Relevance of ERK1/2 Post-retrieval Participation on Memory Processes: Insights in Their Particular Role on Reconsolidation and Persistence of Memories

Abstract

Back in 1968, Misanin and his group posited that reactivation of consolidated memories could support changes in that trace, similar to what might happen during the consolidation process. Not until 2000, when Nader et al. (2000) studied the behavioral effect of a protein synthesis inhibitor on retrieved memories, could this previous statement be taken under consideration once again; suggesting that consolidated memories can become labile after reactivation. The process of strengthening after memory labilization was named memory reconsolidation. In recent years, many studies pointed towards a critical participation of the extracellular signal-regulated kinase (ERK)/mitogen activated protein kinases (MAPKs) pathway in different memory processes (e.g., consolidation, extinction, reconsolidation, among others). In this review article, we will focus on how this system might be modulating the processes triggered after retrieval of well-consolidated memories in mice.

Keywords: ERK/MAPK; PD098059; inhibitory avoidance; memory persistence; memory reconsolidation; mice.

Figure 1

Role of hippocampal cytosolic extracellular signal-regulated kinase 2 (ERK2) in memory reconsolidation (stabilization, strengthening and persistence). Schematic representation of cytosolic ERK2 activation levels at different time points after memory reactivation on mice trained in the IA task. Solid lines represent cytosolic ERK2 activation levels at 15 min, 45 min and 3 h post-retrieval session in animals trained with a low (LFS), high (HFS) footshock intensity or without shock (unshocked, USh). Dashed line represents LFS-trained animals that received a dHIP infusion of PD098059 40 min after the reactivation session ended (T1). ERK2 activation levels between 15 and 45 or between 45 and 180 min have not been determined, but are represented as continuous lines in order to simplify interpretations. T1: reactivation session.