This hub page provides navigation to all hippocampal neuron types in the NeuroWiki knowledge base. The hippocampus is a bilateral seahorse-shaped brain structure (Greek: ἱππόκαμπος) critical for episodic memory formation, spatial navigation, and memory consolidation. Hippocampal neurons exhibit highly organized laminar architecture and are among the most vulnerable populations in Alzheimer's disease, with early and severe pathology.
The hippocampal formation comprises several subregions with distinct neuronal populations:
flowchart TD
subgraph Hippocampal_Formation["Hippocampal Formation"]
EC["Entorhinal Cortex"]
DG["Dentate Gyrus"]
CA3["CA3"]
CA2["CA2"]
CA1["CA1"]
SUB["Subiculum"]
EC -->|"Perforant path"| DG
DG -->|"Mossy fibers"| CA3
CA3 -->|"Schaffer collaterals"| CA1
CA3 -->|"Associational"| CA3
CA1 --> SUB
SUB --> EC
end
subgraph Trisynaptic_Circuit["Trisynaptic Circuit"]
INPUT["Entorhinal Input"]
GRAN["Granule Cells"]
PYR3["CA3 Pyramidal"]
PYR1["CA1 Pyramidal"]
OUTPUT["Subiculum Output"]
INPUT --> GRAN
GRAN --> PYR3
PYR3 --> PYR1
PYR1 --> OUTPUT
end
flowchart TD
subgraph Principal_Neurons["Principal Neurons"]
HN["Hippocampal Neurons"]
HN --> HCA1["CA1 Pyramidal Neurons"]
HN --> HCA2["CA2 Pyramidal Neurons"]
HN --> HCA3["CA3 Pyramidal Neurons"]
HN --> HCA4["CA4/CA3c Neurons"]
HN --> HSUB["Subiculum Pyramidal"]
HN --> HDG["Dentate Granule Cells"]
HN --> HEC["Entorhinal Stellate Cells"]
end
subgraph Interneurons["Interneurons"]
INT["Hippocampal Interneurons"]
INT --> PV["PV+ Basket Cells"]
INT --> SSTOLM["SST+ OLM Cells"]
INT --> CCK["CCK+ Interneurons"]
INT --> CR["Calretinin+ Cells"]
INT --> MOSS["Mossy Cells"]
INT --> HIL["Hilar Interneurons"]
end
- Dentate Gyrus Granule Cells — Main DG excitatory neurons
- Dentate Granule Epilepsy — Epileptogenesis mechanisms
Key characteristics:
- Hippocampal CA1 Neurons — Most vulnerable to AD
- CA3 Pyramidal Neurons — Recurrent collaterals, pattern completion
- CA2 Pyramidal Neurons — Social memory, resistant to AD
CA1 characteristics:
CA3 characteristics:
¶ Subiculum and Entorhinal Cortex
- Subiculum Pyramidal Neurons — Hippocampal output
- Entorhinal Stellate Cells — Layer II grid cells
Entorhinal cortex:
- Basket Cells (Fast-Spiking)
- PV Interneurons
Functions: Perisomatic inhibition, gamma oscillation generation, feedforward inhibition
- SST Interneurons
- OLM (oriens-lacunosum moleculare) cells
Functions: Dendritic inhibition, theta rhythm modulation, feedback circuits
- Mossy Cells — DG hilar excitatory interneurons
- CCK Interneurons — Cannabinoid-modulated
- Calretinin Interneurons — Calbindin family
| Neuron Type |
Specific Markers |
Transcription Factors |
| DG Granule |
Prox1, Calbindin |
NeuroD1, Tbr2 |
| CA1 Pyramidal |
Satb2, Calbindin |
Lhx2, Emx2 |
| CA3 Pyramidal |
Calbindin, KA1 |
Lhx2, Emx2 |
| PV+ Interneurons |
Pvalb, GAD67 |
Lhx6, Nkx2.1 |
| SST+ Interneurons |
Sst, GAD67 |
Lhx6, Nkx2.1 |
| Mossy Cells |
Calretinin, GluR2-4 |
Prox1 |
The hippocampus is ground zero for early AD pathology:
- Granule cell dispersion — Abnormal granule cell layer organization
- Mossy fiber sprouting — Recurrent excitatory circuits
- Interneuron loss — Reduced inhibition
- Hilar cell loss — Endfolium sclerosis
- Schizophrenia — Hippocampal volume reduction, hyperactivity
- Depression — Reduced neurogenesis, stress effects
- PTSD — Contextual fear conditioning abnormalities
- Aging — Normal age-related changes vs pathology
- Perforant path — Entorhinal cortex layer II → DG granule cells
- Mossy fibers — DG granule cells → CA3 pyramidal cells
- Schaffer collaterals — CA3 → CA1 pyramidal cells