| Background:Subthreshold depression (SD) is a form of depression that does not meet the diagnostic criteria for depression. SD, a sub-healthy state between health and depression, includes depressed state in normal range and mild depression caused by systemic diseases. SD is prevalent in the crowd. According to relevant epidemiological investigation in American, up to about30%-40%people have subthreshold depressive symptoms in the general population. For patients with SD, their symptoms do not meet the diagnostic criteria for depression, but they are likely to worsen to the extent of depression if not intervened promptly.At present, the research of subthreshold depression mainly focus on the research of descriptive analysis and behavioral research and few studies on cognitive experimental level. In the related studies in China, There is few using event related potential (ERP) Technology to study specific subthreshold depression group.Objective:(1) This thesis investigates and analyzes the epidemic situation of depression of the medical students, which provides the basis for further study on the epidemiological characteristics of depression.(2) This design plan adopts with the Oddball paradigm and Event Related Potential(ERP) technology, analysing of the effects of different valence emotional picture stimuli (positive, neutral, negative) characteristics on behavioral and cognitiveprocessing effects of subthreshold depression group and the differences of subthreshold depression group and Healthy people in the behavioral and ERP.Methods:In this thesis, from the Chinese Affective Picture System(CAPS) selected three kinds of emotional stimuli picture with different types. Through CES-D and HAMD questionnaire selected subthreshold depression group and normal control group from the college students of Beijing University of Chinese Medicine. The two groups matched the behavioral experiment and event related potential experiment, following with the relevant epidemiological investigation at the same time. The design plan adopts with the Oddball paradigm and divided into three blocks. In each block, the emotional picture as the target stimulus (probability20%), were positive, neutral, negative. There is expected to reveal the effect of stimulus type to the control of cognitive to subthreshold depression from two aspects of the behavioral experiment and event related potential experiment.Results:(1) The Analysis results of Epidemiology:The rate of depression prevalence was15.32%in medical students. The different grade, different professional, only child or not, different home address and educational background influence the rate of depression prevalence of medical students.(2) The analysis results of behavioral research:At the RT, the main effect of group was significant (F=16.043,P<0.05); the main effect of stimulus type was significant (F=13.786,P<0.05).(3) The analysis results of ERP research:①In the N2components:At the amplitude of N2, the main effect of group was not significant (F=1.175,P>0.05); the main effect of stimulus type was significant (F=7.328,P<0.05); the main effect of brain area was significant (F=162.252,P<0.05). At the latency of N2, the main effect of group was not significant (F=0.186,P>0.05); the main effect of stimulus type was significant (F=5.925,P<0.05); the main effect of brain area was not significant (F=0.640,P>0.05).②In the P3components:At the amplitude of P3, the main effect of group was not significant (F=0.018,P>0.05); the main effect of stimulus type was significant (F=4.540,P<0.05); the main effect of brain area was significant (F=167.798, P<0.05). At the latency of P3, the main effect of group was not significant (F=0.243,P>0.05); the main effect of stimulus type was significant (F=4.453, P<0.05); the main effect of brain area was significant (F=4.453, P<0.05).Conclusion:(1) In the behavioral research, subthreshold depression group and normal control group were different significantly, normal control group was significantly faster than subthreshold depression group at the RT.(2) In the event related potential research, the Group differences of the amplitude and latency of N2and P3between subthreshold depression group and normal control group were not significant. Research is still unable to verify the subthreshold depression group was the lack of cognition control which is significant difference between Healthy people. Reasons for this result need further study and may be due to a lesser extent of subthreshold depression subjects which did not meet all criteria for depression. |
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