Auftreten von Gedächtnisspuren im Hippocampus von Nagern
Kognitive und systemische Humanneurowissenschaften
Zusammenfassung der Projektergebnisse
The hippocampus is decisive for the storage of conscious memories. Memory-specific neuronal ensembles – so called engrams – exist in all subfields of the rodent hippocampus. However, knowledge about how these engrams develop and maintain memory-specific activity during long-term learning is scarce. In the here proposed and finished project, we implanted chronic two-photon calcium imaging windows above the hippocampus of mice to image population activity in the dentate gyrus of head-fixed mice performing a goal-oriented spatial memory tasks in a virtual reality. We record granule cell (GC) activity in the dentate gyrus and compared it with the one of principal cells (PCs) in CA1 and CA3. Since the discovery of place cells, which fire in specific fields within the environment by O’Keefe in 1978, the urgent question emerged on how place cell assemblies as a whole representing spatial contexts emerge in the three hippocampal subfields during learning. Here, we addressed this question by establishing a behavioural paradigm in which head-fixed mice explore a ‘familiar’ virtual environment in which they have been trained over several days to obtain food rewards at specific locations. After training in the familiar context, mice are exposed to a ‘novel’ virtual environment to explore new reward locations. We found first, that place cell assemblies emerge slowly during the learning process in the ‘novel’ context on subsequent days (3-4) and showed a high day-by-day stability. Second, we found that reliability in the representation of the learned novel spatial environment as well as the differentiation between both contexts differed among the three hippocampal areas. Representation showed some overlap between the two environments in the DG but strong remapping in CA1-3. Finally, we observed a strong difference in the pattern separation between the left and right DG with the left DG expressing a stronger spatial tuning and discrimination between environments than the right DG. Thus, within this project we shed new light on the emergence and stabilization of spatial memories in the DG and the differences in spatial representations along the classic hippocampal tri-synaptic loop.
Projektbezogene Publikationen (Auswahl)
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Parallel emergence of stable and dynamic memory engrams in the hippocampus. Nature, 558(7709), 292-296.
Hainmueller, Thomas & Bartos, Marlene
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Dentate gyrus circuits for encoding, retrieval and discrimination of episodic memories. Nature Reviews Neuroscience, 21(3), 153-168.
Hainmueller, Thomas & Bartos, Marlene
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Hemisphere-specific spatial representation by hippocampal granule cells. Nature Communications, 13(1).
Cholvin, Thibault & Bartos, Marlene
