BDD from UD.In recent years,resting functional magnetic resonance imaging has been widely used in the exploration of the pathological mechanism of various mental diseases due to its non-invasive and high resolution features.In this paper,the brain connection patterns of reward networks in BDD and UD patients were analyzed based on magnetic resonance imaging.Functional connectivity and effective connectivity were used to compare the connectivity patterns between the reward networks of BDD and UD patients and other brain regions and internal nodes of reward networks,and the relationship between abnormal connectivity and depression severity and anhedonia was analyzed to explore the potential pathologic mechanisms of the two diseases.This paper mainly includes the following two parts:1.The dynamic functional connection analysis method was used to construct the dynamic functional connection network from reward system to the whole brain and analyzed whether there was abnormal dynamic functional connection pattern in BDD,UD and normal subjects,and whether abnormal connection was related to clinical symptoms(depression severity and lack of pleasure).The results showed that compared with the normal subjects,BDD and UD had significantly higher dynamic functional connections from the right nucleus accumbens to the right dorsolateral prefrontal lobe and the right middle occipital gyrus.Compared with BDD and normal subjects,the dynamic functional connection between the right nucleus accumbens and the left cuneus was significantly increased in UD.Compared with UD and normal subjects,the dynamic functional connections between the right nucleus accumbens to the left hippocampus and the left thalamus were significantly increased in BDD.In addition,the correlation analysis results showed that the anhedonia score of BDD patients increased with the increase of the dynamic functional connection between the right nucleus accumbens and the left hippocampus.The above results indicated that,compared with the normal subjects,BDD and UD had abnormal dynamic functional connection patterns from the right nucleus accumbens to the whole brain,and the connection patterns between BDD and UD were also different and related to clinical symptoms.These results provide new ideas and clues for us to explore the pathophysiological mechanism of BDD and UD and to distinguish BDD from UD.2.Using granger causality connection analysis method,selecting a reward of 11 important nodes in the network as the interested area(left and right ventral striatum,left and right anterior insula,anterior and posterior cingulate gyrus,left and right thalamus,ventral tegmental area,pre-supplementary motor area and ventromedial prefrontal cortex),build the reward system internal causal connection between network nodes.In this study,we analyzed whether BDD,UD,and normal subjects had abnormal patterns of causal connectivity and the relationship between abnormalities and clinical symptoms.The results showed that the inhibitory effect of BDD and UD in the ventral tegmental area on the pre-supplementary motor area was higher than that of normal subjects,and the anhedonia severity of UD patients became more serious with the increase of inhibition;the excitatory effect of BDD and UD in the pre-supplementary motor area on ventral dorsal tegmental area was higher than that of normal subjects;while the excitatory effect of left and right thalamus on the ventral tegmental area was lower than that of normal subjects.The above results indicated that the causal connection pattern between nodes in the reward network of BDD and UD patients was abnormal compared with the normal subjects and was closely related to the degree of anhedonia of the patients.In summary,the two studies in this paper found that BDD and UD had abnormal connection patterns of reward network with nucleus accumbens(in Chapter 2)and ventral tegmental area(in Chapter 3),and BDD and UD had common and specific abnormal connection patterns.In addition,abnormal connection patterns were significantly associated with the patient’s key clinical symptoms,namely,lack of pleasure.The abnormal connection pattern of reward network may reveal the common and specific physiological and pathological characteristics of BDD and UD,and may serve as a potential biological marker for BDD and UD,providing a reference for clinical differentiation of two diseases.