Long-term memory persistence

Abstract

Memories lasting 6–24 h or more are usually called long-term memories. Some of them, however, persist just a couple of days, and others last months or years. Recent studies have described a delayed post-training phase that induces memory persistence. Two mechanisms have been described in rodents immediately after hippocampal cellular consolidation is over that have been suggested to pave the way for systems consolidation. One consists of the single, delayed activation of a hippocampal set of processes initiated by the local release and action of brain-derived neurotrophic factor, triggered by D1 receptor activation by dopaminergic fibers coming from the ventral tegmental area 12 h after acquisition. The other involves a circadian activation of another mechanism that involves repeated cyclic AMP and ERK activation, also in the hippocampus. Both mechanisms may be related; brain-derived neurotrophic factor action is mediated by ERKs.