715. Hippocampal cellular and molecular representations of fear memory reconsolidation and extinction

Abstract

Abstract Background Memory retrieval is not a passive phenomenon. Previous studies have presented evidence that memory retrieval is a dynamic process during which memories can be made stronger, weakened, or their content can be altered. Recent studies have shown that reactivated memory becomes labile after retrieval and is re-stabilized through a gene expression-dependent process known as memory reconsolidation. Memory reconsolidation after retrieval may be used to maintain or update long-term memories, reinforcing or integrating new information into them. In classical Pavlovian fear conditioning paradigms, the reactivation of conditioned fear memory by re-exposure to the conditioned stimulus (CS) in the absence of the unconditioned stimulus (US) also initiates extinction as a form of new learning that weakens fear memory expression (i.e., a new CS-no US inhibitory memory that competes with the original CS-US memory trace). Thus, in the fear conditioning paradigms, memory retrieval also includes extinction learning. Aims & Objectives Therefore, when fear memory is retrieved, the dominance of the original (fear) or new (extinction) memory traces is thought to determine the fate of memory through their competition. We have tried to understand the mechanisms by which the fate of retrieved fear memory is determined. Method We compared cellular and molecular signatures of reconsolidation and extinction of contextual fear memory at the molecular and cellular levels. Results We found that the hippocampus shows contrasting molecular representations of reconsolidation and extinction of contextual fear memory. Discussion & Conclusions These changes of hippocampal molecular and cellular representations must be important for the transition of memory phases from reconsolidation to extinction.