Trends in Neurosciences
Mechanisms of memory stabilization: are consolidation and reconsolidation similar or distinct processes?
Section snippets
Mechanisms of memory consolidation
Memory consolidation has been studied for more than a century 3, 9. It has been defined on the basis of observations that a newly formed memory undergoes a transformation process, becoming stronger and more resilient over time until it is insensitive to disruption. Factors shown to interfere with consolidation include cerebral trauma, electroconvulsive shock, protein synthesis inhibitors and several drugs [3]. In several species and memory systems, many molecular, anatomical and system-level
Molecular requirements of reconsolidation
The reconsolidation hypothesis, first suggested in the 1960s [10] and recently re-proposed following the work of Nader et al. [7], implies that every time a memory is reactivated it must undergo again a process of consolidation to be maintained. This idea contrasts with the classical view that a memory consolidates only once and, over time, becomes stronger and more stable.
To unravel this controversy, a great deal of effort has recently focused on determining whether reconsolidation, as implied
Temporal requirements of reconsolidation
Further distinctions between the two processes became evident when the temporal requirements for protein synthesis during reconsolidation were analyzed. In IA, the protein synthesis requirement induced by recall is a function of the age of the memory, with recent (2- and 7-day-old) but not remote (14- and 28-day-old) memories becoming sensitive to protein synthesis inhibitors upon reactivation [35]. Similar results, indicating a temporally graded requirement for protein synthesis after recall,
Concluding remarks and future directions
The knowledge accumulated so far indicates that reconsolidation of a reactivated memory and consolidation of an initial learning are characterized by distinctive features. First, they involve different brain areas and circuits. Consolidation appears to require several areas that are not essential for reconsolidation and, as will be suggested in this section, reconsolidation might involve mostly modulatory systems. Second, consolidation and reconsolidation also differ in their temporal dynamics.
Acknowledgements
I thank Maria Milekic and Stephen Taubenfeld for helpful comments and discussions.
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