Abstract
Several reports have shown that after specific reminders are presented, consolidated memories pass from a stable state to one in which the memory is reactivated. This reactivation implies that memories are labile and susceptible to amnesic agents. This susceptibility decreases over time and leads to a re-stabilization phase usually known as reconsolidation. With respect to the biological role of reconsolidation, two functions have been proposed. First, the reconsolidation process allows new information to be integrated into the background of the original memory; second, it strengthens the original memory. We have previously demonstrated that both of these functions occur in the reconsolidation of human declarative memories. Our paradigm consisted of learning verbal material (lists of five pairs of nonsense syllables) acquired by a training process (L1-training) on Day 1 of our experiment. After this declarative memory is consolidated, it can be made labile by presenting a specific reminder. After this, the memory passes through a subsequent stabilization process. Strengthening creates a new scenario for the reconsolidation process; this function represents a new factor that may transform the dynamic of memories. First, we analyzed whether the repeated labilization-reconsolidation processes maintained the memory for longer periods of time. We showed that at least one labilization-reconsolidation process strengthens a memory via evaluation 5 days after its re-stabilization. We also demonstrated that this effect is not triggered by retrieval only. We then analyzed the way strengthening modified the effect of an amnesic agent that was presented immediately after repeated labilizations. The repeated labilization-reconsolidation processes made the memory more resistant to interference during re-stabilization. Finally, we evaluated whether the effect of strengthening may depend on the age of the memory. We found that the effect of strengthening did depend on the age of the memory. Forgetting may represent a process that weakens the effect of strengthening.
Highlights
Animals’ brains constantly encode the features of their surrounding environment; this is a critical function for everyday animal survival as well as for learning new information to successfully interact with the external world
Considering the lack of significant differences in List 1 performance and the high number of errors made by the NR 8d group, we proposed that the absence of retrieval-induced forgetting (RIF) could reflect interference and forgetting of List 1 over time
We have demonstrated that mere retrieval does not affect the stability of retrieved memories, which is invulnerable to different treatments [20,21]
Summary
Animals’ brains constantly encode the features of their surrounding environment; this is a critical function for everyday animal survival as well as for learning new information to successfully interact with the external world In this context, the process of transforming new information into long-lasting memory has been of great interest in neurobiology over the last century. The seminal studies of Muller and Pilzecker [1] using verbal learning led to the idea that memories become enduring through a process of consolidation. This theory assumes that memories are labile during a window of time after acquisition; memories become stable and resistant to amnesic agents over time. The term reconsolidation does not represent the recapitulation of initial consolidation, but rather, it refers to the functional role of this process: to stabilize memories [7]
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