CorpusHuman Anatomy
NervousBrain region

Occipital lobe

Lobus occipitalis

The posterior pole of each hemisphere, devoted to vision: the primary visual (striate) cortex lines the calcarine sulcus, and the surrounding visual association areas analyse form, colour and motion.

Show on body map Brain — Lateral View

Overview

Primary visual cortexBrodmann 17 (V1, striate cortex)
Visual association cortexBrodmann 18, 19
V1 above calcarine sulcus representsInferior visual field

The occipital lobe lies behind the parieto-occipital sulcus on the medial surface and rests on the tentorium cerebelli. Its most important landmark is the calcarine sulcus on the medial surface. The primary visual cortex (V1, area 17, "striate cortex", named for the myelinated stria of Gennari in layer IV) lines both banks of the calcarine sulcus and extends only slightly onto the lateral surface at the occipital pole. V1 receives the optic radiation from the lateral geniculate nucleus and is precisely retinotopic:
• the cortex above the calcarine sulcus (cuneus) represents the lower contralateral visual field;
• the cortex below it (lingual gyrus) represents the upper field;
• the macula is magnified onto a large area at the occipital pole, and the periphery is represented anteriorly.

Surrounding V1 are the visual association areas (V2, V3: areas 18, 19). From there processing divides into two streams:
• a dorsal (occipitoparietal) "where/how" stream, which includes the motion area V5/MT and guides spatial vision and action;
• a ventral (occipitotemporal) "what" stream, which includes the colour area V4 and leads to the object and face areas of the temporal lobe.

Location

Posterior part of each hemisphere, beneath the occipital bone, above the tentorium cerebelli and cerebellum.

Parts & subdivisions

  1. Primary visual cortex (V1, area 17)
    Banks of the calcarine sulcus; receives the optic radiation; retinotopic map of the contralateral visual hemifield with a magnified macula at the pole.
  2. Visual association cortex (areas 18, 19)
    V2, V3 and beyond; analysis of contour, depth and form; origin of the dorsal and ventral streams.
  3. Cuneus
    Wedge above the calcarine sulcus; lower contralateral quadrant.
  4. Lingual gyrus
    Below the calcarine sulcus; upper contralateral quadrant; also colour processing (V4 extends onto the adjacent fusiform gyrus).
  5. V5/MT
    At the occipitotemporal junction laterally; motion perception.

Anatomy

Arterial supply

Posterior cerebral artery (calcarine and parieto-occipital branches) supplies V1. The occipital pole (macular cortex) also receives MCA branches in many people, a dual supply that explains macular sparing after PCA occlusion.

Function

  • Conscious vision of the contralateral visual hemifield
  • Analysis of form, colour, depth and motion
  • Visual association and recognition (with temporal and parietal lobes)
  • Visual fixation and pursuit (with frontal and parietal eye fields)

Clinical significance

PCA infarction

Causes a contralateral homonymous hemianopia with macular sparing. A lesion of the left occipital lobe together with the splenium of the corpus callosum produces alexia without agraphia: the patient can write but cannot read what they have written.

Cortical blindness

Bilateral occipital infarction (top-of-basilar embolism, hypoxia, PRES) causes cortical blindness with preserved pupillary light reflexes, because the reflex arc bypasses the cortex. In Anton syndrome the patient denies being blind and confabulates. Bilateral parieto-occipital lesions cause Balint syndrome: simultanagnosia, optic ataxia and oculomotor apraxia.

Mnemonics

Calcarine map

"Cuneus — Ceiling is the floor": the cuneus (above the sulcus) sees the lower field; the lingual gyrus ("tongue", below) sees the upper field.

Compiled from standard anatomy and physiology references — see the Nervous System sources. For education only; not medical advice.