Acute Stress Impairs The Process Of Intentional Memory Suppression In Individuals With High Trait Rumination

BackgroundThe intentional suppression for the retrieval of unwanted memories is an adaptive regulatory ability,which can help individuals to actively forget the memories that will bring them painful experiences to a certain extent,so as to adapt to the adverse environment effectively.Acute stress events are proven to impair this ability of intentional inhibition,and even induce a variety of stress-related mental disorders,including post-traumatic stress disorder,depression,and anxiety.The people with high trait rumination are the high risky group of the above mental disorders,of which impairment for intentional memory suppression is highly similar to patients with above disorders to some extent.However,there are not enough neuroimaging studies to explore whether acute stress impairs the process of memory suppression in high trait ruminators and its potential neural mechanism up to now.Under this context,it is of necessity to deeply explore the impact of acute stress on the behavioral performance and underlying brain mechanisms of high trait ruminators in the process of intentional memory suppression by using the neuroimaging technology.This research could not only deepen our understanding of the process of active memory suppression,but also provide certain clinical significance for prevention and early intervention in the development of high trait ruminators into various stress-related disorders.MethodsBehavioral research:60 healthy college students were randomly selected by convenient sampling and divided into high and low trait rumination groups.Participants were required to complete a Think/No Think(TNT)task after completing the stress-induced task and the control task respectively in the two experiments to measure the performance of the intentional memory suppression of subjects.The scores of salivary cortisol and subjective stress scale were collected during the whole experiment.Neuroimaging research:In the process of behavioral research,functional near-infrared spectroscopy technology was used to scan the brain of the subjects during the process of the Think/No think experiment.Taking the inferior frontal gyrus,the middle frontal gyrus,the superior temporal gyrus,and the superior parietal lobule of both hemispheres in the brain as the regions of interest,we analyzed neuroimaging data and explore the brain mechanisms related to the effect of acute stress on the intentional memory suppression in individuals with high trait rumination.ResultsBehavioral research:Compared with stress control conditions,salivary cortisol,and subjective stress of participants in high and low trait rumination groups significantly increased after completing the TSST.That is,the stress of participants was successfully induced.As a behavioral indicator to measure the task performance of Think/No Think task,the main effect of the experimental conditions,the subject group and the valence of the stimulus materials were significant in the suppression induced forgetting index.Additionally,the interaction effect between the experimental conditions and the subject group was significant.To be specific,compared to the low trait ruminators,more significant differences can be found in performance of the memory suppression in high trait ruminators when completing the TSST and the stress control task.These results also showed that the impairment of acute stress on the process of intentional memory suppression was significantly affected by the level of trait rumination in participants.Neuroimaging research:The interaction effect of experimental conditions and subject group was significant in the left middle frontal gyrus,the left superior temporal gyrus,and the right inferior frontal gyrus.Results from further simple effect analysis found that the activation level of high trait ruminators who completed TSST task in the above brain areas was significantly lower than that of individuals who performed stress control tasks,while in the low trait ruminators,only the activation level of the left middle frontal gyrus under stress was significantly lower than that under pressure control.Results from correlation analysis showed that the activations of the left middle frontal gyrus and the right inferior frontal gyrus were significantly negatively correlated with the suppression induced forgetting index,while the activation of the left superior temporal gyrus was significantly positively correlated with the suppression induced forgetting index,indicating that the higher the activation level of the left middle frontal gyrus and the right inferior frontal gyrus were and the lower the activation level of the left superior temporal gyrus was,the better the behavioral performance of the subjects during the intentional memory suppression was.The above results showed that the induction of acute stress has an impact on the brain activation level of high and low ruminators in the process of memory suppression,but there was a difference in the degree of impact on these two groups,and the low trait ruminators were less affected.ConclusionsThe results showed that worse performance of intentional memory suppression can be found in individuals who completed stress induced task.Compared to low trait ruminators,individuals with high trait rumination suffered more impairment under acute stress and performed worse in memory suppression task.In addition,brain regions including the dorsal lateral prefrontal gyrus,the superior temporal gyrus and other areas related to inhibitory control and memory functions have distinct activation patterns in the process of acute stress impairing the intentional memory suppression.The above results could help us to further understand the higher order cognitive processes of memory suppressing extraction of individuals.