| Attachment theory originally elaborated the bonding processes between infants and mothers;then,it was applied to adult personal relational processes.Based on the attachment formation process,the internal working model(IWM)or mental representation formed by interactions between individuals and other intimate individuals can also influence an individual’s cognitive strategies in intimate relationships.Individuals with high avoidant attachment have an insecure attachment style and use more deactivating strategies in attachment-related negative cognitive tasks,demonstrating a processing mode intended to avoid or reduce the high activation of attachment-related emotional memory.The previous study found that the dorsolateral prefrontal cortex(DLPFC)brain activation level was weak when individuals with high avoidant attachment viewed attachment-related threatening events.However,the results of the above neuroimaging studies cannot prove that the lower DLPFC activity level is the direct reason for the overrapid memory representation of threat information in individuals with high avoidant attachment.With the development of cognitive neuroscience,researchers have adopted transcranial direct current stimulation(tDCS)to more accurately investigate the causal relationship between specific brain regions and WM.Based on the similarities and differences in cognitive processing patterns of nonemotional and emotional information between high avoidant and low avoidant individuals,this study aimed to explore the causal relationship between the weaker activation of the L-DLPFC and the overrapid memory representation of threat information and to extend the mechanism of the ability of high-definition transcranial direct current stimulation(HD-tDCS)applied to the L-DLPFC to enhance emotional working memory(WM).An emotional condition and a nonemotional condition in the IST were used to distinguish emotional and nonemotional WM representation,the rithness and strength of WM representation were tested by the “remember/ know” task,and the cortical excitability of L-DLPFC was controlled by anodal HD-tDCS and sham HD-t DCS.To avoid the influence of gender differences in emotional regulation and WM on this experiment and to better activate individuals’ existing attachment system,we selected women who had at least one romanticrelationship via questionnaires.To rule out the effects of emotions and state attachment changes on the results of the study,we evaluated these factors before and after stimulation.In Experiment 1,which was a 3-factor mixed design with Stimulation(anodal/sham)and Condition(emotional/nonemotional)as the within-subject factors and Group(high-/low avoidant individuals)as the between-subjects factor,two groups of participants volunteered to take part in this study,including 23 individuals with high avoidant attachment and 24 individuals with low avoidant attachment.All participants received 20 min of HD-tDCS on the L-DLPFC with a 24-h interval between each stimulation session to prevent transfer and confounding effects of the stimulation.The order of stimulation(anodal 1st session and sham2 nd session vs.sham 1st session and anodal 2nd session)was counterbalanced between participants.After stimulation,all participants performed the IST.In Experiment 2,we utilized the 3-factor mixed design with Stimulation(anodal/sham)and Judgment(remember/know/guess/new)as the within-subject factors and Group(high-/low avoidant individuals)as the between-subjects factor and explored how anodal L-DLPFC HD-tDCS influences strength and richness in the attachment-related threat WM.25 individuals with high avoidant attachment and 25 individuals with low avoidant attachment were volunteered to take part in the second study.Results: the results of Experiment 1 showed that the highly avoidant participants performed faster on the emotional IST than low avoidant participants in the sham condition.Interestingly,in the emotional IST,highly avoidant participants were slower after receiving anodal HD-tDCS than in the sham condition.In the emotional IST,the switching cost of highly avoidant individuals was significantly greater in the anodal stimulation group than the sham stimulation group.Conversely,the switching cost of low avoidant individuals was significantly smaller with anodal stimulation than for sham stimulation.The results of Experiment 2 found that,in sham conditions,the memory performances of individuals with high attachment avoidance were better than individuals with low attachment avoidance for the “know” judgments.Compared to the sham condition,the“remember” memory performances of individuals with low attachment avoidance were better after receiving anodal L-DLPFC HD-tDCS,and the“know”memory performances ofindividuals with high attachment avoidance were better after receiving anodal L-DLPFC HD-t DCS.Conclusion:(1)There were differences in the memory representation of threat information among the attachment avoidance individuals.Compared with low attachment avoidance individuals,high attachment avoidance individuals had lower response time to threat memory representation under sham conditions,which was in line with their defensive processing behavior mode for threat information.At the same time,the strength of threat memory representation in individuals with high attachment avoidance was not strong enough.(2)Under the anodal condition,the response time of high avoidance attachment individuals to threat memory representation increased significantly,and the representation speed of threat memory representation slowed down.On the contrary,the individuals with low attachment avoidance accelerated the speed of threat working memory representation.(3)Stimulating the L-DLPFC improved the richness of threat memory representation in individuals with low attachment avoidance,and the strength of threat memory representation in individuals with high attachment avoidance.This study not only confirmed the path of activating L-DLPFC to affect the threat memory representation of attachment avoidance individuals,but also supported the social information processing model.Through the way of mobilizing cognitive resource allocation from the top to the bottom,a new idea for the plasticity of defensive mechanism of attachment avoidance individuals was put forward.In addition,from the perspective of the relative balance of strength and richness of memory representation,the mechanism of L-DLPFC activation on emotional working memory representation was also expanded.This study expanded the application field of HD-tDCS,provided important theoretical and empirical support for the improvement of cognitive control ability and training intervention of clinical subjects,and developed the plasticity research of insecure attachment individuals. |
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