How are LGN layers organized with respect to input eye and cell type?

• A. Three layers receiving input from both eyes
• B. No separation by eye
• C. Only magnocellular layers exist
• D. Six layered structure with magnocellular layers (1-2) and parvocellular layers (3-6); each layer receives input from one eye, with contralateral/ipsilateral eye input distributed across layers

Answer: (D)

The key idea is that the LGN is organized into six layers that segregate input by eye and by cell type. The two outer layers are magnocellular, and the inner four are parvocellular. Each layer receives input from only one eye, so there’s no mixing of left and right eye information within a single layer. The contralateral (opposite side) eye feeds layers 1, 4, and 6, while the ipsilateral (same side) eye feeds layers 2, 3, and 5. This arrangement preserves eye-specific channels through the LGN and assigns each layer a distinct cell-type family, setting up parallel pathways for different aspects of vision.