Dentate gyrus circuits for encoding, retrieval and discrimination of episodic memories

Abstract

The dentate gyrus (DG) has a key role in hippocampal memory formation. Intriguingly, DG lesions impair many, but not all hippocampus-dependent mnemonic functions, indicating that the rest of the hippocampus (CA1-CA3) can operate autonomously under certain conditions. An extensive body of theoretical work has proposed how the architectural elements and various cell types of the DG may underlie its function in cognition. Recent studies recorded and manipulated the activity of different neuron types in the DG during memory tasks and opened exciting new insights in the mechanisms of DG computational processes, particularly for encoding, retrieval and discrimination of similar memories. Here, we review these DG-dependent mnemonic functions in light of the new findings and explore mechanistic links between cellular and network properties and the computations performed by the DG.

cFos Ensembles in the Dentate Gyrus Rapidly Segregate Over Time and do not Form a Stable Map of Space

“…Thus, cFos is not only an indicator of intense neuronal activity but also reflects a clock signal 6,45 that is crucial for LTP, perhaps selecting a specific subset of neurons for memory storage. Our results support the concept that cFos+ neurons in DG encode an episode, but not a spatial position 46 . The disconnect between cFos expression and place cell activity has also been reported in a recent study of CA1 pyramidal cells 48 and is therefore not a specific property of DG granule cells.…”

cFos ensembles in the dentate gyrus rapidly segregate over time and do not form a stable map of space

“…Thus, cFos is not only an indicator of intense neuronal activity but also reflects a clock signal (Frank, 2016;McCauley et al, 2019) that is crucial for LTP, perhaps selecting a specific subset of neurons for memory storage. Our results support the concept that cFos+ neurons in DG encode an episode, but not a spatial position (Hainmueller & Bartos, 2020). The disconnect between cFos expression and place cell activity has also been reported in a recent study of CA1 pyramidal cells (Poll et al, 2020;Tanaka et al, 2018) and is therefore not a specific property of DG granule cells.…”

Dentate gyrus development requires a cortical hem-derived astrocytic scaffold

“…The dentate gyrus (DG) of the hippocampus, is a packed V-shaped layer of granule neurons involved in spatial memory formation and pattern separation 12 , which hosts a niche of radial glia-like cells supporting adult neurogenesis 13 . During embryonic development, DG granule neuron progenitors originate from the dentate neuroepithelium (DNE) or primary (1ry) matrix of the archicortex.…”