Nerve pathway · one in each half of the brain
Optic radiation
Also called Geniculocalcarine tract, Geniculostriate pathway, Gratiolet's radiation
A fan of fibers carrying vision from the thalamus to the back of the brain.
The optic radiation is the last leg of the visual pathway. It fans out from a relay station in the thalamus and sweeps back to the visual cortex at the very back of the brain. Each side carries the opposite half of your view, from both eyes. Some of its fibers take a surprising detour forward into the temporal lobe before heading back.
Where it is
Deep inside the side and back of the brain. It starts in the thalamus, wraps around the side of the fluid-filled lateral ventricle, and ends in the occipital lobe, at the back of your head.
What it does
Delivers the picture
It carries signals from the lateral geniculate nucleus to the primary visual cortex, the first cortex stop for seeing.
Keeps the map in order
Its fibers stay neatly arranged, so neighboring points in your view land on neighboring points in the cortex.
Splits the view
The upper part of your view travels in a lower bundle through the temporal lobe, while the lower part travels in an upper bundle through the parietal lobe.
Think of it as a wide fan of highway lanes spreading out from a junction, each lane carrying one slice of the picture to its exact spot on the big screen at the back.
Works with
- Lateral geniculate nucleusIt starts at this relay station in the thalamus, which receives the signals from the eyes.
- Primary visual cortexIt ends here, delivering a neat map of your view to the brain's first visual area.
- Optic chiasmThanks to the crossing at the chiasm, each optic radiation carries the opposite half of the world from both eyes.
- Lateral ventriclesIt sweeps around the side of these fluid-filled spaces on its way to the back.
- Temporal lobeFibers for the upper part of your view loop forward into the temporal lobe before turning back.
- Parietal lobeFibers for the lower part of your view travel back through the parietal lobe.
When it goes wrong
Meyer's loop and "pie in the sky"
The fibers for the upper part of your view make a forward loop into the temporal lobe called Meyer's loop. Damage there, for example from surgery or a stroke, can wipe out the upper quarter of vision on the opposite side, a pattern doctors call "pie in the sky".
"Pie on the floor"
Damage to the upper fibers in the parietal lobe can instead remove the lower quarter of vision on the opposite side.
Losing half the view
A larger injury can remove the whole opposite half of vision in both eyes. People may bump into things on that side without realizing why.
For learning only, not medical advice. If you have a health concern, talk to a doctor.
Surprising facts
- Meyer's loop is named after Adolf Meyer, a Swiss-American psychiatrist who described it in the early 1900s.
- Before operating on the temporal lobe, for example in epilepsy surgery, surgeons can now map this tract with special brain scans to avoid cutting it.
- The left optic radiation carries the right half of the world, from both eyes, and the right one carries the left half.
Where the name comes from
Radiation means "spreading out like rays", describing how the fibers fan out. It was first described by the anatomist Louis Pierre Gratiolet in the mid-1800s.
Learn it in a lesson
- SeeingFrom the eye to the back of the brain. A short guided lesson in 3D.
Quick quiz
3 questions. Your answers are saved and come back in your daily review.
Which of these is a job of the optic radiation?
Show the answer
Delivers the picture. It carries signals from the lateral geniculate nucleus to the primary visual cortex, the first cortex stop for seeing.
Delivers the picture. It carries signals from the lateral geniculate nucleus to the primary visual cortex, the first cortex stop for seeing.
The optic radiation is part of which larger structure?
Show the answer
White matter pathways. It belongs to the white matter pathways.
White matter pathways. It belongs to the white matter pathways.
Which part fits this description? "Like a wide fan of highway lanes spreading out from a junction, each lane carrying one slice of the picture to its exact spot on the big screen at the back."
Show the answer
Optic radiation. It is the optic radiation. A fan of fibers carrying vision from the thalamus to the back of the brain.
Optic radiation. It is the optic radiation. A fan of fibers carrying vision from the thalamus to the back of the brain.
These parts now come back in your daily review, just before you would forget them.
Practice it and its neighbors in 3DSources
- Optic radiation, Radiopaedia
- Meyer loop, Radiopaedia
- Neuroscience Online, Chapter 15: Visual Processing: Cortical Pathways, McGovern Medical School at UTHealth Houston
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Explore the optic radiation in 3D
Turn it around, zoom inside and see how it connects to the rest of the brain, then test yourself with quick quizzes.
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