Learning Objectives
Distinguish between the 6-layered neocortex and the 3-layered paleocortex of the hippocampus. Identify the low-magnification anatomical structure of the hippocampal formation. Understand the clinical significance of the hippocampus in memory and pathology (e.g., Alzheimer’s, epilepsy).
Normal Histology: The Hippocampus
The hippocampus is a critical component of the limbic system, located in the medial temporal lobe. Unlike the majority of the cerebral cortex, it is classified as paleocortex (or archicortex).
- Paleocortex Structure: The hippocampus consists of only three layers, compared to the six layers found in the neocortex.
- Anatomical Organization: At low magnification, it appears as a distinct, curved structure (often described as resembling a seahorse or a jelly roll) tucked into the floor of the lateral ventricle’s temporal horn.
- Key Subregions: The formation includes the Dentate Gyrus, the Hippocampus Proper (Cornu Ammonis – CA1 through CA4), and the Subiculum.
Comparative Histology Summary
| Feature | Neocortex | Hippocampus (Paleocortex) |
|---|---|---|
| Layer Count | 6 Layers | 3 Layers |
| Evolutionary Age | Newer (Higher functions) | Older (Limbic/Memory) |
| Vulnerability | Variable | Highly sensitive to hypoxia (CA1/Sommer’s Sector) |
Activity
