Laminar Organization of the Entorhinal Cortex in Macaque Monkeys Based on Cell-Type-Specific Markers and Connectivity

The entorhinal cortex (EC) is a major gateway between the hippocampus and telencephalic structures, and plays a critical role in memory and navigation. Through the use of various molecular markers and genetic tools, neuron types constituting EC are well studied in rodents, and their layer-dependent...

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Published in:Frontiers in neural circuits 2021-12, Vol.15, p.790116-790116
Main Authors: Ohara, Shinya, Yoshino, Rintaro, Kimura, Kei, Kawamura, Taichi, Tanabe, Soshi, Zheng, Andi, Nakamura, Shinya, Inoue, Ken-Ichi, Takada, Masahiko, Tsutsui, Ken-Ichiro, Witter, Menno P
Format: Article
Language:English
Subjects:
Amygdala
Animals
Calbindin
Cortex (entorhinal)
Entorhinal Cortex
Gene expression
Haplorhini
Hippocampus
Immunohistochemistry
lateral entorhinal cortex
Macaca
medial entorhinal cortex
Monkeys & apes
Neural Circuits
Neural networks
Neurons
Nucleus accumbens
primates
Purkinje cell protein 4
reelin
Reelin protein
Telencephalon
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Summary:The entorhinal cortex (EC) is a major gateway between the hippocampus and telencephalic structures, and plays a critical role in memory and navigation. Through the use of various molecular markers and genetic tools, neuron types constituting EC are well studied in rodents, and their layer-dependent distributions, connections, and functions have also been characterized. In primates, however, such cell-type-specific understandings are lagging. To bridge the gap between rodents and primates, here we provide the first cell-type-based global map of EC in macaque monkeys. The laminar organization of the monkey EC was systematically examined and compared with that of the rodent EC by using immunohistochemistry for molecular markers which have been well characterized in the rodent EC: reelin, calbindin, and Purkinje cell protein 4 (PCP4). We further employed retrograde neuron labeling from the nucleus accumbens and amygdala to identify the EC output layer. This cell-type-based approach enabled us to apply the latest laminar definition of rodent EC to monkeys. Based on the similarity of the laminar organization, the monkey EC can be divided into two subdivisions: rostral and caudal EC. These subdivisions likely correspond to the lateral and medial EC in rodents, respectively. In addition, we found an overall absence of a clear laminar arrangement of layer V neurons in the rostral EC, unlike rodents. The cell-type-based architectural map provided in this study will accelerate the application of genetic tools in monkeys for better understanding of the role of EC in memory and navigation.
ISSN:1662-5110
1662-5110
DOI:10.3389/fncir.2021.790116