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

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.

Long-Term Treatment with Fluvoxamine Decreases Nonmotor Symptoms and Dopamine Depletion in a Postnatal Stress Rat Model of Parkinson’s Disease

“…To correlate changes in a marker of oxidative stress, neurotransmitter levels, and PD symptoms, malondialdehyde (MDA), dopamine (DA), and serotonin levels were evaluated in brain tissues. Our results showed that MDA levels were increased in the striatum, the prefrontal cortex, and the hippocampus of maternally separated (MS) rats in agreement with studies by Mabandla and Russell [29], who showed that 6-OHDA is an oxidative stress-induced neurodegeneration [77][78][79][80][81][82]. As our stereotaxic injection of 6-OHDA into the MFB (to disrupt striatal, prefrontal cortex, and hippocampal innervation) also provided a good measurement of oxidative damage in the brain, it was evident that the lesion contributed to the observed decreased use of the right forelimb (impaired) of MS rats in the cylinder test.…”

Durable memories and efficient neural coding through mnemonic training using the method of loci

“…Third, mentally placing arbitrary to-be-remembered information at salient locations along the imagined path likely produces relatively bizarre associations, thereby triggering neural mechanisms related to novelty 35,37 . This in turn cranks up dopaminergic and noradrenergic release from the brainstem and ventral striatum towards the hippocampus 38,39 , which is thought to promote memory persistence by triggering synaptic 40 and systems consolidation 25 . Overall, we suggest that the method of loci favorably combines the abovementioned aspects (visuo-spatial processing, prior knowledge, novelty) to boost durable memories, leading to exceptional memory performance in athletes and initially mnemonics-naïve participants after training.…”

Dopamine and Noradrenaline in the Brain; Overlapping or Dissociate Functions?

“…Overall these studies confirmed the DA-NA cotransmission and the significant role of LC-DA in spatial memory encoding and novelty induced memory consolidation. Whether DA-NA release from LC contributes to distinct memory processes from VTA-DA remains elusive (Yamasaki and Takeuchi, 2017;Duszkiewicz et al, 2019).…”