Projections of hippocampal CA2 pyramidal neurons: Distinct innervation patterns of CA2 compared to CA3 in rodents

The hippocampus is a center for spatial and episodic memory formation in rodents. Understanding the composition of subregions and circuitry maps of the hippocampus is essential for elucidating the mechanism of memory formation and recall. For decades, the trisynaptic circuit (entorhinal cortex layer...

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Bibliographic Details
Published in:Hippocampus 2023-06, Vol.33 (6), p.691-699
Main Authors: Shinohara, Yoshiaki, Kohara, Keigo
Format: Article
Language:English
Subjects:
Animals
CA2
Cortex (entorhinal)
Cortex (temporal)
Dentate gyrus
Entorhinal Cortex - physiology
Hippocampus
Hippocampus - physiology
Innervation
Neural networks
Pyramidal cells
Pyramidal Cells - physiology
pyramidal neuron
rodent
Rodentia
Spatial memory
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Summary:The hippocampus is a center for spatial and episodic memory formation in rodents. Understanding the composition of subregions and circuitry maps of the hippocampus is essential for elucidating the mechanism of memory formation and recall. For decades, the trisynaptic circuit (entorhinal cortex layer II—dentate gyrus — CA3—CA1) has been considered the neural network substrate responsible for learning and memory. Recently, CA2 has emerged as an important area in the hippocampal circuitry, with distinct functions from those of CA3. In this article, we review the historical definition of the hippocampal area CA2 and the differential projection patterns between CA2 and CA3 pyramidal neurons. We provide a concise and comprehensive map of CA2 outputs by comparing (1) ipsi versus contra projections, (2) septal versus temporal projections, and (3) lamellar structures of CA2 and CA3 pyramidal neurons.
ISSN:1050-9631
1098-1063
DOI:10.1002/hipo.23519