The precuneus is a part of the parietal lobe of the brain, lying on the medial surface of the cerebral hemisphere. It plays a role in visuo-spatial imagery, episodic memory retrieval and self-processing operations .
While highly variable, the main arterial supply arises from the posterior cerebral artery, predominantly the P2 segment. The precuneus derives blood supply from the occipito-parietal artery, a terminal branch of the internal occipital artery.
The parieto-occipital sulcus joins with the anterior end of the calcarine sulcus to form a 'lazy Y' configuration, sometimes referred to as the parieto-occipito-calcarine sign . The precuneus lies superior to the upper limb of the Y (parieto-occipital sulcus), whereas the cuneus lies in between the two limbs, and the lingual gyrus below the lower limb.