| People made approach and avoidance behaviors everyday unconsciously.Approach referred to the behaviors trying to close positive stimulus like rewarding stimulus,oppositely,avoidance could be defined as attempts to prevent,escape,or reduce contact with subjectively aversive or minimally rewarding internal or external stimuli.Approach and avoidance behaviors were basic behavioural patterns of human beings,which were also closely linked with organism' major theme of avoiding injuries,avoiding deaths,survival and reproduction.Compared with the general population,depressed persons showed different approach-avoidance characteristics,that was reduced approach behaviors to positive stimuli.Some studies also had found depressed persons were more aversive to negative stimulus.What's the characteristics of subthreshold subjects' approach-avoidance behavior? Whether subthreshold subjects had similar characteristics of approach-avoidance behaviors with depression subjects?This was still little known.ObjectiveComparative experiment was adopted to compare subthreshold depression subjects' characteristics of approach and avoidance behaviors with normal subjects' characteristics.Explicit feedback joystick task was adopted to explore subthreshold depression subjects' explicit characteristics of approach and avoidance behaviors,implicit feedback joystick task was adopted to explore subthreshold depression subjects' implicit characteristics of approach and avoidance behaviors and related neural mechanism.This study also attempted to answer the question of subthreshold depression was a single disease or a transition stage of depression by analyzing characteristics of approach and avoidance behaviors and related neural characteristics among subthreshold depression subjects,control group subjects and depressed subjects that previous research reported.Materials and MethodsThe aim of Experiment One was to explore subthreshold depression subjects' characteristics of explicit approach and avoidance behaviors.Selecting the appropriate subjects by distributing psychology measuring scale.Accepting criteria of experimentalgroup were:(1)The scores of The Center for Epidemiological Studies Depression Scale and Beck Depression Inventory-II was higher than 16;(2)Having 2~4 symptoms of depression in SCID interview,including one core symptom,which were low spirits or decreased appetite,at least 2 weeks in duration.(3)Right handedness.Exclusion criteria of experimental group were:(1)One had major physical disease,nervous system disease or took psychotropic drugs within this month;(2)Who met criteria for diagnoses of major depressive disorder(MDD).Accepting criteria of health control group were:(1)CES-D<16,BDI-II<16;(2)Right handedness.Control group's exclusion criteria were same with those in experimental group.Two groups were matched on age,gender.The two groups of subjects completed the explicit feedback-joystick tasks,at the same time their reaction time data were recorded.Data were analyzed by 2(group:experimental group/ control group)× 3(facial picture : sad/happy/ disgust)× 2(motion :approach/avoidance)repeated measures analysis of variance,group was a between-subject factor,facial picture and motion were within-subject factors.The aim of Experiment Two was to explore subthreshold depression subjects' characteristics of implicit approach and avoidance behaviors.The screening process and screening criteria of experimental group and control group were the same as those in Experiment One.The two groups of subjects completed the implicit feedback-joystick task,at the same time their reaction time data were recorded.Data analysis using 2(group:experimental group/ control group)×3(facial picture:anger /happy/sad /disgust)×2(motion:approach/avoidance)repeated measures analysis of variance,group was a between-subject factor,facial picture and motion were within-subject factors.The aim of Experiment Three was to explore neural mechanism of subthreshold depression subjects when they completing the approach—avoidance behaviors.The EEG data were recorded by event-related potential technique.Selected biggest average amplitude among F3,FZ,F4,C3,CZ,C4,P3,PZ,P4 to make a 2(group:experimental group/control group)× 3(facial picture : anger /happy sad/disgust)× 2(motion :approach/avoidance)repeated variance analysis.Group was a between-subject factor,facial picture and motion were within-subject factors.Results1.In explicit feedback joysticks task,experimental group(1208.18 ±338.92ms)had significantly longer reaction time than those in control group(1058.40±204.22ms)when approaching happy expression(t=2.02,p<0.05).When presented negative facial pictures,there were no difference between experimental group and control group.2.In implicit feedback joysticks task experimental group had longer reaction time than control group(F3,165=5.267,p=0.002)when made approach and avoidance behaviors,experimental group and control group did not show dominant trend of action.3.The amplitude of P2 wave in experimental group was higher than that in control group in event-related potentials of implicit feedback joystick task(F1,39=4.364,p=0.043),appeared a between groups effect.There also appeared a 2(group:experimental group/control group)×3(facial picture:anger /happy sad/disgust)×2(motion:approach/avoidance)interaction effect.ConclusionSubthreshold depression group had different characteristics of approach and avoidance behaviors with control group.Subthreshold depression was a transitional state between no depression and major depression,not a single form of disease. |
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