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Structure

Occipital lobe

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The occipital lobe, at the posterior pole of the cerebrum, is the primary centre for visual processing. It contains the striate cortex (Brodmann area 17) lining the calcarine sulcus and surrounding visual association areas.

Terminologia Anatomica (Latin): Lobus occipitalis · Open in the 3D atlas

Location

It lies behind the parieto-occipital sulcus on the medial surface and behind the preoccipital notch laterally, resting on the tentorium cerebelli; its lateral borders with the parietal and temporal lobes are conventional. On the medial surface the calcarine sulcus separates the cuneus above from the lingual gyrus below.

Structure

Primary visual cortex (V1, area 17) lies along the calcarine sulcus; the upper bank (cuneus) receives the lower visual field and the lower bank (lingual gyrus) the upper field, with the macula represented at the occipital pole. Areas 18 and 19 are visual association cortex, feeding the dorsal (where and how) stream to the parietal lobe and the ventral (what) stream to the temporal lobe.

Blood supply

The posterior cerebral artery (calcarine branch) supplies the visual cortex; the occipital pole often receives collateral supply from the middle cerebral artery, which explains macular sparing in PCA occlusion. Venous drainage is to the superior sagittal and transverse sinuses.

Innervation

Afferent: the optic radiation (geniculocalcarine tract) from the lateral geniculate nucleus, with the inferior retinal fibres looping in the temporal lobe (Meyer loop) and superior fibres passing through the parietal lobe. Efferent: association connections to parietal and temporal cortex, superior colliculus and callosal fibres.

Function

It receives and maps the contralateral visual field in a retinotopic pattern and analyses edges, orientation, motion, colour and depth; association areas support visual recognition and spatial vision together with the temporal and parietal lobes.

Clinical correlations

PCA infarction produces a contralateral homonymous hemianopia, often with macular sparing. Bilateral occipital lesions cause cortical blindness, sometimes with denial of blindness (Anton syndrome) and preserved pupillary reflexes. Visual association lesions cause agnosias (including prosopagnosia with ventral lesions); occipital seizures produce visual phenomena.

Common exam points

  • Primary visual cortex (area 17) lies along the calcarine sulcus; the cuneus receives the lower field, the lingual gyrus the upper field.
  • PCA stroke: contralateral homonymous hemianopia with macular sparing.
  • Bilateral occipital infarction: cortical blindness with preserved pupillary light reflex (Anton syndrome if blindness is denied).
  • Visual pathway lesions: optic nerve (monocular), chiasm (bitemporal), tract/radiation/cortex (homonymous).

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Kandel ER, Koester JD, Mack SH, Siegelbaum SA. Principles of Neural Science. McGraw-Hill, 6th edition (2021) — Tier 3 (textbook)
  3. Haines DE, Mihailoff GA. Fundamental Neuroscience for Basic and Clinical Applications. Elsevier, 5th edition (2018) — Tier 3 (textbook)

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