Primary visual cortex (V1, striate cortex)
Cortex & pupil · Congruous hemianopia Macular sparing
Brodmann area 17 on the banks of the calcarine sulcus on the medial occipital lobe. Each hemisphere maps the contralateral hemifield: the upper bank (cuneus) holds the inferior field and the lower bank (lingual gyrus) the superior field, with the macula represented posteriorly at the occipital pole and the periphery anteriorly.
Traced from the start
Detail
- Retinotopy
- Macula at the occipital pole with a large cortical area; peripheral field anterior; the monocular temporal crescent most anterior
- Blood supply
- Calcarine branch of the posterior cerebral artery; the occipital pole also receives middle cerebral collaterals
- Input
- Optic radiation to layer 4 (stria of Gennari)
- Output
- V2 to V5: dorsal 'where' stream to parietal cortex, ventral 'what' stream to inferotemporal cortex
When it goes wrong
Posterior cerebral artery infarct of one occipital lobe
Contralateral congruous homonymous hemianopia with macular sparing, because the occipital pole stays perfused by middle cerebral collaterals; acuity and pupillary reflexes normal
Bilateral occipital infarction (basilar-tip embolus, profound hypotension)
Cortical blindness with preserved pupillary light reflexes and a normal fundus; Anton syndrome when the patient denies the blindness and confabulates
Lesion confined to the occipital pole (head injury, small embolus)
Homonymous central (macular) scotoma with the peripheral field intact
Practise this structure
2 questions in the bank tagged Posterior Circulation.
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