The Neural Basis Of Motivated Forgetting

As a higher cognitive function,on one hand memory can make us remembered the wonderful memory in the past.However,on the other hand,there are always some events beyond our control in life,such as earthquakes,traffic accident,bereavement,failure and so on.These unwanted memories often came to our brain without control.If could not be controlled well,it will make individual immersed themselves in these adverse events,then suffer from some mental disorders,such as depression and post-traumatic stress disorder(PTSD).Therefore,it is important for our physical and psychological health and improving our well-being to regulate the unwanted memories.Motivated forgetting was defined as the ability to suppress the unwanted memories though by the motivated top-down control.With the development of neuroimaging technology,there have been some achievements in the neural basis researches of motivated forgetting.Many of previous cognitive neuroscience studies have indicated that the activations of the dl PFC,lateral primary motor cortex and some other executive control regions were increased during performing the motivated forgetting task.Meanwhile,activation of the hippocampus decreased under memory control.These results have suggested that during memory control performing,the activation of the hippocampus may be regulated by the prefrontal regions.Indeed,functional connectivity analysis has shown that the increased activity of dlPFC could predict the decrease of the hippocampus.Recently,dynamic modeling causal studies have proved this theoretical assumption.There is a top-down regulatory mechanism from dlPFC to the hippocampus.However,recent fMRI studies mostly focused on the active pattern of motivated forgetting,which could only reflect the total differences between different conditions,and could not reflect the interaction pattern between different brain regions during the task phase.Functional connectivity of task fMRI could solve this problem,while there are only few studies on it.And there are no studies combining the task fMRI functional connectivity and related behavioral index to inspect whether the functional connectivity could predict the subsequent performance of suppression-induced forgetting.eA mass of behavioral studies has shown that,as a cognitive function,there are individual differences in motivated forgetting ability.That is to say,someone may have a higher motivated ability,while another may have a bad one.The individual differences of motivated forgetting might be represented by the spontaneous neural activation.However,most of the previous studies have concentrated on the task fMRI analysis,few of them concern the correlations between the individual differences of motivated forgetting ability and the spontaneous neural activation during the resting state.Based on these mentioned above,we put forward two hypotheses,and proved them through following two studies.Study 1: Aiming to explore the neural basis and the brain activation patterns of motivated forgetting based on the task fMRI analysis,and then using the task fMRI functional connectivity method to analysis the active pattern of dlPFC and HC,and to inspect whether these connectivity pattern could predict the following behavioral performance.Behavioral analysis indicated that the memory performance of suppressed items was significantly below the performance of recalled items,means that memory control effect was induced successfully.Group results of activation analysis were consistent with previous related studies.Activations of the right dlPFC?supplementary motor area?ventral lateral prefrontal lobe were increased.Meanwhile,activations of the bilateral hippocampus?occipital lobe?ventral medial prefrontal lobe and posterior cingulate gyrus were decreased significantly.It suggested that during subjects performing the motivated memory control task,abundant executive control network was referred,meanwhile the default mode network and hippocampus related to memory retrieve were suppressed.More importantly,task fMRI functional connectivity analysis indicates that during the memory suppressing phase,the increased activity of dlPFC could predict the decrease of the hippocampus,this means there is an antagonism pattern between dlPFC and HC.Besides,the functional connectivity could predict the performance of suppression-induced forgetting.Study 2: Aiming to explore the resting state neural basis of motivated forgetting ability from the perspective of individual differences.In this study,we collected the behavioral data of the classical TNT and the resting state neural imaging data.Then analysis the correlations between two resting state fMRI index(Reho and ALFF)and the motivated forgetting ability.We observed that the spontaneous neural activation of the mass of the executive control network was correlated with the motivated forgetting ability.The ALFF in dlPFC,supplementary motor area and SFG were correlated with the motivated forgetting ability.The Reho in dlPFC,OFC,supplementary motor area.These brain regions were consistent with the previous task fMRI studies.These results suggested that the brain regions involving executive control were not only important for performing the memory control task,but for the individual differences of motivated forgetting ability.The spontaneous neural activation of these key brain regions could be concerned as a valuable index to predict the individual differences of motivated forgetting.In summary,combining the results of task fMRI and resting state fMRI analysis,we suggested that some brain regions of the executive control network play an important role in motivated forgetting,such as the dlPFC?IFG and supplementary motor area.Besides,there is an antagonism pattern between dlPFC and HC during subjects operating the memory inhibition task,and the functional connectivity could predict the performance of suppression-induced forgetting.Then,future studies on motivated forgetting should combine multi-mode methods and combine the group analysis and individual differences to investigate the neural basis of motivated forgetting.