Cortical area · one in each half of the brain

Primary visual cortex

Also called V1, Striate cortex, Brodmann area 17, Calcarine cortex

V1: the first cortical stop for sight, a precise map of what your eyes see.

Open in 3D

V1 lines the calcarine sulcus, a deep groove on the inner surface of the occipital lobe. It receives signals from the eyes by way of the thalamus and builds a point-by-point map of what you see. Its cells pick out simple features, such as edges at certain angles, the direction of movement and color. Every other visual area builds on its work.

Where it is

At the very back of the brain, mostly on the inner surface where the two halves face each other, lining the calcarine sulcus. A small part wraps around the back tip of the brain.

What it does

Think of it as a giant screen of tiny pixel detectors, each one watching its own small patch of your view for edges and lines.

Works with

• Lateral geniculate nucleusThis relay station in the thalamus sends V1 almost all of its input from the eyes.
• Optic radiationThis fan of fibers is the cable that carries visual signals from the thalamus to V1.
• CuneusThe area above the groove takes V1's output for the lower half of your view.
• Lingual gyrusThe area below the groove takes V1's output for the upper half of your view.
• Lateral occipital cortexV1's simple edges are passed on here to be built into whole objects and motion.
• Layer IV · Internal granularV1's input layer is split into several sublayers, and the stripe of Gennari runs through it.

When it goes wrong

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

Surprising facts

• Scientists David Hubel and Torsten Wiesel found V1's edge-detecting cells partly by accident, when the edge of a slide moving through their projector made a cell fire wildly. The work earned them a Nobel Prize in 1981.
• The small area at the center of your vision, around where you look directly, gets a far bigger share of V1 than its size would suggest. That matches the much finer detail you see there compared with your side vision.
• The stripe of Gennari is one of the few features of the brain's cell layers you can see without a microscope.

By the numbers

Where the name comes from

"Striate" means "striped". A pale stripe of nerve fibers runs through it, visible to the naked eye in a slice of brain. It is called the stripe of Gennari, after the Italian anatomist Francesco Gennari, who described it in the late 1700s. "Calcarine" comes from the Latin "calcar", a spur.

Learn it in a lesson

• SeeingFrom the eye to the back of the brain. A short guided lesson in 3D.

Sources

1. The Thalamus and Primary Visual Cortex, OpenStax, Introduction to Behavioral Neuroscience
2. Primary visual cortex, Radiopaedia
3. Neuroanatomy, Visual Pathway, StatPearls, NCBI Bookshelf

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