| Associative memory refers to the memory of the relationship between items or between items and background.As an important form of episodic memory,associative memory is severely impaired in some special groups,such as patients with mild cognitive impairment and depression.Previous studies have found that the resting memory consolidation stage after encoding information is a critical period for memory stability.This consolidation stage is beneficial for converting initial memory representations into stable long-term memory,and is an important stage for exploring the mechanism of associative memory.The default mode network(DMN)is a resting-state brain network that is highly correlated with memory consolidation.Previous studies have explored the neural mechanism involved in sleepdependent memory consolidation,and found that the DMN regions play an important role in the process of memory consolidation.However,the mechanism of the role of DMN in the resting-state memory consolidation is still unclear.In view of this,the experiment 1a of this study explored the mechanism of functional integration of DMN in the memory consolidation of awake state.Exploring the influencing factors and mechanisms of resting associative memory consolidation is also of great significance for subsequent associative memory interventions.United encoding is an important factor affecting associative memory,which refers to individuals integrating multiple independent items into a whole for representation when encoding information.The united theory suggests that familiarity also promotes associative memory when individuals engage in united encoding.Previous studies have confirmed that united encoding promotes familiarity-based associative recognition during the retrieval stage,but it is unclear how united encoding affects the associative memory consolidation.This study will explore the effect of united encoding on brain functional connectivity during the associative memory consolidation stage from the perspective of familiarity.The mediodorsal thalamus(MDt),parahippocampal gyrus,and perirhinal cortex are highly correlated with familiarity,and the functional connectivity(FC)of MDt with parahippocampal gyrus and perirhinal cortex has been confirmed to positively predict familiarity-based memory.Therefore,experiment 1b explored the effect of united encoding on the FC between MDt and parahippocampal gyrus and perirhinal cortex in the associative memory consolidation.Most of the previous studies on memory consolidation in the awake state were based on static FC methods,ignoring the dynamic nature of functional integration between brain regions.The dynamic FC metric provides the time-varying characteristics of functional integration and is a powerful supplement to static FC.In order to comprehensively analyze the FC characteristics,experiment 1a and 1b used static and dynamic FC methods to explore the role mechanism of DMN in awake memory consolidation and the influence mechanism of united encoding on associative memory consolidation.In this study,a total of 30 participants were included.The functional magnetic resonance imaging technology and associative recognition three-bond paradigm were combined in this study.Experiment 1a used within-participant design to explore the mechanism of memory consolidation in the awake phase,and this study compared the difference in static and dynamic FC of DMN between the consolidation and baseline resting phases.The results showed that compared with the baseline resting stage,the static and dynamic FC of DMN in the consolidation phase was significantly increased.Experiment 1b used within-participant design to explore the influence mechanism of united encoding on associative memory consolidation.This study compared the differences in MDt-based static and dynamic FC in the awake consolidation stage after united encoding and non-united encoding.The results of dynamic FC analysis showed that compared with the non-united condition,the dynamic FC of MDt and right parahippocampal gyrus in united condition were significantly increased.In summary,this study concludes that the increased FC of the default mode network is of great significance for the memory consolidation process in the awake stage.United encoding promotes the functional integration of familiarity-related brain regions in memory consolidation stage,and is accompanied by better associative memory effect,supporting the united theory of associative memory. |
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