Novelty and Dopaminergic Modulation of Memory Persistence: A Tale of Two Systems.

Duszkiewicz AJ
McNamara CG
Takeuchi T
Genzel L

This article reviews recent findings on how - in contrast to more mundane everyday happenings - new or unusual events are better remembered. Recently, two different signaling systems in the brain have been described as being important for this. We suggest that one of these systems is more important for causing new memories to be incorporated in a way that draws on similarities with other previous experiences, allowing the memory to be generalised. In contrast, we also propose that the other signaling system is more important for  remembering the exact details (some of which are often incidental) of that particular novel experience.

Scientific Abstract

Adaptation to the ever-changing world is critical for survival, and our brains are particularly tuned to remember events that differ from previous experiences. Novel experiences induce dopamine release in the hippocampus, a process which promotes memory persistence. While axons from the ventral tegmental area (VTA) were generally thought to be the exclusive source of hippocampal dopamine, recent studies have demonstrated that noradrenergic neurons in the locus coeruleus (LC) corelease noradrenaline and dopamine in the hippocampus and that their dopamine release boosts memory retention as well. In this opinion article, we propose that the projections originating from the VTA and the LC belong to two distinct systems that enhance memory of novel events. Novel experiences that share some commonality with past ones ('common novelty') activate the VTA and promote semantic memory formation via systems memory consolidation. By contrast, experiences that bear only a minimal relationship to past experiences ('distinct novelty') activate the LC to trigger strong initial memory consolidation in the hippocampus, resulting in vivid and long-lasting episodic memories.

diagram of VTA HPC PFC brain system and separately the LC HPC brain system
(A) In this article the authors propose that common novelty activates the ventral tegmental area-hippocampus (VTA-HPC) system to trigger initial memory consolidation, followed by increased systems memory consolidation between HPC and the prefrontal cortex (PFC), with enhance sharp wave-ripple (SWR)-related reactivation aiding long-term retention of the memory trace and associated semantic information. (B) They also propose that distinct novelty causes greater activation of the locus coeruleus (LC)-HPC system, boosting initial memory consolidation in HPC and enhancing retention of unrelated experiences (both preceding and subsequent), which results in long-term retention of a detailed episodic memory trace.
Citation
2019. Trends Neurosci., 42(2):102-114.
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