A Behavior And ERP Study On The Associations Between Deficits Of Internal Switching Abilities And Depressive Symptoms As Well As Rumination

Object and significanceDepression is one of the most common mental disorders and represents a significant public health concern due to its prevalence,associated impairments and economic impact.Although there have been a number of effective pharmacological and psychological interventions,relapse rates of depression remain high.Given its high prevalence and relapse rates,it is pressing to identify the vulnerability factors and underlying mechanisms.Rumination,which is generally defined as repetitive thinking about negative information,has been found to be an important vulnerability factor and a hallmark feature of depression.Understanding rumination can help us find new curing targets of depression and design more effective interventions of it.In recent years,a growing body of literature suggests that depression and rumination may originate from,and be maintained by,dysfunctions in the executive function.Factor analysis of tasks that measure the executive function revealed its three components: inhibition,updating in working memory and switching.In a series of studies,researchers have proved the associations between the former two executive components and depression as well as rumination.However,it still remains unclear that how the deficits of switching abilities can lead to ruminative traits.Researchers have found that switching ability contains two sub-components: non-inhibitory switching processes(NISPs)and backward inhibition(BI).Moreover,two paradigms are used widely in this area,which are cited as the task switching paradigm(TSP)and the internal shifting task(IST).The former one is used to test the subject's ability to switch among different sets of tasks while the latter one is used to test the ability to shift attention among objects within working memory.Studies using TSP have found that depressive symptoms are associated with the deficits in the overall switching ability while rumination is associated with BI.However,the present IST is not able to separate BI from the overall switching ability,so it is impossible for researchers to investigate the associations between BI and depressive symptoms or rumination traits.Moreover,few studies have used the ERP technology to investigate the association between depression as well as rumination,so it is not clear is there any physical trait marks of the deficits of switching abilities in depression or rumination.Thus,this study is aimed to modify the present IST to investigate the associations among BI and depression or rumination,and investigate the possible physical trait marks of the deficits of internal switching abilities in depression as well as rumination.Subjects1.Preparing ExperimentTwenty-three undergraduate students from Third Military Medical University were recruited into this study,including 18 males and 5 females.2.Behavioral study on the associations between depressive symptoms/rumination and internal switching abilities(sad faces)BDI was administrated to 65 undergraduate students from Chongqing City Management College and 145 students from Chongqing Normal University.Those who scored more than 14 or less than 4 in BDI were recruited into the study.The final sample consists of 34 depressive individuals and 31 healthy controls.3.Behavioral study on the associations between depressive symptoms/rumination and internal switching abilities(angry faces)BDI and RRS were administrated to 567 undergraduate students from Third Military Medical University and Southwest University.Those who scored more than 14 or less than 4 in BDI were recruited into the study.The final sample consists of 30 depressive individuals and 24 healthy controls.4.ERP study on the associations between depressive symptoms/rumination and internal switching abilitiesBDI and RRS were administrated to 567 undergraduate students from Third Military Medical University and Southwest University.Those who scored more than 14 or less than 4 in BDI were recruited into the study.The final sample consists of 20 depressive individuals and 19 healthy controls.MethodsThe present study used BDI as the screen tool to recruit dysphoric individuals and non-dysphoric controls.Then a modified TIST was administrated to participants in order to test their internal switching abilities.Mixed ANOVA and correlational analysis were used to investigate the associations between depressive symptoms/rumination and internal switching abilities' deficits.In the following ERP study,the original IST was used to test participants' internal switching abilities while their ERP signals were recorded.Mixed ANOVA was used to analyze the behavioral and ERP results.Analysis to results were stated as follows:Results1.In the preparing experiment,the RTs of the switching trials(2208.30±410.41ms)were significantly longer than the control trials(1677.50±278.68ms).Moreover,the RTs of the ABA trials(2283.58±458.96ms)were significantly longer than the CBA trials(1950.89±389.87ms).2.Using sad faces as the negative emotional stimuli,the behavior study I found that the average RTs of the depressive individuals(2246.41±326.66ms)were significantly longer than healthy controls(2047.23±333.88ms).3.When sad faces were used as the negative emotional stimuli,the higher rumination group's internal switching cost(602±272.78ms)were significantly larger than the lower group(471±159.96ms).4.When sad faces were used as the negative emotional stimuli,neither depressive symptoms nor rumination was associated with BI.5.When angry faces were used as the negative emotional stimuli,the average RTs of the individuals with depressive symptoms(2570.67±466.33ms)were significantly longer than healthy controls(2145.92±429.85ms).6.When angry faces were used as the negative emotional stimuli,neither depressive symptoms nor rumination was associated with internal switching abilities.7.When angry faces were used as the negative emotional stimuli,depression was not associated with BI while rumination was significantly correlated with BI.8.In the ERP study,neither depression nor rumination was associated with the internal switching abilities in the behavior level.9.Analysis to the ERP signal revealed that,in the time bin of 330~540ms,the switch-control differential wave of the depressive individuals were significantly higher than that of healthy controls.Besides,participants' rumination score can effectively predict the differential wave.This effect is significant after controlling participants' depression scores.Conclusions1.The TIST is able to separate the significant switching effect and backward inhibition effect.It is an effective tool for studies of internal switching.2.When sad faces are used as the emotional stimuli,depressive symptoms are associated with an overall delay of the RTs.Meanwhile,rumination is associated with deficits of the internal switching abilities.Surprisingly,BI has no associations with rumination or depression.3.When angry faces are used as the negative stimuli,depressive symptoms are also associated with an overall delay of the RTs.However,rumination is found to be associated with deficits within BI.4.The ERP study's results indicate that deficits of the internal switching abilities in depressive individuals is not revealed in the behavioral level.However,it can be inferred that depressive individuals cost more executive resources when switching internally from ERP results.It is also found that rumination can predict the ERP signal of the internal switching even after controlling depressive symptoms.