Lateral geniculate nucleus
Relay nuclei · Sectoranopia
Six-layered relay in the posterior thalamus where optic-tract axons synapse on the neurones that form the optic radiation. Eye-of-origin and pathway-specific layering is preserved and the retinotopic map is carried through to V1; heavy feedback from cortex makes it a gate rather than a passive relay.
Traced from the start
- Temporal hemiretinaNasal hemiretinaMacula and papillomacular bundle
- Optic nerve (CN II)
- Optic tract
- Lateral geniculate nucleus
Detail
- Eye layering
- Contralateral eye to layers 1, 4 and 6; ipsilateral eye to layers 2, 3 and 5
- Cell types
- Magnocellular layers 1-2 (motion, luminance); parvocellular layers 3-6 (colour, fine detail); koniocellular cells between layers
- Blood supply
- Anterior choroidal artery and the lateral posterior choroidal branch of the posterior cerebral artery
- Output
- Optic radiation (geniculocalcarine tract) to layer 4 of V1
When it goes wrong
Infarction of the LGN (anterior choroidal or lateral posterior choroidal artery)
Contralateral homonymous wedge-shaped sectoranopia or hemianopia with no RAPD, because the pupillary fibres have already left the tract
Practise this structure
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