Amygdala stimulation transforms short-term memory into remote memory by persistent activation of atypical PKC in the anterior cingulate cortex

Abstract

Although many studies have addressed the role of the amygdala in modulating long-term memory, it is not known whether weak training plus amygdala stimulation can transform a short-term memory into a remote memory. Object place recognition (OPR) memory after strong training remains hippocampus-dependent through the persistent action of PKM{zeta} for at least 6 days, but it is unknown whether weak training plus amygdala stimulation can transform short-term memory into an even longer memory, and whether such memory is stored through more persistent action of PKM{zeta} in hippocampus. We trained rats to acquire OPR and 15 min or 5 h later induced a brief pattern of electrical stimulation in basolateral amygdala (BLA). Our results reveal that a short-term memory lasting < 4 h can be converted into remote memory lasting at least 3 weeks if the BLA is activated 15 min, but not 5 h after learning. To examine how this remote memory is maintained, we injected ZIP, an inhibitor of atypical PKCs (aPKCs), PKM{zeta} and PKC{iota}/{lambda}, into either hippocampal CA1, dentate gyrus (DG), or anterior cingulate cortex (ACC). Our data reveal amygdala stimulation produces consolidation into remote memory, not by persistent aPKC activation and capture by synaptic tagging processes in the hippocampal formation, but in ACC. Our data establish a powerful modulating role of the BLA in forming remote memory and open a path in the search for neurological restoration of memory, based on enhancing synaptic plasticity in aging or neurodegenerative disorders such as Alzheimers disease.