Direct comparisons of the size and persistence of anisomycin-induced consolidation and reconsolidation deficits

An issue of increasing theoretical interest in the study of learning is to compare the processes that follow an initial learning experience (such as learning an association between a context and a shock; memory consolidation processes) with those that follow retrieval of that learning experience (such as exposure to the context in the absence of shock; memory reconsolidation and extinction processes). Much of what is known about these processes comes from separate experiments examining one process or the other; there have been few attempts to compare these processes directly in a single experiment. A challenge in between-experiment comparisons of consolidation and reconsolidation deficits is that they frequently involve comparisons between groups that are not matched on factors that may influence the size and persistence of these deficits (e.g., prior learning experience, memory expression prior to deficit). The following experiments examined the size and persistence of these deficits after matching both the amount of experience with a context and the levels of performance in that context prior to delivery of the protein synthesis inhibitor anisomycin. We found that systemic or intrahippocampal administration of anisomycin caused a deficit in groups receiving context conditioning (consolidation groups) or reactivation (reconsolidation groups) immediately prior to the injections. With systemic injections, the deficit was larger and more persistent in consolidation groups; with intrahippocampal injections, the initial deficit was statistically identical, yet was more persistent in the consolidation group. These experiments showed that when experiences and performance are matched prior to anisomycin injections, consolidation deficits are generally larger and more persistent compared to reconsolidation deficits.