Objective Memories are dynamic in nature.Upon retrieval, ample evidence has suggested that memories can enter into a labile, protein-synthesis dependent process, referred to as reconsolidation, from which memories can be modified or strengthened.Understanding the molecular mechanisms underlying memory reconsolidation could provide crucial insight into the dynamic aspects of memory formation and psychological disorders.To investigate the molecular basis underlying this labile state, we have employed an inducible protein activity-manipulation technique and examined the molecular dynamics of αCaMKⅡ during long-term memory reactivation in the mouse brain.We show that an upward-shift of CaMKⅡ activity within the initial 10 minute time-window of synaptic activation is capable of shifting the established long-term potentiation to the higher level.This critical time window parallels the initial labile phase of post-reactive long-term memory since post-reactive upward-shift of CaMKII activity during this period also disrupts post-reactive long-term memory representations.However, post-reactive short-term memory is still intact upon the same manipulation.Thus, we conclude that CaMKⅡ plays a crucial role in numerical and dynamical control and maintenance of synaptic representation of long-term memory traces during reconsolidation process.Methods Using hippocampus-dependent memory (contextual fear memory), or amygdala-dependent memory (auditory fear memory) to test the memory reconsolidation function of animals.Conditioned stimulus (conditioned stimulus, CS) is 85 dB, 2800 HZ sound stimulation, non-conditioned stimulus (unconditioned stimulus, US) is the intensity of 0.5 mA for 30 seconds foot electrical stimulation.US / CS paired training, the mice continued to stay at the training ground for 30 seconds.During the.test process, the mice were put back the original training ground to record 3 minutes freezing response (contextual freezing).Then, mice were placed in a new place, and record CS responses after 3 minutes.Continuously providing the same 3-minute sound stimulation the same as CS, record freezing response by interval of 5 seconds (cued freezing).Repeat the test one hour after the test, as the PR-STM indicators, results 24 hours after the test, as the PR-LTM indicators.Results Analysis the memory of one month, our tests showed that memory retrieval within 30 minutes increase CaMKII activity, test memory 1 hour after the memory retrieval is not affected, but the tests 24 hours after the memory retrieval, we found that memory is impairment.Conclusion CaMKⅡ activity affect the reconsolidation of PR-LTM.