| Depression is a globally prevalent mental disorder with high incidence and recurrence rates,and emotional imagery generation biases is a key risk factor for the occurrence,maintenance and development of depression.The emotional imagery biases is mainly characterized by a more negative imagery and a poor positive imagery.There are two emotional imagery generation pathways: the information perceived immediately in working memory and the information stored in long-term memory,with the long-term memory imagery generation pathway usually typically based on pictorial cues and script cues.Imagery generation is derived from memory,and has a strong emotional effect,which is closely related to the memory bias of depressed individuals,and can amplify the interpretation bias effect of depressed individuals.However,to date,only a small number of questionnaires and behavioral studies have examined the emotional imagery generation bias in depressed individuals,and little is known about the cognitive neural mechanism of emotional imagery generation in depressed individuals.What is the cognitive neural mechanism behind the emotional imagery generation bias in depressed individuals;what changes will occur in the symptoms of depressed individuals after positive imagery generation training.The answers to these questions can help us better understand the performance and mechanism of emotional imagery generation bias in depression.Therefore,this dissertation conducted three studies,a total of five experiments to systematically investigate the cognitive mechanism and intervention effect of long-term memory emotional imagery generation of depressed individuals from emotional imagery generation to positive imagery generation training.In study 1,we explored the electrophysiological mechanism and brain activation of long-term memory emotional pictorial cues imagery generation in depressed individuals and their relationship with depressive symptoms by using ERP technology and f NIRS technology.In study 2,we explored the behavioral response and brain activation of emotional imagery scripts clues generation of long-term memory with in depressed individuals and their relationship with depressive symptoms from the behavioral level and neural basis level.After clarifying the cognitive and neural basis of emotional imagery generation in depressed individuals,study 3 used computerized positive script imagery generation training intervention technique to investigate the changes of depressive symptoms and attention bias after training.The experiment 1 in study 1 used ERP to record the electrophysiological activities of40 depressed individuals and 44 control participants when they imagined emotional pictures during the encoding-imagery task.The behavioral results revealed that depressed participants scored significantly lower in the valence rating of sad and neutral picture imagery compared to control participants,and depressive symptom scores were significantly negatively correlated with valence scores for neutral picture imagery.The vividness of imagery exhibited an emotional effect(happy> neutral > sad),but there was no difference between groups.ERP results showed that the central-parietal LPP response to sad picture imagery in depressed participants were significantly larger than that of the control participants,particularly in the middle(800-1,400ms)and late time windows(1,400-2,000ms).Additionally,depressed individuals exhibited significantly higher LPP amplitudes for sad picture imagery compared to happy picture imagery,whereas control participants showed the opposite pattern.The experiment 2 used f NIRS to record the brain activation of 48 depressed individuals and 42 control participants when they imagined emotional pictures during the encoding-imagery task.The behavioral results revealed that depressed participants scored significantly lower in the valence rating of sad and neutral picture imagery compared to control participants,and depressive symptom scores were significantly negatively correlated with valence scores for happy picture imagery.The vividness of imagery exhibited an emotional effect(happy> neutral > sad),and depressive symptom scores were significantly negatively correlated with vividness scores for happy picture imagery,but there was no difference between groups.f NIRS results revealed that the activation of the medial prefrontal cortex(m PFC),bilateral dorsolateral prefrontal cortex(dl PFC),and left parietal cortex in depressed individuals for happy picture imagery was significantly lower compared to the control group.Furthermore,there was a significant negative correlation between depressive symptom scores and the activation of the m PFC,dl PFC,and left parietal cortex for happy imagery.Additionally,compared to happy or neutral picture imagery,depressed individuals showed significantly increased activation in the m PFC,bilateral dl PFC,left TPJ,and left parietal cortex for sad picture imagery.Conversely,compared to sad or neutral picture imagery,the control control group exhibited significantly increased activation in the right dl PFC,bilateral parietal cortex,and bilateral TPJ for happy imagery.The experiment 3 recorded the behavioral responses of 51 depressed individuals and54 control participants when they imagined emotional scene scripts during the script-driven imagery task.The results revealed that revealed that the valence,vividness,and effective utilization in depressed participants for happy script imagery significantly lower than the control participants,and depressive symptom scores were significantly negatively correlated with these scores.Conversely,depressed participants had a significantly higher proportion of personal experience for sad imagery compared to the control participants,and depressive symptom scores were significantly positively correlated with this proportion.The control participants rated the vividness and utilization of happy imagery significantly higher than sad imagery.Additionally,both depressed individuals and the control participants showed significantly higher ratings of vividness and personal experience proportion for neutral imagery compared to emotional imagery.The experiment 4 used f NIRS to record the brain activation of 42 depressed individuals and 42 control participants when they imagined emotional scene scripts during the script-driven imagery task.The behavioral results repeatedly verified the results of experiment 3,indicating that depressed individuals were more likely to generate poor and low vividness positive imagery.f NIRS results revealed that depressed individuals showed significantly higher activation in the left dl PFC and bilateral TPJ for sad script imagery compared to the control participants,and depressive symptom scores were positively correlated with the neural activity in the bilateral TPJ for sad script imagery.Additionally,depressed individuals showed significantly higher neural activity in the bilateral TPJ for sad script imagery compared to happy script imagery or neutral script imagery,but they also showed significantly higher neural activity in the m PFC and left dl PFC for happy script imagery compared to neutral script imagery.Whereas,control participants showed significantly higher neural activity in the m PFC,left dl PFC,and bilateral TPJ for happy script imagery compared to sad script imagery or neutral script imagery.Furthermore,the right dl PFC also showed an emotional effect,with significantly higher activation for happy script imagery compared to sad script imagery and neutral script imagery.The experiment 5 observed changes of depressive symptoms and attention biases in33 depressed individuals with positive imagery training and 33 depressed individuals with neutral imagery training after computerized imagery training.The results revealed that compared to the neutral imagery training group,depressed individuals in positive imagery training group showed significant increases in positive affect,as well as significant decreases in negative affect,depression symptoms,and state anxiety,and had higher accuracy in recognizing familiar faces during the post-test.However,it is worth noting that the depression symptoms,emotion,and imagery ability of depressed individuals in both two groups were improved after imagery generation training.Correlation analysis revealed a significant positive correlation between imagery vividness and changes in negative affect and state anxiety scores from pre-post or pre-follow imagery training.The imagery arousal score was also significantly positively correlated with changes in depression symptoms,positive affect,and state anxiety scores from pre-post or pre-follow imagery training.Based on the above results,the main findings of this study are as follows:(1)Depressed individuals exhibited both negative imagery bias and impaired positive imagery,supporting the view of mood-congruency emotional imagery generation bias in depression and providing empirical evidence for the expanded model of depression.(2)Depressed individuals exhibited an enhanced LPP effect to sad imagery.The different LPP activity patterns during emotional imagery generation between depressed individuals and control control participants can serve as a neural biomarker for identifying depressed individuals.(3)Impaired of happy picture imagery generation in depressed individuals may be influenced by reduced abnormal activation in the prefrontal cortex,parietal lobe,and bilateral TPJ.The more severe the depressive symptoms,the lower the activation of the prefrontal lobe and the left TPJ in the happy picture imagery generation.Furthermore,the different activity patterns in the prefrontal cortex,parietal lobe,and TPJ during emotional imagery generation between depressed individuals and control control participants can serve as neuroimaging biomarkers to identify depressed individuals.(4)Biases of sad script imagery generation in depressed individuals may be influenced by increased abnormal activation in the prefrontal cortex and TPJ.The more severe the depressive symptoms,the higher the activation of bilateral TPJ in sad script imagery generation.Moreover,the different activity patterns in the left dl PFC and TPJ during emotional imagery generation between depressed individuals and control participants can serve as neuroimaging biomarkers to identify depressed individuals.(5)The computerized positive script imagery training improved positive affect,imagery vividness,and spontaneous use of imagery in depressed individuals,meanwhile reducing negative affect,state anxiety,rumination,depressive symptoms,and attentional biases.In addition,the higher the vividness and arousal of imagery during the computerized emotional imagery generation training,the better the improvement of depression-related symptoms in depressed individuals. |
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