Interplay Between Alpha 2-Chimaerin And Rac1 Activity Determines Dynamic Maintenance Of Long-Term Memory

Memory consolidation theory suggests that once memory formation has been completed, memory is maintained at a stable strength and is incapable of further enhancement. However, the current study reveals that even long after formation, contextual fear memory could be further enhanced. Such unexpected enhancement is possible because memory is dynamically maintained at an intermediate level that allows for bidirectional regulation. Here we find that both Rac1 activation and expression of alpha 2-chimaerin are stimulated by single-trial contextual fear conditioning. Such sustained Rac1 activity mediates reversible forgetting, and alpha 2-chimaerin acts as a memory molecule that reverses forgetting to sustain memory through inhibition of Rac1 activity during the maintenance stage. Therefore, the balance between activated Rac1 and expressed alpha 2-chimaerin defines dynamic long-term memory maintenance. Our findings demonstrate that consolidated memory maintains capacity for bidirectional regulation.