Calcarine sulcus

At a glance

English

Calcarine sulcus

Latin (TA2)

Sulcus calcarinus

System

Brain and spinal cord

Region

Head

Side

Paired, left and right

About the calcarine sulcus

Also called the calcarine fissure, this is one of the most constant grooves of the brain. It lies on the medial face of each cerebral hemisphere, in the occipital lobe, and is seen best when the brain is cut down the midline. The name is taken from calcar, Latin for a spur. It is a complete sulcus, meaning it is so deep that it pushes the wall of the lateral ventricle inwards: its front part raises a ridge, the calcar avis, on the medial wall of the posterior horn of that ventricle.

It starts close to the occipital pole, often as two small branches that come together, and runs forwards in a gentle curve to end a little below the splenium, the thick back end of the corpus callosum. On the way the parieto-occipital sulcus comes down from above to meet it at a sharp angle, and the two together form a Y. The part in front of this junction is called the anterior or stem part, and the part behind it the posterior part. The wedge-shaped area of cortex between the parieto-occipital and calcarine sulci is the cuneus, and the area below the calcarine sulcus is the lingual gyrus.

The primary visual cortex, Brodmann area 17, lines the banks and floor of the calcarine sulcus, mainly in its posterior part, and spreads onto the cuneus and lingual gyrus beside it. It is also called the striate cortex because a white stripe, the line of Gennari, can be seen in it with the naked eye. It receives the optic radiation from the lateral geniculate body. The map is inverted: the lower field is represented on the upper bank and cuneus, the upper field on the lower bank and lingual gyrus. The central field, used for detailed vision, is mapped at the back near the occipital pole, and the periphery further forward.

Damage to the cortex of the sulcus, usually from a stroke of the posterior cerebral artery, causes loss of the opposite half of the visual field in both eyes (homonymous hemianopia). Central vision is often spared, because the occipital pole may also receive blood from the middle cerebral artery. A lesion of only the upper or lower bank produces a quarter-field defect.

Function and supply

Function

Marks the site of the primary visual cortex, which receives the optic radiation and maps the opposite half of the visual field in inverted order, central vision at the back and peripheral vision in front.

Blood supply

The calcarine branch of the posterior cerebral artery; the occipital pole may also receive branches of the middle cerebral artery.