Context memories and reactivation: constraints on the reconsolidation hypothesis.

Recent evidence suggests that the maintenance of a reactivated contextual-fear memory requires a protein-synthesis-dependent reconsolidation process in the hippocampus (K. Nader, 2003). In contrast, the authors report a systematic set of experiments that failed to find evidence that the rat's reactivated memory for context becomes labile and requires a new protein to restabilize. Although injecting the protein-synthesis inhibitor into the dorsal hippocampus or intracerebroventricularly following the reactivation of the context memory had no effect, these same treatments did impair the initial consolidation of the context memory and the consolidation of a contextual-fear memory. These results suggest that there may be important constraints determining when a reactivated memory requires reconsolidation. The authors offer 2 hypotheses about the nature of these constraints.