Nucleus · one in each half of the brain

Lateral geniculate nucleus

Also called LGN, Lateral geniculate body

Vision's relay station: a six-layered bent knee where signals from your eyes arrive.

Open in 3D

The lateral geniculate nucleus is a small bump on the underside of the thalamus that receives signals from your eyes. It passes the picture on to the primary visual cortex at the back of the brain through a fan of fibers called the optic radiation. It is stacked in six neat layers, each getting input from only one eye. Surprisingly, most of its incoming connections come not from the eyes but from other brain areas, such as the visual cortex feeding back, so it may help tune what you see.

Where it is

On the underside of the back of the thalamus, on its outer side, where the optic tract from the eyes ends.

What it does

Think of it as a six-lane highway toll booth, where each lane carries traffic from just one eye before it heads to the visual cortex.

Works with

• Optic nerve (II)Carries signals from the eye that end here.
• Optic chiasmWhere fibers cross so each LGN sees the opposite half of the world.
• Optic radiationThe fan of fibers that carries its output to the visual cortex.
• Primary visual cortexReceives its signals and sends a large stream of feedback back down.
• Relay neuronThe kind of nerve cell that carries its signals up to the cortex.

When it goes wrong

For learning only, not medical advice. If you have a health concern, talk to a doctor.

Surprising facts

• Most of the nerve fibers leaving your eyes end in the LGN.
• Most of its incoming connections come from other brain areas, like the cortex feeding back, rather than from the eyes, so what reaches your awareness is already being tuned.
• The left LGN handles the right half of what you see, and the right LGN handles the left half, thanks to the crossing at the optic chiasm.

By the numbers

Where the name comes from

"Geniculate" comes from Latin "genu", meaning "knee", because its layers bend like a knee. "Lateral" means toward the side.

Learn it in a lesson

• SeeingFrom the eye to the back of the brain. A short guided lesson in 3D.
• The thalamusThe brain's relay station. A short guided lesson in 3D.

Sources

1. Neuroanatomy, Nucleus Lateral Geniculate, StatPearls, NCBI Bookshelf
2. Parallel Streams of Information from Retina to Cortex, Neuroscience (Purves et al.), NCBI Bookshelf
3. 14.2 Central Processing, OpenStax, Anatomy and Physiology 2e

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