Aberrant brain network reorganization underlies emotional memory suppression under long-term stress

1092 

Abstract Submission 

Tan Wenlong¹, Shaozheng Qin²

¹Beijjing normal university, Beijing city, Beijing, ²Beijing Normal University, Beijing, Beiijng

Wenlong Tan  
Beijjing normal university
Beijing city, Beijing

Shaozheng Qin  
Beijing Normal University
Beijing, Beiijng

Long-term stress (LTS) is believed to result in a tendency to be more sensitive and unforgettable to emotional information (e.g, threat or adversity) as seen in various stress-related mental disorders (Joels,2006; McGaugh,2015), which could be maladaptive for mental health (Anderson,2021). Memory suppression, specifically through voluntarily impeding the retrieval of unwanted memories (Anderson, 2001), holds the potential to serve as a strategy to alleviate this tendency. However, the extent to which memory suppression can alleviate the over persistence of aversive memories caused by long-term stress, as well as its underlying neural mechanisms, remains elusive. We conducted a fMRI study to investigate neural pattern reorganization associated with the influence of suppression on emotional memories before and after overnight under long-term stress.

Sixty-one young male college students participated in this experiment: 40 of them who were in a long-term high academic stress environment (all were preparing for the Chinese National Postgraduate Entrance Exam (CNPEE) for at least 6 months) were assigned to the Long-term stress group, the other 21 participants, who had not been exposured to other any major stressors in past 6 months, were the healthy control group. (Fig. 1A). The experiment consisted of four phases, including two training sessions which were conducted two days respectively, "Think/NoThink" paradigm, post-scan memory test and questionnaire (Fig. 1B). Brain images were acquired on a 3T Siemens scanner using an echo-planar imaging sequence. Imaging data were preprocessed and analyzed by using SPM12. We employed several analytical techniques, including univariate general linear models (GLM), representational similarity analysis (RSA), functional connectivity analysis, and network topology analysis, to analyze the brain data.

Behaviorally, Exposure to long-term stress increases the SCL90 scores (Fig. 1 C). Long-term stress group showed less decay of emotional memories over time, and this trend could be intercepted by memory suppression(Fig. 1 D,E). The decay of memories under baseline conditions mediated the difference in inhibition scores between the two groups in the remote condition(Fig. 1 G).

Neurally, at network level, the increase of communication efficiency in suppression-related brain network over time was attenuated under long-term stress(Fig. 2 B,C), and the most affected node was the left amygadala, which had an enhanced hubness in control from recent to remote and an abnormal decreased hubness over time in long-term stress(Fig. 2 D,E). The correlation patterns of brain connnectivity and suppression efficiency are distinct during suppression before and after overnight, indicated that consolidation reconfigures brain system involved in suppression, however, these is no similar reconfiguration under long-term stress. The long-term stress group showed change of suppression network communication over time was negatively associated with suppression efficiency of remote memories(Fig. 2 F,H).

Participants under long-term stress exhibited less aversive memories loss from 30 minutes to 24 hours delay, indicated altered consolidation and forgetting process. Neurally, consolidation is manifested by significant reorganization of neural activity patterns during suppression at different time points, However, in the long-term stress group, these corresponding reorganization patterns are altered or even reversed, especially in the left amygadala. Due to the insufficient consolidation and forgetting of emotional memories, the long-term stress group demonstrated a higher efficiency in suppressing remote memories, which was characterized by the extent of reorganization of neural activity patterns was negatively associated with more effective suppression of remote memories. Our findings have significant implications for the application of memory suppression strategies in the treatment of stress-related disorders

Emotion and Motivation Other

Long-Term Memory (Episodic and Semantic) ¹

Connectivity (eg. functional, effective, structural)

fMRI Connectivity and Network Modeling ²

Cognition

Emotions

Memory