Hippocampal Neurons Hub

Hippocampal Neurons Hub

<table class="infobox infobox-cell">
<tr>
<th class="infobox-header" colspan="2">Hippocampal Neurons Hub</th>
</tr>
<tr>
<td class="label">Neuron Type</td>
<td>Specific Markers</td>
</tr>
<tr>
<td class="label">DG Granule</td>
<td>Prox1, Calbindin</td>
</tr>
<tr>
<td class="label">CA1 Pyramidal</td>
<td>Satb2, Calbindin</td>
</tr>
<tr>
<td class="label">CA3 Pyramidal</td>
<td>Calbindin, KA1</td>
</tr>
<tr>
<td class="label">PV+ Interneurons</td>
<td>Pvalb, GAD67</td>
</tr>
<tr>
<td class="label">SST+ Interneurons</td>
<td>Sst, GAD67</td>
</tr>
<tr>
<td class="label">Mossy Cells</td>
<td>Calretinin, GluR2-4</td>
</tr>
</table>

Overview

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.

Hippocampal Organization

The hippocampal formation comprises several subregions with distinct neuronal populations:

```mermaid
flowchart TD
subgraph Hippocampal_Formation["Hippocampal Formation"]
EC["Entorhinal Cortex"]
DG["Dentate Gyrus"]
CA3["CA3"]
CA2["CA2"]
CA1["CA1"]
SUB["Subiculum"]

Hippocampal Neurons Hub

<table class="infobox infobox-cell">
<tr>
<th class="infobox-header" colspan="2">Hippocampal Neurons Hub</th>
</tr>
<tr>
<td class="label">Neuron Type</td>
<td>Specific Markers</td>
</tr>
<tr>
<td class="label">DG Granule</td>
<td>Prox1, Calbindin</td>
</tr>
<tr>
<td class="label">CA1 Pyramidal</td>
<td>Satb2, Calbindin</td>
</tr>
<tr>
<td class="label">CA3 Pyramidal</td>
<td>Calbindin, KA1</td>
</tr>
<tr>
<td class="label">PV+ Interneurons</td>
<td>Pvalb, GAD67</td>
</tr>
<tr>
<td class="label">SST+ Interneurons</td>
<td>Sst, GAD67</td>
</tr>
<tr>
<td class="label">Mossy Cells</td>
<td>Calretinin, GluR2-4</td>
</tr>
</table>

Overview

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.

Hippocampal Organization

The hippocampal formation comprises several subregions with distinct neuronal populations:

Hippocampal Neuron Hierarchy

Principal Neuron Populations

Dentate Gyrus Granule Cells

• Dentate Gyrus Granule Cells — Main DG excitatory neurons
• Dentate Granule Epilepsy — Epileptogenesis mechanisms

CA Pyramidal Neurons

• Hippocampal CA1 Neurons — Most vulnerable to AD
• CA3 Pyramidal Neurons — Recurrent collaterals, pattern completion
• CA2 Pyramidal Neurons — Social memory, resistant to AD

CA3 characteristics:
[@rebola2016]: Receives mossy fiber input from DG
[@rolls2013]: Extensive recurrent collaterals (autoassociative network)
[@ishizuka1990]: Projects via Schaffer collaterals to CA1
[@west1994]: Relatively preserved in early AD

Subiculum and Entorhinal Cortex

• Subiculum Pyramidal Neurons — Hippocampal output
• Entorhinal Stellate Cells — Layer II grid cells

Hippocampal Interneurons

PV+ Interneurons

• Basket Cells (Fast-Spiking)
• PV Interneurons

SST+ Interneurons

• SST Interneurons
• OLM (oriens-lacunosum moleculare) cells

Other Interneurons

• Mossy Cells — DG hilar excitatory interneurons
• CCK Interneurons — Cannabinoid-modulated
• Calretinin Interneurons — Calbindin family

Molecular Markers

Disease Relevance

Alzheimer's Disease

The hippocampus is ground zero for early AD pathology:

[@braak2006]: Entorhinal cortex — First region affected (Braak I-II), layer II stellate cell loss
[@west1994a]: CA1 neurons — Severe early loss, NFT accumulation
[@selkoe2002]: Synaptic dysfunction — LTP impairment before cell death
[@west1990]: Granule cell sparing — DG relatively preserved early
[@small2011]: Memory impairment — Episodic memory loss correlates with CA1 pathology

Temporal Lobe Epilepsy

• Granule cell dispersion — Abnormal granule cell layer organization
• Mossy fiber sprouting — Recurrent excitatory circuits
• Interneuron loss — Reduced inhibition
• Hilar cell loss — Endfolium sclerosis

Other Conditions

• Schizophrenia — Hippocampal volume reduction, hyperactivity
• Depression — Reduced neurogenesis, stress effects
• PTSD — Contextual fear conditioning abnormalities
• Aging — Normal age-related changes vs pathology

Hippocampal Circuits

Trisynaptic Circuit

Place Cell System

[@okeefe1971]: Place cells — CA1/CA3 neurons fire at specific locations
[@moser2017]: Grid cells — Entorhinal cortex hexagonal spatial representation
[@taube2007]: Head direction cells — Postsubiculum directional encoding

• Hippocampus Anatomy
• Memory Circuits
• Spatial Navigation
• LTP and Memory
• Entorhinal Cortex
• [Neurons](/cell-types/neurons) Major brain cell type
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• Temporal Lobe Epilepsy

External Links

• [Allen Brain Atlas - Hippocampus](https://portal.brain-map.org/explore/classes/multimodal-connectivity) — Connectivity data
• [Hippocampome](http://hippocampome.org/) — Hippocampal neuron encyclopedia
• [PubMed](https://pubmed.ncbi.nlm.nih.gov/) — Biomedical literature