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14th of June, Neuroseminar: Tomonori Takeuchi

Dopaminergic memory modulation by two distinct novelty systems

Tomonori Takeuchi Department of Biomedicine and Dandrite, Aarhus University The talk will take place in Faculty Club 16.6 on Thursday June 14th at 3 pm. Please join us prior to the talk for coffee and cookies. ABSTRACT It is difficult to remember what you had for dinner a few weeks ago. Everyday memories, including our experiences and remembered facts, are automatically encoded in the hippocampus, and then decay very rapidly (Morris et al., EJN, 2006). In contrast, many people have vivid memories of the first dinner date with their partner, including details like the name of the restaurant and the food they had. What makes memories last? Memory retention can be boosted by a mechanism that involves novelty-associated dopamine release in the hippocampus (Wang et al., PNAS, 2010). Recent our studies (Takeuchi et al., Nature, 2016) revealed that projections from neurons in the locus coeruleus to the hippocampus can drive the environmental novelty-associated enhancement of memory retention through non-canonical release of dopamine in the hippocampus. Our results are complemented with the subsequent finding of direct detection of dopamine co-release from hippocampal axons of the locus coeruleus (Kempadoo et al., PNAS, 2016). These studies also raise a possibility that the impact of distinct novel experiences which by their very nature bare minimal relationship to past experiences (‘distinct novelty’) may differ from novel experiences that share some commonality with past experiences (‘common novelty’).Projections from neurons in the ventral tegmental area to the hippocampus might mediate common novelty which modulates the memory retention with a narrow time window. We now propose that memory of events accompanied by novelty can be selectively retained through two distinct dopaminergic mechanisms, depending on the nature of the novel experience itself (Yamasaki and Takeuchi, Neural Plasticity, 2017; Duszkiewicz et al., submitted).